Antihistamine for plasma-substitute and experimental histamine-induced reactions
It is unclear whether prophylactic antihistamine reduces plasma substitute and histamine-induced anaphylaxis because the certainty of evidence is very low (supplement S7d). One trial about prophylactic antihistamine prior to plasma substitute haemaccel found a 24% reduction in the incidence of anaphylaxis (statistically significant, CI not reported, very low certainty).11Lorenz W, Doenicke A, Dittmann I, Hug P, Schwarz B. Anaphylactoid reactions following administration of plasma substitutes in man. Prevention of this side-effect of haemaccel by premedication with H1- and H2-receptor antagonists. Anaesthesist 1977;26(12):644-648. Another trial of prophylactic antihistamine prior to intravenous histamine infusion found that intramuscular H1+H2 receptor-antagonist pre-treatment reduced reactions (numbers not reported, very low certainty).22Tryba M, Zevounou F, Zenz M. Prevention of anaphylactoid reactions using intramuscular promethazine and cimetidine. Studies of a histamine infusion model. Anaesthesist 1984;33(5):218-223.