chlorzoxazone (Rx)

Brand and Other Names:Parafon Forte DSC, Lorzone
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Dosing & Uses

AdultPediatricGeriatric

Dosage Forms & Strengths

tablet

  • 375mg
  • 500mg
  • 750mg

Musculoskeletal Pain

Indicated as an adjunct to rest, physical therapy, and other measures for the relief of discomfort associated with acute, painful musculoskeletal conditions

250-750 mg PO q6-8hr

Dosage Forms & Strengths

tablet

  • 375mg
  • 500mg
  • 750mg

Muscle Spasms

20 mg/kg/day PO divided q6-8hr or 600 mg/m²/day PO divided q6-8hr

Musculoskeletal conditions

250 mg PO q6-12hr; increase PRN to 750 mg PO q6-8hr

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Interactions

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              Serious - Use Alternative (7)

              • benzhydrocodone/acetaminophen

                benzhydrocodone/acetaminophen, chlorzoxazone. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

              • calcium/magnesium/potassium/sodium oxybates

                chlorzoxazone, calcium/magnesium/potassium/sodium oxybates. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

              • hydrocodone

                hydrocodone, chlorzoxazone. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

              • lonafarnib

                chlorzoxazone will increase the level or effect of lonafarnib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Avoid or Use Alternate Drug. If coadministration of lonafarnib (a sensitive CYP3A substrate) with weak CYP3A inhibitors is unavoidable, reduce to, or continue lonafarnib at starting dose. Closely monitor for arrhythmias and events (eg, syncope, heart palpitations) since lonafarnib effect on QT interval is unknown.

              • metoclopramide intranasal

                chlorzoxazone, metoclopramide intranasal. Either increases effects of the other by Other (see comment). Avoid or Use Alternate Drug. Comment: Avoid use of metoclopramide intranasal or interacting drug, depending on importance of drug to patient.

              • sodium oxybate

                chlorzoxazone, sodium oxybate. Either increases effects of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

              • sufentanil SL

                sufentanil SL, chlorzoxazone. Either increases toxicity of the other by pharmacodynamic synergism. Avoid or Use Alternate Drug. Coadministration may result in hypotension, profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

              Monitor Closely (159)

              • abobotulinumtoxinA

                chlorzoxazone increases effects of abobotulinumtoxinA by pharmacodynamic synergism. Use Caution/Monitor. Muscle relaxants may enhance botulinum toxin effects. Closely monitor for increased neuromuscular blockade.

              • alfentanil

                chlorzoxazone and alfentanil both increase sedation. Use Caution/Monitor.

              • alprazolam

                alprazolam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • amitriptyline

                chlorzoxazone and amitriptyline both increase sedation. Use Caution/Monitor.

              • amobarbital

                amobarbital and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • amoxapine

                chlorzoxazone and amoxapine both increase sedation. Use Caution/Monitor.

              • apomorphine

                chlorzoxazone and apomorphine both increase sedation. Use Caution/Monitor.

              • aripiprazole

                chlorzoxazone and aripiprazole both increase sedation. Use Caution/Monitor.

              • atogepant

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

              • avapritinib

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

              • axitinib

                chlorzoxazone increases levels of axitinib by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor.

              • azelastine

                azelastine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • baclofen

                baclofen and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • belladonna and opium

                chlorzoxazone and belladonna and opium both increase sedation. Use Caution/Monitor.

              • benperidol

                chlorzoxazone and benperidol both increase sedation. Use Caution/Monitor.

              • benzphetamine

                chlorzoxazone increases and benzphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

              • brexanolone

                brexanolone, chlorzoxazone. Either increases toxicity of the other by sedation. Use Caution/Monitor.

              • brompheniramine

                brompheniramine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • buprenorphine

                chlorzoxazone and buprenorphine both increase sedation. Use Caution/Monitor.

              • buprenorphine buccal

                chlorzoxazone and buprenorphine buccal both increase sedation. Use Caution/Monitor.

