Methocarbamol (Robaxin)
Central-acting muscle relaxant related to guaifenesin. Mechanism not fully understood — likely acts through CNS depression at the level of the spinal cord and subcortical areas, reducing hyperactive stretch reflexes. Less sedating than cyclobenzaprine. Available OTC in some countries. Used for acute musculoskeletal pain and spasm. Well-absorbed orally, hepatically metabolized by dealkylation and hydroxylation.
Projected serum levels — 750 mg, once daily
Maintenance schedule: 750 mg once daily (oral).
Modeled steady state after ~1 days: peak ≈ 418 mg, trough ≈ 0.28 mg body load. Population-based estimate over 15 days for a 750 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.
Key facts
- Category
- Muscle Relaxant
- Route modeled
- Oral
- Model confidence
- inferred
- Half-life
- 1.5 h
- Common dose
- 750 mg
- Suggested maximum
- 6k mg/day
- Reference dose range
- 375–6k mg (single dose)
- Suggested cadence
- once daily
- Validated against
- 1.5k mg oral — Cmax 18 mg/L at 2 h
Research behind this entry
-
Efficacy of methocarbamol for acute low back pain: a randomized, double-blind, placebo-controlled trial
ED-based RCT (240 patients) evaluating methocarbamol as adjunct to naproxen for acute low back pain, with modest improvement in functional outcomes though the effect size was clinically small.
-
Comparative efficacy of skeletal muscle relaxants
Systematic review finding methocarbamol effective for acute musculoskeletal spasm with fewer CNS side effects than cyclobenzaprine, though lower potency, supporting its use when sedation must be minimized.
2 published studies referenced in the app, each with a plain-language summary.