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Regimen-dependent variations in adherence to therapy and virological suppression in patients initiating protease inhibitor-based highly active antiretroviral therapy.

Moore DM, Hogg RS, Yip B, Wood E, Harris M, Montaner JS

BC Centre for Excellence in HIV/AIDS, Vancouver, British Columbia, Canada. dmoore@cfenet.ubc.ca

OBJECTIVE: To examine differences among four protease inhibitor (PI)-based drug regimens in adherence to therapy and rate of achievement of virological suppression in a cohort of antiretroviral-naive patients initiating highly active antiretroviral therapy (HAART). METHODS: Participants were antiretroviral-naive and were first dispensed combination therapy containing two nucleosides and a ritonavir (RTV)-boosted PI, or unboosted nelfinavir, between 1 January 2000 and 30 September 2003. Logistic regression analysis was used to examine associations between the prescribed PI and other baseline factors associated with being >90% adherent to therapy and then to determine the associations of prescribed drug regimen, adherence to therapy and baseline variables with the odds of achieving two consecutive viral loads of <500 HIV-1 RNA copies/mL. RESULTS A total of 385 subjects were available for analysis. Lopinavir (LPV)/RTV was prescribed for 168 patients (42% of total); 86 (22%) received indinavir (IDV)/RTV; 91 (24%) received nelfinavir (NFV) and 40 (10%) received saquinavir (SQV)/RTV. SQV/RTV-based HAART was associated with reduced adherence to therapy [odds ratio (OR)=0.40; 95% confidence interval (CI) 0.19-0.83]. In multivariate models, IDV/RTV (OR=0.45; 95% CI 0.22-0.92), SQV/RTV (OR=0.18; 95% CI 0.07-0.43) and NFV were associated with reduced odds of achieving virological suppression within 1 year in comparison to LPV/RTV-based therapy. For patients receiving NFV, adjusting for adherence (OR=0.73; 95% CI 0.36-1.47) rendered this association nonsignificant. CONCLUSION: Patients prescribed IDV/RTV, NFV or SQV/RTV were less likely to achieve virological suppression on their first regimen compared with patients prescribed LPV/RTV. Reduced adherence to these therapies only partly explained these observed differences.

Published 1 September 2006 in HIV Med, 7(5): 311-6.
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