              • buprenorphine, long-acting injection

                buprenorphine, long-acting injection increases effects of chlorzoxazone by Other (see comment). Modify Therapy/Monitor Closely. Comment: Buprenorphine may enhance the neuromuscular blocking action of skeletal muscle relaxants and increase risk for respiratory depression. Monitor for signs of respiratory depression that may be greater than otherwise expected and decrease muscle relaxant dosage as necessary.

              • butabarbital

                butabarbital and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • butalbital

                butalbital and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • butorphanol

                chlorzoxazone and butorphanol both increase sedation. Use Caution/Monitor.

              • carbinoxamine

                carbinoxamine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • cenobamate

                cenobamate, chlorzoxazone. Either increases effects of the other by sedation. Use Caution/Monitor.

              • chloral hydrate

                chloral hydrate and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • chlordiazepoxide

                chlordiazepoxide and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • chlorpheniramine

                chlorpheniramine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • chlorpromazine

                chlorzoxazone and chlorpromazine both increase sedation. Use Caution/Monitor.

              • cinnarizine

                cinnarizine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • clemastine

                clemastine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • clobazam

                chlorzoxazone, clobazam. Other (see comment). Use Caution/Monitor. Comment: Concomitant administration can increase the potential for CNS effects (e.g., increased sedation or respiratory depression).

              • clomipramine

                chlorzoxazone and clomipramine both increase sedation. Use Caution/Monitor.

              • clonazepam

                clonazepam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • clorazepate

                clorazepate and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • clozapine

                chlorzoxazone and clozapine both increase sedation. Use Caution/Monitor.

              • codeine

                chlorzoxazone and codeine both increase sedation. Use Caution/Monitor.

              • cyclizine

                cyclizine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • cyproheptadine

                cyproheptadine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • dantrolene

                chlorzoxazone and dantrolene both increase sedation. Use Caution/Monitor.

              • desipramine

                chlorzoxazone and desipramine both increase sedation. Use Caution/Monitor.

              • dexchlorpheniramine

                dexchlorpheniramine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • dexfenfluramine

                chlorzoxazone increases and dexfenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

              • dexmedetomidine

                dexmedetomidine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • dextromoramide

                chlorzoxazone and dextromoramide both increase sedation. Use Caution/Monitor.

              • diamorphine

                chlorzoxazone and diamorphine both increase sedation. Use Caution/Monitor.

              • diazepam

                diazepam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • diazepam intranasal

                diazepam intranasal, chlorzoxazone. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Coadministration may potentiate the CNS-depressant effects of each drug.

              • difenoxin hcl

                chlorzoxazone and difenoxin hcl both increase sedation. Use Caution/Monitor.

              • dimenhydrinate

                dimenhydrinate and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • diphenhydramine

                diphenhydramine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • diphenoxylate hcl

                chlorzoxazone and diphenoxylate hcl both increase sedation. Use Caution/Monitor.

              • dipipanone

                chlorzoxazone and dipipanone both increase sedation. Use Caution/Monitor.

              • dopexamine

                chlorzoxazone increases and dopexamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

              • dosulepin

                chlorzoxazone and dosulepin both increase sedation. Use Caution/Monitor.

              • doxepin

                chlorzoxazone and doxepin both increase sedation. Use Caution/Monitor.

              • doxylamine

                doxylamine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • droperidol

                chlorzoxazone and droperidol both increase sedation. Use Caution/Monitor.

              • esketamine intranasal

                esketamine intranasal, chlorzoxazone. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely.

              • estazolam

                estazolam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • ethanol

                chlorzoxazone and ethanol both increase sedation. Use Caution/Monitor.

              • etomidate

                etomidate and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • fenfluramine

                chlorzoxazone increases and fenfluramine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

              • flibanserin

                chlorzoxazone will increase the level or effect of flibanserin by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Increased flibanserin adverse effects may occur if coadministered with multiple weak CYP3A4 inhibitors.

              • fluphenazine

                chlorzoxazone and fluphenazine both increase sedation. Use Caution/Monitor.

              • flurazepam

                flurazepam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • haloperidol

                chlorzoxazone and haloperidol both increase sedation. Use Caution/Monitor.

              • hydromorphone

                chlorzoxazone and hydromorphone both increase sedation. Use Caution/Monitor.

