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Drug Interactions between ritonavir and Torisel

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

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Interactions between your drugs

Major

ritonavir temsirolimus

Applies to: ritonavir and Torisel (temsirolimus)

GENERALLY AVOID: Coadministration of temsirolimus with potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of sirolimus, a major active metabolite of temsirolimus and known substrate of CYP450 3A4. According to the product labeling, administration of temsirolimus in combination with the CYP450 3A4 inhibitor ketoconazole resulted in a 2.2-fold and 3.1-fold increase in sirolimus peak plasma concentration (Cmax) and systemic exposure (AUC), respectively, compared to administration of temsirolimus alone. No significant effect on the pharmacokinetics of temsirolimus was reported.

MANAGEMENT: Concomitant use of temsirolimus with potent CYP450 3A4 inhibitors should generally be avoided. Some authorities recommend avoiding concomitant use of intravenous temsirolimus during and for 2 weeks after treatment with itraconazole (US). If coadministration is required, the manufacturer recommends reducing the temsirolimus dosage to 12.5 mg once a week. Based on pharmacokinetic studies, this dosage is predicted to adjust the sirolimus systemic exposure (AUC) to the range observed without inhibitors. However, clinical data are lacking. Following discontinuation of the potent CYP450 3A4 inhibitor, a washout period of approximately one week should be allowed before the temsirolimus dosage is adjusted upward to the normally recommended dosage (i.e., 25 mg once a week) or the dosage used prior to initiation of the CYP450 3A4 inhibitor.

References (3)
  1. (2002) "Product Information. Sporanox (itraconazole)." Janssen Pharmaceuticals
  2. (2007) "Product Information. Torisel (temsirolimus)." Wyeth-Ayerst Laboratories
  3. Cerner Multum, Inc. "Australian Product Information."

Drug and food interactions

Moderate

ritonavir food

Applies to: 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
Moderate

temsirolimus food

Applies to: Torisel (temsirolimus)

GENERALLY AVOID: Coadministration of temsirolimus with grapefruit juice may increase the plasma concentrations of sirolimus, a major active metabolite of temsirolimus and known substrate of CYP450 3A4. The proposed mechanism is inhibition of CYP450 3A4-mediated metabolism by certain compounds present in grapefruits.

MANAGEMENT: Patients treated with temsirolimus should preferably avoid the consumption of grapefruit or grapefruit juice.

References (1)
  1. (2007) "Product Information. Torisel (temsirolimus)." Wyeth-Ayerst Laboratories

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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