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Drug Interactions between nirmatrelvir / ritonavir and oxtriphylline

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

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Interactions between your drugs

Moderate

oxtriphylline ritonavir

Applies to: oxtriphylline and nirmatrelvir / ritonavir

MONITOR: The coadministration with ritonavir may decrease the plasma concentrations of theophylline. The proposed mechanism is ritonavir induction of CYP450 1A2, the isoenzyme responsible for the metabolic clearance of theophylline. In a study involving 27 subjects, ritonavir (500 mg orally every 12 hours for 10 days) decreased the steady-state peak plasma concentration (Cmax), area under the concentration-time curve (AUC), and trough concentration (Cmin) of theophylline (3 mg/kg every 8 hours) by 32%, 43%, and 57%, respectively, compared to placebo. The half-life also decreased from 8.4 hours at baseline to 3.6 hours after 10 days of ritonavir.

MANAGEMENT: During coadministration with ritonavir, the possibility of a diminished therapeutic response to theophylline should be considered. Dosage adjustment as well as clinical and laboratory monitoring may be appropriate whenever ritonavir is added to or withdrawn from therapy.

References (2)
  1. (2001) "Product Information. Norvir (ritonavir)." Abbott Pharmaceutical
  2. Hsu A, Granneman GR, Witt G, Cavanaugh JH, Leonard J (1996) "Assessment of multiple doses of ritonavir on the pharmacokinetics of theophylline." Int Conf AIDS, 11, 89(ab.no.mo.b.1200)

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.

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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

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