Drug Interactions between abiraterone and nirmatrelvir / ritonavir

ADJUST DOSING INTERVAL: Administration with food may modestly affect the bioavailability of ritonavir from the various available formulations. When the oral solution was given under nonfasting conditions, peak ritonavir concentrations decreased 23% and the extent of absorption decreased 7% relative to fasting conditions. Dilution of the oral solution (within one hour of dosing) with 240 mL of chocolate milk or a nutritional supplement (Advera or Ensure) did not significantly affect the extent and rate of ritonavir absorption. When a single 100 mg dose of the tablet was administered with a high-fat meal (907 kcal; 52% fat, 15% protein, 33% carbohydrates), approximately 20% decreases in mean peak concentration (Cmax) and systemic exposure (AUC) were observed relative to administration after fasting. Similar decreases in Cmax and AUC were reported when the tablet was administered with a moderate-fat meal. In contrast, the extent of absorption of ritonavir from the soft gelatin capsule formulation was 13% higher when administered with a meal (615 KCal; 14.5% fat, 9% protein, and 76% carbohydrate) relative to fasting.

MANAGEMENT: Ritonavir should be taken with meals to enhance gastrointestinal tolerability.

ADJUST DOSING INTERVAL: Food may significantly increase the oral bioavailability of some formulations of abiraterone acetate. Compared to administration in the fasted state, abiraterone peak plasma concentration (Cmax) and systemic exposure (AUC) were approximately 7- and 5-fold higher, respectively, when a single dose of abiraterone acetate was administered with a low-fat meal (7% fat; 300 calories) and approximately 17- and 10-fold higher, respectively, when it was administered with a high-fat meal (57% fat; 825 calories). Given the normal variation in the content and composition of meals, taking abiraterone acetate with meals has the potential to result in increased and highly variable exposures. The safety of these increased exposures during multiple dosing has not been assessed. However, the abiraterone acetate 125 mg tablet, commonly marketed as Yonsa, was found to have an approximately 6.5-fold higher Cmax and 4.4-fold higher AUC when a single dose of 500 mg (4 tablets) was administered with a high-fat meal (56% - 60% fat, 900 - 1000 calories) compared to overnight fasting in healthy volunteers. These differences were not considered clinically significant for this formulation.

MANAGEMENT: Some formulations of abiraterone acetate must be taken on an empty stomach. No food should be consumed for at least two hours before and one hour after the abiraterone acetate dose. However, the abiraterone acetate 125 mg tablet, commonly marketed as Yonsa, can be taken with or without food. The manufacturer's product labeling should be consulted for specific guidance.