Dosing & Uses
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
Interactions
Interaction Checker
No Results
Contraindicated
Serious - Use Alternative
Significant - Monitor Closely
Minor
Contraindicated (0)
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.
Adverse Effects
1-10%
Lightheadedness
Dizziness
Drowsiness
Excitement, Paradoxical
Somnolence
Malaise
Rash
Angioneurotic edema
<1%
Gastrointestinal hemorrhage (rare)
Hepatotoxicity (rare)
Anaphylaxis (rare)
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
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.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)
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 | |
Copyright © 2010 First DataBank, Inc.
Patient Handout
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.
Formulary
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.
