[Prevention of anaphylactoid reactions using intramuscular promethazine and cimetidine. Studies of a histamine infusion model].

The effect of combined intramuscular premedication with H1 + H2-receptor-antagonists on histamine-induced cardiovascular and cutaneous reactions was studied in 8 volunteers in a randomized placebo-controlled double-blind crossover trial and compared with premedication with H1-receptor antagonist alone and with the histamine-induced effects without premedication. As H1-receptor antagonist the volunteers received 0.5 mg/kg promethazine i.m. 45 min before the start of histamine infusion; as H2-receptor antagonist we used 400 mg cimetidine i.m. 120 min before application of histamine. While the premedication with promethazine alone could prevent histamine-induced tachycardia, fall of blood pressure and cutaneous reactions only partially, these reactions were almost completely prevented by combined premedication. Like intravenous application of H1 + H2-receptor antagonists shortly injected before induction of anesthesia, intramuscular premedication with promethazine and cimetidine can prevent anaphylactoid reactions. In contrast to intravenous application, the latter application is also effective in reducing the risk of acid aspiration syndrome and as a sedative.