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Drug Interactions between guaifenesin / oxtriphylline and zafirlukast

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

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Interactions between your drugs

Moderate

oxtriphylline zafirlukast

Applies to: guaifenesin / oxtriphylline and zafirlukast

MONITOR: The coadministration of theophylline with zafirlukast may modestly reduce zafirlukast plasma concentrations. The mechanism is unknown. A single study in 13 asthmatic patients reported a 30% decrease in mean zafirlukast concentration. The clinical significance of this reduction is unclear. In addition, a single case report suggested that zafirlukast may significantly increase theophylline serum concentrations. According to the manufacturer, coadministration of zafirlukast and theophylline in 16 healthy 6- to 11-year-old subjects did not resulted in significant changes to theophylline pharmacokinetics. However, there have been rare postmarketing reports of increased theophylline levels with or without clinical toxicity after zafirlukast was added to the regimen. The mechanism and clinical significance are unknown.

MANAGEMENT: If there is any change in either drug's regimen, the patient should be observed for altered theophylline and zafirlukast effect, and theophylline levels should be monitored closely. Other methylxanthines may interact with zafirlukast in a similar manner.

References (4)
  1. (2001) "Product Information. Accolate (zafirlukast)." Astra-Zeneca Pharmaceuticals
  2. Katial RK, Stelzle RC, Bonner MW, Marino M, Cantilena LR, Smith LJ (1998) "A drug interaction between zafirlukast and theophylline." Arch Intern Med, 158, p. 1713-5
  3. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  4. Cerner Multum, Inc. "Australian Product Information."

Drug and food interactions

Moderate

zafirlukast food

Applies to: zafirlukast

ADJUST DOSING INTERVAL: Food may reduce the oral absorption and bioavailability of zafirlukast. In two separate studies, one using a high-fat and the other a high-protein meal, administration of zafirlukast with food reduced the mean bioavailability by approximately 40%.

MANAGEMENT: To ensure maximal oral absorption, zafirlukast should be administered at least 1 hour before or 2 hours after meals.

References (1)
  1. (2001) "Product Information. Accolate (zafirlukast)." Astra-Zeneca 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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