Increased prevalence and analysis of risk factors for indinavir nephrolithiasis

Purpose: Indinavir is a protease inhibitor used for treating HIV-1. The dru g is lithogenic and was thought to cause a 3% incidence of kidney stones. W e evaluated a cohort of patients positive for HIV on indinavir to determine the incidence of indinavir nephrolithiasis and identify risk factors for i ndinavir stone formation. Materials and Methods: Our cohort study of the prevalence of indinavir neph rolithiasis included 155 patients with HIV for 5,732 patient-weeks. The sam e cohort was then used for a retrospective chart review to assess patient a ge, weight, duration of drug use, time to stone formation, CD4 count, creat inine, alanine transaminase, and urinary pH and specific gravity as risk fa ctors for stone formation. Results: We estimated the cumulative incidence of indinavir stone formation by the Kaplan-Meier product limit estimator method. At 78 weeks 43.2% of p atients had stones (95% confidence interval [CI] 0.292 to 0.543). Increasin g age was the only variable that was a statistically significant predictor of indinavair urolithiasis (relative risk 0.955, 95% CI 0.918 to 0.993, p = 0.0159). The mean duration plus or minus standard deviation of indinavir u se was statistically the same in each group (42.5 +/- 27.2 and 40.3 +/- 27. 1 weeks in those without and with stones, respectively) despite the observe d mean time to stone formation of 23.0 +/- 19.8 weeks. Conclusions: The clinical prevalence of indinavir nephrolithiasis is much g reater than initially reported. Nephrolithiasis during indinavir use does n ot appear to induce patients to withdraw from the drug.