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Drug Interactions between amprenavir and gefitinib

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

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Interactions between your drugs

Moderate

amprenavir gefitinib

Applies to: amprenavir 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 Pharmacologic response to gefitinib should be monitored more closely whenever a CYP450 3A4 inhibitor is added to or withdrawn from therapy, and the dosage adjusted as necessary.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 (2)
  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

Drug and food interactions

Moderate

amprenavir food

Applies to: amprenavir

GENERALLY AVOID: Administration with a high-fat meal may decrease the oral bioavailability of amprenavir. The mechanism is unknown. In healthy volunteers, consumption of a standardized high-fat meal decreased the peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of amprenavir (1200 mg single oral dose) by 36% and 21%, respectively, compared to administration in the fasted state. The time to reach Cmax (Tmax) was increased 44% following a high-fat meal.

Grapefruit juice does not appear to significantly affect the pharmacokinetics of amprenavir. In 12 healthy volunteers, administration with grapefruit juice (200 mL) decreased the mean peak plasma concentration (Cmax) of amprenavir (1200 mg single oral dose) by 22% compared to water. The median time to reach Cmax (Tmax) was prolonged from 0.75 to 1.13 hours. These pharmacokinetic changes are not thought to be clinically significant, since antiretroviral response is more closely associated with systemic exposure (AUC) and trough plasma concentration (Cmin), which were not affected in the study.

MANAGEMENT: Amprenavir may be taken with or without food, but should not be taken with a high-fat meal.

References (2)
  1. (2001) "Product Information. Agenerase (amprenavir)." Glaxo Wellcome
  2. Demarles D, Gillotin C, Bonaventure-Paci S, Vincent I, Fosse S, Taburet AM (2002) "Single-dose pharmacokinetics of amprenavir coadministered with grapefruit juice." Antimicrob Agents Chemother, 46, p. 1589-1590

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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