Stumbling blocks in the study of diamorphine.

Although the centenary of the discovery of diamorphine is soon to be celebrated, much work remains to be done before its mode of action is thoroughly understood. The main stumbling blocks facing the would-be investigator can be summarized as follows: (1) Diamorphine in solution has a limited shalf-life. (2) The potency ratio of diamorphine to morphine is still a matter of dispute. (3) No basic studies appear to have been carried out on the fate of orally administered diamorphine. (4) Current methods of assay are not sensitive enough to detect diamorphine or its metabolites in serum after the administration of the drug when given in therapeutic amounts. (5) The undersirable side-effects of diamorphine may vary according to posture and mobility. (6) As the metabolic handling of the drug may be different in the two sexes, provision for a between-sex comparison should be included in the design of a clinical trial of diamorphine.