abacavir (Rx)

Brand and Other Names:Ziagen
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Dosing & Uses

AdultPediatric

Dosage Forms & Strengths

oral solution

  • 20mg/mL

tablet

  • 300mg

HIV Infection

Indicated for treatment of HIV infection in combination with other antiretroviral agents

300 mg PO q12hr, OR

600 mg PO qDay

Dosage Modifications

Renal impairment: No dosage adjustment required

Hepatic impairment

  • Mild (Child-Pugh A); adults and adolescents aged ≥16 years: Reduce dose to 200 mg q12hr (use oral solution)
  • Moderate-to severe (Child-Pugh B or C): Contraindicated

Dosage Forms & Strengths

oral solution

  • 20mg/mL

tablet

  • 300mg

HIV Infection

Indicated for treatment of HIV infection in combination with other antiretroviral agents

Neonates/infants <3 months: Safety and efficacy not established

Oral solution

  • ≥3 months: 8 mg/kg PO q12hr or 16 mg/kg/day; not to exceed 600 mg/day 

Tablet

  • Available as a scored tablet; if unable to reliably swallow tablets, prescribe the oral solution
  • ≥14 kg to <20 kg: 150 mg PO q12hr, OR 300 mg qDay
  • ≥20 to <25 kg: 150 mg AM and 300 mg PM, OR 450 mg qDay
  • ≥25 kg: 300 mg PO q12hr, OR 600 mg PO qDay in combination with other antiretroviral agents

Dosage Modifications

Renal impairment: No dosage adjustment required

Hepatic impairment

  • Mild (Child-Pugh A); adults and adolescents aged ≥16 years: Reduce dose to 200 mg q12hr (use oral solution)
  • Moderate-to severe (Child-Pugh B or C): Contraindicated

Dosing Considerations

Once daily dosing: NIH pediatric HIV guidelines (March, 2016) recommend initiation of therapy with once-daily dosing in children who can be treated with the tablet formulation

Twice daily dosing: Use twice daily dosing in infants and young children initiating therapy with liquid formulations; consider switching to once-daily dosing after 6 months when viral load is undetectable and CD4 cell count is stable

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Interactions

Interaction Checker

and abacavir

No Results

     activity indicator 
    No Interactions Found
    Interactions Found

    Contraindicated

      Serious - Use Alternative

        Significant - Monitor Closely

          Minor

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            Adverse Effects

            >10%

            Nausea (17-19%)

            Headache (9-13%)

            Malaise/Fatigue (12%)

            Nausea & vomiting (10%)

            1-10%

            Hypersensitivity reaction (2-8%)

            Diarrhea (5-7%)

            Musculoskelatal pain (5-7%)

            Hypertriglyceridemia (6%)

            Hepatic: AST Increased (6%)

            Depression (4-6%)

            Fever/chills (3-6%)

            Viral respiratory infections (5%)

            Ear/nose /throat infections (4-5%)

            Rash (4-5%)

            Anxiety (3-5%)

            Thrombocytopenia (1%)

            <1%

            Anaphylactoid reaction

            Pulmonary hypertension

            Erythema multiforme

            Redistribution/accumulation of body fat

            Stevens-Johnson syndrome

            Toxic epidermal necrolysis

            Pancreatitis

            GGT increased

            Hepatic steatosis

            Heptaomegaly

            Hepatotoxicity

            Lactic acidosis

            MI

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            Warnings

            Black Box Warnings

            Hypersensitivity reactions

            • Severe and sometimes fatal hypersensitivity reaction, with multiple organ involvement, have occurred
            • Patients who carry the HLA-B*5701 allele are at a higher risk of a hypersensitivity reaction; although, hypersensitivity reactions have occurred in patients who do not carry the HLA-B*5701 allele
            • Contraindicated with history of prior hypersensitivity reaction to abacavir and in patients who are HLA-B*5701-positive
            • All patients should be screened for the HLA-B*5701 allele before initiating or reinitiating abacavir, unless patients have a previously documented HLA-B*5701 allele assessment
            • If hypersensitivity is suspected, discontinue abacavir immediately, regardless of HLA-B*5701 status and even when other diagnoses are possible

            Contraindications

            Prior hypersensitivity reaction to abacavir

            Presence of HLA-B*5701 allele

            Moderate or severe hepatic impairment

            Cautions

            Increased risk of serious or fatal hypersensitivity reactions; patients with human leukocyte antigen allele, HLA-B*5701 are at a higher risk; do not restart abacavir following hypersensitive reaction; may cause hypotension, multiorgan failure, and/or death (see Contraindications and Black Box Warnings)

