Comparative plasma concentration profiles after I.V., I.M. and rectal administration of pethidine in children

Abstract

Summary: Plasma concentration-time curves of pethidine and norpethidine were studied in 25 children allocated after operation to three groups to receive pethidine 1 mg kg-1 i.v., i.m. or rectally. Peak concentrations occurred after 5± 1, 10 ± 2, and 60 ± 10 min, respectively, while the maximum concentrations amounted to 2800±462, 1609 ± 367 and 531 ±179 nmol litre-1, respectively. The area under the curve (0-240 min) was similarly reduced in the group with rectal administration (P < 0.05). Compared with the i.v. data, approximately 40% systemic availability occurred after rectal application, although considerable individual variastion was noted. In one child very high plasma concentrations were observed after rectal administration, possibly as a result of redistribution/recirculation phenomena. The average results are similar to those obtained when other opioids are given rectally. © 1988 Copyright: 1988 British Journal of Anaesthesia.