Based on 1 source · Recall-safety score from FDA recall history — this product's own recalls and its manufacturer's record. Not an efficacy or quality rating. methodology →
Key facts
- Active ingredient
- Chlorzoxazone
- Drug class
- Muscle Relaxant
- Form
- Tablet
- Strength
- Chlorzoxazone 250MG
- Type
- Prescription (Rx)
- Brand or generic
- Generic
- May treat
- muscle cramp, muscle rigidity, myositis
- Manufacturer
- Ohm Labs
- What the pharmacy pays
- ~$16.14 for 30 — not your price
- FDA application
- ANDA081298
- Availability
- Discontinued (per FDA)
What is Chlorzoxazone?
From the FDA label:Chlorzoxazone USP is a centrally acting skeletal muscle relaxant, available as tablets of 500 mg for oral administration. Its chemical name is 5-Chloro-2-benzoxazolinone, and its structural formula is: Chlorzoxazone,USP is a white or practically white, practically odorless, crystalline powder. Chlorzoxazone is slightly soluble in water; sparingly soluble in alcohol, in isopropyl alcohol, and in methanol; soluble in solutions of alkali hydroxides and ammonia. Chlorzoxazone tablets contain the inactive ingredients -Lactose monohydrate USNF, Microcrystalline cellulose USNF, FD&C Yellow 6/Sunset Yellow FCF Aluminium lake, D&C Red 27/Phloxine Aluminium lake, Hypromellose USP (a) Binder solution Hypromellose USP (b), Polysarbate 80 USNF, Ethanol (96%v/v). Extragranrular Pregelatinized Starch USNF, Sodium starch glycolate USNF, Magnesium stearate USNF. FDA approved dissolution method differs from that of the USP. structure
How to use
Usual Adult Dosage One tablet three or four times daily. If adequate response is not obtained with this dose, it may be increased to one and one-half tablets (750 mg) three or four times daily. As improvement occurs dosage can usually be reduced.
Side effects
Chlorzoxazone containing products are usually well tolerated. It is possible in rare instances that chlorzoxazone may have been associated with gastrointestinal bleeding. Drowsiness, dizziness, lightheadedness, malaise, or over-stimulation may be noted by an occasional patient. Rarely, allergic type skin rashes, petechiae, or ecchymoses may develop during treatment. Angioneurotic edema or anaphylactic reactions are extremely rare. There is no evidence that the drug will cause renal damage. Rarely, a patient may note discoloration of the urine resulting from a phenolic metabolite of chlorzoxazone. This finding is of no known clinical significance. To report SUSPECTED ADVERSE EVENTS, contact Aurobindo Pharma USA, Inc. at 1-866-850-2876 or FDA at 1-800- FDA-1088 or http://www.fda.gov/ for voluntary reporting of adverse reactions.
Warnings
Important safety information
Serious (including fatal) hepatocellular toxicity has been reported rarely in patients receiving chlorzoxazone. The 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. Chlorzoxazone should be discontinued immediately and a physician consulted if any of these signs or symptoms develop. Chlorzoxazone use should also be discontinued if a patient develops abnormal liver enzymes (e.g., AST, ALT, alkaline phosphatase and bilirubin.) The concomitant use of alcohol or other central nervous system depressants may have an additive effect. Usage in Pregnancy The safe use of chlorzoxazone has not been established with respect to the possible adverse effects upon fetal development. Therefore, it should be used in women of childbearing potential only when, in the judgment of the physician, the potential benefits outweigh the possible risks.
Who should not take Chlorzoxazone
Chlorzoxazone is contraindicated in patients with known intolerance to the drug.
Overdose — what happens if you take too much
Symptoms Initially, gastrointestinal disturbances such as nausea, vomiting, or diarrhea together with drowsiness, dizziness, lightheadedness or headache may occur. Early in the course there may be malaise or sluggishness followed by marked loss of muscle tone, making voluntary movement impossible. The deep tendon reflexes may be decreased or absent. The sensorium remains intact, and there is no peripheral loss of sensation. Respiratory depression may occur with rapid, irregular respiration and intercostal and substernal retraction. The blood pressure is lowered, but shock has not been observed. Treatment Gastric lavage or induction of emesis should be carried out, followed by administration of activated charcoal. Thereafter, treatment is entirely supportive. If respirations are depressed, oxygen and artificial respiration should be employed and a patent airway assured by use of an oropharyngeal airway or endotracheal tube. Hypotension may be counteracted by use of dextran, plasma, concentrated albumin or a vasopressor agent such as norepinephrine. Cholinergic drugs or analeptic drugs are of no value and should not be used.
U.S. Poison Control: call or text 1-800-222-1222 (free, 24/7). In an emergency call 911. From the FDA label; not medical advice.
Drug class
How this class works, per Cyclobenzaprine - StatPearls - NCBI Bookshelf.
