Important note: Information in this article was accurate in May 2002. The state of the art may have changed since the publication date. 
Some HIV treatment regimens can be complex — people with HIV/AIDS (PHAs) may have to take their medications several times daily, with food and water restrictions. As well, some treatments need to be taken on a strict schedule. Such complexities may make it difficult for PHAs to take their medicines exactly as prescribed and directed — an issue called adherence. Not adhering to one's drug regimen will lead to the growth of HIV that is drug resistant. Having drug-resistant virus reduces treatment options and possibly increases the risk of developing AIDS-related complications.
In the hope of improving adherence, researchers are trying to create once-daily dosing regimens. In order to do this with protease inhibitors (PIs), large doses of these drugs need to be taken with another PI, usually ritonavir (Norvir). This is because ritonavir boosts the level of the other PI in the blood for prolonged periods of time. Ritonavir is often used to boost the following PIs:
Two formulations of saquinavir are currently available:
After Invirase was released (it was the first protease inhibitor on the market), researchers found that levels of saquinavir in the blood were relatively low. To improve absorption, the manufacturer, Hoffmann-La Roche, created a new formulation of saquinavir called Fortovase. Although Fortovase could be taken as a single PI in combination therapy, it was often taken twice daily, either in combination with ritonavir or without this boost.
At first, saquinavir and ritonavir were often prescribed in a combination of 400 mg of each drug taken twice a day. Because the large amount of ritonavir in this combination was not always well tolerated, doctors conducted experiments — increasing the dose of saquinavir to 1,000 mg twice daily while reducing the dose of ritonavir to 100 mg or 200 mg twice daily. To compare the effects of these dose regimens (400/400 vs. 1,000/100), researchers across the U.S. conducted a study. The results of this small study suggest that both regimens are equally effective. Details about this study appear in the next CATIE News story : Saquinavir with low-dose ritonavir twice daily.
REFERENCE
O'Brien WA, Acosta E, Felizarta F, et al. Switch of saquinavir 400 mg/Ritonavir 400 mg to saquinavir 1,000 mg/Ritonavir 100 mg during BID four drug antiretroviral therapy.3rd International Workshop on Clinical Pharmacology of HIV Therapy, Washington D.C., 11-13 April, 2002; abstract 2.1.
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