Baclofen
Baclofen. GABA-B receptor agonist — pre- and post-synaptic K+ conductance activation reduces spinal cord motor neuron excitability. First-line… Oral half-life 3.9 h.
GABA-B receptor agonist — pre- and post-synaptic K+ conductance activation reduces spinal cord motor neuron excitability. First-line for spasticity in MS, spinal cord injury, cerebral palsy. Intrathecal pump for severe cases. Withdrawal seizures + rebound spasticity if abruptly stopped.
PK: Chevillard 2018 (PMID:29091319), population fit in 143 adults on oral baclofen, verbatim "mean values for clearance (CL/F), volume of distribution (V/F) and absorption rate constant at 8.0 L/h, 44.5 L and 2.23 h-1". Half-life is that fit's own ln2 x V/CL = 3.86 h. Taking all three from one fit keeps them mutually consistent; F is pinned to 1 because V is apparent. None of the values stored until 2026-09-06 came from the cited paper: PMID:27879195 is a two-tablet bioequivalence study reporting only tmax, Cmax and AUClast, and its "1.50" is a median tmax in HOURS, not the stored ka. The record's other reference (PMID:23973998) is a synthetic-chemistry SAR paper with no human PK. Alternatives not adopted, to avoid mixing fits: absolute bioavailability 74% in 12 healthy adults against IV (PMID:25028414), and healthy single-dose half-lives of 5.24 h PO / 5.79 h IV (PMID:27867020). CAVEAT: baclofen is renally cleared and clearance scales with GFR as 13.5 x (GFR/103)^0.839 (PMID:30826461), so a fixed-clearance curve understates exposure in renal impairment.
Pharmacokinetics
- Oral — t½ 3.9 h · F 100% · ka 2.23 h⁻¹ · Vd 44.5 L
Sources: PMID:23973998, PMID:29091319, PMID:25028414, PMID:27867020, PMID:30826461, PMID:2336342