Acute isoniazid exposures and antidote availability

Over the past 10 years the reported incidence of acute isoniazid (INH)-related poisonings has increased, with 507 cases reported in 1996. Parenteral pyridoxine is the antidote for INH-induced seizures, but 5-g aliquot recommended to treat an ingestion of unknown quantity of INH is not always readily available to emergency physicians.

To determine the hospital availability of pyridoxine.

One hundred thirty questionnaires were distributed nationwide to the pharmacies and emergency departments (ED) of hospitals containing pediatric emergency medicine (PEM) fellowships and/or emergency medicine (EM) residencies. Questions were posed regarding the availability, quantity, location, and deemed importance of pyridoxine at each institution.

Responses were received from 81% of the hospitals with fellowships and 80% of the hospitals with residencies. Half of the former and one third of the latter reported not having the recommended 5-g aliquot available. Eighty percent of the hospitals with PEM programs and 71% with EM residencies with an adequate stock store it in the hospital's pharmacy, as opposed to in the ED. Thirty-four states were represented, 18 of which have experienced an increase in tuberculosis (TB) from 1993 to 1994; 6/18 (33%) of those did not have the pyridoxine available, and 7/18 (39%) did not deem it necessary.

Our results imply that between one third and one half of the respondents would be ill-equipped to treat acute INH neurotoxicity. Establishing regional distribution centers may alleviate this deficiency, specifically in urban areas with a high incidence or a positive percent increase in TB.