New Dosing Regimen for Agenerase and Norvir
February 13, 2002
Recent reports have indicated that low doses of ritonavir significantly slow the metabolism rates of several protease inhibitors (PIs). This enables people living with HIV to take fewer doses of the medications, which ultimately leads to lower drug costs and, hopefully, more tolerable regimens. Ritonavir was originally developed as a potent antiviral, but its effect on PIs also makes it possible for PIs to stay in the body longer with a smaller dose of the PI.
On February 5, 2002, the FDA approved a new dosing regimen for Agenerase (amprenavir) and Norvir (ritonavir) used in combination. Agenerase is a PI, a class of potent HIV medications. The FDA recommendations indicate if Agenerase and Norvir are used in combination, the suggested dosage regimens are: Agenerase (1,200 mg) with Norvir (200 mg) once daily or Agenerase (600 mg) with Norvir (100 mg) twice daily. When Agenerase is co-administered with Norvir, there may be a possibility of elevated cholesterol, triglyceride and liver transaminases. Another note of caution when Agenerase is prescribed with a non-nucleoside reverse transcriptase inhibitor (NNRTI): Sustiva and Viramune lower Agenerase blood levels, while Rescriptor raises Agenerase blood levels. The Agenerase product insert states that "appropriate doses of the combinations with respect to safety and efficacy have not been established" for the combination of Agenerase and an NNRTI. However, clinicians are combining these drugs. One way to offset the decrease in Agenerase levels that occurs when it is combined with either Viramune or Sustiva, is to increase to Norvir dose to 200 mg twice a day. Further drug interaction studies are needed, and it is inexcusable that these studies have not yet been performed, because these drugs are commonly being prescribed together.
The label hyperlinked below in PDF format: www.glaxowellcome.com/pi/agenerase.pdf.
If you need PDF Reader software, it may be downloaded for free at www.adobe.com/products/acrobat/readstep.html.
This article was provided by Seattle Treatment Education Project. It is a part of the publication STEP Ezine.