Dimenhydrinate
Dimenhydrinate. Salt of diphenhydramine + 8-chlorotheophylline — anti-motion-sickness via H1 + muscarinic blockade. OTC. Same anticholinergic… Oral half-life 8.4 h.
Salt of diphenhydramine + 8-chlorotheophylline — anti-motion-sickness via H1 + muscarinic blockade. OTC. Same anticholinergic burden as diphenhydramine; the theophylline component is incidental.
PK: the old citation was a CHEWING-GUM study, so the intravenous row had no arm behind it and the stored 8 h came from a sustained-release formulation. Re-sourced to PMID:3760245, ten subjects given 50 mg intravenously and orally: half-life 8.4 h, steady-state volume 4.5 L/kg (315 L at 70 kg, a true intravenous volume) and oral F 0.72. THE MOLECULAR WEIGHT IS THE SALT AND THE PHARMACOLOGY IS NOT: dimenhydrinate is diphenhydramine paired with 8-chlorotheophylline, so all of the above describes DIPHENHYDRAMINE at mw 255.35 while the record carries 469.97. About 54% of a dimenhydrinate dose is active drug, and any molar conversion here is 1.84x wrong until the schema can express a salt-to-active factor. ka 0.7 /h dropped; the 2.6 h beside it is a Tmax.
Pharmacokinetics
- Oral — t½ 8.4 h · F 72% · Vd 315 L
- IV — t½ 8.4 h · F 100% · Vd 315 L
Sources: PMID:12851661, PMID:3760245