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Drug Interactions between amiodarone and darifenacin

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

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Interactions between your drugs

Moderate

amiodarone darifenacin

Applies to: amiodarone and darifenacin

MONITOR: Coadministration with inhibitors of CYP450 2D6 and/or 3A4 may increase the plasma concentrations of darifenacin, which is a substrate of these isoenzymes. According to the product labeling, coadministration of darifenacin (30 mg once daily) with the mixed CYP450 inhibitor cimetidine resulted in a 42% increase in the mean darifenacin steady-state peak plasma concentration (Cmax) and a 34% increase in the systemic exposure (AUC) compared to administration of darifenacin alone. The potent CYP450 2D6 inhibitor paroxetine (20 mg) increased steady-state AUC of darifenacin (30 mg once daily) by 33%. Erythromycin, a CYP450 3A4 inhibitor, increased the mean steady-state Cmax and AUC of darifenacin (30 mg once daily) by 128% and 95%, respectively. Fluconazole, another 3A4 inhibitor, increased these values by 88% and 84%, respectively.

MANAGEMENT: Pharmacologic response to darifenacin should be monitored more closely whenever a CYP450 2D6 and/or 3A4 inhibitor is added to or withdrawn from therapy, and the darifenacin dosage adjusted if necessary. Patients should be advised to contact their physician if they experience undue adverse effects of darifenacin such as severe abdominal pain or constipation for 3 or more days.

References (2)
  1. (2005) "Product Information. Enablex (darifenacin)." Novartis Pharmaceuticals
  2. (2021) "Product Information. Qelbree (viloxazine)." Supernus Pharmaceuticals Inc

Drug and food interactions

Major

amiodarone food

Applies to: amiodarone

GENERALLY AVOID: Grapefruit juice may significantly increase the plasma concentrations of orally administered amiodarone. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. In 11 nonsmoking, healthy volunteers, grapefruit juice (300 mL with drug administration, then 3 hours and 9 hours later) increased the mean peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of amiodarone (17 mg/kg single dose) by 84% and 50%, respectively, compared to water. Formation of the pharmacologically active metabolite, N-desethylamiodarone (N-DEA), was completely inhibited. Clinically, this interaction can lead to altered efficacy of amiodarone, since antiarrhythmic properties of amiodarone and N-DEA appear to differ. In the study, mean increases in PR and QTc intervals of 17.9% and 11.3%, respectively, were observed 6 hours postdose with water, while increases of 10.2% and 3.3%, respectively, were observed after administration with grapefruit juice.

ADJUST DOSING INTERVAL: Food increases the rate and extent of absorption of amiodarone. The mechanism appears to involve the effect of food-induced physiologic changes on drug release from its formulation. In 30 healthy volunteers, administration of a single 600 mg dose of amiodarone following a high-fat meal resulted in a Cmax and AUC that were 3.8 and 2.4 times the respective values under fasting conditions. The time to reach peak plasma concentration (Tmax) was decreased by 37%, indicating an increased rate of absorption. Mean Cmax and AUC for the active metabolite, N-DEA, also increased by 32% and 55%, respectively, but there was no change in the Tmax.

MANAGEMENT: Patients treated with oral amiodarone should avoid consumption of grapefruits and grapefruit juice. In addition, oral amiodarone should be administered consistently with regard to meals.

References (3)
  1. (2002) "Product Information. Cordarone (amiodarone)." Wyeth-Ayerst Laboratories
  2. Libersa CC, Brique SA, Motte KB, et al. (2000) "Dramatic inhibition of amiodarone metabolism induced by grapefruit juice." Br J Clin Pharmacol, 49, p. 373-8
  3. Meng X, Mojaverian P, Doedee M, Lin E, Weinryb I, Chiang ST, Kowey PR (2001) "Bioavailability of Amiodarone tablets administered with and without food in healthy subjects." Am J Cardiol, 87, p. 432-5
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)
  1. Cerner Multum, Inc. "UK Summary of Product Characteristics."

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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