This study analyzes the effectiveness of extracts from five plant species used for treating venomous snakebites in the region of Santarém, in central Brazilian Amazonia. The aqueous extracts of Bellucia dichotoma Cogn., Connarus favosus Planch., Aniba fragrans Ducke, Plathymenia reticulata Benth., and Philodendron megalophyllum Schott were prepared by decoction at 70°C and lyophilized. Inhibition of the enzymatic activity and biological effects of the crude venom of Bothrops atrox was tested by preincubating different concentrations (1:1 to 1:30 venom:extract, w/w) for 30 min at 37°C. These results confirm traditional local knowledge on the anti-toxin powers of the native plants of the Amazon basin and the potential of these extracts as toxin inhibitors and as an alternative or complement for the standard treatment of snakebite based on the application of antisera.