by Steven J. Wamback

Created on: April 07, 2007   Last Updated: May 02, 2007

Introduction

Among the first lines of defense in the prevention of the exacerbation of Human Immunodeficiency Virus to "full-blown" CDC-defined AIDS among HIV infected individuals is the prevention of or the reduction of the virus' ability to replicate its genetic material, RNA. Certain RNA protease inhibitors and nucleosides are among the antiretroviral compounds which have been shown to be effective medications in achieving this goal.

Indinavir (an HIV RNA protease inhibitor) and abacavir (a nucleoside analogue and inhibitor of HIV RNA reverse transcriptase) have been shown to be effective both alone and in combination with lamivudine and zidovudine nucleosides in the suppression of human immunodeficiency virus (HIV) replication. Abacavir is marketed in the United States as abacavir, (abacavir sulfate), trizivir (the triple nucleoside combination), or the trade name Ziagen (Glaxo-Smith-Kline). Indinavir (indinavir sulfate) is marketed in the United States as Crixivan (Merck & Co., Inc., PDR, 2005).

This report addresses some of the safety and efficacy considerations in prescribing indinavir vs. abacavir in combination with lamivudine and zidovudine nucleosides in the virologic suppression of HIV.

A Clinical Trial

In a multicenter, phase 3, randomized, double-blind, placebo-controlled study, Staszewski et al. (2001) evaluated the safety and efficacy of these two regimens for the initial antiretroviral treatment of 562 antiretroviral-nave patients diagnosed with HIV and whose plasma concentrations of HIV RNA were at least 10,000 copies per milliliter (mL) and who had CD4 cell counts of at least 100X106/L. Virologic suppression was defined as achieving HIV RNA concentrations of 400 copies/mL or fewer at week 48 of the study.

Findings and Conclusions

The study concluded that the triple-nucleoside regimen of abacavir-lamivudine-zidovudine (triziver) was equivalent to the protease inhibitor-containing regimen of indinavir-lamivudine-zidovudine in reducing plasma concentrations of HIV RNA to fewer than 400 copies/mL at 48 weeks in antiretroviral-naive HIV-infected adults. The authors concluded that there were no significant differences between the two treatment groups in effects on CD4 cell counts, in adverse events, in overall genotypic resistance-conferring mutagenesis, or in laboratory abnormalities.

Among high baseline patients whose baseline HIV RNA concentrations were initially greater than 100,000 copies/mL, the proportion ultimately achieving fewer than 50 copies/mL

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