MethocarbamolRx

Trade Names: Robaxin

Drug Class: Skeletal muscle relaxant

Preparations
Tablets: 500- and 750 mg
Injection: 100 mg/mL (10 mL)

Dose: Oral: between 2 and 4 g/day in three to six divided doses (the intravenous preparation is rarely indicated in the treatment of musculoskeletal disorders)

Indications: Treatment of painful muscle spasm; fibromyalgia

Mechanism of Action: Reduces spinal nerve traffic to skeletal muscle

Contraindications: Hypersensitivity to methocarbamol, renal impairment

Precautions: Use caution in hepatic and renal dysfunction and patients with seizures.

Pregnancy Risk: C

Adverse Effects
Common: Dizziness, drowsiness (although methocarbamol is less sedating than other muscle relaxants)
Uncommon: Allergy, flushing, rash, nausea, leukopenia. Urine may turn dark when left to stand.

Drug Interactions
Increased toxicity of CNS depressants

Patient Instructions: Avoid alcohol; may cause drowsiness

Comments: Nighttime sedative effect is sometimes useful in improving sleep in fibromyalgia. Little high-quality data to support or guide use.

Clinical Pharmacology: Rapid oral absorption; hepatic metabolism; renal excretion. Half-life is 1–2 hours.

Cost: $$