A Comparison of the Acute Toxicity of Two Forms of Thiamine.

Summary There is little difference in the lethal dose of either thiamine hydrochloride or mononitrate and the symptoms of toxicity are the same for both forms of the drug. The toxic effects of both forms of the vitamin on respiration and blood pressure are due to their thiamine content and not to the pH of the injected solutions or to the substituent groups on the nitrogen of the thiazole nucleus. In lethal doses either form of the vitamin causes death by a direct paralyzing action on the respiratory center followed by cardiac failure.