Cyclobenzaprine
FLEXERIL
What it isTricyclic-related central muscle relaxant with H1 and muscarinic antagonism; short-term treatment of acute muscle spasm.
Why this onePronounced sedation can make it useful when nighttime spasm dominates, unlike less sedating relaxants.
What limits itAnticholinergic effects, falls and next-day sedation limit it, especially in older adults. Avoid with MAOIs.
FDA-approved for
- muscle spasm (1977)
Off-label
- fibromyalgia
- insomnia
FDA label
Read the full label on DailyMed ↗
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| Muscle spasm, adjunct to rest/PT for acute musculoskeletal conditions | Adults | 5 mg TID | 5 mg TID | 10 mg TID |
Renal Undefined
Hepatic Use less frequent dosing in hepatic impairment
Instructions
- Do not use for periods longer than 2–3 weeks
- Use less frequent dosing in the elderly
Contraindications
- MAOIs (concurrently or within 14 days) due to risk of hyperpyretic crises, severe convulsions, and death
- Acute recovery phase of myocardial infarction
- Arrhythmias, heart block or conduction disturbances, or congestive heart failure
- Hyperthyroidism
Adverse reactions
- Drowsiness
- Dry mouth
- Fatigue
- Dizziness
- Headache
Pregnancy Undefined
Lactation Undefined
NO BOXED WARNINGS
Principal riskAnticholinergic burden and sedation
Cost, est. cash$4–$80/month
Generic entry1989
Classes and tags
Clinical profile
Legacy pregnancy categoryUnknown / historical label unavailable
Defining liabilityGenerally tolerated at therapeutic doses; clinically important risks are agent-specific and increase with interactions or organ impairment.
Mechanism of action: Cyclobenzaprine ballicule
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