Istradefylline 40 mg/working day elevated peak levels and AUC of CYP3A4 substrates in clinical trials. This effect wasn't observed with istradefylline 20 mg/working day. Consider dose reduction of delicate CYP3A4 substrates.If coadministration of CYP3A4 inhibitors with fentanyl is necessary, watch patients for respiratory depression and sedation at… Read More