Choice of strong analgesic in terminal cancer: diamorphine or morphine?

A controlled trial of diamorphine (diacetylmorphine, heroin) and morphine is reported in which the two drugs were administered regularly by mouth in individually determined effective analgesic doses. Elixirs contained cocaine hydrochloride 10 mg/dose; other drugs were prescribed when indicated clinically. 699 patients entered the trial and, of these, 146 crossed from diamorphine to morphine, or vice versa, after about two weeks using an oral potency ratio of 1.5/1 determined in a pilot trial. Additional medication and survival were closely similar in both treatment groups. In the female crossover patients, no difference was noted in relation either to pain or the other symptoms evaluated. On the other hand, male crossover patients experienced more pain, and were more depressed, while receiving diamorphine. In these, the potency ratio of diamorphine to morphine appeared to be less than 1.5/1. If this is allowed for, then the difference in mood is probably not significant. Compared with male patients, fewer females required a dose of 10 mg or more, but more were prescribed an anxiolytic. The ability to do without a 2 a.m. dose appeared to be related more to the size of the dose than to gender or treatment. It is concluded that, provided allowance is made for the difference in potency, morphine is a satisfactory substitute for orally administered diamorphine. However, when injections are necessary, the greater solubility of its hydrochloride gives diamorphine an important practical advantage over morphine, especially when large doses are required.