Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

tablet

  • 250mg

Breast Cancer

HER2-overexpressing metastatic breast cancer

  • Indicated in combination with capecitabine for treatment of patients with advanced or metastatic breast cancer whose tumors overexpress HER2 and who have received prior therapy including an anthracycline, a taxane, and trastuzumab
  • 1250 mg PO qDay on Days 1-21 continuously in combination with capecitabine (2000 mg/m²/day PO divided q12hr) on Days 1-14 in a repeating 21-day cycle

Hormone-positive and HER2-positive advanced breast cancer

  • Indicated in combination therapy with letrozole for treatment of postmenopausal women with hormone receptor-positive and HER2-positive breast cancer for whom hormonal therapy is indicated
  • 1500 mg PO qDay administered continuously in combination with letrozole 2.5 mg PO qDay

Dosage Modifications

Decreased LVEF

  • Discontinue with decreased LVEF ≥Grade 2 or an LVEF that drops below the institution’s lower limit of normal; lapatinib may be restarted at 1000 mg/day after recovery

Diarrhea

  • Interrupt dosing for diarrhea which is Grade 3 or Grade 1 or 2 with complicating features (moderate-to-severe abdominal cramping, nausea or vomiting ≥Grade 2, decreased performance status, fever, sepsis, neutropenia, frank bleeding, or dehydration)
  • May be reintroduced at a lower dose (reduced from 1,250 mg/day to 1,000 mg/day or from 1,500 mg/day to 1,250 mg/day) when diarrhea resolves to ≤Grade 1
  • Grade 4: Permanently discontinue

Other toxicities

  • Discontinue or interrupt dose for other toxicities ≥Grade 2
  • May be restarted at standard dose when the toxicity improves to ≤Grade 1
  • Toxicity recurs: May be reintroduced at a lower dose (reduced from 1,250 mg/day to 1,000 mg/day or from 1,500 mg/day to 1,250 mg/day)

CYP3A4 inhibitors or inducers

  • Concomitant strong CYP3A4 inhibitors: Reduce dose to 500 mg/day
  • Concomitant strong CYP3A4 inducers: Gradually titrate from 1250 mg/day up to 4500 mg/day (HER2 positive metastatic breast cancer) or from 1500 mg/day up to 5500 mg/day (Hormone receptor positive, HER2 positive breast cancer)

Severe hepatic impairment (Child-Pugh class C)

  • HER2 positive metastatic breast cancer: Reduce dose from 1250 mg/day to 750 mg/day
  • Hormone receptor positive, HER2 positive breast cancer: Reduce dose from 1500 mg/day to 1000 mg/day

Gastric Cancer (Orphan)

Treatment of ErbB2 positive gastric cancer

Orphan indication sponsor

  • GlaxoSmithKline; 1250 S. Collegeville Rd, P. O. Box 5089;Collegeville, PA 19426-0989

Esophageal Cancer (Orphan)

Treatment of ErbB2 positive esophageal cancer

Orphan indication sponsor

  • GlaxoSmithKline; 1250 S. Collegeville Rd, P. O. Box 5089;Collegeville, PA 19426-0989

Safety and efficacy not established

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Interactions

Interaction Checker

and lapatinib

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            Contraindicated (5)

            • flibanserin

              lapatinib will increase the level or effect of flibanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Coadministration of flibanserin with moderate or strong CYP3A4 inhibitors is contraindicated. Severe hypotension or syncope can occur.

            • lefamulin

              lefamulin will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Lefamulin is contraindicated with CYP3A substrates know to prolong the QT interval.

            • lomitapide

              lapatinib increases levels of lomitapide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Increases lomitapide levels several folds.

            • lonafarnib

              lapatinib will increase the level or effect of lonafarnib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated. Lonafarnib is a sensitive CYP3A4 substrate. Coadministration with strong or moderate CYP3A4 inhibitors is contraindicated.

            • pimozide

              lapatinib increases levels of pimozide by decreasing metabolism. Contraindicated. Risk of QT interval prolongation.

            Serious - Use Alternative (106)

            • abametapir

              abametapir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. For 2 weeks after abametapir application, avoid taking drugs that are CYP3A4 substrates. If not feasible, avoid use of abametapir.

            • afatinib

              lapatinib increases levels of afatinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Reduce afatinib daily dose by 10 mg if not tolerated when coadministered with P-gp inhibitors.

            • alpelisib

              lapatinib will increase the level or effect of alpelisib by Other (see comment). Avoid or Use Alternate Drug. Coadministration of alpelisib (BCRP substrate) with a BCRP inhibitor may increase alpelisib concentration, which may increase the risk of toxicities. If unable to avoid or use alternant drugs, closely monitor for increased adverse reactions.

            • amiodarone

              amiodarone and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • apalutamide

              apalutamide will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of apalutamide, a strong CYP3A4 inducer, with drugs that are CYP3A4 substrates can result in lower exposure to these medications. Avoid or substitute another drug for these medications when possible. Evaluate for loss of therapeutic effect if medication must be coadministered. Adjust dose according to prescribing information if needed.

            • arsenic trioxide

              arsenic trioxide and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • artemether

              artemether and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • avapritinib

              lapatinib will increase the level or effect of avapritinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of avapritinib with moderate CYP3A4 inhibitors. If unable to avoid, reduce avapritinib starting dose. See drug monograph Dosage Modifications.

            • axitinib

              lapatinib increases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If unable to avoid coadministration with moderate CYP3A4 inhibitors, monitor closely and reduce dose if necessary .

            • bosutinib

              lapatinib increases levels of bosutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

              lapatinib increases levels of bosutinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

            • carbamazepine

              carbamazepine will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If carbamazepine is started in a patient already taking lapatinib, gradually titrate lapatinib dose upward; reduce lapatinib dose if carbamazepine is discontinued

            • ceritinib

              ceritinib and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • chloramphenicol

              chloramphenicol will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • clarithromycin

              clarithromycin will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • cobicistat

              cobicistat will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If concomitant administration cannot be avoided, administer 500 mg lapatinib once daily and increase lapatinib dose to indicated dose once cobicistat discontinued

            • cobimetinib

              lapatinib will increase the level or effect of cobimetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If concurrent short term (14 days or less) use of moderate CYP3A inhibitors is unavoidable for patients who are taking cobimetinib 60 mg, reduce the cobimetinib dose to 20 mg. After discontinuation of a moderate CYP3A inhibitor, resume cobimetinib 60 mg. Use an alternative to a moderate CYP3A inhibitor in patients who are taking a reduced dose of cobimetinib (40 or 20 mg daily).

            • colchicine

              lapatinib will increase the level or effect of colchicine by Other (see comment). Avoid or Use Alternate Drug. Colchicine is a P-gp and CYP3A4 substrate. Avoid use with drugs that are both P-gp and strong CYP3A4 inhibitors. If coadministration is necessary, decrease colchicine dose or frequency as recommended in prescribing information. Use of any colchicine product in conjunction with strong CYP3A4 inhibitors is contraindicated in patients with renal or hepatic impairment.

            • darolutamide

              darolutamide will increase the level or effect of lapatinib by Other (see comment). Avoid or Use Alternate Drug. Darolutamide is a BCRP inhibitor. Avoid coadministration with BCRP inhibitors. If use is unavoidable, closely monitor for adverse reactions and consider dose reduction of BCRP substrate drug (refer BCRP substrate prescribing information).

            • desflurane

              desflurane and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • dihydroergotamine

              lapatinib will increase the level or effect of dihydroergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • dihydroergotamine intranasal

              lapatinib will increase the level or effect of dihydroergotamine intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • disopyramide

              disopyramide and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • dronedarone

              lapatinib will increase the level or effect of dronedarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • edoxaban

              lapatinib will increase the level or effect of edoxaban by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Dose adjustment may be required with strong P-gp inhibitors. DVT/PE treatment: Decrease dose to 30 mg PO once daily. NVAF: No dose reduction recommended

            • eliglustat

              lapatinib increases levels of eliglustat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Moderate CYP3A4 inhibitors are not recommended with eliglustat poor or intermediate metabolizers; reduce eliglustat dose from 84 mg BID to 84 mg once daily in extensive metabolizers .

            • entrectinib

              lapatinib will increase the level or effect of entrectinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of moderate CYP3A4 inhibitors with entrectinib, a CYP3A4 substrate. If coadministration unavoidable, reduce dose to 200 mg/day for patients aged 12 y or older with BSA >1.50m2. Resume previous entrectinib dose after discontinuing moderate CYP3A inhibitor for 3-5 elimination half-lives.

              lapatinib and entrectinib both increase QTc interval. Avoid or Use Alternate Drug.

            • enzalutamide

              enzalutamide will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • erdafitinib

              erdafitinib will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If coadministration unavoidable, separate administration by at least 6 hr before or after administration of P-gp substrates with narrow therapeutic index.

            • ergotamine

              lapatinib will increase the level or effect of ergotamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • erythromycin base

              erythromycin base will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

              lapatinib will increase the level or effect of erythromycin base by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • erythromycin ethylsuccinate

              erythromycin ethylsuccinate will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

              lapatinib will increase the level or effect of erythromycin ethylsuccinate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • erythromycin lactobionate

              erythromycin lactobionate will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

              lapatinib will increase the level or effect of erythromycin lactobionate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • erythromycin stearate

              erythromycin stearate will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

              lapatinib will increase the level or effect of erythromycin stearate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • everolimus

              lapatinib will increase the level or effect of everolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

              lapatinib will increase the level or effect of everolimus by P-glycoprotein (MDR1) efflux transporter. Contraindicated.

            • fentanyl

              lapatinib will increase the level or effect of fentanyl by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

            • fentanyl intranasal

              lapatinib will increase the level or effect of fentanyl intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

            • fentanyl transdermal

              lapatinib will increase the level or effect of fentanyl transdermal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

            • fentanyl transmucosal

              lapatinib will increase the level or effect of fentanyl transmucosal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of CYP3A4 inhibitors with fentanyl is necessary, monitor patients for respiratory depression and sedation at frequent intervals and consider fentanyl dose adjustments until stable drug effects are achieved.

