Atazanavir and Fosamprenavir

In the database of official manuals used in the service creation an interaction registered by statistical results of studies was found, which can either lead to negative consequences for the patient health or strengthen a mutual positive effect. A doctor should be consulted to address the issue of joint drug administration.

Using atazanavir together with fosamprenavir can decrease the effects of atazanavir. Contact your doctor if your condition worsens. You may need a dose adjustment or special test to safely use both medications. It is important to tell your doctor about all other medications you use, including vitamins and herbs. Do not stop using any medications without first talking to your doctor.

MONITOR: Coadministration with fosamprenavir may decrease the plasma concentrations of atazanavir, even in the presence of low-dose ritonavir as a pharmacokinetic booster. The mechanism has not been described. In 22 study subjects, administration of atazanavir (300 mg once a day) with fosamprenavir/ritonavir (700 mg/100 mg twice a day) for 10 days decreased the peak plasma concentration (Cmax) and area under the concentration-time curve (AUC) of atazanavir by 24% and 22%, respectively, compared to administration of atazanavir with ritonavir alone (300 mg/100 mg once a day) for 10 days. The clinical significance of these changes is unknown. In a study consisting of patients who have been intolerant to or have failed lopinavir/ritonavir, 14 patients who received atazanavir/fosamprenavir/ritonavir (150 or 200 mg/700 mg/100 mg twice a day, with or without nucleoside reverse transcriptase inhibitors) for 24 weeks all demonstrated plasma trough concentrations of atazanavir and amprenavir well above the minimum acceptable concentrations. In addition, the patients tolerated the regimen and had good antiretroviral response. At 24 weeks, 10 patients (60%) achieved HIV RNA levels below 400 copies/mL, and four had less than 50 copies/mL. Four patients required concomitant statins because of hyperlipidemia, which is a known side effect of protease inhibitors, in particular ritonavir. One patient developed grade 3 hyperlipidemia at week 8 and discontinued ritonavir with improvement. Three patients who did not tolerate ritonavir were switched to atazanavir/fosamprenavir (400 mg/700 mg twice a day), which also yielded good tolerance and antiretroviral response. Atazanavir reportedly does not significantly affect the pharmacokinetics of amprenavir from fosamprenavir.

MANAGEMENT: Appropriate dosages of atazanavir, fosamprenavir, and ritonavir with respect to safety and efficacy have not been established when used in combination. Limited data suggest that an atazanavir dosage of 150 or 200 mg twice daily may be adequate in combination with fosamprenavir 700 mg and ritonavir 100 mg twice daily. Therapeutic drug monitoring is recommended if this regimen is used, and antiretroviral response should be monitored closely.

Atazanavir

Generic Name: atazanavir

Brand name: Reyataz

Synonyms: n.a.

What is Atazanavir?

Fosamprenavir

Generic Name: fosamprenavir

Brand name: Lexiva, Telzir

Synonyms: n.a.

What is Fosamprenavir?