Poster 08 - Early anaphylactic reactions after premedication with dexametasone in Bothrops snakebites

Poster 8. Congresso da Sociedade Brasileira de Toxinologia, 8., Symposium of the Pan American Section of the International Society on Toxinology, 8., 2004, Angra dos Reis, Brasil. Abstracts... J. Venom. Anim. Toxins incl.Trop. Dis., 2004, 10, 3, p.367.

Early anaphylactic reactions after premedication with dexametasone in Bothrops snakebites antivenom therapy.

^{1Fan, H.W.; ¹Málaque, C.M.S.; ¹Medeiros, C.R.; ¹Cardoso, J.L.C.; ¹Ferrari, R.F.; ¹Vicente, P.M.; ²Sano-Martins, I.S.; ²Gonçalves, L.R.; ²Tomy, S.C.; ³Rocha, G.C.; ³Clissa, P.B.; ³}Barbaro, K.C.; ¹França, F.O.S.

1 Vital Brazil Hospital, 2 Laboratory of Pathophysiology, 3 Laboratory of Immunopathology Butantan Institute, São Paulo, Brazil

In Brazil, more than 20,000 snakebites are registered yearly and almost 90% are caused by the genus Bothrops. Specific treatment is based on infusion of heterologous antibodies which may cause side effects. Symptomatology of early anaphylactic reactions, such as urticaria, vomiting, bronchospasm may occur during antivenom infusion and, in some cases, lead to glotis edema and shock. Different drugs have been used to prevent or reduce frequency of these reactions, but few clinical trials have been conducted to test the efficacy of pre-medication. This study evaluated the effect of diphenydramine and dexamethasone in preventing early anaphylactic reactions caused by specific antivenom. A randomized double-blinded clinical trial was performed at Hospital Vital Brazil, Instituto Butantan, during January 2002 to April 2004. Antivenom therapy was given in accordance to Ministry of Health’s guidelines and based on clinical severity. All patients received diphenydramine 50 mg i.v. During the period 115 patients were randomly allocated to receive either placebo (n=58) or dexamethasone (n=57), 12 mg or 0.15mg/kg, i.v. previously to antivenom therapy. Eight to 12 hours after antivenom therapy capsules of placebo or dexamethasone 0.15 mg/kg were given orally each 12 hours for 3 days to test the efficacy of corticosteroid in reducing local inflammatory signs. Both groups are homogeneous in terms of age and sex of patients, severity of envenoming, time elapsed between accident and treatment and other clinical parameters. Of the 115 patients, 10 (17.2%) of the placebo group and 8 (14.0%) of the dexametasone group presented early reactions (p=0.826): urticaria, wheeziness, cough, bronchospasm, nausea/vomiting, abdominal pain, itching, hypotension and sudoresis. Number of vials was not statistically associated to reaction appearance. Severity of reactions was not different between groups. These results indicate that dexamethasone is not able to prevent or reduce the occurrence of early anaphylactic reactions. On the other hand, comparison with previous studies suggests that reduction of the global frequency of early reactions may be associated with the use of antihistamines, specifically diphenydramine given intravenously.