              • hydroxyzine

                hydroxyzine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • iloperidone

                chlorzoxazone and iloperidone both increase sedation. Use Caution/Monitor.

              • imipramine

                chlorzoxazone and imipramine both increase sedation. Use Caution/Monitor.

              • incobotulinumtoxinA

                chlorzoxazone, incobotulinumtoxinA. Either increases effects of the other by pharmacodynamic synergism. Use Caution/Monitor. Muscle relaxants may enhance botulinum toxin effects. Closely monitor for increased neuromuscular blockade.

              • isavuconazonium sulfate

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

              • ivacaftor

                chlorzoxazone increases levels of ivacaftor by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Monitor when coadministered with weak CYP3A4 inhibitors .

              • ketamine

                ketamine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • ketotifen, ophthalmic

                chlorzoxazone and ketotifen, ophthalmic both increase sedation. Use Caution/Monitor.

              • lasmiditan

                lasmiditan, chlorzoxazone. Either increases effects of the other by sedation. Use Caution/Monitor. Coadministration of lasmiditan and other CNS depressant drugs, including alcohol have not been evaluated in clinical studies. Lasmiditan may cause sedation, as well as other cognitive and/or neuropsychiatric adverse reactions.

              • lemborexant

                chlorzoxazone will increase the level or effect of lemborexant by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Modify Therapy/Monitor Closely. Lower nightly dose of lemborexant recommended if coadministered with weak CYP3A4 inhibitors. See drug monograph for specific dosage modification.

                lemborexant, chlorzoxazone. Either increases effects of the other by sedation. Modify Therapy/Monitor Closely. Dosage adjustment may be necessary if lemborexant is coadministered with other CNS depressants because of potentially additive effects.

              • levorphanol

                chlorzoxazone and levorphanol both increase sedation. Use Caution/Monitor.

              • lofepramine

                chlorzoxazone and lofepramine both increase sedation. Use Caution/Monitor.

              • lofexidine

                chlorzoxazone and lofexidine both increase sedation. Use Caution/Monitor.

              • lomitapide

                chlorzoxazone increases levels of lomitapide by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Lomitapide dose should not exceed 30 mg/day.

              • loprazolam

                loprazolam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • lorazepam

                lorazepam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • lormetazepam

                lormetazepam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • loxapine

                chlorzoxazone and loxapine both increase sedation. Use Caution/Monitor.

              • loxapine inhaled

                chlorzoxazone and loxapine inhaled both increase sedation. Use Caution/Monitor.

              • lurasidone

                lurasidone, chlorzoxazone. Either increases toxicity of the other by Other (see comment). Use Caution/Monitor. Comment: Potential for increased CNS depressant effects when used concurrently; monitor for increased adverse effects and toxicity.

              • maprotiline

                chlorzoxazone and maprotiline both increase sedation. Use Caution/Monitor.

              • marijuana

                chlorzoxazone and marijuana both increase sedation. Use Caution/Monitor.

              • melatonin

                chlorzoxazone and melatonin both increase sedation. Use Caution/Monitor.

              • meperidine

                chlorzoxazone and meperidine both increase sedation. Use Caution/Monitor.

              • meprobamate

                chlorzoxazone and meprobamate both increase sedation. Use Caution/Monitor.

              • metaxalone

                chlorzoxazone and metaxalone both increase sedation. Use Caution/Monitor.

              • methadone

                chlorzoxazone and methadone both increase sedation. Use Caution/Monitor.

              • methocarbamol

                chlorzoxazone and methocarbamol both increase sedation. Use Caution/Monitor.

              • methylenedioxymethamphetamine

                chlorzoxazone increases and methylenedioxymethamphetamine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

              • midazolam

                midazolam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • midazolam intranasal

                chlorzoxazone will increase the level or effect of midazolam intranasal by affecting hepatic/intestinal enzyme CYP3A4 metabolism. Use Caution/Monitor. Coadministration of mild CYP3A4 inhibitors with midazolam intranasal may cause higher midazolam systemic exposure, which may prolong sedation.

                midazolam intranasal, chlorzoxazone. Either increases effects of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Concomitant use of barbiturates, alcohol, or other CNS depressants may increase the risk of hypoventilation, airway obstruction, desaturation, or apnea and may contribute to profound and/or prolonged drug effect.

