RANDOMIZED COMPARATIVE TRIAL OF 3 ANTIVENOMS IN THE TREATMENT OF ENVENOMING BY LANCE-HEADED VIPERS (BOTHROPS-JARARACA) IN SAO-PAULO, BRAZIL

In Sao Paulo City, Brazil, 121 patients with moderately severe envenom ing by Bothrops snakes (principally B. jararaca) were randomized for t reatment with Brazilian polyspecific Bothrops antivenoms: Instituto Bu tantan (39 patients), Instituto Vital Brazil (41), Fundacao Ezequiel D ias (FUNED) (41). The initial dose was four ampoules (40 ml) in 89 pat ients with less severe envenoming and eight ampoules (80 ml) in 32 pat ients with more severe envenoming. A second dose of four ampoules was required in 20 patients. Patients receiving the three antivenoms were comparable in all respects before treatment. There were no deaths. The majority showed rapid clinical improvement, resolution of local enven oming, cessation of bleeding and restoration of blood coagulability. N o differences in the efficacy of the three antivenoms were revealed by clinical or laboratory observations, including measures of haematolog ical, haemostatic and biochemical abnormalities. Twelve patients devel oped abscesses (Butantan 1, Vital Brazil 6, FUNED 5) and seven develop ed local necrosis (3,1,3). Of 88 patients followed up 20-30 days after the bite 33 (37.5%) still had symptoms or signs of local envenoming, especially swelling. Early (anaphylactic) reactions were unexpectedly frequent after all three antivenoms but were significantly more freque nt with Butantan (87%) than with Vital Brazil (37%) or FUNED (56%) ant ivenoms (p < 0.001). A possible explanation was the higher total prote in content and percentage immunoglobulin of Butantan antivenom. The do ses of antivenom recommended in Brazil and used in this study may be u nnecessarily high, resulting in an unacceptably high incidence of reac tions. Results of the study should prompt a critical re-evaluation of antivenom production techniques and dosage recommendations in Brazil.