Ritonavir
An HIV protease inhibitor whose strong CYP3A blockade is used to boost other HIV protease inhibitors and nirmatrelvir for COVID-19.
Drug card
- How it works
- Blocking HIV protease, so new virus particles stay immature and non-infectious
- Used for
- HIV-1 infection, mainly to boost another protease inhibitor
- COVID-19, as the booster in nirmatrelvir-ritonavir
- Known for
- Diarrhea
- High triglycerides and cholesterol
- Its name
- -vir means an antiviral; -navir means an HIV protease inhibitor
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does ritonavir work?
A peptide-like inhibitor of HIV-1 and HIV-2 protease, which stops the Gag-Pol polyprotein being cut and leaves new particles immature. It strongly inhibits CYP3A, so a low dose raises the levels of drugs it is paired with, such as darunavir and nirmatrelvir. It has no activity against the SARS-CoV-2 protease itself.
Uses
What is ritonavir used for?
- HIV-1 infection, mainly to boost another protease inhibitor
- COVID-19, as the booster in nirmatrelvir-ritonavir
Side effects
Side effects of ritonavir
- DiarrheaKnown for
- High triglycerides and cholesterolKnown for
- Nausea and vomiting
- Tingling around the mouth and in the limbs
- Altered taste
- High blood sugar and new diabetesSerious
- HepatitisSerious
- PancreatitisSerious
- PR prolongation and heart blockSerious
- Severe skin reactions and anaphylaxisSerious
- Body fat redistribution
- Bleeding in people with hemophiliaSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Boxed warning: interactions can be life-threatening; amiodarone, simvastatin, oral midazolam and ergot drugs are contraindicated.
- Contraindicated with strong inducers such as St John's wort and apalutamide, which cut its levels.
- Check liver tests, lipids and blood sugar before and during treatment.
- Take care in heart conduction disease, as it can prolong the PR interval.
Good to know: Darunavir, for example, must be taken with ritonavir and food or it loses efficacy; in COVID-19 ritonavir only raises nirmatrelvir levels.
Remember it
A way to remember it
Protease is the scissors: without it the new virus is born but never grows up.
HIV protease cuts Gag-Pol into working viral proteins. Block it and the particles still bud off the cell, but they stay immature and cannot infect.
Written for biofideX
Its name
-vir means antiviral
Sub-stems name the target: -ciclovir, -amivir, -fovir, -tegravir, -navir, -buvir, -virine (NNRTIs). Lamivudine and zidovudine are antivirals without it.
-navir means HIV protease inhibitor
Ritonavir, atazanavir and darunavir block HIV protease. Ritonavir also strongly inhibits CYP3A, so it raises the levels of many other drugs.
- Every drug name stem
Its class
HIV protease inhibitors
HIV protease cuts the long Gag-Pol polyprotein into the working proteins of a new virus. Protease inhibitors are peptide-like molecules that block the enzyme, so new particles are released but stay immature and cannot infect. Ritonavir also strongly blocks CYP3A, so a low dose is given with others, such as darunavir, to keep their levels up (boosting).
Easily mixed up with integrase inhibitors and non-nucleoside reverse transcriptase inhibitors.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Ritonavir tablets: label (DailyMed)
- Ritonavir (NCI Thesaurus)
- Nirmatrelvir and ritonavir tablets: label (DailyMed)
- Darunavir tablets: label (DailyMed)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Antivirals
Ritonavir is one of 10 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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