Drug Interaction Report

MONITOR CLOSELY: Coadministration of ponesimod with antineoplastic, immunosuppressive, or other immune-modulating therapies may increase the risk of unintended additive immunosuppressive effects. Ponesimod causes reversible sequestration of lymphocytes in lymphoid tissues. When administered daily, ponesimod produces a dose-dependent reduction in peripheral lymphocyte count to 30% to 40% of baseline values, which may increase the risk of infections. Life-threatening and rare fatal infections have been reported in association with sphingosine 1-phosphate (S1P) receptor modulators. Decreased lymphocyte counts persist during chronic daily dosing and generally return to normal within 1 week after stopping the medication. Because residual pharmacodynamic effects, such as decreased peripheral lymphocytes, may persist for 1 to 2 weeks after the last dose, use of immunosuppressants during this time may also lead to additive immune effects.

MANAGEMENT: The safety and efficacy of ponesimod in combination with antineoplastic, immunosuppressive, or immune-modulating agents have not been evaluated. Caution is advised during coadministration and for 1 to 2 weeks after the last dose of ponesimod. When switching from drugs with prolonged immune effects to ponesimod, the half-life and mode of action of these drugs must be considered to avoid unintended additive immunosuppressive effects while at the same time minimizing risk of disease reactivation.

Food may have variable effects on the oral bioavailability of zidovudine. Fatty foods have been reported to decrease the rate and extent of zidovudine absorption following oral administration. In a study of 13 AIDS patients, mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of zidovudine were 2.8 and 1.4 times higher, respectively, in fasting patients than in those administered the medication with breakfast. In addition, variations in plasma zidovudine concentrations were increased when administered in the fed state. In another study of eight patients, the time to reach peak concentration (Tmax) was increased from 0.68 to 1.95 hours, and Cmax was reduced by 50% when zidovudine was administered with a liquid high-fat meal relative to fasting. Protein meals can also delay the absorption and reduce the Cmax of zidovudine, although the extent of absorption is not significantly affected. The clinical significance of these alterations, if any, is unknown. The product labeling states that zidovudine may be taken with or without food.