This is a prescription medicine. Only take it if it has been prescribed for you after a medical assessment, and follow your doctor’s and pharmacist’s instructions.
Cyclobenzaprine (Flexeril, Amrix) is a muscle relaxant used alongside rest and physical therapy for short-term muscle spasm from strains and sprains.
Short-term use only
It’s meant for 2 to 3 weeks; there’s little evidence it helps beyond that. The schedule depends on whether you receive immediate-release tablets or extended-release capsules. Follow the prescription for your specific formulation.
Side effects
- Drowsiness, dizziness: don’t drive until you know how it affects you
- Dry mouth
- Constipation
- Confusion, especially in older adults (often avoided over 65)
Who should avoid it
- Recent heart attack, heart rhythm problems, heart failure, overactive thyroid
- Tell the prescriber about glaucoma or difficulty urinating; these conditions need particular caution.
- Taking MAO inhibitors now or within the past 14 days
Interactions
- Alcohol, opioids, sleeping pills
- SSRIs, SNRIs, tramadol, bupropion (serotonin syndrome risk)
Frequently asked questions
Is cyclobenzaprine addictive?
It isn’t a controlled substance, but it’s sedating and should be used short-term.
General information only. It isn’t a substitute for advice from your doctor or pharmacist.
Source and further reading
MedlinePlus patient medicine information. This overview does not list every warning or interaction; read the leaflet supplied with your medicine.
