Orphenadrine
Orphenadrine. Anticholinergic + NMDA antagonist + weak NET inhibitor — centrally-acting muscle relaxant for acute musculoskeletal pain.… Oral half-life 20 h.
Anticholinergic + NMDA antagonist + weak NET inhibitor — centrally-acting muscle relaxant for acute musculoskeletal pain. Anticholinergic burden similar to cyclobenzaprine; Beers-list problematic.
PK: the intravenous row hung on an ORAL-ONLY study of five subjects and one tablet, so F 0.9 was not merely unsourced but unmeasurable from it; that route is removed, as is the intramuscular one, which has no parameters and no citation anywhere. The stored 16.5 h was the MIDPOINT of a stated "The elimination half-life ranged from 13.2-20.1h". THE UPPER ENDPOINT IS STORED DELIBERATELY, against this batch usual lower-endpoint convention, because the same paper shows the kinetics are NON-STATIONARY: "The elimination half-lives after discontinuation of treatment showed a 2 to 3-fold increase over the single dose values", attributed to product inhibition by its own N-demethyl metabolite. Any single-dose value is therefore too short for a chronically dosed subject, and the lower endpoint would be the least representative. V 400 L is unsourced; logged for future readers, 400 appears in this literature as a DOSE in mg, from a paediatric ingestion.
Pharmacokinetics
- Oral — t½ 20.1 h
Sources: PMID:7056281