            • fexinidazole

              fexinidazole and lapatinib both increase QTc interval. Avoid or Use Alternate Drug. Avoid coadministration of fexinidazole with drugs known to block potassium channels or prolong QT interval.

              fexinidazole will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Fexinidazole inhibits CYP3A4. Coadministration may increase risk for adverse effects of CYP3A4 substrates.

            • glasdegib

              lapatinib and glasdegib both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, monitor for increased risk of QTc interval prolongation.

            • hydroxychloroquine sulfate

              hydroxychloroquine sulfate and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • ibutilide

              ibutilide and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • idelalisib

              idelalisib will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Idelalisib is a strong CYP3A inhibitor; avoid coadministration with sensitive CYP3A substrates

            • indapamide

              indapamide and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • infigratinib

              lapatinib will increase the level or effect of infigratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • inotuzumab

              inotuzumab and lapatinib both increase QTc interval. Avoid or Use Alternate Drug. If unable to avoid concomitant use, obtain ECGs and electrolytes before and after initiation of any drug known to prolong QTc, and periodically monitor as clinically indicated during treatment.

            • itraconazole

              itraconazole will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of strong CYP3A4 inhibitors with lapatinib. If an overlap in therapy cannot be avoided, consider reducing lapatinib dose to 500 mg/day during, and within 1 week of completing treatment with strong CYP3A4 inhibitor.

            • ivabradine

              lapatinib will increase the level or effect of ivabradine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of ivabradine with moderate CYP3A4 inhibitors.

            • ivosidenib

              ivosidenib and lapatinib both increase QTc interval. Avoid or Use Alternate Drug. Avoid coadministration of QTc prolonging drugs with ivosidenib or replace with alternate therapies. If coadministration of a QTc prolonging drug is unavoidable, monitor for increased risk of QTc interval prolongation.

              ivosidenib will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of sensitive CYP3A4 substrates with ivosidenib or replace with alternative therapies. If coadministration is unavoidable, monitor patients for loss of therapeutic effect of these drugs.

            • ketoconazole

              ketoconazole will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • lasmiditan

              lasmiditan increases levels of lapatinib by Other (see comment). Avoid or Use Alternate Drug. Comment: Lasmiditan inhibits BCRP in vitro. Avoid coadministration of lasmiditan with BCRP substrates.

            • lemborexant

              lapatinib will increase the level or effect of lemborexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of lemborexant with moderate or strong CYP3A inhibitors.

            • lopinavir

              lopinavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • lovastatin

              lapatinib will increase the level or effect of lovastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • lurbinectedin

              lapatinib will increase the level or effect of lurbinectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • macimorelin

              macimorelin and lapatinib both increase QTc interval. Avoid or Use Alternate Drug. Macimorelin causes an increase of ~11 msec in the corrected QT interval. Avoid coadministration with drugs that prolong QT interval, which could increase risk for developing torsade de pointes-type ventricular tachycardia. Allow sufficient washout time of drugs that are known to prolong the QT interval before administering macimorelin.

            • midazolam intranasal

              lapatinib will increase the level or effect of midazolam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of moderate CYP3A4 inhibitors with midazolam intranasal causes higher midazolam systemic exposure, which may prolong sedation.

            • mobocertinib

              lapatinib will increase the level or effect of mobocertinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If use of moderate CYP3A4 inhibitor unavoidable, reduce mobocertinib dose by ~50% (eg, 160 to 80 mg); closely monitor QTc interval.

              mobocertinib and lapatinib both increase QTc interval. Avoid or Use Alternate Drug. If coadministration unavoidable, reduce mobocertinib dose and monitor QTc interval more frequently.

            • naloxegol

              lapatinib will increase the level or effect of naloxegol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministation of naloxegol with moderate CYP3A4 inhibitors is unavoidable, reduce naloxegol dose to 12.5 mg qDay

            • nefazodone

              nefazodone will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • neratinib

              lapatinib will increase the level or effect of neratinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of neratinib with strong/moderate CYP3A4 inhibitors.

            • olaparib

              lapatinib will increase the level or effect of olaparib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with moderate CYP3A inhibitors cannot be avoided, reduce olaparib dose to 200 mg (capsule) or 150 mg (tablet) PO BID. Do not substitute tablets with capsules.

            • ondansetron

              lapatinib and ondansetron both increase QTc interval. Avoid or Use Alternate Drug. Avoid with congenital long QT syndrome; ECG monitoring recommended with concomitant medications that prolong QT interval, electrolyte abnormalities, CHF, or bradyarrhythmias. Potential for increased ondansetron levels.

            • ozanimod

              lapatinib increases toxicity of ozanimod by Other (see comment). Avoid or Use Alternate Drug. Comment: Coadministration of ozanimod (a BCRP substrate) with BCRP inhibitors increases the exposure of the minor (RP101988, RP101075) and major active metabolites (CC112273, CC1084037) of ozanimod, which may increase the risk of ozanimod adverse reactions. .

            • palifermin

              palifermin increases toxicity of lapatinib by Other (see comment). Avoid or Use Alternate Drug. Comment: Palifermin should not be administered within 24 hr before, during infusion of, or within 24 hr after administration of antineoplastic agents. Coadministration of palifermin within 24 hr of chemotherapy resulted in increased severity and duration of oral mucositis.

            • panobinostat

              lapatinib and panobinostat both increase QTc interval. Avoid or Use Alternate Drug. Panobinostat is known to significantly prolong QT interval. Panobinostat prescribing information states use with drugs known to prolong QTc is not recommended.

            • pazopanib

              lapatinib will increase the level or effect of pazopanib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of pazopanib with strong CYP3A4 inhibitors if possible; if must coadminister, decrease pazopanib dose to 400 mg/day

            • pemigatinib

              lapatinib will increase the level or effect of pemigatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong or moderate CYP3A4 inhibitors is unavoidable, reduce pemigatinib dose (refer to drug monograph dosage modifications). After discontinuing the CYP3A4 inhibitor for 3 elimination half-lives, may resume previous pemigatinib dose.

            • pentamidine

              lapatinib and pentamidine both increase QTc interval. Avoid or Use Alternate Drug.

            • pexidartinib

              lapatinib will increase the level or effect of pexidartinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong or moderate CYP3A4 inhibitors is unavoidable, reduce pexidartinib dose (refer to drug monograph dosage modifications). After discontinuing the CYP3A4 inhibitor for 3 elimination half-lives, may resume previous pexidartinib dose.

            • pimozide

              lapatinib and pimozide both increase QTc interval. Avoid or Use Alternate Drug.

            • pitolisant

              lapatinib and pitolisant both increase QTc interval. Avoid or Use Alternate Drug.

            • pomalidomide

              lapatinib increases levels of pomalidomide by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

            • procainamide

              lapatinib and procainamide both increase QTc interval. Avoid or Use Alternate Drug.

            • quinidine

              quinidine will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

              quinidine and lapatinib both increase QTc interval. Avoid or Use Alternate Drug.

            • ranolazine

              lapatinib will increase the level or effect of ranolazine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • ribociclib

              ribociclib increases toxicity of lapatinib by QTc interval. Avoid or Use Alternate Drug.

            • rifabutin

              rifabutin will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • rifampin

              rifampin will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • rimegepant

              lapatinib will increase the level or effect of rimegepant by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug.

              lapatinib will increase the level or effect of rimegepant by Other (see comment). Avoid or Use Alternate Drug. Avoid coadministration of rimegepant (a BCRP substrate) with inhibitors of BCRP.

            • riociguat

              lapatinib will increase the level or effect of riociguat by decreasing metabolism. Avoid or Use Alternate Drug. Coadministration of riociguat (substrate of CYP isoenzymes 1A1, 2C8, 3A, 2J2) with strong CYP inhibitors may require a decreased initial dose of 0.5 mg PO TID; monitor for signs of hypotension and reduce dose if needed

              lapatinib will increase the level or effect of riociguat by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Coadministration of riociguat (P-gp substrate) with strong P-gp inhibitors may require a decreased initial dose of 0.5 mg PO TID; monitor for signs of hypotension and reduce dose if needed

            • ritonavir

              ritonavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • saquinavir

              saquinavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • selumetinib

              lapatinib will increase the level or effect of selumetinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration with strong or moderate CYP3A4 inhibitors cannot be avoided, reduce selumetinib dosage (refer to selumetinib monograph for further information). After discontinuation of the strong or moderate CYP3A4 inhibitor for 3 elimination half-lives, resume selumetinib dose that was taken before initiating the inhibitor.

            • silodosin

              lapatinib will increase the level or effect of silodosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • simvastatin

              lapatinib will increase the level or effect of simvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • siponimod

              lapatinib will increase the level or effect of siponimod by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Coadministration of siponimod with a moderate or strong CYP3A4 inhibitor PLUS a moderate or strong CYP2C9 inhibitor is not recommended.

            • sirolimus

              lapatinib will increase the level or effect of sirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • sotalol

              lapatinib and sotalol both increase QTc interval. Avoid or Use Alternate Drug.

            • sotorasib

              sotorasib will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If use is unavoidable, refer to the prescribing information of the P-gp substrate for dosage modifications.

            • St John's Wort

              St John's Wort will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • talazoparib

              lapatinib will increase the level or effect of talazoparib by Other (see comment). Avoid or Use Alternate Drug. BCRP inhibitors may increase systemic exposure of talazoparib (a BCRP substrate). If coadministration cannot be avoided, monitor for potential adverse reactions.

            • tazemetostat

              lapatinib will increase the level or effect of tazemetostat by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid coadministration of tazemetostat with moderate CYP3A4 inhibitors. If coadministration is unavoidable, reduce tazemetostat current dose (see drug monograph Dosage Modifications).

            • tepotinib

              tepotinib will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If concomitant use unavoidable, reduce the P-gp substrate dosage if recommended in its approved product labeling.

            • tipranavir

              tipranavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug.

            • tolvaptan

              lapatinib will increase the level or effect of tolvaptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Contraindicated.

