Abstract: Pharmaceutical formulation for the prophylaxis, pretreatment and treatment of a poisoning caused by exposure to (either singly or as a mixture of agents) organophosphorus cholinesterase inhibitors, vesicating agents, polycyclic aromatic hydrocarbons, and aflatoxin B1. This invention is characterized by active substance comprised of a metaloporphyrin molecule with an associated metal moiety (Cu, Mg) of suitable purity and chemical composition to provide a bioavailable oral dosage form to attain predictable concentrations in target tissues and bodily fluids (plasma, bronchial secretions, etc.) sufficient to counteract the effects of toxic substances through chemical complexation or catalysis of toxin degradation. Although these metaloporphyrins are semisynthetic products of chlorophyll, the preferred starting material is chlorophyll a (Chla) extracted and purified from Spirulina pacifica or other sources.