            Lactic acidosis and severe hepatomegaly with steatosis, including fatal cases, reported with nucleoside analogues, including abacavir; a majority of these cases have been in women; female gender and obesity may be risk factors; suspend dosing in those who develop clinical or laboratory findings suggestive of lactic acidosis or pronounced hepatotoxicity

            Immune reconstitution syndrome reported with combination ART; during the initial treatment phase, patients whose immune systems respond may develop an inflammatory response to indolent or residual opportunistic infections (eg, Mycobacterium avium infection, cytomegalovirus, Pneumocystis jirovecii pneumonia [PCP], or tuberculosis); autoimmune disorders (eg, Grave disease, polymyositis, and Guillain-Barré syndrome) have also been reported

            Use has been associated with increased risk of myocardial infarction in observational studies, but not in a meta-analysis of 26 randomized trials; caution with risks for coronary heart disease and minimizing modifiable risk factors, including smoking, hypertension, and hyperlipidemia, prior to use

            Drug interaction overview

            • Methadone
              • In a trial of 11 HIV-1-infected subjects receiving methadone-maintenance therapy with abacavir 600 mg BID (twice the currently recommended dose), PO methadone clearance increased
              • This alteration will not result in a methadone dose modification in the majority of patients; however, an increased methadone dose may be required in a small number of patients
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            Pregnancy & Lactation

            Pregnancy

            Healthcare Providers are encouraged to register patients by calling the Antiretroviral Pregnancy Registry (APR) at 1-800-258-4263

            Available data from the APR show no difference in the overall risk of birth defects for abacavir compared with the background rate for birth defects of 2.7% in the Metropolitan Atlanta Congenital Defects Program (MACDP) reference population

            In animal reproduction studies, oral administration of abacavir to pregnant rats during organogenesis resulted in fetal malformations and other embryonic and fetal toxicities at exposures 35 times the human exposure (AUC) at the recommended clinical daily dose; however, no adverse developmental effects were observed following oral administration of abacavir to pregnant rabbits during organogenesis, at exposures approximately 9 times the human exposure (AUC) at the recommended clinical dose

            Lactation

            Abacavir is present in human milk; there is no information on effects of abacavir on breastfed infant or effects of drug on milk production; because of potential for (1) HIV-1 transmission (in HIV-negative infants), (2) developing viral resistance (in HIV- positive infants), and (3) serious adverse reactions in breastfed infant, instruct mothers not to breastfeed if they are receiving abacavir

            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

            Guanosine analog that inhibits HIV-1 reverse transcriptase by competing with dGTP as substrate, which in turn inhibits viral replication

            Pharmacokinetics

            Absorption: Rapid & extensive absorption

            Vd: 0.86 L/kg

            Protein Bound: 50%

            Metabolism: hepatic via alcohol dehydrogenase & glucuronyl transferase to inactive carboxylate & glucuronide metabolites

            Bioavailability: 83%

            Half-life elimination: 1.5 hr

            Peak Plasma Time: 0.7-1.7 hr

            Excretion: Urine (80%); feces (16%)

            Absorption

            Rapid and extensive PO absorption

            Bioavailability: 83%

            Peak plasma concentration: 3 mcg/mL (300 mg); 4.26 mcg/mL (600 mg)

            AUC: 6.02 mcg·h/mL (300 mg); 11.95 mcg·h/mL (600 mg)

            Distribution

            Vd: 0.86 L/kg

            Protein Bound: 50%

            Metabolism

            Hepatic via alcohol dehydrogenase and glucuronyl transferase to inactive carboxylate and glucuronide metabolites

            Elimination

            Half-life: 1.5 hr

            Peak Plasma Time: 0.7-1.7 hr

            Excretion: Urine (80%); feces (16%)

            Pharmacogenomics

            Patients who carry the HLA-B*5701 allele are at high risk for experiencing a hypersensitivity reaction

            Prior to initiating therapy with abacavir, screening for the HLA-B*5701 allele is recommended

            For HLA-B*5701-positive patients, treatment with an abacavir-containing regimen is not recommended

            Genetic testing laboratories

            • The following companies provide genetic testing for HLA variants
            • Kashi Clinical Laboratories (www.kashilab.com)
            • LabCorp (http://www.labcorp.com/)
            • Specialty Laboratories (http://www.specialtylabs.com)
            • Quest (http://www.questdialgnotics.com)
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            Administration

            Oral Administration

            May take with or without food

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            Formulary

            FormularyPatient Discounts

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            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.
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            Drugs that have quantity limits associated with each prescription. This restriction typically limits the quantity of the drug that will be covered.
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            Drugs that have step therapy associated with each prescription. This restriction typically requires that certain criteria be met prior to approval for the 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.