Ritonavir boosting is not recommended with which of the following protease inhibitor of HIV?
**Core Concept**
Ritonavir boosting is a pharmacokinetic enhancement technique used to increase the plasma concentrations of other protease inhibitors in HIV treatment. This is achieved by inhibiting the cytochrome P450 3A4 enzyme, which is responsible for the metabolism of many protease inhibitors.
**Why the Correct Answer is Right**
The correct answer is **A. Atazanavir**. Ritonavir boosting is not recommended with Atazanavir because it is a less potent inhibitor of the cytochrome P450 3A4 enzyme compared to other protease inhibitors. Additionally, Atazanavir is susceptible to degradation by the cytochrome P450 3A4 enzyme, which is further reduced by the presence of Ritonavir. This results in decreased plasma concentrations and reduced efficacy of Atazanavir when boosted with Ritonavir.
**Why Each Wrong Option is Incorrect**
**Option B:** Darunavir is a protease inhibitor that can be boosted with Ritonavir to achieve higher plasma concentrations and improved efficacy. Ritonavir boosting is a recommended strategy for Darunavir.
**Option C:** Lopinavir is another protease inhibitor that is commonly boosted with Ritonavir to increase its plasma concentrations and improve its efficacy.
**Option D:** Saquinavir is a protease inhibitor that can also be boosted with Ritonavir to enhance its plasma concentrations and improve its efficacy.
**Clinical Pearl / High-Yield Fact**
It is essential to note that Ritonavir boosting is not a universal strategy and should be used judiciously, as it can lead to increased toxicity and drug interactions. Always consult the most recent treatment guidelines and consider individual patient factors before initiating Ritonavir boosting.
**Correct Answer: A. Atazanavir**