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Drug Interactions between fosamprenavir and nelfinavir

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

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Interactions between your drugs

Minor

nelfinavir fosamprenavir

Applies to: nelfinavir and fosamprenavir

Coadministration with nelfinavir may increase the plasma concentrations of amprenavir. The mechanism is nelfinavir inhibition of amprenavir metabolism via CYP450 3A4. In 6 study subjects, coadministration of nelfinavir (750 mg three times a day) and amprenavir (750 or 800 mg three times a day) for 2 weeks resulted in a 14% decrease in amprenavir peak plasma concentration (Cmax) but a 189% increase in its trough plasma concentration (Cmin) compared to administration of amprenavir alone. Overall systemic exposure (AUC) was unchanged. The clinical significance of these findings is unknown. Patients receiving amprenavir or fosamprenavir with nelfinavir should be monitored for potentially increased side effects of both drugs. Appropriate dosages of the drugs in combination with respect to safety and efficacy have not been established.

References (2)
  1. (2001) "Product Information. Agenerase (amprenavir)." Glaxo Wellcome
  2. (2003) "Product Information. Lexiva (fosamprenavir)." GlaxoSmithKline

Drug and food interactions

Moderate

fosamprenavir food

Applies to: fosamprenavir

ADJUST DOSING INTERVAL: Food may reduce the systemic bioavailability of amprenavir from fosamprenavir oral suspension. The mechanism of interaction has not been described. According to the product labeling, administration of fosamprenavir oral suspension (1400 mg single dose) with a high-fat meal (967 kcal, 67 g fat, 33 g protein, 58 g carbohydrate) reduced amprenavir peak plasma concentration (Cmax) by 46% and systemic exposure (AUC) by 28% compared to administration in a fasted state. The time to reach peak plasma level (Tmax) was delayed by 0.72 hours. In contrast, the same high-fat meal did not affect the pharmacokinetics of amprenavir from fosamprenavir tablets.

MANAGEMENT: Fosamprenavir suspension should be administered on an empty stomach in adults, but with food in pediatric patients to aid palatability and compliance. If emesis occurs within 30 minutes after dosing the suspension, the dose should be repeated. Fosamprenavir tablets may be taken with or without food.

References (1)
  1. (2003) "Product Information. Lexiva (fosamprenavir)." GlaxoSmithKline

Therapeutic duplication warnings

Therapeutic duplication is the use of more than one medicine from the same drug category or therapeutic class to treat the same condition. This can be intentional in cases where drugs with similar actions are used together for demonstrated therapeutic benefit. It can also be unintentional in cases where a patient has been treated by more than one doctor, or had prescriptions filled at more than one pharmacy, and can have potentially adverse consequences.

Duplication

Protease inhibitors

Therapeutic duplication

The recommended maximum number of medicines in the 'protease inhibitors' category to be taken concurrently is usually one. Your list includes two medicines belonging to the 'protease inhibitors' category:

  • fosamprenavir
  • nelfinavir

Note: In certain circumstances, the benefits of taking this combination of drugs may outweigh any risks. Always consult your healthcare provider before making changes to your medications or dosage.

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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