SOFOSBUVIR IS A SUBSTRATE OF DRUG TRANSPORTER P-GP AND BREAST CANCER RESISTANCE PROTEIN (BCRP). DRUGS THAT ARE P-GP INDUCERS IN THE INTESTINE (E.G., RIFAMPIN OR ST. JOHN'S WORT) MAY DECREASE SOFOSBUVIR PLASMA CONCENTRATION, LEADING TO REDUCED THERAPEUTIC EFFECT OF SOFOSBUVIR. COADMINISTRATION OF AMIODARONE WITH SOFOSBUVIR IN COMBINATION WITH ANOTHER DAA MAY RESULT IN SERIOUS SYMPTOMATIC BRADYCARDIA. COADMINISTRATION OF SOFOSBUVIR WITH CARBAMAZEPINE, PHENYTOIN, PHENOBARBITAL OR OXCARBAZEPINE IS EXPECTED TO DECREASE THE CONCENTRATION OF SOFOSBUVIR. COADMINISTRATION OF SOFOSBUVIR WITH RIFABUTIN OR RIFAPENTINE (HIV PROTEASE INHIBITOR) IS EXPECTED TO DECREASE THE CONCENTRATION OF SOFOSBUVIR. COADMINISTRATION OF SOFOSBUVIR WITH TIPRANAVIR/RITONAVIR IS EXPECTED TO DECREASE THE CONCENTRATION OF SOFOSBUVIR.
IN CLINICAL TRIALS NO DOSE ADJUSTMENT WAS NEEDED FOR EITHER DRUG IN CASE OF CYCLOSPORINE, DARUNAVIR/RITONAVIR, EFAVIRENZ, EMTRICITABINE, METHADONE, ORAL CONTRACEPTIVES, RALTEGRAVIR, RILPIVIRINE, TACROLIMUS, OR TENOFOVIR DISOPROXIL FUMARATE.