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Drug Interactions between st. john's wort and Telzir

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

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Interactions between your drugs

Major

St. John's wort fosamprenavir

Applies to: st. john's wort and Telzir (fosamprenavir)

CONTRAINDICATED: Coadministration with St. John's wort may significantly reduce the plasma concentrations of HIV protease inhibitors and result in a potential loss of virologic response. The mechanism is induction of CYP450 3A4 metabolism by constituents of St. John's wort. In 8 healthy volunteers, St. John's wort (300 mg, standardized to 0.3% hypericin, 3 times a day for 14 days) decreased the 8-hour area under the plasma concentration-time curve (AUC) and extrapolated 8-hour trough of indinavir (800 mg every 8 hours for 4 doses) by a mean of 57% and 81%, respectively, compared to administration of indinavir alone. All participants showed a reduction in the indinavir 8-hour postdose concentration ranging from 49% to 99%.

MANAGEMENT: Given the risk of reduced viral susceptibility and resistance development associated with subtherapeutic antiretroviral drug levels, concomitant use of HIV protease inhibitors with St. John's wort is considered contraindicated. The enzyme induction may last for up to 2 weeks after the last dose of St. John's wort. Patients should be advised to consult with their caregivers before using any herbal or alternative medicines.

References

  1. (2001) "Product Information. Norvir (ritonavir)." Abbott Pharmaceutical
  2. Cerner Multum, Inc. "UK Summary of Product Characteristics."
  3. Cerner Multum, Inc. "Australian Product Information."
  4. Cerner Multum, Inc. (2015) "Canadian Product Information."
View all 4 references

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Drug and food interactions

Moderate

St. John's wort food

Applies to: st. john's wort

GENERALLY AVOID: An isolated case report suggests that foods containing large amounts of tyramine may precipitate a hypertensive crisis in patients treated with St. John's wort. The mechanism of interaction is unknown, as St. John's wort is not thought to possess monoamine oxidase (MAO) inhibiting activity at concentrations achieved in vivo. The case patient was a 41-year-old man who had been taking St. John's wort for seven days prior to presentation at the emergency room with confusion and disorientation. The patient recalled last eating aged cheese and having a glass of red wine approximately 10 hours prior to admission. No other cause of delirium or hypertension could be identified. In addition, alcohol may potentiate some of the pharmacologic effects of St. John's wort. Use in combination may result in additive central nervous system depression and/or impairment of judgment, thinking, and psychomotor skills.

MANAGEMENT: Until further information is available, patients treated with St. John's wort should consider avoiding consumption of protein foods in which aging or breakdown of protein is used to increase flavor. These foods include cheese (particularly strong, aged or processed cheeses), sour cream, wine (particularly red wine), champagne, beer, pickled herring, anchovies, caviar, shrimp paste, liver (particularly chicken liver), dry sausage, figs, raisins, bananas, avocados, chocolate, soy sauce, bean curd, yogurt, papaya products, meat tenderizers, fava beans, protein extracts, and dietary supplements. Caffeine may also precipitate hypertensive crisis so its intake should be minimized as well. Patients should also be advised to avoid or limit consumption of alcohol.

References

  1. Patel S, Robinson R, Burk M (2002) "Hypertensive crisis associated with St. John's Wort." Am J Med, 112, p. 507-8

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Moderate

fosamprenavir food

Applies to: Telzir (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. (2003) "Product Information. Lexiva (fosamprenavir)." GlaxoSmithKline

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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

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