Cyclobenzaprine is a centrally-acting skeletal muscle relaxant structurally related to tricyclic antidepressants (TCAs). It is indicated as an adjunct to rest and physical therapy for the relief of muscle spasm associated with acute, painful musculoskeletal conditions. Its primary effect is on the central nervous system (CNS) at the brainstem level, reducing tonic somatic motor activity, influencing both gamma and alpha motor neurons, without directly affecting skeletal muscle fibers or the neuromuscular junction.
Adult: 5 mg orally three times a day. Based on patient response, the dose may be increased to 10 mg three times a day. Use should not exceed 2-3 weeks.
Note: May be taken with or without food. Taking with food may reduce gastrointestinal upset. Tablet should be swallowed whole with a glass of water. Avoid alcohol. Typically prescribed for short-term use (2-3 weeks).
Cyclobenzaprine reduces tonic somatic motor activity, influencing both gamma (fusimotor) and alpha motor neurons. Its primary site of action is the brainstem, specifically the locus coeruleus and the reticular formation. It does not act at the neuromuscular junction or directly on skeletal muscle.
Pregnancy: Pregnancy Category B (US FDA). Animal studies have shown no risk, but no adequate and well-controlled studies in pregnant women. Use only if clearly needed. Consider risk-benefit.
Driving: ADVISE NOT TO DRIVE or operate heavy machinery. The drug causes drowsiness, dizziness, and blurred vision which impair abilities.
| Monoamine Oxidase Inhibitors (MAOIs) e.g., Phenelzine, Selegiline | Risk of hyperpyretic crisis, seizures, death. Serotonin syndrome. | Contraindicated |
| Other CNS Depressants (Alcohol, Benzodiazepines, Opioids) | Additive CNS depression, impaired alertness, respiratory depression. | Major |
| Tramadol, SSRIs (e.g., Fluoxetine), SNRIs (e.g., Venlafaxine) | Increased risk of serotonin syndrome. | Major |
| Anticholinergics (e.g., Atropine, Oxybutynin, TCAs) | Additive anticholinergic effects (dry mouth, constipation, urinary retention, confusion). | Moderate |
| QT-prolonging agents (e.g., Fluoroquinolones, Antiarrhythmics) | Additive risk of QT prolongation and torsades de pointes. | Moderate |
| CYP3A4 Inhibitors (e.g., Ketoconazole, Clarithromycin) | Increased cyclobenzaprine plasma levels, risk of toxicity. | Moderate |
| CYP3A4 Inducers (e.g., Rifampicin, Carbamazepine) | Decreased cyclobenzaprine plasma levels, reduced efficacy. | Moderate |