Comparison of injection techniques for soluble and protamine zinc insulins in diabetes mellitus

Soluble and protamine zinc insulins were given to six insulin-dependent diabetic patients using three different techniques of administration to determine whether the recommended single injection of the insulins, from separate syringes with the needle redirected, compared more closely with separate injections or with a single injection from the same syringe. It was shown that the mixture of the two insulins in the same syringe resulted in both a significant loss of the initial rapid effect of soluble insulin and an increased protamine zinc action with the risk of late night-time hypoglycaemia. A single injection of the insulins, using separate syringes and redirecting needle, gave at least as satisfactory control of the 24-hour blood glucose profile as when they were given by separate injections.