May treat (source: NIH RxClass)
See how Chlorzoxazone ranks — best-rated muscle relaxant for:
Dosage forms
Tablet
The forms currently marketed in the U.S., per the FDA National Drug Code Directory.
Ways to save
Ask for the generic
Same active ingredient, far cheaper. Is there a generic? →
Request a 90-day supply
Bulk fills usually lower the per-dose price vs monthly refills.
Use copay cards
Manufacturer copay cards & patient-assistance programs — especially for brand drugs.
Compare alternatives
A same-class option may cost less. See alternatives →
Frequently asked questions
- What does Chlorzoxazone treat?
- Chlorzoxazone (Chlorzoxazone) may be used to treat muscle cramp, muscle rigidity, myositis, pain, spasm, based on NIH RxClass drug-classification data (conditions a drug may treat — not a verbatim copy of the FDA-approved label). This is general reference, not medical advice.
- How does Chlorzoxazone work?
- Chlorzoxazone is a muscle relaxant. Most muscle relaxants work in the brain and spinal cord rather than on the muscle itself: they damp down the overactive nerve signals and reflexes that keep muscles tense, easing spasms and tightness. Some specialized agents instead act directly on muscle calcium release.
- How is Chlorzoxazone rated?
- pharmaranks gives Chlorzoxazone a composite score of 3.5 out of 5, currently based on 1 weighted source (FDA regulatory recall-safety data weighted highest). See our methodology at /how-we-rate.
- How much does Chlorzoxazone cost?
- Nobody can tell you what you will pay — your price is set by your insurer's formulary, your deductible and the pharmacy's markup, and none of those are published. What IS published is what the pharmacy paid to acquire it: about $16.14 for 30, per the CMS NADAC survey. Treat that as the floor, not the quote — ask the pharmacist for the cash price as well as your copay, because for cheap generics the cash price often wins. Pharmacies pay less for a same-class option, Amrix — about $0.63 on the same basis.
- Is there a coupon or discount for Chlorzoxazone?
- pharmaranks is an independent ratings site, not a pharmacy — we don't issue coupons or sell Chlorzoxazone. To pay less, Chlorzoxazone is already a generic — usually the lowest-cost version — so the main levers are comparing cash prices between pharmacies and using a pharmacy discount-card service. Prices vary by pharmacy, insurance, and location, so always confirm at the counter. This is general reference, not medical or financial advice.
- Who makes Chlorzoxazone?
- Chlorzoxazone is marketed by Ohm Labs. You can see Ohm Labs's full profile, rating, and other products on pharmaranks.
- Is Chlorzoxazone a brand-name or generic drug?
- Chlorzoxazone is a generic medication; its active ingredient is Chlorzoxazone. Generics contain the same active ingredient as the brand-name original and are usually lower cost.
- Is Chlorzoxazone available over the counter?
- No. Chlorzoxazone is a prescription (Rx) medication in the US — you need a prescription from a licensed clinician (in person or via telehealth); it isn't sold over the counter. For some conditions there are OTC alternatives — ask your pharmacist.
- What forms does Chlorzoxazone come in?
- Chlorzoxazone is currently marketed as tablet, per the FDA's National Drug Code Directory.
- What class of drug is Chlorzoxazone?
- Chlorzoxazone is classified as muscle relaxant, per the FDA's Established Pharmacologic Class.
- Is Chlorzoxazone FDA-registered?
- Chlorzoxazone is on record with the U.S. FDA under application number ANDA081298. You can verify this on its official FDA label.
- Has Chlorzoxazone been recalled by the FDA?
- Chlorzoxazone has no FDA recalls recorded under its own application in the openFDA enforcement database. Its recall-safety score reflects its manufacturer's overall recall record. This is general reference, not medical advice — check the FDA recall database for the latest alerts.
- Is Chlorzoxazone safe?
- There's no single safe-or-not verdict. pharmaranks gives Chlorzoxazone a recall-safety score of 70/100, based on its FDA recall history (no recalls under its own FDA application) — not an efficacy or side-effect rating. Review its FDA-label side effects and warnings before use, and always consult a licensed professional.
- What are the side effects of Chlorzoxazone?
- Chlorzoxazone's side effects are taken directly from its FDA label. From the label: Chlorzoxazone containing products are usually well tolerated. It is possible in rare instances that chlorzoxazone may have been associated with gastrointestinal bleeding. Drowsiness, dizziness, lightheadedness, malaise, or over-stimulation may be noted by an occasional patient. Rarely,… Both common and serious reactions are documented in full on this page. This is general reference from the FDA, not medical advice — always consult a professional.
Clinical content sourced from the FDA label via openFDA (U.S. FDA). View the FDA label on DailyMed → Provided for general reference only — not medical advice. Always consult a licensed professional and the current prescribing information.
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