RESUMEN
Heparin, in some regions of Brazil has been used in the treatment of bothropic accidents, but the data found in the literature are inconclusive about its effectiveness. The venoms of Bothrops atrox and of B. erythromelas were characterized according to their biological activities. The capacity of heparin in neutralizing these activities was tested with doses of 3 and 6 IU in isolated form and associated to Antibothropic Serum (ABS). It was verified that heparin, in doses of 3 and 6 IU, was not effective in neutralizing the desfibrinating and edema-forming activities of B. atrox venom and the hemorrhagic and coagulant actions of both venoms. Heparin diminished the effectiveness of the ABS in the neutralization of the hemorrhagic and edema-forming activities of the B. atrox venom. However, heparin in the 6 IU dose was capable of neutralize the edema-forming of the B. erythromelas and increase the effectiveness of the ABS. Heparin also neutralized the phospholipasic A2 activity of B. atrox (14.3 percent) and B. erythromelas (28.0 percent) venoms. For B. erythromelas venom, the associated treatment, heparin and ABS, was more effective in the neutralization of its lethal activity