Double-blind comparison of the efficacy of extradural diamorphine, extradural phenoperidine and i.m. diamorphine following caesarean section.

A randomized, double-blind study of the efficacy, duration of action and side effects of three analgesic regimens following Caesarean section is described. Patients received i.m. diamorphine 5 mg, extradural phenoperidine 2 mg or extradural diamorphine 5 mg. Analgesia was of rapid onset in all groups, as judged by reductions in linear analogue pain scores and rank pain scores. Time to next analgesia was significantly greater after extradural phenoperidine (5.96 h) and extradural diamorphine (8.39 h) than after i.m. diamorphine (3.40 h) (P less than 0.001). Itching was reported on direct questioning by 50% of patients in the extradural groups. No serious side effects were reported. Factors affecting the disposition of extradurally administered diamorphine are discussed.