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Drug Interactions between grepafloxacin and lapatinib

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

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Interactions between your drugs

Major

grepafloxacin lapatinib

Applies to: grepafloxacin and lapatinib

CONTRAINDICATED: Grepafloxacin can cause dose-related prolongation of the QT interval. Theoretically, coadministration with other agents that can prolong the QT interval may result in additive effects and increased risk of ventricular arrhythmias including torsade de pointes and sudden death.

MANAGEMENT: Coadministration of grepafloxacin with other drugs that can prolong the QT interval is considered contraindicated.

References (7)
  1. Thomas M, Maconochie JG, Fletcher E (1996) "The dilemma of the prolonged QT interval in early drug studies." Br J Clin Pharmacol, 41, p. 77-81
  2. (2001) "Product Information. Raxar (grepafloxacin)." Glaxo Wellcome
  3. Lode H, Vogel F, Elies W (1999) "Grepafloxacin: A review of its safety profile based on clinical trials and postmarketing surveillance." Clin Ther, 21, p. 61-74
  4. Ball P (2000) "Quinolone-induced QT interval prolongation: a not-so-unexpected class effect." J Antimicrob Chemother, 45, p. 557-9
  5. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  6. Canadian Pharmacists Association (2006) e-CPS. http://www.pharmacists.ca/function/Subscriptions/ecps.cfm?link=eCPS_quikLink
  7. Cerner Multum, Inc. "Australian Product Information."

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.

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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