The rate of viral rebound after attainment of an HIV load <50 copies/mL according to specific antiretroviral drugs in use: results from a multicenter cohort study.

BACKGROUND Relatively few data are available on the association between the use of specific antiretroviral drugs and the rate of viral rebound in those attaining a viral load (VL) <50 copies/mL while receiving highly active antiretroviral therapy (HAART). METHODS Patients achieving a VL <50 copies/mL for the first time while receiving HAART were followed until viral rebound (2 consecutive VLs >500 copies/mL). Pre-HAART antiretroviral-naive patients were analyzed separately from those with nucleoside reverse transcriptase inhibitor (NRTI) experience. RESULTS Of 3565 suppressed antiretroviral-naive patients, 381 experienced viral rebound (rate, 6.26 events/100 person-years of follow-up [pyrs] [95% confidence interval {CI}, 5.63-6.89 events/100 pyrs]). For those receiving efavirenz, the rate was 4.08 (95% CI, 3.16-5.01) events/pyrs. Compared with this, the rebound rate for those receiving indinavir was 1.52 times higher (rate ratio [RR], 1.52 [95% CI, 0.82-2.84]). RRs (95% CIs) for other drugs were: soft-gel saquinavir, 0.54 (0.07-3.97); nelfinavir, 2.44 (1.68-3.54); indinavir/ritonavir, 1.96 (1.02-3.77); saquinavir/ritonavir, 1.12 (0.48-2.61); lopinavir/ritonavir, 1.23 (0.58-2.59); nevirapine, 1.53 (1.11-2.10); and abacavir, 2.03 (1.26-3.25). Of 810 NRTI-exposed patients, 145 experienced viral rebound (rate, 8.29 [95% CI, 6.94-9.64] events/pyrs). For those receiving efavirenz, the rate was 5.25 (95% CI, 3.11-8.30) events/pyrs. Compared with this, the RRs (95% CIs) were: indinavir, 1.75 (0.82-3.73); hard-gel saquinavir, 3.48 (0.36-33.37); nelfinavir, 2.64 (1.37-5.08); indinavir/ritonavir, 0.32 (0.04-2.49); saquinavir/ritonavir, 0.64 (0.23-1.80); nevirapine, 1.65 (0.90-3.02); and abacavir, 1.82 (0.73-4.52). CONCLUSIONS We must make comparisons of antiretroviral outcomes in observational data with caution; however, our results suggest that, in those with VLs <50 copies/mL, certain drugs may be associated with higher rebound rates than others.