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Drug Interactions between echinacea and Quin-G

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

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Interactions between your drugs

Moderate

quiNIDine echinacea

Applies to: Quin-G (quinidine) and echinacea

MONITOR: Coadministration with echinacea may alter the plasma concentrations and therapeutic effects of drugs that are substrates of CYP450 3A4. Echinacea appears to inhibit intestinal CYP450 3A4, which would lead to an increase in oral midazolam (a sensitive 3A4 substrate) bioavailability; however, plasma levels of midazolam following oral administration do not appear to be affected by echinacea. In contrast, it appears that echinacea may also induce hepatic CYP450 3A4; thereby increasing the hepatic clearance of drugs that are substrates of CYP450 3A4. According to reports, echinacea may increase the hepatic clearance of intravenous (IV) midazolam by 34% and decrease the area under the concentration-time curve (AUC) and half-life of IV midazolam by 20% and 42%, respectively.

MANAGEMENT: In general, patients should be advised to consult their healthcare provider before using any herbal or alternative medicines. If echinacea is prescribed with a drug that is a CYP450 3A4 substrate, the possibility of an altered (increased or decreased) therapeutic response should be considered. Patients should be monitored more closely following the addition or withdrawal of echinacea and the dosage of the CYP450 3A4 substrate adjusted as necessary.

References (2)
  1. Gorski JC, Huang SM, Pinto A, et al. (2004) "The effect of echinacea (Echinacea purpurea root) on cytochrome P450 activity in vivo." Clin Pharmacol Ther, 75, p. 89-100
  2. Cerner Multum, Inc. "Australian Product Information."

Drug and food interactions

Moderate

quiNIDine food

Applies to: Quin-G (quinidine)

GENERALLY AVOID: In a small, randomized, crossover study, the administration of quinidine with grapefruit juice (compared to water) to healthy volunteers significantly prolonged the time to reach peak plasma quinidine concentrations and decreased the plasma concentrations of its major metabolite, 3-hydroxyquinidine. These changes were associated pharmacodynamically with both a delay and a reduction in the maximal effect on QTc interval. The proposed mechanism is delay of gastric emptying as well as inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall induced by certain compounds present in grapefruits.

MANAGEMENT: Given the drug's narrow therapeutic index, patients receiving quinidine therapy should avoid the consumption of grapefruits and grapefruit juice to prevent any undue fluctuations in plasma drug levels.

References (4)
  1. Ace LN, Jaffe JM, Kunka RL (1983) "Effect of food and an antacid on quinidine bioavailability." Biopharm Drug Dispos, 4, p. 183-90
  2. Min DI, Ku YM, Geraets DR, Lee HC (1996) "Effect of grapefruit juice on the pharmacokinetics and pharmacodynamics of quinidine in healthy volunteers." J Clin Pharmacol, 36, p. 469-76
  3. Ha HR, Chen J, Leuenberger PM, Freiburghaus AU, Follah F (1995) "In vitro inhibition of midazolam and quinidine metabolism by flavonoids." Eur J Clin Pharmacol, 48, p. 367-71
  4. Bailey DG, Dresser GR, Kreeft JH, Munoz C, Freeman DJ, Bend JR (2000) "Grapefruit-felodipine interaction: Effect of unprocessed fruit and probable active ingredients." Clin Pharmacol Ther, 68, p. 468-77

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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