<p>In breast cancer patients with moderate hepatic dysfunction, no dosage adjustment is necessary, but caution is recommended since letrozole elimination depends mainly on intrinsic metabolic clearance. Renal impairment (calculated creatinine clearance: 20 to 50 ml/min) did not affect steady-state plasma letrozole concentration at a dose of 2.5 mg or 5 mg. Hence, no dose adjustment is necessary for such renal function impairment. It is anticipated that letrozole could be removed from blood by dialysis since it is weakly bound to plasma proteins. The potential risks and benefits to such patients should be considered carefully before prescribing letrozole. In some cases, fatigue and dizziness have been observed with the use of letrozole. Patients should therefore, be advised that their physical and/or mental abilities required for operating machinery or driving a car may be impaired.</p>