Sequential randomised and double blind trial of promethazine prophylaxis against early anaphylactic reactions to antivenom for bothrops snake bites

Abstract

Objective To investigate the efficacy of the H 1 antihistamine promethazine against early anaphylactic reactions to antivenom. Design Sequential randomised, double blind, placebo controlled trial. Setting Public hospital in a venom research institute, São Paulo, Brazil. Participants 101 patients requiring antivenom treatment after being bitten by bothrops snakes. Intervention Intramuscular injection of promethazine (25 mg for adults and 0.5/kg for children) or placebo given 15-20 min before starting intravenous infusion of antivenom. Main outcome measures Incidence and severity of anaphylactic reactions occurring within 24 hours after antivenom. Results Reactions occurred in 12 of 49 patients treated with promethazine (24%) and in 13 of 52 given placebo (25%); most were mild or moderate. Continuous sequential analysis indicated that the study could be interrupted at the 22nd untied pair, without preference for promethazine or placebo. Conclusion Prophylaxis with promethazine does not prevent early reactions. Patients should be observed carefully during antivenom infusion and the subsequent few hours.

Clinical and epidemiological features of definitive and presumed loxoscelism in São Paulo, Brazil

“…In this way, antivenom is routinely given, in our hospital, in patients in which necrosis is still not present. The proportion of early anaphylactic reactions was not exceptionally high and similar to that observed for other antivenoms 10,12 , and manifestations were promptly reversed by proper measures.…”

Venomous snakebites and antivenom treatment according to a protocol for pediatric patients in taiwan

“…Subcutaneous adrenaline premedication produced a significant reduction in the incidence of early adverse reactions, and the effect was preserved when stratified for severity (23). But antihistamine appears to be of no obvious benefit in preventing acute reactions from antivenom (24). There is also no good evidence that hydrocortisone should be given before antivenom (25).…”

“…Although few patients presented skin rash, no anaphylaxis occurred in these 35 patients. However, in the last decade, studies of the efficacy and safety of premedication strategies have been conducted in Sri Lanka and Brazil (23,24). Subcutaneous adrenaline premedication produced a significant reduction in the incidence of early adverse reactions, and the effect was preserved when stratified for severity (23).…”

Adverse drug reaction profile of anti-snake venom in a rural tertiary care teaching hospital

“…Attempts to prevent early reactions which included pretreatment with epinephrine, anti-histaminics, corticosteroids and reduction in speed and concentration of intravenous antivenom administration have not been effective in adequately designed clinical trials. 13,14,15 However the studies by Premawardhena et al, 16 Gawarammana et al 17 and de Silve et al 18 have shown the efficacy of low dose adrenaline and combination of chlorpheniramine and hydrocortisone in reduction of antivenom reactions. A recent systematic review and meta-analysis 19 has shown the beneficial role of premedication with adrenaline in reduction of early antivenom reactions.…”