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Drug Interactions between indinavir and Zelboraf

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

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Interactions between your drugs

Moderate

indinavir vemurafenib

Applies to: indinavir and Zelboraf (vemurafenib)

MONITOR: Coadministration with potent inhibitors of CYP450 3A4 may increase the plasma concentrations of vemurafenib, which has been shown in vitro to be a substrate of the isoenzyme. Because vemurafenib is associated with concentration-dependent prolongation of the QT interval, increased levels may potentiate the risk of ventricular arrhythmias such as torsade de pointes and sudden death. However, clinical and pharmacokinetic data are currently lacking. A reverse interaction may also occur, since many CYP450 3A4 inhibitors are also substrates of the isoenzyme and vemurafenib is an inducer. The possibility of diminished pharmacologic effects of these agents should be considered during coadministration with vemurafenib.

MANAGEMENT: Caution is advised if vemurafenib is prescribed in combination with potent CYP450 3A4 inhibitors such as itraconazole, ketoconazole, voriconazole, nefazodone, delavirdine, protease inhibitors, and ketolide and certain macrolide antibiotics. ECG and serum electrolytes, including potassium, magnesium and calcium, should be monitored regularly, and treatment interrupted if QTc exceeds 500 ms. Any electrolyte abnormalities must then be corrected and cardiac risk factors for QT prolongation (e.g., congestive heart failure, bradyarrhythmias) under control prior to resuming treatment. Vemurafenib may be restarted once QTc decreases below 500 ms, but at a reduced dosage as described in the product labeling. Permanent discontinuation of treatment is recommended if, after correction of associated risk factors, both the QTc is greater than 500 ms and the QTc increase is greater than 60 ms from pretreatment values. Patients should be advised to seek medical attention if they experience symptoms that could indicate the occurrence of torsade de pointes such as dizziness, palpitations, irregular heartbeat, shortness of breath, or syncope. In addition, many CYP450 3A4 inhibitors are also substrates of the isoenzyme, thus pharmacologic response to these agents should be monitored during coadministration with vemurafenib.

References

  1. "Product Information. Zelboraf (vemurafenib)." Genentech (2011):

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Drug and food interactions

Moderate

indinavir food

Applies to: indinavir

ADJUST DOSING INTERVAL: According to the manufacturer, coadministration with a meal high in calories, fat, and protein reduces the absorption of indinavir. In ten patients given indinavir in this manner, the peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of indinavir decreased by an average of 84% and 77%, respectively. In contrast, grapefruit juice may have only minor effects on the oral bioavailability of indinavir. The manufacturer's package labeling states that administration of a single 400 mg dose of indinavir with 8 oz. of grapefruit juice decreased indinavir AUC by an average of 26%. Likewise, a study consisting of 14 HIV-infected subjects found no uniform nor significant changes in steady-state indinavir AUC during administration with double-strength grapefruit juice compared to water. There was, however, a delay in absorption (Tmax) due to grapefruit juice that is unlikely to be of clinical significance.

MANAGEMENT: To ensure maximal oral absorption, indinavir should be administered without food but with water 1 hour before or 2 hours after a meal. Alternatively, indinavir may be administered with other liquids such as skim milk, juice, coffee, or tea, or with a light meal (e.g., dry toast with jelly, juice, and coffee with skim milk and sugar; corn flakes, skim milk and sugar).

References

  1. "Product Information. Crixivan (indinavir)." Merck & Co., Inc PROD (2001):
  2. Yeh KC, Deutsch PJ, Haddix H, Hesney M, Hoagland V, Ju WD, Justice SJ, Osborne B, Sterrett AT, Stone JA, Woolf E, Waldman S "Single-dose pharmacokinetics of indinavir and the effect of food." Antimicrob Agents Chemother 42 (1998): 332-8
  3. Shelton MJ, Wynn HE, Newitt RG, DiFrancesco R "Effects of grapefruit juice on pharmacokinetic exposure to indinavir in HIV-positive subjects." J Clin Pharmacol 41 (2001): 435-42

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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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