Indinavir (Crixivan) is able to reduce HIV viral load below the limit of detection and increase CD4 cell counts in the majority of people who take it in combination with at least two other antiretroviral drugs.

Indinavir was approved on the basis of two studies. ACTG 320 demonstrated that patients taking the combination of indinavir, AZT (zidovudine, Retrovir) and 3TC (lamivudine, Epivir) were less likely to progress to AIDS or death than those taking AZT and 3TC alone. This was paralleled by a higher proportion of these patients having undetectable viral loads and increased CD4 cell counts^[1]. Similarly, study 035 demonstrated that indinavir plus AZT and 3TC had a more favourable outcome than either indinavir alone or AZT and 3TC^[2].

More recent studies have demonstrated that combinations including indinavir and two nucleoside reverse transcriptase inhibitors (NRTIs) are at least as effective as combinations based on the protease inhibitor saquinavir (Invirase) or the non-nucleoside reverse transcriptase inhibitor (NNRTI) nevirapine (Viramune), and triple NRTI combinations^[3][4][5]. However, one study found that the NNRTI efavirenz (Sustiva) was more effective than indinavir, when combined with AZT and 3TC over 72 weeks, in patients who had mostly taken no antiretroviral drugs before^[6].

Indinavir can also be boosted with low-dose ritonavir (Norvir), which increases indinavir levels and allows the drug to be taken less often. A range of doses of indinavir and ritonavir have been tested in trials^{[7][8][9][10][11][12][13][14]}. It is not yet clear which dose is the best option, although 400mg indinavir and 100mg ritonavir twice a day, or possibly 600 and 200mg, seems to produce adequate levels of indinavir with a low incidence of side-effects in most patients, particularly if therapeutic drug monitoring is available to ensure adequate drug exposure. Although higher doses of indinavir or ritonavir can improve exposure to indinavir, the increased rate of side-effects limits their usefulness, especially when other ritonavir-boosted protease inhibitors have similar anti-HIV efficacy to indinavir, but with fewer side-effects^[15][16][17].

Highly treatment-experienced individuals can often benefit from salvage combinations containing indinavir, with or without ritonavir boosting^[18][19]. Patients with hepatitis B or C can take 200 or 400mg indinavir boosted with 100mg ritonavir twice a day^[20][21].

There is some evidence that indinavir can penetrate the blood-brain barrier and reach sufficient concentrations in the cerebrospinal fluid to be active against HIV in the central nervous system^[22][23][24]. It can also reach anti-HIV levels in the semen^[25].