Brand name Flexeril, Amrix among others.
A muscle relaxant used to relieve skeletal muscle spasms and associated pain in acute musculoskeletal conditions.
Bioavailabilitys 33% to 55%.
Metabolism: CYP3A4, CYP1A2 and minor: CYP2D6, N-demethylation.
Elimination half-life 32 hours
Excretion is renal.
Used to treat such muscle spasms associated with acute, painful musculoskeletal conditions, decreasing pain in the first two weeks.
Pain relief peaks in the first few days, but has no proven benefit after two weeks, and therapy should not be continued long-term.
Not useful for spasticity due to neurologic conditions.
Effectiveness in the treatment of fibromyalgia symptoms, has been reported with 1 in 4.8 patients out of every 4.8 benefits deriving pain reduction, but no change in fatigue or tender points.
Inside effects include: drowsiness, dry mouth, and dizziness, which intensify with increasing dose.
Some serious but unlikely side effects may be experienced, including mental or mood changes, possible confusion and hallucinations, difficulty urinating, irregular heartbeat, yellowing of eyes or skin, fainting, abdominal pain including stomach ache, nausea or vomiting, lack of appetite, seizures, dark urine, or loss of coordination.
Rarely, dysphagia may occur.
The sedative effects are likely due to its antagonistic effect on histamine, serotonin, and muscarinic receptors.
In the elderly agitation is a common side effect
Use in the elderly is discouraged because of the potential for more severe side effects, including confusion, delirium, and cognitive impairment.
Has major contraindications with monoamine oxidase inhibitors (MAOIs).
These substances may interact with cyclobenzaprine:
Central nervous system depressants
Monoamine oxidase inhibitors taken within two weeks of cyclobenzaprine may result in serious, life-threatening side effects.
Cyclobenzaprine is not inferior to tizanidine, orphenadrine, and carisoprodol in the treatment of acute lower back pain, or spasms, although none have been proven to be effective for long-term use.
Cyclobenzaprine 5-10 mg three times/day.