              • mirtazapine

                chlorzoxazone and mirtazapine both increase sedation. Use Caution/Monitor.

              • morphine

                chlorzoxazone and morphine both increase sedation. Use Caution/Monitor.

              • motherwort

                chlorzoxazone and motherwort both increase sedation. Use Caution/Monitor.

              • moxonidine

                chlorzoxazone and moxonidine both increase sedation. Use Caution/Monitor.

              • nabilone

                chlorzoxazone and nabilone both increase sedation. Use Caution/Monitor.

              • nalbuphine

                chlorzoxazone and nalbuphine both increase sedation. Use Caution/Monitor.

              • nortriptyline

                chlorzoxazone and nortriptyline both increase sedation. Use Caution/Monitor.

              • olanzapine

                chlorzoxazone and olanzapine both increase sedation. Use Caution/Monitor.

              • oliceridine

                oliceridine, chlorzoxazone. Either increases toxicity of the other by pharmacodynamic synergism. Modify Therapy/Monitor Closely. Profound sedation, respiratory depression, coma, and death may result if coadministered. Reserve concomitant prescribing of these drugs in patients for whom other treatment options are inadequate. Limit dosages and durations to the minimum required. Monitor closely for signs of respiratory depression and sedation.

                chlorzoxazone increases toxicity of oliceridine by Other (see comment). Modify Therapy/Monitor Closely. Comment: Anticholinergic drugs may increase risk of urinary retention and/or severe constipation, which may lead to paralytic ileus. Monitor for signs of urinary retention or reduced gastric motility if oliceridine is coadministered with anticholinergics.

              • opium tincture

                chlorzoxazone and opium tincture both increase sedation. Use Caution/Monitor.

              • orphenadrine

                chlorzoxazone and orphenadrine both increase sedation. Use Caution/Monitor.

              • oxazepam

                oxazepam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • oxycodone

                chlorzoxazone and oxycodone both increase sedation. Use Caution/Monitor.

              • oxymorphone

                chlorzoxazone and oxymorphone both increase sedation. Use Caution/Monitor.

              • paliperidone

                chlorzoxazone and paliperidone both increase sedation. Use Caution/Monitor.

              • papaveretum

                chlorzoxazone and papaveretum both increase sedation. Use Caution/Monitor.

              • papaverine

                chlorzoxazone and papaverine both increase sedation. Use Caution/Monitor.

              • pentazocine

                chlorzoxazone and pentazocine both increase sedation. Use Caution/Monitor.

              • pentobarbital

                pentobarbital and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • perphenazine

                chlorzoxazone and perphenazine both increase sedation. Use Caution/Monitor.

              • phenobarbital

                phenobarbital and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • phenylephrine PO

                chlorzoxazone increases and phenylephrine PO decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor. .

              • pholcodine

                chlorzoxazone and pholcodine both increase sedation. Use Caution/Monitor.

              • pimozide

                chlorzoxazone and pimozide both increase sedation. Use Caution/Monitor.

              • prabotulinumtoxinA

                chlorzoxazone increases effects of prabotulinumtoxinA by pharmacodynamic synergism. Use Caution/Monitor. Muscle relaxants may enhance botulinum toxin effects. Closely monitor for increased neuromuscular blockade.

              • primidone

                primidone and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • prochlorperazine

                chlorzoxazone and prochlorperazine both increase sedation. Use Caution/Monitor.

              • promethazine

                promethazine and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • propofol

                propofol and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • propylhexedrine

                chlorzoxazone increases and propylhexedrine decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

              • protriptyline

                chlorzoxazone and protriptyline both increase sedation. Use Caution/Monitor.

              • quazepam

                quazepam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • quetiapine

                chlorzoxazone and quetiapine both increase sedation. Use Caution/Monitor.

              • ramelteon

                chlorzoxazone and ramelteon both increase sedation. Use Caution/Monitor.

