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Drug Interactions between Quin-Release and saquinavir

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

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Interactions between your drugs

Major

quiNIDine saquinavir

Applies to: Quin-Release (quinidine) and saquinavir

CONTRAINDICATED: Coadministration with saquinavir may significantly increase the plasma concentrations of some antiarrhythmic agents such as amiodarone, bepridil, flecainide, lidocaine, propafenone, and quinidine. The mechanism is decreased clearance due to inhibition of CYP450 3A4- and 2D6-mediated metabolism by saquinavir, particularly when coadministered with ritonavir as a pharmacokinetic booster. Although clinical data are lacking, the interaction could conceivably lead to serious and/or life-threatening reactions including QT interval prolongation and ventricular arrhythmias such as ventricular tachycardia and torsade de pointes.

MANAGEMENT: The use of saquinavir-ritonavir in combination with amiodarone, bepridil, flecainide, lidocaine, propafenone, and quinidine is considered contraindicated.

References

  1. "Product Information. Invirase (saquinavir)." Roche Laboratories PROD (2001):
  2. "Product Information. Fortovase (saquinavir)." Roche Laboratories PROD (2001):

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Drug and food interactions

Moderate

quiNIDine food

Applies to: Quin-Release (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

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

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Moderate

saquinavir food

Applies to: saquinavir

ADJUST DOSING INTERVAL: Food significantly increases the absorption of saquinavir.

MONITOR: Coadministration with grapefruit juice may increase the plasma concentrations of saquinavir. The primary mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. In eight healthy volunteers, ingestion of 400 mL of grapefruit juice prior to administration of a 600 mg dose of saquinavir mesylate increased the area under the plasma concentration-time curve and oral bioavailability of saquinavir by 50% and 100%, respectively, compared to water; however, the increase is not considered clinically relevant. A high degree of intersubject variability in the grapefruit juice effect was also observed. The extent to which this interaction may occur with the saquinavir free base soft gelatin capsule is unknown. However, the saquinavir soft gelatin capsule formulation is no longer commercially available.

MANAGEMENT: Saquinavir mesylate should be taken with meals or within 2 hours after eating to enhance bioavailability. Patients should be advised to avoid the consumption of large amounts of grapefruit and grapefruit juice during saquinavir therapy unless otherwise directed by their doctor, as the interaction is unreliable and subject to a high degree of interpatient variation.

References

  1. "Product Information. Invirase (saquinavir)." Roche Laboratories PROD (2001):
  2. Kupferschmidt HHT, Fattinger KE, Ha HR, Follath F, Krahenbuhl S "Grapefruit juice enhances the bioavailability of the HIV protease inhibitor saquinavir in man." Br J Clin Pharmacol 45 (1998): 355-9
  3. Bailey DG, Malcolm J, Arnold O, Spence JD "Grapefruit juice-drug interactions." Br J Clin Pharmacol 46 (1998): 101-10
  4. Eagling VA, Profit L, Back DJ "Inhibition of the CYP3A4-mediated metabolism and P-glycoprotein-mediated transport of the HIV-I protease inhibitor saquinavir by grapefruit juice components." Br J Clin Pharmacol 48 (1999): 543-52
  5. Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
  6. Cerner Multum, Inc. "Australian Product Information." O 0
View all 6 references

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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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