A randomized blinded clinical trial of two antivenoms, prepared by caprylic acid or ammonium sulphate fractionation of IgG, in Bothrops and Porthidium snake bites in Colombia: correlation between safety and biochemical characteristics of antivenoms

A randomized blinded clinical trial was performed in 53 patients bitten by Bothrops sp. and Porthidium. sp. in Antioquia and Choco,Colombia, in order to compare the efficacy and safety of two antivenoms made of whole IgG obta ined by either ammonium sulphate (monovalent anti-B. atrox) or caprylic aci d (polyvalent) fractionation. Additionally, antivenoms were compared by ele ctrophoretic and chromatographic analyses and anticomplementary activity in vitro. With a protocol of 2, 4 and 6 antivenom vials for the treatment of mild, moderate and severe envenomings, respectively, both antivenoms were e qually efficient to neutralize the most relevant signs of envenoming and to clear serum venom levels in patients from the first hour and later on. Thr ee patients with severe envenoming and initially treated with less than six vials on admission had persistent or recurrent venom antigenemia within 12 -48 h. Monovalent antivenom fractionated by ammonium sulphate precipitation had higher amounts of protein aggregates and nonimmunoglobulin proteins th an polyvalent antivenom fractionated by caprylic acid precipitation. Both a ntivenoms presented anticomplementary activity in vitro, being higher in th e monovalent product. In agreement, monovalent antivenom induced a signific antly higher incidence of early antivenom reactions (52%) than polyvalent a ntivenom (25%). (C) 1999 Elsevier Science Ltd. All rights reserved.