Drug Interactions between saquinavir and Telzir
This report displays the potential drug interactions for the following 2 drugs:
- saquinavir
- Telzir (fosamprenavir)
Interactions between your drugs
saquinavir fosamprenavir
Applies to: saquinavir and Telzir (fosamprenavir)
Coadministration of saquinavir with amprenavir or fosamprenavir may result in a reduction in the plasma concentrations and therapeutic effects of both drugs. The mechanism of the interaction has not been described. In 7 study subjects, saquinavir (800 mg three times a day for 2 weeks) decreased the peak plasma concentration (Cmax), area under the concentration-time curve (AUC) and trough plasma concentration (Cmin) of amprenavir (750 or 800 mg three times a day for 2 weeks) by 37%, 32%, and 14%, respectively, compared to administration of amprenavir alone. In another report, fosamprenavir (700 mg twice daily) decreased the AUC and Cmax of saquinavir (saquinavir-ritonavir 1000/100 mg twice daily) by 15% and 9%, respectively. The clinical significance of these changes is unknown. No dose adjustment is required for saquinavir-ritonavir. The need for a dosage adjustment for amprenavir or fosamprenavir has not been established.
References
- "Product Information. Agenerase (amprenavir)." Glaxo Wellcome PROD (2001):
- "Product Information. Lexiva (fosamprenavir)." GlaxoSmithKline (2003):
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
Drug and food interactions
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
- "Product Information. Invirase (saquinavir)." Roche Laboratories PROD (2001):
- 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
- Bailey DG, Malcolm J, Arnold O, Spence JD "Grapefruit juice-drug interactions." Br J Clin Pharmacol 46 (1998): 101-10
- 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
- Cerner Multum, Inc. "UK Summary of Product Characteristics." O 0
- Cerner Multum, Inc. "Australian Product Information." O 0
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
- "Product Information. Lexiva (fosamprenavir)." GlaxoSmithKline (2003):
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.
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:
- saquinavir
- Telzir (fosamprenavir)
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
Drug Interaction Classification
Highly clinically significant. Avoid combinations; the risk of the interaction outweighs the benefit. | |
Moderately clinically significant. Usually avoid combinations; use it only under special circumstances. | |
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. | |
No interaction information available. |
Further information
Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.
Check Interactions
To view an interaction report containing 4 (or more) medications, please sign in or create an account.
Save Interactions List
Sign in to your account to save this drug interaction list.