Ritonavir

Ritonavir is an antiretroviral medication belonging to the protease inhibitor (PI) class. It is primarily used to "boost" the effectiveness of other protease inhibitors, rather than as a primary treatment for HIV infection itself. This "boosting" effect is achieved by ritonavir inhibiting the CYP3A enzymes in the liver and intestines, which are responsible for metabolizing many protease inhibitors. By inhibiting these enzymes, ritonavir slows the breakdown of other PIs, leading to higher blood concentrations and longer half-lives of those drugs. This allows for less frequent dosing and lower overall dosages of the boosted PI, potentially reducing side effects and improving treatment adherence.

While ritonavir does possess some intrinsic antiviral activity against HIV, its boosting effect is its primary clinical utility. It is rarely used as a single-agent treatment due to the higher doses required for effective viral suppression and the associated side effects.

Ritonavir is available in several formulations, including tablets and oral solutions. Common side effects can include gastrointestinal issues (nausea, vomiting, diarrhea), paresthesias (tingling or numbness), and elevated cholesterol levels.

It is crucial to note that ritonavir has significant drug interactions due to its effects on CYP3A enzymes and other metabolic pathways. Healthcare providers must carefully consider potential interactions with other medications the patient is taking. Contraindications include co-administration with certain drugs metabolized by CYP3A enzymes where increased plasma concentrations could lead to serious or life-threatening adverse events.