Ritonavir (Norvir)

Published January 25, 2001; Updated October 19, 2011
Susa Coffey, MD
Selected References
2. Kirk  O, Katzenstein  TL, Gerstoft  J, Mathiesen  L, Nielsen  H, Pedersen  C, Lundgren  JD.
Combination therapy containing ritonavir plus saquinavir has superior short-term antiretroviral efficacy: a randomized trial. AIDS. 1999 Jan;13(1):F9-16
[PubMed ID: 10207539]
OBJECTIVES: To compare the efficacy and safety of indinavir 800 mg three times a day, ritonavir 600 mg twice a day, and a combination of ritonavir 400 mg twice a day and saquinavir 400 mg twice a day, when administered with two nucleoside analogues. DESIGN: A randomized, open-labelled, controlled trial. Two hundred and eighty-four patients started randomized treatment. The primary end-point was the proportion of patients with HIV RNA of 200 copies/ml or less (Roche Amplicor) and HIV RNA of 20 copies/ml or less (Roche ultradirect assay) at 6 months. Analysis was performed as intent-to-treat, and missing values were accounted for as failures. RESULTS: As of 1 May 1998, 269 patients should have completed 24 weeks of treatment. The proportion of patients with HIV RNA of 200 copies/ml or less was 71% (indinavir), 67% (ritonavir), and 82% (ritonavir + saquinavir), P = 0.07. In antiretroviral drug-naive patients (n = 119), the corresponding figures were 63, 57, and 89% (P < 0.01), whereas among drug-experienced patients (n = 165) 77, 74, and 77% had HIV RNA of 200 copies/ml or less (P = 0.90). The same pattern was observed in the ultradirect analysis. All three regimens were generally safe, but significantly more patients in the ritonavir group (37%) stopped treatment because of adverse drug reactions compared with the indinavir group (8%) and the ritonavir plus saquinavir group (16%) (P < 0.001). CONCLUSIONS: Treatment with saquinavir plus ritonavir in combination with two nucleoside analogues is generally safe, and has superior short-term antiviral efficacy compared with indinavir and ritonavir also combined with two nucleoside analogues in antiretroviral drug-naive patients. Further follow-up is needed to determine the durability of the viral response.
3. Walmsley  S, Bernstein  B, King  M, Arribas  J, Beall  G, Ruane  P, Johnson  M, Johnson  D, Lalonde  R, Japour  A, Brun  S, Sun  E; M98-863 Study Team.
Lopinavir-ritonavir versus nelfinavir for the initial treatment of HIV infection. N Engl J Med. 2002 Jun;346(26):2039-46
[PubMed ID: 12087139]
BACKGROUND: Lopinavir is a newly developed inhibitor of human immunodeficiency virus (HIV) protease that, when formulated with ritonavir, yields mean trough plasma lopinavir concentrations that are at least 75 times as high as that needed to inhibit replication of wild-type HIV by 50 percent. METHODS: We conducted a double-blind trial in which 653 HIV-infected adults who had not received antiretroviral therapy for more than 14 days were randomly assigned to receive either lopinavir-ritonavir (400 mg of lopinavir plus 100 mg of ritonavir twice daily) with nelfinavir placebo or nelfinavir (750 mg three times daily) with lopinavir-ritonavir placebo. All patients also received open-label stavudine and lamivudine. The primary efficacy end points were the presence of fewer than 400 HIV RNA copies per milliliter of plasma at week 24 and the time to the loss of virologic response through week 48. RESULTS: At week 48, greater proportions of patients treated with lopinavir-ritonavir than of patients treated with nelfinavir had fewer than 400 copies of HIV RNA per milliliter (75 percent vs. 63 percent, P<0.001) and fewer than 50 copies per milliliter (67 percent vs. 52 percent, P<0.001). The time to the loss of virologic response was greater in the lopinavir-ritonavir group than in the nelfinavir group (hazard ratio, 2.0; 95 percent confidence interval, 1.5 to 2.7; P<0.001). The estimated proportion of patients with a persistent virologic response through week 48 was 84 percent for patients receiving lopinavir-ritonavir and 66 percent for those receiving nelfinavir. Both regimens were well tolerated, with the rate of discontinuation related to the study drugs at 3.4 percent among patients receiving lopinavir-ritonavir and 3.7 percent among patients receiving nelfinavir. Among patients with more than 400 copies of HIV RNA per milliliter at some point from week 24 through week 48, resistance mutations in HIV protease were demonstrated in viral isolates from 25 of 76 nelfinavir-treated patients (33 percent) and none of 37 patients treated with lopinavir-ritonavir (P<0.001). CONCLUSIONS: For the initial treatment of HIV-infected adults, a combination regimen that includes lopinavir-ritonavir is well tolerated and has antiviral activity superior to that of a nelfinavir-containing regimen.