| Indication |
For use as an adjunct to rest and physical therapy for relief of
muscle spasm associated with acute, painful musculoskeletal conditions. |
| Pharmacodynamics |
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. |
| Absorption |
Slowly but well absorbed after oral administration |
| Volume of distribution |
Not Available |
| Protein binding |
Very high (93%) |
| Metabolism |
Extensively metabolized (gastrointestinal and hepatic). |
| Route of elimination |
Cyclobenzaprine is extensively metabolized, and is excreted primarily as glucuronides via the kidney. |
| Half life |
18 hours (range 8-37 hours) |
| Clearance |
|
| Toxicity |
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. |
