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Drug Interactions between Enablex and mifepristone

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

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Interactions between your drugs

Major

miFEPRIStone darifenacin

Applies to: mifepristone and Enablex (darifenacin)

ADJUST DOSE: Coadministration with potent inhibitors of CYP450 3A4 may significantly increase the plasma concentrations of darifenacin, which is partially metabolized by the isoenzyme. Darifenacin is also metabolized by CYP450 2D6, but 3A4 is the major pathway of metabolism in so-called poor metabolizers of 2D6 (approximately 7% of Caucasians and 2% of Asians and those of African descent). In a drug interaction study involving 10 extensive metabolizers and 1 poor metabolizer of 2D6, coadministration with the potent 3A4 inhibitor ketoconazole (400 mg) increased the mean steady-state peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of darifenacin (extended-release 7.5 mg once a day) approximately 5-fold each compared to values previously reported for extensive metabolizers of 2D6. In the poor metabolizer, Cmax and AUC of darifenacin increased approximately 13-fold each compared to values previously reported for poor metabolizers. When a 15 mg daily dose of extended-release darifenacin was given with ketoconazole, mean darifenacin Cmax and AUC in 3 extensive metabolizers increased approximately 12-fold compared to historical values, while Cmax and AUC increased approximately 6-fold in the poor metabolizer compared to historical values.

MANAGEMENT: The dosage of darifenacin should not exceed 7.5 mg/day when used with potent CYP450 3A4 inhibitors. Some authorities recommend avoiding concomitant use of darifenacin during and for 2 weeks after treatment with itraconazole.

References

  1. (2002) "Product Information. Sporanox (itraconazole)." Janssen Pharmaceuticals
  2. (2005) "Product Information. Enablex (darifenacin)." Novartis Pharmaceuticals
  3. Cerner Multum, Inc. "Australian Product Information."
  4. Niwa T, Shiraga T, Takagi A (2005) "Effect of antifungal drugs on cytochrome P450 (CYP) 2C9, CYP2C19, CYP3A4 activities in human liver microsomes." Biol Pharm Bull, 28, p. 1805-8
View all 4 references

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Drug and food interactions

Moderate

miFEPRIStone food

Applies to: mifepristone

ADJUST DOSING INTERVAL: Food may significantly increase the plasma concentrations of mifepristone.

GENERALLY AVOID: Grapefruit juice may increase the plasma concentrations of mifepristone. The proposed mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruit. Because pharmacokinetic interactions involving grapefruit juice are often subject to a high degree of interpatient variability, the extent to which a given patient may be affected is difficult to predict.

MANAGEMENT: When mifepristone is used daily to control hyperglycemia secondary to hypercortisolism in patients with endogenous Cushing's syndrome, it should be taken with food to achieve consistent plasma drug levels. Patients should be advised to avoid consuming grapefruit or grapefruit juice during treatment with mifepristone, as it may cause increased adverse effects such as headache, dizziness, fatigue, nausea, vomiting, cramping, diarrhea, hypokalemia, adrenal insufficiency, vaginal bleeding, arthralgia, peripheral edema, and hypertension. Because mifepristone is eliminated slowly from the body, the interaction with grapefruit juice may be observed for a prolonged period.

References

  1. (2001) "Product Information. Mifeprex (mifepristone)." Danco Laboratories
  2. (2012) "Product Information. Korlym (mifepristone)." Corcept Therapeutics Incorporated

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Minor

darifenacin food

Applies to: Enablex (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."

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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.

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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