Like other tricyclic antidepressants, cyclobenzaprine exhibits anticholinergic activity, potentiation of norepinephrine, and antagonism of reserpine. Cyclobenzaprine does not directly act on the neuromuscular junction or the muscle but relieves muscle spasms through a central action, possibly at the brain stem level. Cyclobenzaprine binds to the serotonin receptor and is considered a 5-HT2 receptor antagonist that reduces muscle tone by decreasing the activity of descending serotonergic neurons.
Cyclobenzaprine, closely related to the antidepressant amitriptyline, is used as a skeletal muscle relaxant to reduce pain and tenderness and improve mobility. Unlike dantrolene, cyclobenzaprine cannot be used to treat muscle spasm secondary to cerebral or spinal cord disease.
Extensively metabolized (gastrointestinal and hepatic).
Oral mouse and rat LD50 are 338 mg/kg and 425 mg/kg respectively. Signs of overdose include agitation, coma, confusion, congestive heart failure, convulsions, dilated pupils, disturbed concentration, drowsiness, hallucinations, high or low temperature, increased heartbeats, irregular heart rhythms, muscle stiffness, overactive reflexes, severe low blood pressure, stupor, and vomiting.