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Drug Interactions between Crixivan and gefitinib

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

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Interactions between your drugs

Moderate

indinavir gefitinib

Applies to: Crixivan (indinavir) and gefitinib

MONITOR: Coadministration with inhibitors of CYP450 3A4 may increase the plasma concentrations of gefitinib, which is primarily metabolized by the isoenzyme. According to the product labeling, administration of gefitinib (250 mg single dose) with the potent inhibitor itraconazole (200 mg once a day for 12 days) increased the mean gefitinib systemic exposure (AUC) by 88% in healthy male volunteers. This increase may be clinically significant, as adverse events of gefitinib are related to dose and exposure.

MANAGEMENT: Caution is advised if gefitinib is administered with CYP450 3A4 inhibitors, particularly potent ones like itraconazole, ketoconazole, posaconazole, voriconazole, clarithromycin, telithromycin, conivaptan, idelalisib, nefazodone, cobicistat, delavirdine, and most protease inhibitors. Pharmacologic response to gefitinib should be monitored more closely whenever a CYP450 3A4 inhibitor is added to or withdrawn from therapy, and the dosage adjusted as necessary. Patients should be advised to contact their physician if they experience possible symptoms of gefitinib toxicity such as severe diarrhea, nausea, dyspnea, cough, and fever.

References

  1. (2003) "Product Information. Iressa (gefitinib)." Astra-Zeneca Pharmaceuticals
  2. Li J, Zhao M, He P, Hidalgo M, Baker SD (2007) "Differential metabolism of gefitinib and erlotinib by human cytochrome p450 enzymes." Clin Cancer Res, 13, p. 3731-7

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Drug and food interactions

Moderate

indinavir food

Applies to: Crixivan (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. (2001) "Product Information. Crixivan (indinavir)." Merck & Co., Inc
  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 (1998) "Single-dose pharmacokinetics of indinavir and the effect of food." Antimicrob Agents Chemother, 42, p. 332-8
  3. Shelton MJ, Wynn HE, Newitt RG, DiFrancesco R (2001) "Effects of grapefruit juice on pharmacokinetic exposure to indinavir in HIV-positive subjects." J Clin Pharmacol, 41, p. 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.

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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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