chlorzoxazone
Brand names: Parafon Forte
Chlorzoxazone is a muscle relaxant. It helps to relieve discomfort from painful muscle problems.
Drug Pricing (NADAC)
Generic Price
$0.19/unit
Generic Available
Yes (11 manufacturers)
Pricing data from NADAC (CMS), effective December 18, 2024. Compare all drug costs →
What it does
This medicine treats discomfort from muscle problems.
Common side effects
Drowsiness, Dizziness, Lightheadedness
Key warnings
If you are intolerant to chlorzoxazone, you should not take this medicine.
How It Works
The way this drug works is not fully known. It may work by making you feel sleepy. This medicine does not directly relax your muscles.
How to Take It
Take one tablet three or four times each day. If that doesn't help enough, your doctor may increase your dose to one and a half tablets (750 mg) three or four times a day. Your doctor will lower your dose as you start feeling better.
Pregnancy & Breastfeeding
Talk to your doctor if you are pregnant or breastfeeding. It is not known if this medicine will harm your unborn baby. It is also not known if this medicine passes into breast milk.
Missed Dose
If you miss a dose, take it as soon as you remember. If it is close to your next dose, skip the missed dose and continue with your regular schedule.
Storage
Store at room temperature between 59° and 86°F.
Side Effects (from patient reports)
Based on 749 FDA adverse event reports.
FDA Adverse Event Report Analysis
Detailed analysis of 1,256 reports from the FDA Adverse Event Reporting System (FAERS). Reports span 2004–2025.
Total Reports
1,256
Death-Related Reports
130
Hospitalization Reports
346
Top Indication
Product Used For Unknown Indication
Gender Distribution
Age Distribution
Most Reported Adverse Reactions (FAERS)
| # | Reaction | Reports |
|---|---|---|
| 1 | DIZZINESS | 94 |
| 2 | NAUSEA | 94 |
| 3 | FATIGUE | 92 |
| 4 | PAIN | 90 |
| 5 | DRUG INEFFECTIVE | 81 |
| 6 | HEADACHE | 72 |
| 7 | ANXIETY | 66 |
| 8 | CHRONIC KIDNEY DISEASE | 56 |
| 9 | DIARRHOEA | 53 |
| 10 | SOMNOLENCE | 51 |
| 11 | DYSPNOEA | 47 |
| 12 | WEIGHT DECREASED | 46 |
| 13 | FALL | 45 |
| 14 | BACK PAIN | 44 |
| 15 | COMPLETED SUICIDE | 43 |
Reactions in Death Reports
Reactions in Hospitalization Reports
Source: FDA FAERS (Adverse Event Reporting System) FDA FAERS (Adverse Event Reporting System) Reports are voluntary and do not establish causation
Serious Warnings
If you are intolerant to chlorzoxazone, you should not take this medicine.
Known Drug Interactions
Examples: Strong CYP3A inhibitors: itraconazole, clarithromycin Moderate CYP3A inhibitors: fluconazole, verapamil Weak CYP3A inhibitors: chlorzoxazone, ranitidine Strong and Moderate CYP3A Inducers Clinical Impact: Concomitant use with a strong or moderate CYP3A inducer decreases lemborexant exposure, which may reduce DAYVIGO efficacy [see Clinical Pharmacology ( 12.3 )].
Mechanism: Chlorzoxazone slows down the process your body uses to get rid of lemborexant. This may lead to higher levels of the sleep medicine in your blood.
What to do: Your doctor may need to monitor you more closely for extra sleepiness or adjust your dose.
Common Questions
Can this medicine make me sleepy?
How often should I take this medicine?
What should I do if I have side effects?
Can I take this with other medicines?
How long does it take for this medicine to work?
Can I drive while taking this medicine?
What does the tablet look like?
How should I store this medicine?
What if the regular dose doesn't work?
Can this medicine cause allergic reactions?
What are the common side effects of chlorzoxazone?
Does chlorzoxazone interact with other medications?
What drug class is chlorzoxazone?
Is chlorzoxazone safe during pregnancy?
Related Medications in Muscle Relaxant
Other drugs grouped near chlorzoxazone — same-class peers and common alternatives.
baclofen
Lioresal, Gablofen
Baclofen is a muscle relaxant.
Compare with chlorzoxazone →
botulinum toxin A
Botox
Botox is a drug that blocks nerve signals to muscles.
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carisoprodol
Soma
Carisoprodol is a muscle relaxant.
Compare with chlorzoxazone →
cyclobenzaprine
Flexeril, Amrix
Cyclobenzaprine is a muscle relaxant.
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dantrolene
Dantrium
Dantrolene is a muscle relaxant.
Compare with chlorzoxazone →
Medication Guides
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How CYP450 enzymes, inhibitors, and inducers affect your medications
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What the FDA Data Shows for chlorzoxazone
The FDA label for chlorzoxazone (sold under brand names such as Parafon Forte) classifies it as a prescription-only medication in the Muscle Relaxant class. This medicine treats discomfort from muscle problems. Official labeling lists 5 commonly reported side effects, including Drowsiness, Dizziness, Lightheadedness.
Post-market surveillance from the FDA Adverse Event Reporting System (FAERS) captures real-world experience. For this drug, FAERS contains 749 voluntary reports. The database also lists 1 documented drug interaction derived from FDA labeling, with the top-flagged interaction rated minor severity. NADAC pricing from CMS shows a generic unit cost of $0.19.
Report counts do not establish causation — a FAERS entry documents a temporal association, not proof that the drug produced the outcome. Widely prescribed medications naturally accumulate more reports than niche therapies, so raw totals must be interpreted alongside total exposure. Shortage status, recall history, and patent information further shape supply and switching decisions. This page summarizes public FDA data for educational purposes only and is not a substitute for professional medical advice — always consult a licensed healthcare provider before starting, stopping, or changing any medication.
Data Sources
Drug labeling: FDA Drug Labels (SPL/DailyMed). Adverse events: FDA Adverse Event Reporting System (FAERS). Pricing: CMS National Average Drug Acquisition Cost (NADAC).
FAERS reports are voluntary and do not establish causation. Drug interactions are derived from FDA labeling and clinical references. Always consult a healthcare professional before making medication decisions.
Last updated: March 1, 2025
Read our methodology — how this data is sourced, computed, and verified.
All federal data sources used on this page
- FDA Orange Book — approved drug products with therapeutic equivalence. accessdata.fda.gov/cder/ob
- FDA DailyMed — NIH-hosted drug labeling for FDA-approved meds. dailymed.nlm.nih.gov
- FDA Adverse Event Reporting System (FAERS) — post-marketing safety surveillance. fda.gov/drugs/faers
- NLM RxNorm — standardized clinical drug nomenclature. nlm.nih.gov/research/umls/rxnorm
- CMS Medicare Part B Drug Average Sales Price Files — federal drug pricing data. cms.gov/medicare/part-b-drugs/asp
- FDA Drug Shortages Database — current and resolved drug shortage tracking. accessdata.fda.gov/drugshortages