            • topotecan

              lapatinib will increase the level or effect of topotecan by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. Product labeling for PO topotecan recommends avoiding concomitant use of P-gp inhibitors; the interaction with IV topotecan may be less severe but is still likely of clinical significance

            • toremifene

              lapatinib and toremifene both increase QTc interval. Avoid or Use Alternate Drug. Concurrent use of toremifene with agents causing QT prolongation should be avoided. If concomitant use is required it's recommended that toremifene be interrupted. If interruption not possible, patients requiring therapy with a drug that prolongs QT should be closely monitored. ECGs should be obtained for high risk patients.

            • tucatinib

              lapatinib will increase the level or effect of tucatinib by Other (see comment). Avoid or Use Alternate Drug. Coadministration of tucatinib (a CYP2C8 substrate) with a strong or moderate CYP2C8 inhibitors increases tucatinib plasma concentrations and risk of toxicities.

              tucatinib will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Avoid concomitant use of tucatinib with CYP3A substrates, where minimal concentration changes may lead to serious or life-threatening toxicities. If unavoidable, reduce CYP3A substrate dose according to product labeling.

            • umeclidinium bromide/vilanterol inhaled

              lapatinib increases toxicity of umeclidinium bromide/vilanterol inhaled by QTc interval. Avoid or Use Alternate Drug. Exercise extreme caution when vilanterol coadministered with drugs that prolong QTc interval; adrenergic agonist effects on the cardiovascular system may be potentiated.

            • vandetanib

              lapatinib, vandetanib. Either increases toxicity of the other by QTc interval. Avoid or Use Alternate Drug. Avoid coadministration with drugs known to prolong QT interval; if a drug known to prolong QT interval must be used, more frequent ECG monitoring is recommended.

            • vemurafenib

              vemurafenib and lapatinib both increase QTc interval. Avoid or Use Alternate Drug. Concomitant use of vemurafenib with drugs that prolong QT interval is not recommended. Lapatinib may also increase vemurafenib levels.

            • venetoclax

              lapatinib will increase the level or effect of venetoclax by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If a moderate CYP3A inhibitor must be used, reduce the venetoclax dose by at least 50%. Monitor more closely for signs of venetoclax toxicities.

              lapatinib will increase the level or effect of venetoclax by P-glycoprotein (MDR1) efflux transporter. Avoid or Use Alternate Drug. If a P-gp inhibitor must be used, reduce the venetoclax dose by at least 50%. Monitor more closely for signs of venetoclax toxicities.

            • vilanterol/fluticasone furoate inhaled

              lapatinib increases toxicity of vilanterol/fluticasone furoate inhaled by QTc interval. Avoid or Use Alternate Drug. Exercise extreme caution when vilanterol coadministered with drugs that prolong QTc interval; adrenergic agonist effects on the cardiovascular system may be potentiated.

            • vilazodone

              lapatinib increases levels of vilazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If intolerable adverse effects occur when coadministered with moderate CYP3A4 inhibitors, reduce daily dose to 20 mg.

            • voxelotor

              voxelotor will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. Voxelotor increases systemic exposure of sensitive CYP3A4 substrates. Avoid coadministration with sensitive CYP3A4 substrates with a narrow therapeutic index. Consider dose reduction of the sensitive CYP3A4 substrate(s) if unable to avoid.

            Monitor Closely (306)

            • acalabrutinib

              lapatinib will increase the level or effect of acalabrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Decrease acalabrutinib dose to 100 mg once daily if coadministered with a moderate CYP3A inhibitor.

              acalabrutinib increases levels of lapatinib by Other (see comment). Use Caution/Monitor. Comment: Acalabrutinib may increase exposure to coadministered BCRP substrates by inhibition of intestinal BCRP.

            • albuterol

              albuterol and lapatinib both increase QTc interval. Use Caution/Monitor.

            • alfuzosin

              lapatinib and alfuzosin both increase QTc interval. Use Caution/Monitor.

              alfuzosin and lapatinib both increase QTc interval. Use Caution/Monitor.

            • almotriptan

              lapatinib will increase the level or effect of almotriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • alprazolam

              lapatinib will increase the level or effect of alprazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • amiodarone

              lapatinib will increase the level or effect of amiodarone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              amiodarone will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • amitriptyline

              amitriptyline and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • amobarbital

              amobarbital will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • amoxapine

              amoxapine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • apalutamide

              apalutamide will decrease the level or effect of lapatinib by increasing elimination. Use Caution/Monitor. Apalutamide weakly induces BCRP and may decrease systemic exposure of drugs that are BCRP substrates.

            • apomorphine

              apomorphine and lapatinib both increase QTc interval. Use Caution/Monitor.

            • aprepitant

              aprepitant will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • arformoterol

              arformoterol and lapatinib both increase QTc interval. Use Caution/Monitor.

            • aripiprazole

              lapatinib will increase the level or effect of aripiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              aripiprazole and lapatinib both increase QTc interval. Use Caution/Monitor.

            • armodafinil

              armodafinil will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • artemether/lumefantrine

              lapatinib will increase the level or effect of artemether/lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib and artemether/lumefantrine both increase QTc interval. Modify Therapy/Monitor Closely.

            • atazanavir

              atazanavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • atogepant

              lapatinib will increase the level or effect of atogepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • atomoxetine

              atomoxetine and lapatinib both increase QTc interval. Use Caution/Monitor.

            • atorvastatin

              lapatinib will increase the level or effect of atorvastatin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              atorvastatin will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • avanafil

              lapatinib will increase the level or effect of avanafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. CYP3A4 inhibitors may reduce avanafil clearance increasing systemic exposure to avanafil; increased levels may result in increased associated adverse events; the maximum recommended dose of STENDRA is 50 mg, not to exceed once every 24 hours for patients taking concomitant moderate CYP3A4 inhibitors

            • bazedoxifene/conjugated estrogens

              lapatinib will increase the level or effect of bazedoxifene/conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of bazedoxifene/conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • bedaquiline

              lapatinib and bedaquiline both increase QTc interval. Modify Therapy/Monitor Closely. ECG should be monitored closely

            • berotralstat

              lapatinib increases levels of berotralstat by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Reduced berotralstat dose to 110 mg/day when coadministered with P-gp inhibitors.

              lapatinib increases levels of berotralstat by Other (see comment). Modify Therapy/Monitor Closely. Comment: Reduced dose of berotralstat (a BCRP substrate) to 110 mg/day when coadministered with BCRP inhibitors.

              berotralstat will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor or titrate P-gp substrate dose if coadministered.

            • betrixaban

              lapatinib increases levels of betrixaban by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Decrease betrixaban dose to 80 mg PO once, then 40 mg PO qDay if coadministered with a P-gp inhibitor.

            • bexarotene

              lapatinib will increase the level or effect of bexarotene by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • bortezomib

              lapatinib will increase the level or effect of bortezomib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • bosentan

              bosentan will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • brexpiprazole

              lapatinib will increase the level or effect of brexpiprazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Administer a quarter of brexpiprazole dose if coadministered with a moderate CYP3A4 inhibitor PLUS a strong/moderate CYP2D6 inhibitor.

            • budesonide

              lapatinib will increase the level or effect of budesonide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              budesonide will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • buprenorphine subdermal implant

              lapatinib will increase the level or effect of buprenorphine subdermal implant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Monitor patients already on buprenorphine subdermal implant who require newly-initiated treatment with CYP3A4 inhibitors for signs and symptoms of overmedication. If the dose of the concomitant CYP3A4 inhibitor cannot be reduced or discontinued, implant removal may be necessary and the patient should then be treated with a buprenorphine dosage form that permits dose adjustments. If a CYP3A4 inhibitor is discontinued in a patient who has been stabilized on buprenorphine, monitor the patient for withdrawal.

            • buprenorphine, long-acting injection

              lapatinib will increase the level or effect of buprenorphine, long-acting injection by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Patients who transfer to buprenorphine long-acting injection from transmucosal buprenorphine coadministered with CYP3A4 inhibitors should be monitored to ensure buprenorphine plasma levels are adequate. Within 2 weeks, if signs and symptoms of buprenorphine toxicity or overdose occur and the concomitant CYP3A4 inhibitor cannot be reduced or discontinued, transition the patient back to a buprenorphine formulation that permits dose adjustments.

            • buspirone

              lapatinib will increase the level or effect of buspirone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • butabarbital

              butabarbital will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • butalbital

              butalbital will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • cabazitaxel

              lapatinib will increase the level or effect of cabazitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Caution should be exercised with concomitant use of moderate CYP3A4 inhibitors.

            • cabozantinib

              lapatinib will increase the level or effect of cabozantinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • cannabidiol

              lapatinib will increase the level or effect of cannabidiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Consider reducing the cannabidiol dose when coadministered with a moderate CYP3A4 inhibitor.

            • carbamazepine

              lapatinib will increase the level or effect of carbamazepine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • cenobamate

              cenobamate will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Increase dose of CYP3A4 substrate, as needed, when coadministered with cenobamate.

            • ceritinib

              lapatinib increases levels of ceritinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • chlorpromazine

              chlorpromazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • cholera vaccine

              lapatinib decreases effects of cholera vaccine by immunosuppressive effects; risk of infection. Modify Therapy/Monitor Closely. Immunosuppressive therapies, including irradiation, antimetabolites, alkylating agents, cytotoxic drugs and corticosteroids (used in greater than physiologic doses), may reduce the immune response to cholera vaccine.

            • cilostazol

              lapatinib will increase the level or effect of cilostazol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • cimetidine

              cimetidine will decrease the level or effect of lapatinib by increasing gastric pH. Applies only to oral form of both agents. Use Caution/Monitor.

            • cinacalcet

              lapatinib will increase the level or effect of cinacalcet by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • citalopram

              lapatinib and citalopram both increase QTc interval. Use Caution/Monitor. ECG monitoring is recommended, along with drugs that may prolong the QT interval.

            • clarithromycin

              clarithromycin will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              clarithromycin and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • clobetasone

              lapatinib will increase the level or effect of clobetasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of clobetasone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • clomipramine

              clomipramine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • clopidogrel

              lapatinib will decrease the level or effect of clopidogrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Inhibition of CYP3A4 will reduce clopidogrel bioactivation

            • clotrimazole

              clotrimazole will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • clozapine

              clozapine and lapatinib both increase QTc interval. Use Caution/Monitor.

