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Drug Interactions between lapatinib and montelukast

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

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Interactions between your drugs

Moderate

montelukast lapatinib

Applies to: montelukast and lapatinib

MONITOR: Coadministration with inhibitors of CYP450 2C8 and/or 2C9 may increase the plasma concentrations of montelukast, which is metabolized by these isoenzymes in addition to CYP450 3A4. When montelukast was administered with the potent CYP450 2C8/2C9 inhibitor gemfibrozil, montelukast systemic exposure (AUC) increased by 4.4-fold. The addition of itraconazole, a potent CYP450 3A4 inhibitor, to gemfibrozil and montelukast did not further increase the AUC of montelukast. Administration of itraconazole alone with montelukast also resulted in no significant increase in the AUC of montelukast, which would suggest that montelukast is primarily metabolized by CYP450 2C8 and 2C9 in vivo.

MANAGEMENT: According to the product labeling, no dosage adjustment of montelukast is required when used in combination with gemfibrozil. However, it may be advisable to monitor patients for potentially increased adverse effects during coadministration with gemfibrozil or other CYP450 2C8/2C9 inhibitors.

References (2)
  1. (2001) "Product Information. Singulair (montelukast)." Merck & Co., Inc
  2. Karonen T, Filppula A, Laitila J, Niemi M, Neuvonen PJ, Backman JT (2010) "Gemfibrozil Markedly Increases the Plasma Concentrations of Montelukast: A Previously Unrecognized Role for CYP2C8 in the Metabolism of Montelukast." Clin Pharmacol Ther

Drug and food interactions

Moderate

lapatinib food

Applies to: lapatinib

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of lapatinib. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits.

ADJUST DOSING INTERVAL: Food can significantly increase the oral bioavailability of lapatinib. According to the manufacturer, lapatinib peak plasma concentration (Cmax) was approximately 2.5- and 3-fold higher and systemic exposure (AUC) 3- and 4-fold higher when administered with a low fat meal (5% fat; 500 calories) or with a high-fat meal (50% fat; 1000 calories), respectively, compared to fasting. Dividing the daily dose also resulted in an approximately 2-fold higher systemic exposure at steady state compared to the same total dose administered once daily.

MANAGEMENT: Patients treated with lapatinib should preferably avoid the consumption of grapefruit or grapefruit juice. The manufacturer recommends that lapatinib be administered at least one hour before or one hour after a meal. The lapatinib dose is administered once daily and should not be divided.

References (1)
  1. (2007) "Product Information. Tykerb (lapatinib)." Novartis Pharmaceuticals

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

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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