Darunavir

• HIV-1 Infection
• Antiretroviral Therapy
• Treatment-Experienced HIV
• Protease Inhibitor-Based Regimens

Darunavir is a protease inhibitor (PI) antiretroviral medication used in the treatment of HIV-1 infection. This second-generation protease inhibitor offers high potency, a favorable resistance profile, and is a key component of many preferred HIV treatment regimens when combined with a pharmacokinetic booster.

Mechanism of Action

Darunavir inhibits the HIV-1 protease enzyme, which is essential for cleaving the viral Gag-Pol polyprotein into individual functional proteins required for viral maturation. By binding to the active site of HIV protease with high affinity, darunavir prevents the production of mature, infectious viral particles. Newly produced virions remain non-infectious. Darunavir has a flexible molecular structure allowing it to adapt to protease mutations, contributing to its activity against many PI-resistant HIV strains. However, it must be co-administered with a pharmacokinetic enhancer (ritonavir or cobicistat) to achieve adequate plasma levels.

Available Formulations

Darunavir is available as tablets (75 mg, 150 mg, 600 mg, 800 mg) and oral suspension (100 mg/mL). It is also available in fixed-dose combination tablets with cobicistat (darunavir 800 mg/cobicistat 150 mg) and with cobicistat, emtricitabine, and tenofovir alafenamide as a complete single-tablet regimen. All formulations must be taken with food to ensure adequate absorption.

Medical Uses

Darunavir is FDA-approved for the treatment of HIV-1 infection in adults and pediatric patients 3 years of age and older, weighing at least 10 kg. It must be co-administered with ritonavir or cobicistat as a pharmacokinetic enhancer. Darunavir is used both in treatment-naive patients and in treatment-experienced patients with HIV strains resistant to other protease inhibitors. It is included in several guideline-recommended initial regimens, particularly for patients with high viral loads.

Dosing Guidelines

For treatment-naive or treatment-experienced patients with no darunavir resistance mutations, darunavir 800 mg plus ritonavir 100 mg (or cobicistat 150 mg) once daily with food is recommended. For treatment-experienced patients with one or more darunavir resistance mutations, darunavir 600 mg plus ritonavir 100 mg twice daily with food is used. Pediatric dosing is weight-based. The medication must always be taken with food and with a pharmacokinetic booster. Fixed-dose combinations simplify dosing.

Important Safety Information

Darunavir contains a sulfonamide moiety; use with caution in patients with sulfa allergy, though cross-reactivity is not well established. Hepatotoxicity, including acute hepatitis and hepatic decompensation, has been reported, particularly in patients with pre-existing liver disease or hepatitis coinfection. Severe skin reactions, including Stevens-Johnson syndrome and toxic epidermal necrolysis, have occurred. New onset or worsening diabetes mellitus and diabetic ketoacidosis have been reported. Drug interactions through CYP3A4 are extensive and must be carefully evaluated.

Drug Interactions

Darunavir is a CYP3A inhibitor and substrate; ritonavir and cobicistat further inhibit CYP3A. Many drugs are contraindicated or require dose adjustment. Contraindicated drugs include alfuzosin, dronedarone, rifampin, ranolazine, certain anticonvulsants (with cobicistat), ergot derivatives, triazolam, oral midazolam, lovastatin, simvastatin, St. John's Wort, and sildenafil (for pulmonary hypertension). Many other medications require monitoring or dose adjustment. Always check for interactions before prescribing.

When a Boosted Protease Inhibitor Is Still the Right Backbone

Integrase inhibitors have taken over first-line HIV treatment, and a single tablet such as bictegravir, emtricitabine, and tenofovir alafenamide is what most people starting therapy now receive. Darunavir keeps a defined role rather than a nostalgic one. Its genetic barrier to resistance is among the highest of any antiretroviral, so it is favored when adherence is likely to be interrupted — unstable housing, incarceration, active substance use, frequent travel — because a missed dose is less likely to cost a whole class of drugs. It is chosen again when resistance to other classes is already documented, when treatment has to start before a genotype comes back in someone with a complicated history, and in selected situations during pregnancy where its pharmacology is well characterized.

The cost of that reliability is the booster. Darunavir needs ritonavir or cobicistat alongside it to reach useful levels, and the booster, not the darunavir, is the source of most of the trouble. Where a simpler regimen will hold, an integrase-based option such as dolutegravir is usually preferred.

Living With a Boosted Regimen

The rule patients are given is blunt: nothing new gets started without a check, including things that do not feel like prescriptions. The boosted regimen raises levels of many common drugs to dangerous concentrations. Inhaled and intranasal corticosteroids are the most-missed example and have caused adrenal suppression. Certain statins are contraindicated outright and others need a reduced dose. Some sedatives, migraine ergots, erectile dysfunction drugs, hormonal contraception, and St. John's wort all appear on the list, as do some acid-reducing medicines. A dentist, a dermatologist, an eye clinic, and an urgent care visit are all points where an interacting drug gets added by someone who does not have the full picture.

The other daily habit is food. Absorption falls substantially without a meal, and a cracker does not count; the dose is anchored to breakfast or dinner rather than taken on the way out of the door. A rash in the first weeks is common and usually mild, but one with fever, blistering, mouth sores, or facial swelling is an emergency. Lipids and glucose are followed, since both can rise on this class. Long-term care for acquired immune deficiencies otherwise looks like ordinary preventive medicine. The MedlinePlus darunavir monograph and the NIH adult and adolescent antiretroviral guidelines are the references we work from, and our immunology team runs the interaction check at every visit.

Special Populations

The Antiretroviral Pregnancy Registry monitors outcomes in pregnant women. Darunavir/ritonavir can be used during pregnancy with appropriate dosing. Once-daily dosing may not be appropriate during pregnancy due to pharmacokinetic changes. Breastfeeding is not recommended in HIV-infected women in resource-rich settings to prevent HIV transmission. Safety and efficacy have been established in pediatric patients 3 years and older. Elderly patients should be monitored for hepatic function. No dose adjustment is needed for renal impairment. Use with caution in hepatic impairment; darunavir is contraindicated in severe hepatic impairment.