Lopinavirritonavir

Lopinavir/ritonavir is a fixed-dose combination antiretroviral medication used to treat HIV-1 infection in adults and children. It combines lopinavir, a protease inhibitor, with ritonavir, a pharmacokinetic enhancer that inhibits hepatic enzymes to increase lopinavir exposure. It is marketed under brand names such as Kaletra and is available in tablet and oral solution forms.

Mechanism of action remains twofold. Lopinavir inhibits HIV-1 protease, blocking cleavage of the Gag-Pol polyprotein and resulting in immature, noninfectious viral particles. Ritonavir inhibits cytochrome P450 3A enzymes, boosting lopinavir blood levels and allowing once- or twice-daily dosing in many regimens.

Administration and dosing are typically oral, taken with meals to improve absorption. The product is used as part of combination antiretroviral therapy (ART) for HIV-1 infection, in adults and in pediatric patients, with dosing and formulation adjusted for weight and age. The oral solution contains alcohol and propylene glycol, which may be a consideration for certain patients.

Contraindications and interactions are important considerations. Co-administration with agents that are contraindicated with ritonavir or that rely on CYP3A metabolism is generally avoided. Drugs with potential for serious interactions include certain antiarrhythmics, sedatives, statins, and others; coadministration with rifampin is typically avoided due to reduced lopinavir levels. Ritonavir’s enzyme inhibition also raises the risk of adverse effects from other drugs.

Common adverse effects include diarrhea, nausea, vomiting, and abdominal pain, as well as hepatotoxicity, lipid abnormalities, and lipodystrophy with long-term use. Treatment decisions, monitoring of viral load, and potential switches to alternative regimens are guided by clinical response and tolerability.