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Drug Interactions between clarithromycin and fosamprenavir

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

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Interactions between your drugs

Minor

clarithromycin fosamprenavir

Applies to: clarithromycin and fosamprenavir

Drugs that act as both substrate and inhibitor of the CYP450 3A4 isoenzyme may alter the plasma concentration of amprenavir. Amprenavir may increase blood levels of the CYP450 3A4 inhibitor. The extent of the alterations in serum drug levels is unknown and the clinical significance is uncertain. When concomitant therapy is required, the patient should be monitored for adverse effects of both drugs and dose adjustments made when indicated.

References

  1. (2001) "Product Information. Agenerase (amprenavir)." Glaxo Wellcome
  2. Polk RE, Crouch MA, Israel DS, et al. (1999) "Pharmacokinetic interaction between ketoconazole and amprenavir after single doses in healthy men." Pharmacotherapy, 19, p. 1378-84
  3. Falloon J, Piscitelli S, Vogel S, Sadler B, Mitsuya H, Kavlick MF, Yoshimura K, Rogers M, LaFon S, Manion DJ, Lane HC, Masur (2000) "Combination therapy with amprenavir, abacavir, and efavirenz in human immunodeficiency virus (HIV)-infected patients failing a protease-inhibitor regimen: Pharmacokinetic drug interactions and antiviral activity." Clin Infect Dis, 30, p. 313-8

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

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Minor

clarithromycin food

Applies to: clarithromycin

Grapefruit juice may delay the gastrointestinal absorption of clarithromycin but does not appear to affect the overall extent of absorption or inhibit the metabolism of clarithromycin. The mechanism of interaction is unknown but may be related to competition for intestinal CYP450 3A4 and/or absorptive sites. In an open-label, randomized, crossover study consisting of 12 healthy subjects, coadministration with grapefruit juice increased the time to reach peak plasma concentration (Tmax) of both clarithromycin and 14-hydroxyclarithromycin (the active metabolite) by 80% and 104%, respectively, compared to water. Other pharmacokinetic parameters were not significantly altered. This interaction is unlikely to be of clinical significance.

References

  1. Cheng KL, Nafziger AN, Peloquin CA, Amsden GW (1998) "Effect of grapefruit juice on clarithromycin pharmacokinetics." Antimicrob Agents Chemother, 42, p. 927-9

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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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