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Megavitamin Therapy for Overdose

Maurice L. Sievers, MD; Richard D. Herrier, Pharm D
Arch Intern Med. 1980;140(12):1676. doi:10.1001/archinte.1980.00330230122036.
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To the Editor.  —We enjoyed reading the informative article by Herbert in the February Archives (140:173-176, 1980), especially the comments regarding megavitamin therapy. His three indications for such treatment-vitamin-dependent genetic disease, disease associated with defective cell membrane transport of vitamins, and as antidote to toxic effect of antivitamins—are comprehensive.In regard to the third category listed, however, it was not mentioned that megadoses of pyridoxine hydrochloride (vitamin B6) can abruptly reverse the dramatic life-threatening effects of acute isoniazid overdoses.1,2 Massive ingestion of isoniazid (in adults, 2 to 3 g is potentially toxic; 10 to 15 g, very high fatality rates) produces disturbed consciousness and intractable convulsions. In the brain, isoniazid interferes with the pyridoxine-mediated steps in the synthesis of γ-aminobutyric acid (GABA), resulting in reduction of GABA levels and seizures.1-3Recent studies in man and animals establish the efficacy and safety of large intravenous doses of pyridoxine


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