            • conivaptan

              conivaptan will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • conjugated estrogens

              lapatinib will increase the level or effect of conjugated estrogens by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of conjugated estrogens by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • conjugated estrogens, vaginal

              lapatinib will increase the level or effect of conjugated estrogens, vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of conjugated estrogens, vaginal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • cortisone

              lapatinib will increase the level or effect of cortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              cortisone will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • crizotinib

              crizotinib increases levels of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Dose reduction may be needed for coadministered drugs that are predominantly metabolized by CYP3A. ECG monitoring is recommended, along with drugs that may prolong the QT interval.

              crizotinib increases levels of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. ECG monitoring is recommended, along with drugs that may prolong the QT interval.

              lapatinib increases levels of crizotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Caution should be exercised with concomitant use of moderate CYP3A inhibitors. .

            • crofelemer

              crofelemer increases levels of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Crofelemer has the potential to inhibit CYP3A4 at concentrations expected in the gut; unlikely to inhibit systemically because minimally absorbed.

            • cyclosporine

              cyclosporine will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of cyclosporine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              cyclosporine will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib will increase the level or effect of cyclosporine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • dabigatran

              lapatinib will increase the level or effect of dabigatran by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Atrial fibrillation: Avoid coadministering dabigatran with P-gp inhibitors if CrCl <30 mL/min. DVT/PE treatment: Avoid coadministering dabigatran with P-gp inhibitors if CrCl <50 mL/min

            • dabrafenib

              dabrafenib will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely.

            • darifenacin

              darifenacin will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of darifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • darolutamide

              lapatinib will increase the level or effect of darolutamide by Other (see comment). Modify Therapy/Monitor Closely. Darolutamide is a P-gp and CYP3A4 substrate. Closely monitor for increased adverse reactions and modify dose of darolutamide as needed when coadministered with drugs that are both P-gp and strong or moderate CYP3A4 inhibitors.

            • darunavir

              darunavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • dasatinib

              dasatinib will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              dasatinib and lapatinib both increase QTc interval. Use Caution/Monitor.

            • daunorubicin

              lapatinib will increase the level or effect of daunorubicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • deferasirox

              deferasirox will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • deflazacort

              lapatinib will increase the level or effect of deflazacort by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Decrease deflazacort dose to one-third of the recommended dose if coadministered with moderate or strong CYP3A4 inhibitors.

              lapatinib will increase the level or effect of deflazacort by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • degarelix

              degarelix and lapatinib both increase QTc interval. Use Caution/Monitor.

            • dengue vaccine

              lapatinib decreases effects of dengue vaccine by immunosuppressive effects; risk of infection. Use Caution/Monitor. Immunosuppressive therapies (eg, irradiation, antimetabolites, alkylating agents, cytotoxic drugs, corticosteroids [greater than physiologic doses]) may reduce immune response to dengue vaccine.

            • desipramine

              desipramine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • deutetrabenazine

              deutetrabenazine and lapatinib both increase QTc interval. Use Caution/Monitor.

            • dexamethasone

              lapatinib will increase the level or effect of dexamethasone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              dexamethasone will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of dexamethasone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • DHEA, herbal

              DHEA, herbal will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • diazepam

              lapatinib will increase the level or effect of diazepam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • diazepam intranasal

              lapatinib will increase the level or effect of diazepam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Strong or moderate CYP3A4 inhibitors may decrease rate of diazepam elimination, thereby increasing adverse reactions to diazepam.

            • dienogest/estradiol valerate

              lapatinib will increase the level or effect of dienogest/estradiol valerate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor for potential adverse effects such as nausea, irregular uterine bleeding, breast tenderness and headache.

            • digoxin

              lapatinib will increase the level or effect of digoxin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • diltiazem

              diltiazem will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • docetaxel

              lapatinib will increase the level or effect of docetaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • dofetilide

              dofetilide and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • dolasetron

              dolasetron and lapatinib both increase QTc interval. Use Caution/Monitor.

            • donepezil

              donepezil and lapatinib both increase QTc interval. Use Caution/Monitor.

            • doxepin

              doxepin and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • doxorubicin

              lapatinib will increase the level or effect of doxorubicin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of doxorubicin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • doxorubicin liposomal

              lapatinib will increase the level or effect of doxorubicin liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of doxorubicin liposomal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • dronedarone

              dronedarone will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              dronedarone will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Use lapatinib with caution in patients who are taking antiarrhythmic agents or other drugs that produce QT prolongation. Possible additive QT prolongation may increase the risk of life-threatening cardiac arrhythmias, including torsade de pointes.

              dronedarone and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • droperidol

              droperidol and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • duvelisib

              duvelisib will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with duvelisib increases AUC of a sensitive CYP3A4 substrate which may increase the risk of toxicities of these drugs. Consider reducing the dose of the sensitive CYP3A4 substrate and monitor for signs of toxicities of the coadministered sensitive CYP3A substrate.

              lapatinib will increase the level or effect of duvelisib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib will increase the level or effect of duvelisib by Other (see comment). Use Caution/Monitor. Coadministration of duvelisib (a BCRP substrate) with a BCRP transport inhibitor may increase levels or effects of duvelisib.

            • efavirenz

              efavirenz will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • elagolix

              elagolix will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              elagolix decreases levels of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Elagolix is a weak-to-moderate CYP3A4 inducer. Monitor CYP3A substrates if coadministered. Consider increasing CYP3A substrate dose if needed.

            • eletriptan

              lapatinib will increase the level or effect of eletriptan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • eliglustat

              eliglustat increases levels of lapatinib by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Monitor therapeutic drug concentrations, as indicated, or consider reducing the dosage of the P-gp substrate and titrate to clinical effect.

            • eluxadoline

              eluxadoline increases levels of lapatinib by decreasing metabolism. Use Caution/Monitor. Eluxadoline may increase the systemic exposure of coadministered BCRP substrates.

            • elvitegravir/cobicistat/emtricitabine/tenofovir DF

              elvitegravir/cobicistat/emtricitabine/tenofovir DF increases levels of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Cobicistat is a CYP3A4 inhibitor; contraindicated with CYP3A4 substrates for which elevated plasma concentrations are associated with serious and/or life-threatening events.

            • encorafenib

              encorafenib, lapatinib. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Encorafenib both inhibits and induces CYP3A4 at clinically relevant plasma concentrations. Coadministration of encorafenib with sensitive CYP3A4 substrates may result in increased toxicity or decreased efficacy of these agents.

            • erlotinib

              lapatinib will increase the level or effect of erlotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • erythromycin base

              erythromycin base will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              erythromycin base and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • erythromycin ethylsuccinate

              erythromycin ethylsuccinate will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              erythromycin ethylsuccinate and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • erythromycin lactobionate

              erythromycin lactobionate will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              erythromycin lactobionate and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • erythromycin stearate

              erythromycin stearate will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              erythromycin stearate and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • escitalopram

              escitalopram increases toxicity of lapatinib by QTc interval. Use Caution/Monitor.

            • eslicarbazepine acetate

              eslicarbazepine acetate will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • estradiol

              lapatinib will increase the level or effect of estradiol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of estradiol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • estrogens conjugated synthetic

              lapatinib will increase the level or effect of estrogens conjugated synthetic by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of estrogens conjugated synthetic by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • estrogens esterified

              lapatinib will increase the level or effect of estrogens esterified by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • estropipate

              lapatinib will increase the level or effect of estropipate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of estropipate by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • ethinylestradiol

              ethinylestradiol will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • etonogestrel

              lapatinib will increase the level or effect of etonogestrel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • etoposide

              lapatinib will increase the level or effect of etoposide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of etoposide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • etravirine

              lapatinib will increase the level or effect of etravirine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              etravirine will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • ezogabine

              ezogabine, lapatinib. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Slight and transient QT-prolongation observed with ezogabine, particularly when dose titrated to 1200 mg/day. QT interval should be monitored when ezogabine is prescribed with agents known to increase QT interval.

            • fedratinib

              fedratinib will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Adjust dose of drugs that are CYP3A4 substrates as necessary.

            • felodipine

              lapatinib will increase the level or effect of felodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              felodipine will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • fesoterodine

              lapatinib will increase the level or effect of fesoterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • finerenone

              lapatinib will increase the level or effect of finerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Monitor serum potassium during initiation and dosage adjustment of either finererone or moderate CYP3A4 inhibitors. Adjust finererone dosage as needed.

            • flecainide

              flecainide and lapatinib both increase QTc interval. Use Caution/Monitor.

            • fluconazole

              fluconazole will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              fluconazole and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • fludrocortisone

              lapatinib will increase the level or effect of fludrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of fludrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • fluoxetine

              fluoxetine and lapatinib both increase QTc interval. Use Caution/Monitor.

            • fluphenazine

              fluphenazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • fluvoxamine

              fluvoxamine and lapatinib both increase QTc interval. Use Caution/Monitor.

            • formoterol

              formoterol and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • fosamprenavir

              fosamprenavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • foscarnet

              foscarnet and lapatinib both increase QTc interval. Use Caution/Monitor.

            • fosphenytoin

              fosphenytoin will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              fosphenytoin will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • fostemsavir

              fostemsavir will increase the level or effect of lapatinib by Other (see comment). Modify Therapy/Monitor Closely. Fostemsavir inhibits BCRP transporters. If possible, avoid coadministration or modify dose of BCRP substrate coadministered with fostemsavir.

              lapatinib and fostemsavir both increase QTc interval. Use Caution/Monitor. QTc prolongation reported with higher than recommended doses of fostemsavir.

            • gemtuzumab

              lapatinib and gemtuzumab both increase QTc interval. Use Caution/Monitor.

            • glecaprevir/pibrentasvir

              lapatinib will increase the level or effect of glecaprevir/pibrentasvir by decreasing metabolism. Use Caution/Monitor. Caution when coadministering glecaprevir/pibrentasvir with P-gp/BCRP inhibitors.

              glecaprevir/pibrentasvir will increase the level or effect of lapatinib by Other (see comment). Use Caution/Monitor. Glecaprevir/pibrentasvir may increase plasma concentration of P-gp and BCRP substrates.

            • goserelin

              goserelin increases levels of lapatinib by QTc interval. Use Caution/Monitor. Increases risk of torsades de pointes.

