High-affinity Fab fragments (2 x 10(10) M-1) specific to colchicine were produced to evaluate their potency in reversing murine colchicine intoxication. Intraperitoneal injection of a 4.46 mg/kg colchicine dose was lethal for 100% of mice. 1.5 h after colchicine administration, a group of 10 mice was treated with colchicine-specific Fab fragments at a half-stoichiometrical dose compared to the colchicine dose by intravenous and intraperitoneal routes. 70% of the Fab-infused mice survived (P less than 0.01). This high efficiency of colchicine-specific Fab fragments in reversing acute murine colchicine toxicity suggests that Fab fragments would be an efficient antidote for the treatment of human colchicine poisoning.