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Drug Interactions between darifenacin and propranolol

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

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Interactions between your drugs

Moderate

propranolol darifenacin

Applies to: propranolol and darifenacin

MONITOR: Coadministration with darifenacin may increase the plasma concentrations of drugs that are metabolized by CYP450 2D6. The mechanism is decreased clearance due to inhibition of the isoenzyme by darifenacin. According to the product labeling, darifenacin (30 mg once daily) increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of imipramine (a CYP450 2D6 substrate) by 57% and 70%, respectively. These changes were accompanied by a 3.6-fold increase in the mean Cmax and AUC of desipramine, the active metabolite of imipramine. Conversely, some CYP450 2D6 substrates may also increase the plasma concentrations of darifenacin, which is itself metabolized by CYP450 2D6 and may participate in enzymatic competitive inhibition with other substrates.

MANAGEMENT: Caution is advised if darifenacin must be used concomitantly with medications that undergo metabolism by CYP450 2D6, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever darifenacin is added to or withdrawn from therapy. Pharmacologic response to darifenacin should also be monitored more closely whenever a CYP450 2D6 inhibitor is added to or withdrawn from therapy, and the darifenacin dosage adjusted if necessary. Patients should be advised to contact their doctor if they experience undue adverse effects of darifenacin such as severe abdominal pain or constipation for 3 or more days.

References

  1. "Product Information. Enablex (darifenacin)." Novartis Pharmaceuticals (2005):

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Drug and food interactions

Moderate

propranolol food

Applies to: propranolol

ADJUST DOSING INTERVAL: The bioavailability of propranolol may be enhanced by food.

MANAGEMENT: Patients may be instructed to take propranolol at the same time each day, preferably with or immediately following meals.

References

  1. Olanoff LS, Walle T, Cowart TD, et al. "Food effects on propranolol systemic and oral clearance: support for a blood flow hypothesis." Clin Pharmacol Ther 40 (1986): 408-14
  2. Byrne AJ, McNeil JJ, Harrison PM, Louis W, Tonkin AM, McLean AJ "Stable oral availability of sustained release propranolol when co-administered with hydralazine or food: evidence implicating substrate delivery rate as a determinant of presystemic drug interactions." Br J Clin Pharmacol 17 (1984): s45-50

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Moderate

propranolol food

Applies to: propranolol

ADJUST DOSING INTERVAL: Concurrent administration with calcium salts may decrease the oral bioavailability of atenolol and possibly other beta-blockers. The exact mechanism of interaction is unknown. In six healthy subjects, calcium 500 mg (as lactate, carbonate, and gluconate) reduced the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of atenolol (100 mg) by 51% and 32%, respectively. The elimination half-life increased by 44%. Twelve hours after the combination, beta-blocking activity (as indicated by inhibition of exercise tachycardia) was reduced compared to that with atenolol alone. However, during a 4-week treatment in six hypertensive patients, there was no difference in blood pressure values between treatments. The investigators suggest that prolongation of the elimination half-life induced by calcium coadministration may have led to atenolol cumulation during long-term dosing, which compensated for the reduced bioavailability.

MANAGEMENT: It may help to separate the administration times of beta-blockers and calcium products by at least 2 hours. Patients should be monitored for potentially diminished beta-blocking effects following the addition of calcium therapy.

References

  1. Kirch W, Schafer-Korting M, Axthelm T, Kohler H, Mutschler E "Interaction of atenolol with furosemide and calcium and aluminum salts." Clin Pharmacol Ther 30 (1981): 429-35

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Minor

darifenacin food

Applies to: darifenacin

The consumption of grapefruit juice may be associated with increased plasma concentrations of darifenacin. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. The clinical significance is unknown.

References

  1. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0

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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

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

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