            • grapefruit

              grapefruit will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • griseofulvin

              griseofulvin will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • guanfacine

              lapatinib will increase the level or effect of guanfacine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Strong or moderate CYP3A4 inhibitors significantly increase guanfacine plasma concentrations. FDA-approved labeling for extended-release (ER) guanfacine recommends that, if coadministered, the guanfacine dosage should be decreased to half of the recommended dose. Specific recommendations for immediate-release (IR) guanfacine are not available.

            • haloperidol

              haloperidol and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • histrelin

              histrelin increases toxicity of lapatinib by QTc interval. Use Caution/Monitor. Increases risk of torsades de pointes.

            • hydrocortisone

              lapatinib will increase the level or effect of hydrocortisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of hydrocortisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • hydroxyprogesterone caproate

              lapatinib will increase the level or effect of hydroxyprogesterone caproate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • ibrutinib

              lapatinib increases levels of ibrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with moderate CYP3A4 inhibitors, reduce ibrutinib dose to 280 mg qDay (B-cell malignancies) or 420 mg qDay (graft versus host disease). After CYP3A inhibitor discontinuation, resume previous dose of ibrutinib.

            • ifosfamide

              lapatinib decreases effects of ifosfamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Use of a CYP3A4 inhibitor may decrease metabolism of ifosfamide, potentially reducing ifosfamide therapeutic effects.

            • iloperidone

              lapatinib will increase the level or effect of iloperidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              iloperidone and lapatinib both increase QTc interval. Use Caution/Monitor.

              iloperidone increases levels of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Iloperidone is a time-dependent CYP3A inhibitor and may lead to increased plasma levels of drugs predominantly eliminated by CYP3A4.

            • imatinib

              lapatinib will increase the level or effect of imatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • imipramine

              imipramine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • indacaterol, inhaled

              lapatinib increases levels of indacaterol, inhaled by Other (see comment). Use Caution/Monitor. Comment: Data suggests that systemic clearance is influenced by modulation of both P-gp and CYP3A4 activities. No dose adjustment is warranted at the 75 mcg dose.

              indacaterol, inhaled, lapatinib. QTc interval. Use Caution/Monitor. Drugs that are known to prolong the QTc interval may have an increased the risk of ventricular arrhythmias.

            • indinavir

              indinavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of indinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              indinavir will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • irinotecan

              lapatinib will increase the level or effect of irinotecan by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib will increase the level or effect of irinotecan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • irinotecan liposomal

              lapatinib will increase the level or effect of irinotecan liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of irinotecan liposomal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • isavuconazonium sulfate

              lapatinib will increase the level or effect of isavuconazonium sulfate by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • isoniazid

              isoniazid will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • istradefylline

              istradefylline will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Istradefylline 40 mg/day increased peak levels and AUC of CYP3A4 substrates in clinical trials. This effect was not observed with istradefylline 20 mg/day. Consider dose reduction of sensitive CYP3A4 substrates.

              istradefylline will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Istradefylline 40 mg/day increased peak levels and AUC of P-gp substrates in clinical trials. Consider dose reduction of sensitive P-gp substrates.

            • ivacaftor

              lapatinib will increase the level or effect of ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce ivacaftor dose if coadministered with moderate CYP3A4 inhibitors. See specific ivacaftor-containing product for precise dosage modification.

              ivacaftor increases levels of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Ivacaftor and its M1 metabolite has the potential to inhibit P-gp; may significantly increase systemic exposure to sensitive P-gp substrates with a narrow therapeutic index.

            • ivermectin

              lapatinib will increase the level or effect of ivermectin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • ivosidenib

              lapatinib will increase the level or effect of ivosidenib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration with moderate CYP3A4 inhibitors may increase ivosidenib plasma concentrations, thus increasing the risk of QTc prolongation. Monitor for increased risk of QTc interval prolongation.

            • ixabepilone

              lapatinib will increase the level or effect of ixabepilone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • ketoconazole

              ketoconazole will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              ketoconazole and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • lefamulin

              lapatinib will increase the level or effect of lefamulin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor for adverse effects if lefamulin is coadministered with moderate CYP3A inhibitors.

            • lenvatinib

              lapatinib and lenvatinib both increase QTc interval. Use Caution/Monitor. Lenvatinib prescribing information recommends monitoring ECG closely when coadministered with QT prolonging drugs.

            • leuprolide

              leuprolide increases toxicity of lapatinib by QTc interval. Use Caution/Monitor. Increases risk of torsades de pointes.

            • levamlodipine

              lapatinib will increase the level or effect of levamlodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Coadministration with moderate and strong CYP3A inhibitors results in increased systemic exposure to amlodipine and may require dose reduction. Monitor for symptoms of hypotension and edema when amlodipine is coadministered with CYP3A inhibitors to determine the need for dose adjustment.

            • levofloxacin

              lapatinib and levofloxacin both increase QTc interval. Use Caution/Monitor.

            • lofepramine

              lofepramine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • lomitapide

              lomitapide increases levels of lapatinib by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Consider reducing dose when used concomitantly with lomitapide.

            • loperamide

              lapatinib will increase the level or effect of loperamide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • lopinavir

              lapatinib will increase the level or effect of lopinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • loratadine

              lapatinib will increase the level or effect of loratadine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              loratadine will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • lorlatinib

              lorlatinib will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • lovastatin

              lapatinib will increase the level or effect of lovastatin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • lumefantrine

              lapatinib will increase the level or effect of lumefantrine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib and lumefantrine both increase QTc interval. Modify Therapy/Monitor Closely.

            • lurasidone

              lapatinib increases levels of lurasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Manufacturer recommends decreasing starting dose of lurasidone to 20 mg/day and maximum daily dose of lurasidone 80 mg when coadministered with moderate CYP3A4 inhibitors. Concurrent use may increase risk of lurasidone-related adverse reactions.

            • maprotiline

              maprotiline and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • maraviroc

              lapatinib will increase the level or effect of maraviroc by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of maraviroc by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • marijuana

              marijuana will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • mefloquine

              lapatinib will increase the level or effect of mefloquine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • mestranol

              lapatinib will increase the level or effect of mestranol by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of mestranol by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • methadone

              lapatinib will increase the level or effect of methadone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib and methadone both increase QTc interval. Use Caution/Monitor.

            • methylprednisolone

              lapatinib will increase the level or effect of methylprednisolone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of methylprednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • metronidazole

              metronidazole will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • miconazole vaginal

              miconazole vaginal will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • midazolam

              lapatinib will increase the level or effect of midazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • mifepristone

              mifepristone will increase the level or effect of lapatinib by Other (see comment). Modify Therapy/Monitor Closely. Inhibits CYP2C8/2C9; use smallest recommended doses for substrates and monitor; combination may increase QT interval. Use alternatives if available

              mifepristone will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. If coadministration necessary, decrease dose of lapatinib to 500 mg PO once daily; use lowest effective dose of mifepristone to reduce risk of QT prolongation; monitor ECGs for QT prolongation and monitor electrolytes; correct electrolyte abnormalities prior to treatment; if mifepristone discontinued, increase lapatinib to indicated dose after a period of approximately 1 week

            • mitotane

              mitotane decreases levels of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Mitotane is a strong inducer of cytochrome P-4503A4; monitor when coadministered with CYP3A4 substrates for possible dosage adjustments.

            • modafinil

              modafinil will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • moxifloxacin

              lapatinib and moxifloxacin both increase QTc interval. Modify Therapy/Monitor Closely.

            • nafcillin

              nafcillin will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • naldemedine

              lapatinib increases levels of naldemedine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor naldemedine for potential adverse effects if coadministered with strong or moderate CYP3A4 inhibitors.

              lapatinib increases levels of naldemedine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor naldemedine for potential adverse effects if coadministered with P-gp inhibitors.

            • nefazodone

              nefazodone will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • nelfinavir

              lapatinib will increase the level or effect of nelfinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              nelfinavir will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of nelfinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • nevirapine

              nevirapine will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • nicardipine

              lapatinib will increase the level or effect of nicardipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              nicardipine will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • nifedipine

              nifedipine will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              nifedipine will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • nilotinib

              lapatinib will increase the level or effect of nilotinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of nilotinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib and nilotinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • nintedanib

              lapatinib increases levels of nintedanib by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. If nintedanib adverse effects occur, management may require interruption, dose reduction, or discontinuation of therapy .

            • nisoldipine

              lapatinib will increase the level or effect of nisoldipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • nortriptyline

              nortriptyline and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • octreotide

              lapatinib and octreotide both increase QTc interval. Modify Therapy/Monitor Closely.

            • octreotide (Antidote)

              lapatinib and octreotide (Antidote) both increase QTc interval. Modify Therapy/Monitor Closely.

            • ofloxacin

              lapatinib and ofloxacin both increase QTc interval. Use Caution/Monitor.

            • oliceridine

              lapatinib will increase the level or effect of oliceridine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. If concomitant use is necessary, may require less frequent oliceridine dosing. Closely monitor for respiratory depression and sedation and titrate subsequent doses accordingly. If inhibitor is discontinued, consider increase oliceridine dosage until stable drug effects are achieved. Monitor for signs of opioid withdrawal.

            • olodaterol inhaled

              lapatinib and olodaterol inhaled both increase QTc interval. Use Caution/Monitor. Drugs that prolong the QTc interval and may potentiate the effects of beta2 agonists on the cardiovascular system; increased risk of ventricular arrhythmias

            • osilodrostat

              osilodrostat and lapatinib both increase QTc interval. Use Caution/Monitor.

            • osimertinib

              osimertinib and lapatinib both increase QTc interval. Use Caution/Monitor. Conduct periodic monitoring with ECGs and electrolytes in patients taking drugs known to prolong the QTc interval.

            • oxaliplatin

              oxaliplatin will increase the level or effect of lapatinib by Other (see comment). Use Caution/Monitor. Monitor for ECG changes if therapy is initiated in patients with drugs known to prolong QT interval.

            • oxcarbazepine

              oxcarbazepine will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • ozanimod

              ozanimod and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely. The potential additive effects on heart rate, treatment with ozanimod should generally not be initiated in patients who are concurrently treated with QT prolonging drugs with known arrhythmogenic properties.

