Brands, Medical Use, Clinical Data
- Tranquilizing Agents
- Muscle Relaxants
- Antidepressive Agents, Tricyclic
- Skeletal Muscle Relaxants
Brands / Synonyms
Amrix; Cyclobenz; Cyclobenzaprine HCL; Fexmid; Flexeril; Flexiban; Proeptatriene; Proheptatriene
For use as an adjunct to rest and physical therapy for relief of muscle spasm associated with acute, painful musculoskeletal conditions.
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.
Mechanism of Action
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.
Slowly but well absorbed after oral administration
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.
Biotrnasformation / Drug Metabolism
Extensively metabolized (gastrointestinal and hepatic).
Hypersensitivity to any component of this product.
Concomitant use of monoamine oxidase (MAO) inhibitors or within 14 days after their discontinuation.
Hyperpyretic crisis seizures, and deaths have occurred in patients receiving cyclobenzaprine (or structurally similar
tricyclic antidepressants) concomitantly with MAO inhibitor drugs.
Acute recovery phase of myocardial infarction, and patients with arrhythmias, heart block or
conduction disturbances, or congestive heart failure.
FLEXERIL may have life-threatening interactions with MAO inhibitors.
FLEXERIL may enhance the effects of alcohol, barbiturates, and other CNS depressants.
Tricyclic antidepressants may block the antihypertensive action of guanethidine and similarly acting
Tricyclic antidepressants may enhance the seizure risk in patients taking tramadol.