              • remimazolam

                remimazolam, chlorzoxazone. Either increases toxicity of the other by sedation. Modify Therapy/Monitor Closely. Coadministration may result in profound sedation, respiratory depression, coma, and/or death. Continuously monitor vital signs during sedation and recovery period if coadministered. Carefully titrate remimazolam dose if administered with opioid analgesics and/or sedative/hypnotics.

              • risperidone

                chlorzoxazone and risperidone both increase sedation. Use Caution/Monitor.

              • scullcap

                chlorzoxazone and scullcap both increase sedation. Use Caution/Monitor.

              • secobarbital

                secobarbital and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • shepherd's purse

                chlorzoxazone and shepherd's purse both increase sedation. Use Caution/Monitor.

              • stiripentol

                stiripentol, chlorzoxazone. Either increases effects of the other by sedation. Use Caution/Monitor. Concomitant use stiripentol with other CNS depressants, including alcohol, may increase the risk of sedation and somnolence.

              • sufentanil

                chlorzoxazone and sufentanil both increase sedation. Use Caution/Monitor.

              • tapentadol

                chlorzoxazone and tapentadol both increase sedation. Use Caution/Monitor.

              • tazemetostat

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

              • temazepam

                temazepam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • thioridazine

                chlorzoxazone and thioridazine both increase sedation. Use Caution/Monitor.

              • thiothixene

                chlorzoxazone and thiothixene both increase sedation. Use Caution/Monitor.

              • tinidazole

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

              • topiramate

                chlorzoxazone and topiramate both increase sedation. Modify Therapy/Monitor Closely.

              • tramadol

                chlorzoxazone and tramadol both increase sedation. Use Caution/Monitor.

              • trazodone

                chlorzoxazone and trazodone both increase sedation. Use Caution/Monitor.

              • triazolam

                triazolam and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • triclofos

                triclofos and chlorzoxazone both increase sedation. Use Caution/Monitor.

              • trifluoperazine

                chlorzoxazone and trifluoperazine both increase sedation. Use Caution/Monitor.

              • trimipramine

                chlorzoxazone and trimipramine both increase sedation. Use Caution/Monitor.

              • watercress

                watercress increases levels of chlorzoxazone by decreasing metabolism. Use Caution/Monitor.

                watercress increases levels of chlorzoxazone by decreasing elimination. Use Caution/Monitor.

              • xylometazoline

                chlorzoxazone increases and xylometazoline decreases sedation. Effect of interaction is not clear, use caution. Use Caution/Monitor.

              • ziconotide

                chlorzoxazone and ziconotide both increase sedation. Use Caution/Monitor.

              • ziprasidone

                chlorzoxazone and ziprasidone both increase sedation. Use Caution/Monitor.

              • zotepine

                chlorzoxazone and zotepine both increase sedation. Use Caution/Monitor.

              Minor (3)

              • eucalyptus

                chlorzoxazone and eucalyptus both increase sedation. Minor/Significance Unknown.

              • ruxolitinib

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

              • sage

                chlorzoxazone and sage both increase sedation. Minor/Significance Unknown.

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              Adverse Effects

              1-10%

              Lightheadedness

              Dizziness

              Drowsiness

              Excitement, Paradoxical

              Somnolence

              Malaise

              Rash

              Angioneurotic edema

              <1%

              Gastrointestinal hemorrhage (rare)

              Hepatotoxicity (rare)

              Anaphylaxis (rare)

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              Warnings

              Contraindications

              Hypersensitivity to drug or excipients

              Cautions

              May cause CNS depression and impair physical and mental alertness; avoid performing tasks that require mental alertness

              May take with food to avoid stomach upset

              Poor tolerance by the elderly

              Hepatotoxicity

              • Serious (including fatal) hepatocellular toxicity has been reported rarely in patients receiving therapy; mechanism is unknown but appears to be idiosyncratic and unpredictable
              • Factors predisposing patients to this rare event are not known
              • Patients should be instructed to report early signs and/or symptoms of hepatotoxicity such as fever, rash, anorexia, nausea, vomiting, fatigue, right upper quadrant pain, dark urine, or jaundice; therapy should be discontinued immediately, and a physician consulted if signs or symptoms develop
              • Therapy should also be discontinued if a patient develops abnormal liver enzymes (eg, AST, ALT, alkaline phosphatase and bilirubin)
              • The concomitant use of alcohol or other central nervous system depressants may have an additive effect
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              Pregnancy & Lactation

