Treatment of Isoniazid Overdose

To the Editor.— The recent article by Wason et al (1981;246:1102) reemphasizes the efficacy of high-dose pyridoxine hydrochloride (vitamin B6) treatment of acute isoniazid overdose. During the past decade, in the Indian Health Service (IHS), more than 150 Native Americans with isoniazid overdose have been successfully treated with intravenous (IV) administration of pyridoxine in doses equivalent to the estimated amount of isoniazid ingested (personal experience of two of us—M.L.S. and R.N.H.—and personal communications from IHS physicians). In sufficient dosage, pyridoxine administered IV can reverse the severe toxic effects of isoniazid overdose and prevent death in humans and animals,1-5but the excessive amount of isoniazid ingested is often unknown. Furthermore, the large dose of pyridoxine that is recommended (equal to the estimated overdose of isoniazid1,2) may not be readily available in all hospitals. These circumstances may result in inadequate antidotal treatment with pyridoxine. If the response to pyridoxine