The antitoxic properties of hepazan (dihydrothiazolexanthine), a new inductor of the microsomal enzyme system (MES) of liver were studied in white mice with the MES disorder induced by P. Aeruginosa toxin. It was found that hepazan not only eliminates the toxin-induced depression, but also decreases the toxic effects of ketoconazole, digoxin, and propranolol under the toxinemia conditions.