Bioequivalence study of tramadol by intramuscular administration in healthy volunteers

Tramadol hydrochloride (CAS 36282-47-0) is a centrally acting analgesic age nt binding toy opiate receptors. The bioavailability of a new tramadol hydr ochloride injection (Limadol(R)) was compared with a commercially available reference product by intramuscular administration in twelve healthy Chines e male volunteers by a standard two-way cross-over trial. Each volunteer re ceived a single 100 mg injection of tramadol HCl in each phase. The bioavai lability was compared using the area under the plasma concentration-time cu rve from time 0 to 30 h (AUC(0-30)), the area under the plasma concentratio n-time curve from time 0 to infinity (AUC(0-infinity)), peak plasma concent ration (C-max), and time to reach peak plasma concentration (T-max). No sta tistically significant difference was observed between the T-max, C-max, AU C(0-30) and AUC(0-infinity) of the two preparations It is concluded that te st and reference formulations of tramadol hydrochloride are bioequivalent f or both the extent and rare of absorption after a single intramuscular inje ction.