Decreased local toxicity with subcutaneous diamorphine (heroin): a preliminary report. We report the cases of 5 patients who developed severe local toxicity during the subcutaneous administration of morphine sulphate and hydromorphone hydrochloride. All patients required site changes more frequently than once every 24 h due to redness, swelling, or pain while receiving morphine or hydromorphone. All patients showed prolongation in the duration of sites of infusion once an equianalgesic dose of diamorphine hydrochloride (heroin) was started. No change in pain control or systemic toxicity was detected with diamorphine. These findings suggest that diamorphine could be a useful alternative for patients who develop severe toxicity to subcutaneous morphine or hydromorphone. 