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Drug Interactions between etravirine and halofantrine

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

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Interactions between your drugs

Moderate

halofantrine etravirine

Applies to: halofantrine and etravirine

MONITOR: Coadministration with etravirine may decrease the plasma concentrations of drugs that are substrates of the CYP450 3A4 isoenzyme. The mechanism is accelerated clearance due to induction of CYP450 3A4 activity by etravirine. In 15 study subjects coadministered etravirine and the CYP450 3A4 substrate sildenafil (50 mg single dose), sildenafil peak plasma concentration (Cmax) and systemic exposure (AUC) decreased by 45% and 57%, respectively, while Cmax and AUC of its active N-desmethyl metabolite decreased by 25% and 41%, respectively.

MANAGEMENT: Caution is advised if etravirine must be used concomitantly with medications that undergo metabolism by CYP450 3A4, particularly those with a narrow therapeutic range. Dosage adjustments as well as clinical and laboratory monitoring may be appropriate for some drugs whenever etravirine is added to or withdrawn from therapy.

References

  1. (2008) "Product Information. Intelence (etravirine)." Ortho Biotech Inc

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Drug and food interactions

Major

halofantrine food

Applies to: halofantrine

GENERALLY AVOID: Grapefruit juice may increase the plasma concentration of halofantrine. The mechanism is inhibition of CYP450 3A4-mediated first-pass metabolism in the gut wall by certain compounds present in grapefruits. After administration of 500 mg with 250 mL regular-strength grapefruit juice daily for 3 days, average halofantrine AUC increased 2.8-fold and peak plasma concentrations increased 3.2-fold, compared to water, in healthy subjects (n=12). QT interval prolongation increased from an average of 17 ms with water to 31 ms with grapefruit juice. Halofantrine, even at recommended doses, can cause dose-related prolongation of the QT interval, resulting in an elevated risk of potentially fatal ventricular arrhythmias including ventricular tachycardia and torsade de pointes.

ADJUST DOSING INTERVAL: The presence of food may increase the absorption and toxicity of halofantrine. Peak plasma concentrations increased seven-fold and AUC increased three-fold in healthy subjects when halofantrine was administered with high-fat food.

MANAGEMENT: The authors of the study recommend that grapefruit juice be avoided during halofantrine therapy. The manufacturer recommends performing an ECG before initiating halofantrine therapy and cardiac monitoring during and for 8 to 12 hours after completion of therapy. Halofantrine should be taken on an empty stomach at least 1 hour before or 2 hours after food.

References

  1. Giao PT, de Vries PJ (2001) "Pharmacokinetic interactions of antimalarial agents." Clin Pharmacokinet, 40, p. 343-73
  2. (2003) "Product Information. Halfan (halofantrine)." GlaxoSmithKline
  3. Charbit B, Becquemont L, Lepere B, Peytavin G, Funck-Bretano C (2002) "Pharmacokinetic and pharmacodynamic interaction between grapefruit juice and halofantrine." Clin Pharmacol Ther, 72, p. 514-23
  4. Abernethy DR, Wesche DL, Barbey JT, et al. (2001) "Stereoselective halofantrine disposition and effect: concentration-related QTc prolongation." Br J Clin Pharmacol, 51, p. 231-7
View all 4 references

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Moderate

etravirine food

Applies to: etravirine

ADJUST DOSING INTERVAL: Coadministration with food increases the oral bioavailability of etravirine. The mechanism is unknown. Compared to administration following a meal, the systemic exposure (AUC) to etravirine was decreased by about 50% when the drug was administered under fasting conditions. The types of meal studied (ranging from 345 kilocalories containing 17 grams fat to 1160 kilocalories containing 70 grams fat) did not appear to make a difference with respect to impact on etravirine bioavailability.

MANAGEMENT: Etravirine should always be administered following a meal.

References

  1. (2008) "Product Information. Intelence (etravirine)." Ortho Biotech Inc

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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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