Severe febrile reaction to isoniazid.

A case of severe febrile reaction to INH is described. The patient had a mild febrile reaction two weeks following INH prophylaxis. Isoniazid was discontinued. Two weeks later and on rechallenge with INH she developed a severe febrile reaction with protracted hypotension. An initial mild febrile reaction to INH is a warning sign that rechallenge can result in a life-threatening situation.