            • paclitaxel

              lapatinib will increase the level or effect of paclitaxel by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib will increase the level or effect of paclitaxel by Other (see comment). Use Caution/Monitor. Paclitaxel levels/toxicity may increase when coadministered with CYP2C8 inhibitors

            • paclitaxel protein bound

              lapatinib will increase the level or effect of paclitaxel protein bound by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib will increase the level or effect of paclitaxel protein bound by Other (see comment). Use Caution/Monitor. Paclitaxel levels/toxicity may increase when coadministered with CYP2C8 inhibitors

            • palbociclib

              lapatinib will increase the level or effect of palbociclib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • paliperidone

              lapatinib will increase the level or effect of paliperidone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib and paliperidone both increase QTc interval. Use Caution/Monitor.

            • paromomycin

              lapatinib will increase the level or effect of paromomycin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • paroxetine

              lapatinib and paroxetine both increase QTc interval. Use Caution/Monitor.

            • pasireotide

              lapatinib and pasireotide both increase QTc interval. Modify Therapy/Monitor Closely.

            • pentobarbital

              pentobarbital will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • perphenazine

              perphenazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • phenobarbital

              phenobarbital will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              phenobarbital will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • phenytoin

              phenytoin will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              phenytoin will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. A reduction in therapeutic effectiveness of lapatinib may occur. Concomitant use of phenytoin with dasatinib, nilotinib, lapatinib, or pazopanib should be avoided.

            • ponatinib

              ponatinib increases levels of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              ponatinib increases levels of lapatinib by Other (see comment). Use Caution/Monitor.

            • posaconazole

              posaconazole will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of posaconazole by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib and posaconazole both increase QTc interval. Use Caution/Monitor.

            • prednisolone

              lapatinib will increase the level or effect of prednisolone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • prednisone

              lapatinib will increase the level or effect of prednisone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of prednisone by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • primidone

              primidone will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • prochlorperazine

              prochlorperazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • promazine

              promazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • promethazine

              promethazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • protriptyline

              protriptyline and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • quercetin

              quercetin will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • quetiapine

              lapatinib will increase the level or effect of quetiapine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              quetiapine, lapatinib. Either increases toxicity of the other by QTc interval. Use Caution/Monitor. Avoid use with drugs that prolong QT and in patients with risk factors for prolonged QT interval. Postmarketing cases show QT prolongation with overdose in patients with concomitant illness or with drugs known to cause electrolyte imbalance or prolong QT.

            • quinidine

              lapatinib will increase the level or effect of quinidine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • quinine

              lapatinib and quinine both increase QTc interval. Use Caution/Monitor.

            • quinupristin/dalfopristin

              quinupristin/dalfopristin will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • ranolazine

              ranolazine will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib and ranolazine both increase QTc interval. Use Caution/Monitor.

            • regorafenib

              regorafenib will increase the level or effect of lapatinib by Other (see comment). Modify Therapy/Monitor Closely. Regorafenib likely inhibits BCRP (ABCG2) transport. Coadministration with a BCRP substrate may increase systemic exposure to the substrate and related toxicity.

            • repaglinide

              lapatinib will increase the level or effect of repaglinide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • ribociclib

              ribociclib will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • rifampin

              rifampin will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • rifapentine

              rifapentine will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • rifaximin

              lapatinib increases levels of rifaximin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • rilpivirine

              rilpivirine increases toxicity of lapatinib by QTc interval. Use Caution/Monitor. Rilpivirine should be used with caution when co-administered with a drug with a known risk of Torsades de Pointes.

            • rimegepant

              lapatinib will increase the level or effect of rimegepant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Avoid repeating rimegepant dose within 48 hr if coadministered with a moderate CYP3A4 inhibitor.

            • risperidone

              lapatinib and risperidone both increase QTc interval. Use Caution/Monitor.

            • ritonavir

              lapatinib will increase the level or effect of ritonavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of ritonavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • rivaroxaban

              lapatinib increases levels of rivaroxaban by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Patients with renal impairment receiving rivaroxaban with drugs that are combined P-gp and weak or moderate CYP3A4 inhibitors may have significant increases in exposure compared with patients with normal renal function and no inhibitor use, since both pathways of rivaroxaban elimination are affected. Since these increases may increase bleeding risk, use rivaroxaban in this situation only if the potential benefit justifies the potential risk.

            • romidepsin

              lapatinib will increase the level or effect of romidepsin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of romidepsin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              lapatinib and romidepsin both increase QTc interval. Use Caution/Monitor.

            • rucaparib

              rucaparib will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Adjust dosage of CYP3A4 substrates, if clinically indicated.

            • rufinamide

              rufinamide will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • ruxolitinib

              lapatinib will increase the level or effect of ruxolitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • safinamide

              safinamide will increase the level or effect of lapatinib by Other (see comment). Use Caution/Monitor. Safinamide and its major metabolite may inhibit intestinal BCRP. Monitor BCRP substrates for increased pharmacologic or adverse effects.

            • saquinavir

              lapatinib will increase the level or effect of saquinavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of saquinavir by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • sarecycline

              sarecycline will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Monitor for toxicities of P-gp substrates that may require dosage reduction when coadministered with P-gp inhibitors.

            • secobarbital

              secobarbital will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • selexipag

              lapatinib will increase the level or effect of selexipag by decreasing metabolism. Modify Therapy/Monitor Closely. Reduce selexipag dose to once daily if coadministered with moderate CYP2C8 inhibitors.

              lapatinib will increase the level or effect of selexipag by Other (see comment). Use Caution/Monitor. Selexipag is a ABCG2 (BCRP) substrate. Monitor selexipag for increased pharmacologic or adverse effects when coadministered with ABCG2 (BCRP) inhibitors.

            • selpercatinib

              selpercatinib increases toxicity of lapatinib by QTc interval. Use Caution/Monitor.

            • sildenafil

              lapatinib will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • silodosin

              lapatinib will increase the level or effect of silodosin by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • siponimod

              siponimod and lapatinib both increase immunosuppressive effects; risk of infection. Use Caution/Monitor. Caution if coadministered because of additive immunosuppressive effects during such therapy and in the weeks following administration. When switching from drugs with prolonged immune effects, consider the half-life and mode of action of these drugs to avoid unintended additive immunosuppressive effects.

            • sirolimus

              lapatinib will increase the level or effect of sirolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • sofosbuvir/velpatasvir

              sofosbuvir/velpatasvir will increase the level or effect of lapatinib by Other (see comment). Use Caution/Monitor. Velpatasvir is an inhibitor of the drug transporter BCRP. Coadministration may increase systemic exposure of drugs that are BCRP substrates.

            • solifenacin

              lapatinib will increase the level or effect of solifenacin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • sonidegib

              lapatinib will increase the level or effect of sonidegib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Avoid coadministration of sonidegib with moderate CYP3A4 inhibitors. If a moderate CYP3A inhibitor must be used, administer the moderate CYP3A inhibitor for <14 days and monitor closely for adverse reactions, particularly musculoskeletal adverse reactions.

            • sorafenib

              sorafenib and lapatinib both increase QTc interval. Use Caution/Monitor.

            • St John's Wort

              St John's Wort will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • stiripentol

              stiripentol, lapatinib. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Stiripentol is a CYP3A4 inhibitor and inducer. Monitor CYP3A4 substrates coadministered with stiripentol for increased or decreased effects. CYP3A4 substrates may require dosage adjustment.

              stiripentol will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Modify Therapy/Monitor Closely. Consider reducing the dose of P-glycoprotein (P-gp) substrates, if adverse reactions are experienced when administered concomitantly with stiripentol.

              stiripentol will increase the level or effect of lapatinib by Other (see comment). Modify Therapy/Monitor Closely. Stiripentol is a BCRP transport inhibitor. Consider dosage reduction for BCRP substrates if adverse effects are experienced when coadministered.

            • sufentanil SL

              lapatinib will increase the level or effect of sufentanil SL by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of sufentanil SL with any CYP3A4 inhibitor may increase sufentanil plasma concentration, and, thereby increase or prolonged adverse effects, including potentially fatal respiratory depression.

            • sulfamethoxazole

              sulfamethoxazole and lapatinib both increase QTc interval. Use Caution/Monitor.

            • sunitinib

              lapatinib will increase the level or effect of sunitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • suvorexant

              lapatinib will increase the level or effect of suvorexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Decrease suvorexant starting dose to 5 mg HS if coadministered with moderate CYP3A4 inhibitors

            • tacrolimus

              lapatinib will increase the level or effect of tacrolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib will increase the level or effect of tacrolimus by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • tadalafil

              lapatinib will increase the level or effect of tadalafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • tafamidis

              tafamidis will increase the level or effect of lapatinib by Other (see comment). Use Caution/Monitor. Tafamidis inhibits breast cancer resistant protein (BCRP) in vitro and may increase exposure of BCRP substrates following tafamidis or tafamidis meglumine administration. Dosage adjustment of these BCRP substrates may be necessary.

            • tafamidis meglumine

              tafamidis meglumine will increase the level or effect of lapatinib by Other (see comment). Use Caution/Monitor. Tafamidis inhibits breast cancer resistant protein (BCRP) in vitro and may increase exposure of BCRP substrates following tafamidis or tafamidis meglumine administration. Dosage adjustment of these BCRP substrates may be necessary.

            • tamsulosin

              lapatinib increases levels of tamsulosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Dose reduction may be needed for coadministered drugs that are predominantly metabolized by CYP3A.

            • tazemetostat

              tazemetostat will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • tecovirimat

              tecovirimat will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Tecovirimat is a weak CYP3A4 inducer. Monitor sensitive CYP3A4 substrates for effectiveness if coadministered.

            • telavancin

              lapatinib and telavancin both increase QTc interval. Use Caution/Monitor.

            • temsirolimus

              lapatinib will increase the level or effect of temsirolimus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • teniposide

              lapatinib will increase the level or effect of teniposide by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • teriflunomide

              teriflunomide increases levels of lapatinib by Other (see comment). Use Caution/Monitor. Comment: Teriflunomide inhibits CYP2C8; caution when coadministered with CYP2C8 substrates.

