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Drug Interactions between Quinidex Extentabs and rifabutin

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

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Interactions between your drugs

Moderate

quiNIDine rifabutin

Applies to: Quinidex Extentabs (quinidine) and rifabutin

MONITOR: Rifamycins may increase the hepatic metabolism of quinidine by inducing CYP450 3A4 isoenzymes. Serum quinidine levels and quinidine effect may be decreased.

MANAGEMENT: Frequent monitoring of quinidine levels and arrhythmia control is recommended. Increased quinidine dosage may be needed. When a rifamycin is discontinued, enzyme induction and increased hepatic metabolism of quinidine may persist for one week. Patients should be advised to notify their physician if they experience an increase in irregular heartbeats.

References (8)
  1. Twum-Barima Y, Carruthers SG (1981) "Quinidine-rifampin interaction." N Engl J Med, 304, p. 1466-9
  2. Venkatesan K (1992) "Pharmacokinetic drug interactions with rifampicin." Clin Pharmacokinet, 22, p. 47-65
  3. Borcherding SM, Baciewicz AM, Self TH (1992) "Update on rifampin drug interactions." Arch Intern Med, 152, p. 711-6
  4. Schwartz A, Brown JR (1984) "Quinidine-rifampin interaction." Am Heart J, 107, p. 789-90
  5. Bussey HI, Merritt GJ, Hill EG (1984) "The influence of rifampin on quinidine and digoxin." Arch Intern Med, 144, p. 1021-3
  6. Reed R, Schwartz H (1983) "Phenytoin-theophylline-quinidine interactions." N Engl J Med, 308, p. 724-5
  7. Ahmad D, Mathur P, Ahuja S, Henderson R, Carruthers G (1979) "Rifampicin-quinidine interaction." Br J Dis Chest, 73, p. 409-11
  8. Strayhorn VA, Baciewicz AM, Self TH (1997) "Update on rifampin drug interactions, III." Arch Intern Med, 157, p. 2453-8

Drug and food interactions

Moderate

quiNIDine food

Applies to: Quinidex Extentabs (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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