It is taken with meals, and its longer half-life means that it probably does not need to be taken on an every 8 hour schedule. Nelfinavir improves drug levels of saquinavir, although to a lesser degree than ritonavir. Loose stools or diarrhea are common. Resistance may require fewer mutations than with ritonavir or indinavir, but it is not known whether that will translate into decreased durability. These combinations are highly potent regimens that do not necessarily require the use of RT inhibitors, making them attractive for heavily pre-treated patients.
Ritonavir allows all other PIs to be taken twice daily.
Ritonavir can be taken at lower, better-tolerated doses when it is combined with other PIs. They may also be more expensive, especially when combined with RT inhibitors. They are not as well tested as single PI combinations. With these regimens, drug interactions become extremely important. In general, nevirapine decreases drug levels of PIs, with the effect being large on saquinavir, intermediate on indinavir and nelfinavir, and negligible on ritonavir.