Brand Name: Agenerase
Active Ingredient: amprenavir
Indication: For combination therapy with other antiretroviral agents for the treatment of HIV-1 infection
Company Name: Glaxo Wellcome
Availability: Prescription only
Introduction
Agenerase (amprenavir) – the first new protease inhibitor in two years – is the fifth protease inhibitor to reach the US market. Agenerase, developed by Vertex Pharmaceuticals, Inc. and licensed to Glaxo Wellcome, was approved by the FDA in April 1999.
Unlike most other protease inhibitors that have to be taken three times daily, Agenerase has a long half-life and can be given twice daily. Agenerase has been studied in treatment-naive HIV patients and those who had previously received reverse transcriptase inhibitors and protease inhibitors.
How It Works
Agenerase (amprenavir) is an inhibitor of HIV-1 protease. It binds to the active site of HIV-1 protease and thereby prevents the processing of viral gag and gag-pol polyprotein precursors, resulting in the formation of immature non-infectious viral particles.
A randomized, double-blind, placebo-controlled, multicenter study in therapy-naive adults is ongoing. Treatment with Agenerase (1200 mg twice daily) plus lamivudine (150 mg twice daily) plus zidovudine (300 mg twice daily) was compared with lamivudine (150 mg twice daily) plus zidovudine (300 mg twice daily) in 232 patients. Throughout the 24 weeks of therapy, there were no significant differences in median CD4 cell count between the treatment arms. At week 24, 53% of the Agenerase group had achieved a viral load of less than 400 copies/ml.
The efficacy of Agenerase was also examined in a randomized, open-label study in previously treated adults. Agenerase (1200 mg twice daily) plus nucleoside reverse transcriptase inhibitors (NRTIs) was compared with indinavir (800 mg every 8 hours) plus NRTIs in 504 patients. These patients were NRTI and non-nucleoside reverse transcriptase inhibitor (NNRI) experienced, and protease inhibitor naive. Through 24 weeks of therapy, there was a smaller increase in median CD4 cell count from baseline in the Agenerase group than in the indinavir group. At week 24, 43% of patients in the Agenerase group had achieved a viral load of less than 400 copies/ml.
The most commonly reported adverse effects in the trials included nausea, diarrhea, vomiting, rash, and perioral paresthesia. Severe and life-threatening skin reactions, including Stevens-Johnson syndrome, have occurred in 1% of patients treated with Agenerase. As with other protease inhibitors, Agenerase may be associated with acute hemolytic anemia, diabetes mellitus, and hyperglycemia. Agenerase does not seem to have a significant effect on the lipid profile.
Agenerase (amprenavir) may be taken with or without food, but should not be taken with a high fat meal. Agenerase is metabolized in the liver by ctyochrome P450 CYP3A4 and also inhibits this enzyme. Therefore, patients with hepatic dysfunction require dose adjustment. Caution should be used when coadministering medications that are substrates, inhibitors, or inducers of CYP3A4 or potentially toxic medications that are metabolized by CYP3A4.
An oral solution of Agenerase is available for pediatric patients. The bioavailability of this formulation is 14% lower than that of the capsules; therefore, the oral solution is not interchangeable with the capsules on a milligram per milligram basis.
What The Patient Should Know
Agenerase does not cure HIV infection and it is not known if Agenerase will help the patient live longer or have fewer medical problems, such as opportunistic infections. There are no data suggesting that Agenerase, or any other anti-HIV medications reduce the risk of viral transmission via sexual contact or blood contamination.
Agenerase (amprenavir) should always be used in combination with other antiretroviral drugs to limit development of resistance. Patients should not alter the dose or discontinue therapy without consulting their doctor.
Common side effects of Agenerase include nausea, vomiting, diarrhea, rash, and a tingling sensation around the mouth. Severe or life-threatening rash has been reported.
Agenerase (amprenavir), as with other protease inhibitors, may interact with many drugs. The patient, therefore, should inform the physician about any other medications that are being used, including non-prescription drugs.
The following medications should not be taken with Agenerase : Halcion ® (triazolam), Hismanal ® (astemizole), Ergot medications (Cafergot ® and others), Propulsid ® (cisapride), Versed ® (midazolam), and Vascor ® (bepridil). There are many other medications that have to be used with caution or not used at all while taking Agenerase.
Since Agenerase capsules and solution both contain large amounts of vitamin E, patients should not to take additional vitamin E while taking Agenerase.
Agenerase may be taken with or without food, but should not be taken with a high fat meal.
Agenerase (amprenavir) is a sulfonamide. Although the potential for cross-sensitivity between Agenerase and other sulfonamides is unknown, patients with a known sulfonamide allergy should be treated with caution.
Jennifer is a clinical pharmacologist. She helps doctors of all medical specialties choose medications. Jennifer consults about drug dosage, interactions, and side effects.