Purpose: We analyzed the influence of the tuberculostatic agent isoniazid on the incidence and severity of adverse effects of intravesical bacillus Calmette-Guerin (BCG) therapy in patients with superficial bladder cancer.
Materials and methods: In a prospective randomized multicenter study the side effects of intravesical instillations with Tice strain BCG with and without isoniazid were compared in patients with stages pTa and pT1 bladder tumors. Isoniazid was given orally at a dose of 300 mg. daily at every instillation in an attempt to decrease the side effects of BCG.
Results: No differences in local or systemic adverse reactions after intravesical immune therapy with BCG could be observed between patients treated with or without prophylactic isoniazid therapy. However, analysis of liver function tests after BCG with isoniazid showed slightly more liver toxicity compared to BCG alone.
Conclusions: Prophylactic administration of isoniazid during BCG instillations provides no decrease in any known side effect of BCG. In contrast, transient liver function disturbances are encountered slightly more frequently when isoniazid is administered. The use of prophylactic isoniazid in patients treated with BCG is not recommended.