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Drug Interactions between fidaxomicin and nirmatrelvir / ritonavir

This report displays the potential drug interactions for the following 2 drugs:

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Interactions between your drugs

Minor

ritonavir fidaxomicin

Applies to: nirmatrelvir / ritonavir and fidaxomicin

Coadministration with inhibitors of P-glycoprotein (P-gp) may increase the plasma concentrations of fidaxomicin and its main metabolite, OP-1118, both of which are substrates of the intestinal efflux transporter. When fidaxomicin 200 mg was administered in combination with cyclosporine 200 mg in 14 study subjects, fidaxomicin peak plasma concentration (Cmax) and systemic exposure (AUC) increased by an average of 4.2- and 1.9-fold, respectively, compared to when administered alone. The Cmax and AUC of OP-1118 was increased by 9.5- and 4.1-fold, respectively, with cyclosporine. Theoretically, concentrations of fidaxomicin and OP-1118 may also be decreased at the site of action (i.e., gastrointestinal tract) due to P-gp inhibition. However, concomitant use of a P-gp inhibitor had no attributable effect on safety or efficacy of fidaxomicin in controlled clinical trials. No dosage adjustment is recommended when fidaxomicin is coadministered with P-gp inhibitors.

References (1)
  1. (2011) "Product Information. Dificid (fidaxomicin)." Optimer Pharmaceuticals

Drug and food interactions

Moderate

ritonavir food

Applies to: 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.

References (1)
  1. (2001) "Product Information. Norvir (ritonavir)." Abbott Pharmaceutical

Therapeutic duplication warnings

No warnings were found for your selected drugs.

Therapeutic duplication warnings are only returned when drugs within the same group exceed the recommended therapeutic duplication maximum.

See also

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Drug Interaction Classification

These classifications are only a guideline. The relevance of a particular drug interaction to a specific individual is difficult to determine. Always consult your healthcare provider before starting or stopping any medication.
Major Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit.
Moderate Moderately clinically significant. Usually avoid combinations; use it only under special circumstances.
Minor Minimally clinically significant. Minimize risk; assess risk and consider an alternative drug, take steps to circumvent the interaction risk and/or institute a monitoring plan.
Unknown No interaction information available.

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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