Istradefylline

Strong CYP3A4 inhibitors: Recommended maximum dosage with concomitant use is 20 mg once daily ( 2.2 , 7.1 ). Strong CYP3A4 inducers: Avoid use ( 2.3 , 7.1 ).

7.1 Effect of Other Drugs on NOURIANZ Strong CYP3A4 Inhibitors Coadministration of NOURIANZ with a strong CYP3A4 inhibitor (ketoconazole) increased istradefylline AUC inf by 2.5-fold [see Clinical Pharmacology (12.3) ] . Therefore, the recommended maximum dosage of NOURIANZ in patients concomitantly using strong CYP3A4 inhibitors (e.g., itraconazole, ketoconazole, clarithromycin) is 20 mg once daily [see Dosage and Administration (2.2) ]. Strong CYP3A4 Inducers Coadministration of NOURIANZ with a strong CYP3A4 inducer (rifampin) decreased istradefylline C max and AUC inf by 45% and 81%, respectively [see Clinical Pharmacology (12.3) ] .

Therefore, it is recommended to avoid use of NOURIANZ with strong CYP3A4 inducers (e.g., carbamazepine, rifampin, phenytoin, St. John's wort) [see Dosage and Administration (2.3) ].

7.2 Effect of NOURIANZ on Other Drugs CYP3A4 Substrates Coadministration of NOURIANZ 20 mg with a CYP3A4 substrate (midazolam) did not affect the CYP3A4 substrate exposure, while concomitant administration of NOURIANZ 40 mg increased the CYP3A4 substrate (atorvastatin) C max and AUC inf by 1.5-fold [see Clinical Pharmacology (12.3) ] . Monitor for an increase in adverse reactions of concomitant drugs that are CYP3A4 substrates when coadministering with NOURIANZ 40 mg. P-glycoprotein (P-gp) Substrates Coadministration of NOURIANZ with a P-gp substrate (digoxin) increased the P-gp substrate C max and AUC inf by 33% and 21%, respectively [see Clinical Pharmacology (12.3) ] .

Monitor for an increase in adverse reactions of concomitant drugs that are P-gp substrates when coadministering with NOURIANZ.

8.1 Pregnancy Risk Summary There are no adequate data on the developmental risk associated with the use of NOURIANZ in pregnant women. In animal studies ( see Data ), oral administration of istradefylline during pregnancy resulted in teratogenicity (increased incidences of fetal structural abnormalities, embryofetal and offspring mortality and growth deficits) at clinically relevant exposures and in the absence of maternal toxicity. The teratogenic effects of istradefylline in pregnant rabbits were substantially greater when administered in combination with levodopa/carbidopa than when administered alone.

The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risks of major birth defects and miscarriage in clinically recognized pregnancies are 2-4% and 15-20%, respectively. Data Animal Data Oral administration of istradefylline (0, 40, 200, or 1000 mg/kg/day) to pregnant rats throughout organogenesis resulted in decreased fetal body weight and increased fetal skeletal and visceral variations at the highest dose tested.

Plasma exposure (AUC) at the no-effect dose for adverse effects on embryofetal development in rats (200 mg/kg/day) is approximately 4 times that in humans at the maximum recommended human dose (MRHD) of 40 mg. Oral administration of istradefylline (0, 50, 200, or 800 mg/kg/day) to pregnant rabbits throughout organogenesis resulted in increased embryofetal mortality at the mid and high doses, increased fetal malformations (external, visceral, skeletal) at all doses, and reduced fetal body weight at the highest dose tested. A no-effect dose for adverse effects on embryofetal development in rabbits was not identified.

Plasma exposure (AUC) at the lowest dose tested (50 mg/kg/day) is less than that in humans at the MRHD. In pregnant rabbits, oral administration of istradefylline (0, 50, 200, or 400 mg/kg/day) alone or in combination with oral levodopa/carbidopa (80/20 mg/kg/day) throughout the period of organogenesis resulted in an increase in embryofetal mortality and an increase (marked at the high dose) in malformations (including limb reduction, craniofacial, and cardiovascular) in fetuses from rats administered istradefylline at all doses in combination with levodopa/carbidopa.

Istradefylline alone resulted in an increase in embryofetal mortality and visceral malformations; no increase in fetal malformations was observed with levodopa/carbidopa alone. Fetal body weight was reduced by istradefylline alone (400 mg/kg/day) and in…