Carisoprodol
Carisoprodol. Skeletal muscle relaxant — pro-drug largely converted to meprobamate (a Schedule IV barbiturate-like sedative). Schedule IV; abuse… Oral half-life 2 h.
Skeletal muscle relaxant — pro-drug largely converted to meprobamate (a Schedule IV barbiturate-like sedative). Schedule IV; abuse potential + physical dependence are concerns. Outpatient acute musculoskeletal pain only short-term.
PK: Calvo 2022 (PMID:35160309), 13 healthy volunteers, 350 mg PO, verbatim "half-life (T1/2): 2 +/- 0.8 h". The half-life stored until 2026-09-06 was 8 h — the METABOLITE's figure. The same paper gives meprobamate 9 +/- 1.9 h, and three further studies put the parent at 1.6-2.1 h (PMID:7974621 "99 +/- 46 min", PMID:16021435 96 min in extensive metabolisers, PMID:24683250 1.74/1.96 h), so the record overstated carisoprodol's persistence roughly fourfold. ka, V and F dropped as unsourced: the previous citation (PMID:27758843) is a model-fitting reanalysis whose abstract says human Vd "has not been reported" and gives only a range, "the Vd for carisoprodol ranged from 0.93 to 1.3 L/kg", left unstored rather than collapsed to a midpoint. No human absolute bioavailability exists. CAVEATS: meprobamate is itself active and accumulates on repeated dosing where the parent does not, so one curve cannot represent both; CYP2C19 poor metabolisers show ~4x parent exposure (PMID:8946470).
Pharmacokinetics
- Oral — t½ 2 h
Sources: PMID:27758843, PMID:35160309, PMID:7974621, PMID:16021435