            • tezacaftor

              lapatinib will increase the level or effect of tezacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Adjust tezacaftor dosage regimen if coadministered with a moderate CYP3A inhibitor.

            • theophylline

              lapatinib will increase the level or effect of theophylline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • thioridazine

              thioridazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • tinidazole

              lapatinib will increase the level or effect of tinidazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • tipranavir

              lapatinib will increase the level or effect of tipranavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • tofacitinib

              lapatinib increases levels of tofacitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. No specific dose adjustment recommended when tofacitinib coadministered with moderate CYP3A4 inhibitors; decrease tofacitinib dose if coadministered with both moderate CYP3A4 and potent CYP2C19 inhibitors.

            • tolterodine

              lapatinib will increase the level or effect of tolterodine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • tolvaptan

              lapatinib will increase the level or effect of tolvaptan by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • topiramate

              topiramate will decrease the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • trabectedin

              lapatinib will increase the level or effect of trabectedin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • trazodone

              lapatinib will increase the level or effect of trazodone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              trazodone will decrease the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

              trazodone and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • triamcinolone acetonide injectable suspension

              lapatinib will increase the level or effect of triamcinolone acetonide injectable suspension by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • triazolam

              lapatinib will increase the level or effect of triazolam by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • triclabendazole

              triclabendazole and lapatinib both increase QTc interval. Use Caution/Monitor.

            • trifluoperazine

              trifluoperazine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • trimipramine

              trimipramine and lapatinib both increase QTc interval. Modify Therapy/Monitor Closely.

            • triptorelin

              triptorelin increases toxicity of lapatinib by QTc interval. Use Caution/Monitor. Increases risk of torsades de pointes.

            • tropisetron

              lapatinib and tropisetron both increase QTc interval. Use Caution/Monitor.

            • tucatinib

              tucatinib will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor. Consider reducing the dosage of P-gp substrates, where minimal concentration changes may lead to serious or life-threatening toxicities.

            • vardenafil

              lapatinib will increase the level or effect of vardenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • venlafaxine

              lapatinib and venlafaxine both increase QTc interval. Use Caution/Monitor.

            • verapamil

              lapatinib will increase the level or effect of verapamil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              verapamil will increase the level or effect of lapatinib by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • vinblastine

              lapatinib will increase the level or effect of vinblastine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • vincristine

              lapatinib will increase the level or effect of vincristine by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • vincristine liposomal

              lapatinib will increase the level or effect of vincristine liposomal by P-glycoprotein (MDR1) efflux transporter. Use Caution/Monitor.

            • voclosporin

              lapatinib will increase the level or effect of voclosporin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce voclosporin daily dosage to 15.8 mg PO in AM and 7.9 mg PO in PM.

              voclosporin, lapatinib. Either increases effects of the other by QTc interval. Use Caution/Monitor.

            • voriconazole

              voriconazole will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              lapatinib and voriconazole both increase QTc interval. Use Caution/Monitor.

            • zafirlukast

              zafirlukast will increase the level or effect of lapatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

            • zanubrutinib

              lapatinib will increase the level or effect of zanubrutinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Reduce zanubrutinib dose when coadministered with a moderate CYP3A4 inhibitor. Interrupt dose as recommended for adverse reactions. After discontinuing the CYP3A4 inhibitor, resume previous dose of zanubrutinib. See zanubrutinib Dosage Modifications for precise recommendation.

            • ziprasidone

              lapatinib and ziprasidone both increase QTc interval. Modify Therapy/Monitor Closely.

            Minor (56)

            • alfentanil

              lapatinib will increase the level or effect of alfentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • alfuzosin

              lapatinib will increase the level or effect of alfuzosin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • aliskiren

              lapatinib will increase the level or effect of aliskiren by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

            • alosetron

              lapatinib will increase the level or effect of alosetron by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • alvimopan

              lapatinib will increase the level or effect of alvimopan by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

            • amitriptyline

              lapatinib will increase the level or effect of amitriptyline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • armodafinil

              lapatinib will increase the level or effect of armodafinil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • atazanavir

              lapatinib will increase the level or effect of atazanavir by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • azithromycin

              azithromycin and lapatinib both increase QTc interval. Minor/Significance Unknown.

            • bosentan

              lapatinib will increase the level or effect of bosentan by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • cevimeline

              lapatinib will increase the level or effect of cevimeline by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • chloroquine

              chloroquine increases toxicity of lapatinib by QTc interval. Minor/Significance Unknown.

            • clarithromycin

              lapatinib will increase the level or effect of clarithromycin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • crizotinib

              crizotinib and lapatinib both increase QTc interval. Minor/Significance Unknown.

            • dapsone

              lapatinib will increase the level or effect of dapsone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • desipramine

              lapatinib will increase the level or effect of desipramine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • disopyramide

              lapatinib will increase the level or effect of disopyramide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • docetaxel

              lapatinib will increase the level or effect of docetaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • donepezil

              lapatinib will increase the level or effect of donepezil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • dutasteride

              lapatinib will increase the level or effect of dutasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • efavirenz

              lapatinib will increase the level or effect of efavirenz by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • eplerenone

              lapatinib will increase the level or effect of eplerenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • estradiol vaginal

              lapatinib will increase the level or effect of estradiol vaginal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • eucalyptus

              lapatinib will increase the level or effect of eucalyptus by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • fexofenadine

              lapatinib will increase the level or effect of fexofenadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

            • finasteride

              lapatinib will increase the level or effect of finasteride by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • galantamine

              lapatinib will increase the level or effect of galantamine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • imatinib

              lapatinib will increase the level or effect of imatinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • isradipine

              lapatinib will increase the level or effect of isradipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • itraconazole

              lapatinib will increase the level or effect of itraconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • ketoconazole

              lapatinib will increase the level or effect of ketoconazole by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • loratadine

              lapatinib will increase the level or effect of loratadine by P-glycoprotein (MDR1) efflux transporter. Minor/Significance Unknown.

            • montelukast

              lapatinib will increase the level or effect of montelukast by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • nifedipine

              lapatinib will increase the level or effect of nifedipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • nimodipine

              lapatinib will increase the level or effect of nimodipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • nitrendipine

              lapatinib will increase the level or effect of nitrendipine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • oxybutynin

              lapatinib will increase the level or effect of oxybutynin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • paclitaxel

              lapatinib will increase the level or effect of paclitaxel by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • paclitaxel protein bound

              lapatinib will increase the level or effect of paclitaxel protein bound by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • parecoxib

              lapatinib will increase the level or effect of parecoxib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • pazopanib

              lapatinib and pazopanib both increase QTc interval. Minor/Significance Unknown.

            • pimozide

              lapatinib will increase the level or effect of pimozide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • propafenone

              lapatinib will increase the level or effect of propafenone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • quinine

              lapatinib will increase the level or effect of quinine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • ramelteon

              lapatinib will increase the level or effect of ramelteon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • saxagliptin

              lapatinib will increase the level or effect of saxagliptin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • sufentanil

              lapatinib will increase the level or effect of sufentanil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • tamoxifen

              lapatinib, tamoxifen. affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown. CYP3A4 inhibition decreases metabolism of tamoxifen to N-desmethyl tamoxifen (active metabolite with similar biologic activity).

            • vinblastine

              lapatinib will increase the level or effect of vinblastine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • vincristine

              lapatinib will increase the level or effect of vincristine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • vincristine liposomal

              lapatinib will increase the level or effect of vincristine liposomal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • vinorelbine

              lapatinib will increase the level or effect of vinorelbine by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • zaleplon

              lapatinib will increase the level or effect of zaleplon by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • ziprasidone

              lapatinib will increase the level or effect of ziprasidone by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • zolpidem

              lapatinib will increase the level or effect of zolpidem by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

            • zonisamide

              lapatinib will increase the level or effect of zonisamide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Minor/Significance Unknown.

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            Adverse Effects

            >10% (lapatinib+capecitabine vs capecitabine)

            Diarrhea (65% vs 40%)

            Anemia (56% vs 53%)

            Hand-foot synd (53% vs 51%)

            Increased LFTs (37-49% vs 30-43%)

            Nausea (44% vs 43%)

            Rash (28% vs 14%)

            Vomiting (26% vs 21%)

            Pain (23% vs 13%)

            Neutropenia (22% vs 31%)

            Thrombocytopenia (18% vs 17%)

            Mucositis (15% vs 12%)

            Stomatitis (14% vs 11%)

            Dyspnea (12% vs 8%)

            Dyspepsia (11% vs 3%)

            Insomnia (10% vs 6%)

            1-10%

            Insomnia

            LVEF decreased

            Postmarketing Reports

            Hypersensitivity reactions including anaphylaxis

            Nail disorders including paronychia

            Stevens Johnson Syndrome (SJS)

            Toxic epidural necrolysis (TEN)

            Ventricular arrhythmias/Torsades de Points (TdP)

            Electrocardiogram QT prolongation

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            Warnings

            Black Box Warnings

            AST or ALT >3 times the upper limit of normal (ULN) or bilirubin >1.5 times ULN reported and may be a severe toxicity and/or fatal; onset may occur within days to several months after initiating therapy

            Contraindications

            Hypersensitivity to any component

            Cautions

            Severe hepatic impairment

            Concomitant QT-prolonging drugs; conditions that increase QT-prolongation risk

            Risk of severe diarrhea

            Substrate of & inhibits P-glycoprotein (ABCB1); caution if using concomitant ABCB1 substrates/inhibitors

            Severe cutaneous reactions reported; discontinue therapy if life-threatening reactions are suspected

            Decreases in left ventricular ejection fraction (LVEF) reported; confirm normal LVEF before initiating therapy and continue evaluations during treatment

            Hepatotoxicity reported with therapy; monitor liver function tests before initiation of treatment, every 4 to 6 weeks during treatment, and as clinically indicated; discontinue and do not restart therapy if patients experience severe changes in liver function tests

            Consider dose reduction in patients with severe hepatic impairment

            Linked to risk of interstitial lung disease & pneumonitis; monitor pulmonary symptoms

            Increased risk of cardiac events with prior exposure to trastuzumab and anthracyclines.

