15th International AIDS Conference Bangkok, Thailand - July 11-16, 2004

Int Conf AIDS 2004 Jul 11-16; 15:(abstract no. B10024)

Dragovic G, Jevtovic DJ
Department of Clinical Pharmacology, Pharmacology and Toxicology

BACKGROUND: Efficacy of Indinavir (IDV) has been known for more than 6 years. Its major disadvantages are limited absorption, a short elimination half-life and adverse events such as nephrolithiasis. IDV in combination with ritonavir (RTV) is believed to ameliorate these disadvantages. We investigate if the use of IDV singly or with boosting dose RTV in combination with nucleoside reverse transcriptase inhibitors (NRTIs) was associated with a higher risk of nephrolithiasis.

METHODS: We performed prospective, open-label study and continuously monitored drug naïve patients for incidence cases of nephrolithiasis. The patients received IDV alone (400mg bid) or IDV plus RTV (400 mg+100 mg bid) in combination with NRTIs. The prevalence of nephrolithiasis between groups of patients on IDV alone (IDV arm) and on IDV with boosting dose RTV (IDV+RTV arm) was compared using the chi-square test. The probability of developing nephrolithiasis was estimated by Univariate and stepwise Multivariate logistic regression.

RESULTS: There were 143 patients. 89 patients were included in the IDV arm and 54 patients in the IDV+RTV arm. Nephrolithiasis developed in 38 (26.57%) patients in total. The prevalence of nephrolithiasis was 26.97% on IDV arm and 25.93% on IDV+RTV arm, respectively (p<0.001; df=1). Multivariate logistic regression shown that the relative risk of developing nephrolithiasis is 1.5 folder greater (RR=1.5; 95%CI 0.98 - 2.39) in IDV arm and 6.6 folder greater in IDV+RTV arm (RR=6.6; 95%CI 1.72 - 16.26). Conclussions: We demonstrate that boosting IDV with RTV increased the risk of developing nephrolithiasis by 6.6-fold. We support the need for therapeutic drug monitoring in patients using IDV with or without RTV in order to monitor the number of patients who discontinued IDV due to toxicity.

040711
B10024

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