Pharmacology · HIV protease inhibitors (PIs)
Ritonavir !
A protease inhibitor now used mainly as a 'booster': it blocks CYP3A4 and raises other PIs' levels. It has a great many interactions.
Updated 2026-11-01
Also called: RTV
The figure shows ritonavir in the active site of HIV-1 protease.
Mechanism of action
It inhibits HIV protease, but at the low doses used today its main role is different: it is a potent CYP3A4 inhibitor in gut and liver. It slows the metabolism of the partner PI (darunavir, atazanavir, lopinavir), whose levels rise and last longer.
- It inhibits CYP3A4 in gut and liver
- The partner PI is metabolised more slowly
- Its levels rise and last longer
Pharmacokinetics
- Metabolism
- Liver, by CYP3A and CYP2D6; strongly inhibits CYP3A
Indications
- Booster of other protease inhibitors in HIV-1 infection HIV infection and AIDS →
Adverse effects
Common
- Nausea, vomiting, diarrhoea, abdominal pain
- Taste disturbance
- Paraesthesia, including around the mouth
- Raised triglycerides and cholesterol
Contraindications
- Drugs highly dependent on CYP3A with serious risk if raised (for example alfuzosin, simvastatin, lovastatin, ergot drugs and certain sedatives and antiarrhythmics)
- Previous severe hypersensitivity (Stevens-Johnson, toxic epidermal necrolysis)
Key interactions
- Fluticasone or budesonide
- The steroid builds up: Cushing's syndrome and adrenal suppression
- Simvastatin, lovastatin
- Rhabdomyolysis: contraindicated
- Ergot drugs
- Ergotism with ischaemia: contraindicated
What is monitored
- Full interaction review at every medication change
- Lipids, glucose and liver tests
- ECG if there is conduction disease
Administration and safety
- By mouth, with the PI it boosts
- It tastes bitter and metallic: the oral solution may be harder to tolerate
- Keep a full list of medicines and herbal products and review it with pharmacy before any new drug
Nursing care
- Review all medicines (including steroid inhalers and herbal products) before starting
- Teach to speak up before receiving any new drug, in any service
- Watch for severe abdominal pain (pancreatitis)
Pregnancy and breastfeeding
Antiretroviral treatment in pregnancy protects the mother and lowers HIV transmission to the baby; the treating team chooses the regimen.
Test yourself
Think of the answer, then tap the question to see it.
What is ritonavir's main use today?
As a pharmacokinetic booster: it inhibits CYP3A4 and raises other PIs' levels.
A patient on ritonavir uses inhaled fluticasone and develops a moon face. What happened?
Ritonavir blocked fluticasone metabolism by CYP3A: iatrogenic Cushing's syndrome and adrenal suppression.
Which statins are contraindicated with ritonavir?
Simvastatin and lovastatin, because of the risk of rhabdomyolysis.
Related drugs
Related conditions
← Back to the class: HIV protease inhibitors (PIs)
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - RITONAVIR tablet, film coated (DailyMed (U.S. National Library of Medicine), 2026); Ritonavir: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 64 (McGraw Hill, 2023).
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Representative model, for educational purposes only.