Drug Interaction Report

GENERALLY AVOID: Antibiotics may interfere with the anti-tumor activity of intravesical BCG, which contains a live, attenuated strain of Mycobacterium bovis. Some researchers have suggested that antibiotic therapy prior to or concurrently with BCG therapy may affect therapeutic efficacy via changes in the urinary microbiome. It is considered contraindicated to use intravesical BCG in patients with concurrent febrile illness, active tuberculosis, and/or urinary tract infections. Intravesical BCG is sensitive to most antibiotics, particularly those that are routinely used in the treatment of tuberculosis such as streptomycin, para-aminosalicylic acid (PAS), isoniazid (INH), rifampin, and ethambutol. It is reportedly not sensitive to pyrazinamide or cycloserine. Regardless of clinical susceptibility data, however, most antibacterials may still interfere with BCG in the bladder due to their high urinary recovery. One retrospective study in 276 high-risk non-muscle invasive bladder cancer patients receiving intravesical BCG reported a significantly higher 5-year recurrence-free survival rate in patients who did not receive antibiotic therapy than in those treated with long-course (>=7 days) antibiotics (ciprofloxacin, levofloxacin, cefaclor, cefpodoxime, or cefixime).

MANAGEMENT: Intravesical BCG should not be used in individuals with concurrent infections. For patients being treated with antibiotics, intravesical instillations of BCG should generally be postponed until completion of antibiotic therapy. If a bacterial urinary tract infection (UTI) occurs, therapy with intravesical BCG should be postponed or interrupted until complete resolution of the infection (e.g., negative urine culture and completion of antibiotic(s) and/or urinary antiseptic(s)), not only because antimicrobial administration may diminish the anti-tumor efficacy of BCG, but also because the combination of a UTI and BCG-induced cystitis may lead to more severe adverse effects in the genitourinary tract. There are no data to suggest that the acute, local urinary tract toxicity common with intravesical administration of BCG is due to mycobacterial infection, thus antituberculosis drugs should not be used to prevent or treat the local, irritative toxicities of intravesical BCG.