May cause elevation of creatine phosphokinase & transaminase levels. Monitor unexplained muscle pain, tenderness or weakness (particularly if accompanied by malaise or fever); rhabdomyolysis w/ acute renal failure secondary to myoglobinuria when used alone or concomitantly w/ immunosuppressive therapy, fibrates or erythromycin in seriously ill patients. Perform liver function tests before initiation of treatment at 6 or 12 wk, after initiation of therapy or elevation in dose & periodically thereafter (ie, semiannually). Concomitant use w/ drugs (eg, ketoconazole, spironolactone, cimetidine) that may decrease the levels of activity of endogenous steroid hormones. Childn.