Arzneimittel Forsch
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Arzneimittel Forsch · Sep 1998
Comparative Study Clinical Trial Controlled Clinical TrialPharmacokinetics of tramadol and bioavailability of enteral tramadol formulations. 3rd Communication: suppositories.
The pharmacokinetics and the absolute bioavailability of tramadol hydrochloride (CAS 36282-47-0) after rectal administration of tramadol suppositories (Tramal) were determined in a balanced crossover study in 10 female volunteers in comparison with the intravenous injection. Each fasting volunteer received two single doses of 100 mg tramadol-HCl, one rectally (1 suppository) and one intravenously (2 ml of a solution for injection). The formulations were administered in the morning, the washout period was one week. ⋯ In the terminal phase the biological half-life (t1/2, beta) was 5.7 +/- 1.0 h (rectal) and 5.7 +/- 0.9 h (i.v.), respectively. The values determined after i.v. injection for the total distribution volume and the total clearance were 216 +/- 231 (Vd, beta) and 447 +/- 56 ml/min (Cltot). The results show that after rectal administration of the tramadol suppositories the absorption of the active ingredient is rapid enough for therapeutic purposes and that the extent of the absolute bioavailability is higher than after oral administration of tramadol-HCl, probably due to a reduced first-pass metabolisation after rectal administration.