            Diarrhea

            • Diarrhea reported and may be severe; deaths reported
            • Generally occurs early during treatment with almost 50% first experiencing it within 6 days, and usually lasts 4-5 days
            • Usually low-grade, with severe diarrhea of NCI CTCAE Grades 3 and 4 occurring in <10% and <1% of patients, respectively
            • Early identification and intervention is critical for the optimal management of diarrhea
            • Instruct patients to report any change in bowel patterns immediately
            • Prompt treatment of diarrhea with anti-diarrheal agents (eg, loperamide) after the first unformed stool is recommended
            • Severe cases may oral or IV electrolytes and fluids, antibiotics (eg, fluoroquinolones) if diarrhea persists beyond 24 hr, fever is present, or Grade 3-4 neutropenia
            • If severe, interrupt or discontinue lapatinib (see Dosage Modifications)
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            Pregnancy & Lactation

            Pregnancy Category: D

            Lactation: Do not nurse

            Pregnancy Categories

            A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.

            B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.

            C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.

            D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.

            X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.

            NA: Information not available.

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            Pharmacology

            Mechanism of Action

            Kinase inhibitor, blocks EGF-receptor HER2 kinase; tyrosing kinase inhibition possibly blocks angiogenesis and cellular proliferation

            Absorption

            Systemic absorption increased by food (AUC increase ~3-4 fold)

            Peak Plasma Time: 4 hr

            Peak Plasma Concentration: 2.43 mcg/mL (1.25 g dose)

            Distribution

            Protein Bound: 99%

            Metabolism

            Primarily metabolized by CYP3A4 and CYP3A5

            Enzymes inhibited: CYP3A4 and CYP2C8

            Eliminiation

            Half-Life: 24 hr

            Excretion: Feces

            Pharmacogenomics

            Mediates antibody-dependent cellular cytotoxicity against cells that overproduce HER2, and lacks effect on cells not overexpressing HER2

            HER2 testing should be performed

            Patients with breast cancers with intensive staining (3+) should definitely receive anti-HER2 therapy; the clinical relevance of 2+ staining is uncertain

            Genetic testing laboratories

            • The following companies currently offer IHC and/or FISH testing for HER2 overexpression
            • Dako (http://www.dakousa.com/)
            • Ventana Medical Systems (http://www.ventanamed.com/)
            • Vysis/Abbott Molecular (http://www.abbottmolecular.com/)
            • Invitrogen (http://www.invitrogen.com/)
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            Administration

            Oral Administration

            Take at least 1 hr before or 1 hr after meals

            Modify dose for diarrhea, cardiac toxicity, other toxicities, severe hepatic impairment, and CYP3A4 interactions (see Dosage Modifications)

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            Images

            BRAND FORM. UNIT PRICE PILL IMAGE
            Tykerb oral
            -
            250 mg tablet

            Copyright © 2010 First DataBank, Inc.

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            Patient Handout

            Patient Education
            lapatinib oral

            LAPATINIB - ORAL

            (la-PA-ti-nib)

            COMMON BRAND NAME(S): Tykerb

            WARNING: Rarely, people taking lapatinib have developed serious (possibly fatal) liver problems. Your doctor will perform liver function tests before and during treatment to monitor for this side effect. Keep all medical/lab appointments. Tell your doctor right away if you develop symptoms of liver disease such as persistent nausea, stomach/abdominal pain, dark urine, or yellowing eyes/skin. Do not restart this medication if you have previously stopped taking it due to liver problems.

            USES: Lapatinib is used to treat a certain type of breast cancer (HER2-positive). It works by slowing or stopping the growth of cancer cells.

            HOW TO USE: Read the Patient Information Leaflet provided by your pharmacist before you start using lapatinib and each time you get a refill. If you have any questions, consult your doctor or pharmacist.Take this medication by mouth 1 hour before or 1 hour after a meal, usually once daily or as directed by your doctor. It is important that you do not take this medication more than once daily.The dosage is based on your medical condition, response to treatment, and certain other drugs you may be taking.Do not increase your dose or take this medication more often than prescribed. Your condition will not improve any faster, and the risk of serious side effects may be increased.Avoid eating grapefruit or drinking grapefruit juice while being treated with this medication unless your doctor instructs you otherwise. Grapefruit can increase the amount of certain medications in your bloodstream. Consult your doctor or pharmacist for more details.Since this drug can be absorbed through the skin and lungs, women who are pregnant or who may become pregnant should not handle this medication or breathe the dust from the tablets.Follow your doctor's instructions on how to correctly take capecitabine or letrozole with lapatinib.

            SIDE EFFECTS: See also Warning section.Nausea, vomiting, upset stomach, mouth sores, mild rash, dry skin, and trouble sleeping may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.Diarrhea is a common side effect and may become severe. Tell your doctor right away if diarrhea occurs or if you have signs of dehydration such as dizziness or decreased urination. Your doctor should prescribe additional medication to help control your symptoms. If your diarrhea becomes severe, your doctor may need to stop or delay your lapatinib treatment.Treatment with this drug may sometimes cause your hands/feet to develop a skin reaction called hand-foot syndrome (palmar-plantar erythrodysesthesia). Tell your doctor right away if you experience swelling, pain, redness, peeling, blisters, or tingling/burning of the hands/feet. The symptoms can be made worse by heat/pressure on your hands/feet. Avoid prolonged sun exposure, tanning booths, and sunlamps, as well as unnecessary exposure to heat (e.g., hot dishwater, long hot baths). Use a sunscreen and wear protective clothing when outdoors. Avoid pressure on elbows, knees, and soles of feet (e.g., leaning on elbows, kneeling, taking long walks). Wear loose clothing and comfortable shoes. Depending on how severe your hand-foot syndrome is, your doctor may give you an additional medication to reduce the symptoms, or stop or delay your lapatinib treatment.Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.Tell your doctor right away if you have any serious side effects, including: unusual tiredness, shortness of breath, swelling ankles/feet.Get medical help right away if you have any very serious side effects, including: fast/pounding/irregular heartbeat, dizziness, fainting.A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

            PRECAUTIONS: Before taking lapatinib, tell your doctor or pharmacist if you are allergic to it; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.Before using this medication, tell your doctor or pharmacist your medical history, especially of: heart disease (e.g., irregular heartbeat), liver disease.Lapatinib may cause a condition that affects the heart rhythm (QT prolongation). QT prolongation can rarely cause serious (rarely fatal) fast/irregular heartbeat and other symptoms (such as severe dizziness, fainting) that need medical attention right away.The risk of QT prolongation may be increased if you have certain medical conditions or are taking other drugs that may cause QT prolongation. Before using lapatinib, tell your doctor or pharmacist of all the drugs you take and if you have any of the following conditions: certain heart problems (heart failure, slow heartbeat, QT prolongation in the EKG), family history of certain heart problems (QT prolongation in the EKG, sudden cardiac death).Low levels of potassium or magnesium in the blood may also increase your risk of QT prolongation. This risk may increase if you use certain drugs (such as diuretics/"water pills") or if you have conditions such as severe sweating, diarrhea, or vomiting. Talk to your doctor about using lapatinib safely.Older adults may be more sensitive to the side effects of this drug, especially QT prolongation (see above).Tell your doctor if you are pregnant or plan to become pregnant. You should not become pregnant while using lapatinib. Lapatinib may harm an unborn baby. Women and men using this medication should ask about reliable forms of birth control during treatment and for 1 week after stopping treatment. If you or your partner become pregnant, talk to your doctor right away about the risks and benefits of this medication.It is unknown if this drug passes into breast milk. Because of the possible risk to the infant, breast-feeding is not recommended while using this medication and for 1 week after stopping this medication. Consult your doctor before breast-feeding.

            DRUG INTERACTIONS: Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.This medication can slow down the removal of other medications from your body, which may affect how they work. Examples of affected drugs include certain "statin" cholesterol medications (simvastatin, lovastatin, atorvastatin), digoxin, irinotecan, tacrolimus, trazodone, among others.Other medications can affect the removal of lapatinib from your body, which may affect how lapatinib works. Examples include dexamethasone, cimetidine, St. John's wort, azole antifungals (such as itraconazole, ketoconazole), macrolide antibiotics (such as erythromycin, clarithromycin), HIV protease inhibitors (such as ritonavir, saquinavir), rifamycins (such as rifabutin), certain anti-seizure medicines (such as phenytoin), among others.Many drugs besides lapatinib may affect the heart rhythm (QT prolongation), including dofetilide, pimozide, procainamide, amiodarone, quinidine, sotalol, macrolide antibiotics (such as erythromycin), among others. Before using lapatinib, report all medications you are currently using to your doctor or pharmacist.

            OVERDOSE: If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: severe diarrhea/vomiting.

            NOTES: Do not share this medication with others.Laboratory and/or medical tests (e.g., EKG, electrolyte levels, heart/liver function) should be performed periodically to monitor your progress or check for side effects. Consult your doctor for more details.

            MISSED DOSE: It is important to take each dose of this medication as scheduled. If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

            STORAGE: Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

            Information last revised August 2021. Copyright(c) 2021 First Databank, Inc.

            IMPORTANT: HOW TO USE THIS INFORMATION: This is a summary and does NOT have all possible information about this product. This information does not assure that this product is safe, effective, or appropriate for you. This information is not individual medical advice and does not substitute for the advice of your health care professional. Always ask your health care professional for complete information about this product and your specific health needs.

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            Formulary

            FormularyPatient Discounts

            Adding plans allows you to compare formulary status to other drugs in the same class.

            To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.

            Adding plans allows you to:

            • View the formulary and any restrictions for each plan.
            • Manage and view all your plans together – even plans in different states.
            • Compare formulary status to other drugs in the same class.
            • Access your plan list on any device – mobile or desktop.

            The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information.

            Tier Description
            1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs.
            2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs.
            3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs.
            4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products.
            NC NOT COVERED – Drugs that are not covered by the plan.
            Code Definition
            PA Prior Authorization
            Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription.
            QL Quantity Limits
            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
            ST Step Therapy
            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the prescription.
            OR Other Restrictions
            Drugs that have restrictions other than prior authorization, quantity limits, and step therapy associated with each prescription.
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            Medscape prescription drug monographs are based on FDA-approved labeling information, unless otherwise noted, combined with additional data derived from primary medical literature.