[Drug-induced fever caused by prophylactic isoniazid in bladder instillations with BCG].

We present of one patient with isolated pharmacological fever probably caused by Isoniazid given prophylactically 24 hours prior to each vesical instillation with BCG as maintenance therapy for in situ vesical carcinoma. The fever appeared in two occasions before the instillation and did not returned once the drug was discontinued. We Review this adverse effect which may lead to diagnostic error.