In subjects receiving a methadone maintenance dose (32-100 mg once daily) coadministration of oral voriconazole (400 mg twice daily for 1 day, then 200 mg twice daily for four days) increased the Cmax and AUC of pharmacologically active R-methadone by 31% and 47%, respectively, whereas the Cmax and AUC of the S-enantiomer increased by approximately 65% and 103%, respectively.