Nourianz Disease Interactions

Istradefylline has not been studied in patients with severe hepatic impairment (Child-Pugh Class C), and its use should be avoided in these patients. In patients with moderate hepatic impairment (Child-Pugh B), the steady-state exposures were predicted to be 3.3-fold higher. Therefore, the maximum recommended dosage of istradefylline in patients with moderate hepatic impairment (Child-Pugh B) is 20 mg once daily. Patients should be closely monitored for adverse events when receiving treatment. No dose adjustment is needed in patients with mild hepatic impairment.

Istradefylline has not been evaluated in patients with end-stage renal disease (ESRD) (CrCl <15 mL/min) or ESRD requiring hemodialysis. Caution is advised if prescribed in these patients. No dosage adjustment is needed in patients with mild, moderate or severe renal impairment.

Because of the potential risk of exacerbating psychosis, patients with a major psychotic disorder should not be treated with istradefylline. Consider dosage reduction or discontinuation if a patient develops hallucinations or psychotic behaviors while taking this drug.

Tobacco smoking decreased systemic exposure to istradefylline by 38% to 54%, which may decrease efficacy. Therefore, the recommended dosage in patients who smoke 20 or more cigarettes per day (or the equivalent amount of another tobacco product) should be increased to 40 mg once daily.