              Pregnancy Category: C

              Lactation: not known if excreted in breast milk

              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

              Blocks interneuronal conduction in spinal cord and subcortical brain areas by depressing polysynaptic reflexes

              Pharmacokinetics

              Half-life: 66 min

              Onset: 1 hr

              Duration: 6-12 hr

              Peak Plasma Time: 1-4 hr

              Peak Plasm Concentration: 9-20 mcg/mL

              Metabolism: Rapid hepatic glucuronidation

              Metabolites: 6-hydroxychlorzoxazone (inactive; rapidly excreted in urine)

              Excretion: Urine (primarily)

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              Images

              BRAND FORM. UNIT PRICE PILL IMAGE
              chlorzoxazone oral
              -
              500 mg tablet
              chlorzoxazone oral
              -
              250 mg tablet
              chlorzoxazone oral
              -
              500 mg tablet
              chlorzoxazone oral
              -
              750 mg tablet
              chlorzoxazone oral
              -
              750 mg tablet
              chlorzoxazone oral
              -
              375 mg tablet
              chlorzoxazone oral
              -
              375 mg tablet
              chlorzoxazone oral
              -
              750 mg tablet
              chlorzoxazone oral
              -
              375 mg tablet
              Lorzone oral
              -
              750 mg tablet
              Lorzone oral
              -
              375 mg tablet

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              Patient Handout

              Patient Education
              chlorzoxazone oral

              CHLORZOXAZONE - ORAL

              (klor-ZOX-a-zone)

              COMMON BRAND NAME(S): Paraflex

              USES: Chlorzoxazone is used to treat muscle spasms/pain. It is usually used along with rest, physical therapy, and other treatment. It works by helping to relax the muscles.

              HOW TO USE: Take this medication by mouth with or without food as directed by your doctor. Do not increase your dose or use this drug more often or for longer than prescribed. Your condition will not improve any faster, and your risk of side effects will increase.The dosage is based on your medical condition and response to treatment.Tell your doctor if your condition does not improve or if it worsens.

              SIDE EFFECTS: Drowsiness, dizziness, lightheadedness, tiredness, upset stomach, or headache may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.This medication may rarely cause your urine to turn orange or reddish-purple. This effect is harmless and will disappear when the medication is stopped.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: confusion, black/bloody stools, vomit that looks like coffee grounds, easy bruising/bleeding, signs of infection (such as fever, persistent sore throat).This medication may rarely cause very serious (possibly fatal) liver disease. Stop taking this medication and get medical help right away if you develop symptoms of liver disease, including: persistent nausea/vomiting, stomach/abdominal pain, yellowing eyes/skin, dark urine.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 chlorzoxazone, 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: liver disease.This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Avoid alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).Older adults may be more sensitive to the side effects of this drug, especially drowsiness, or confusion. These side effects can increase the risk of falling.During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor.It is unknown if this drug passes into breast milk. 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.Tell your doctor or pharmacist if you are taking other products that cause drowsiness such as opioid pain or cough relievers (such as codeine, hydrocodone), alcohol, marijuana (cannabis), drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), other muscle relaxants (such as carisoprodol, cyclobenzaprine), or antihistamines (such as cetirizine, diphenhydramine).Check the labels on all your medicines (such as allergy or cough-and-cold products) because they may contain ingredients that cause drowsiness. Ask your pharmacist about using those products safely.

              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: nausea/vomiting, severe drowsiness, muscle weakness, fast/irregular breathing.

              NOTES: Do not share this medication with others.This medication has been prescribed for your current condition only. Do not use it later for another condition unless your doctor directs you to do so. A different medication may be necessary in that case.If you are taking this medication for a long time, laboratory and/or medical tests (such as liver function) should be performed periodically to check for side effects. Consult your doctor for more details.

              MISSED DOSE: 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.