A Clinical Study of the Combination of 100 mg Ritonavir Plus 800 mg Indinavir as Salvage Therapy: Influence of Increased Plasma Drug Levels in the Rate of Response [Casado JL, et al. HIV Clin Trials 2000; 1: 13]: This is a timely report from Spain on the efficacy of ritonavir plus indinavir in the dose of 800/100 bid in 59 patients who had failed previous treatment with PI-containing regimens. After 24 weeks of treatment, 38% had a viral load less than 50 c/ml, and 13 patients (22%) had nephrolitiasis or other renal toxicity. Compared to standard doses, IDV peak levels in combination with ritonavir were slightly higher (7.1 mg/L versus 6.7 mg/L), but IDV trough levels were much higher (1.75 mg/L versus 0.13 mg/L).
Comment: As possibly expected, this study showed a correlation between plasma drug levels, toxicity and response. The high rate of nephrotoxicity is disappointing. The regimen competing with this combination is 400/400 mg twice daily which seems likely to generate more GI toxicity and possibly less nephrotoxicity. The results of this study also suggest that monitoring trough levels of indinavir may be useful with this combination. posted 8/31/2000