nirmatrelvir + ritonavir at a glance
Medicine class
Systemic antiviral; protease inhibitor combination
Licensed use
COVID-19 in higher-risk adults who do not require supplemental oxygen
Administration
The nirmatrelvir and ritonavir tablets must be taken together and swallowed whole
Food
May be taken with or without food
Key safety issue
A complete check of prescribed, non-prescription, herbal and recreational substances is essential because interactions can be serious
What is nirmatrelvir + ritonavir used for?
The selected UK product is licensed for:
Treating COVID-19 in adults who do not require supplemental oxygen and who are at increased risk of progression to severe COVID-19.
How does nirmatrelvir + ritonavir work?
Nirmatrelvir blocks the SARS-CoV-2 main protease, preventing the virus from processing proteins needed for replication. Ritonavir slows CYP3A-mediated breakdown of nirmatrelvir so effective concentrations are maintained.
nirmatrelvir + ritonavir preparations and strengths
Tablet
Route: Oral
Strengths: 150 mg + 100 mg
How to take nirmatrelvir + ritonavir
Follow the dispensing label and pack instructions carefully, particularly if kidney function is impaired. The two active ingredients are supplied as separate tablets and must be taken together.
Swallow tablets whole; do not chew, break or crush them.
Take with or without food.
Do not share the tablets or save them for a later infection.
Do not stop early without discussing this with the prescriber, even if symptoms improve.
nirmatrelvir + ritonavir side effects
Common or expected effects
- Altered or metallic taste
- Diarrhoea
- Nausea
- Headache
Get urgent medical advice
- Severe allergic reaction, including facial or tongue swelling and breathing difficulty
- Severe skin reaction with painful redness, blistering, peeling or mouth sores
- Possible liver injury, including jaundice, particularly in someone with pre-existing liver disease
nirmatrelvir + ritonavir in pregnancy
Pregnancy data remain limited. Nirmatrelvir + ritonavir can be used when recommended by a healthcare professional, following an individual assessment of the benefits of treating COVID-19 and the remaining uncertainties. Ritonavir may reduce the effectiveness of combined hormonal contraception, so alternative or additional barrier contraception is advised as specified in the product information.
nirmatrelvir + ritonavir while breastfeeding
The product information advises temporarily interrupting breastfeeding during treatment and for 48 hours afterwards. SPS considers cautious use with infant monitoring acceptable for a full-term, healthy infant; seek specialist advice if the infant is premature or unwell, or if several medicines are being taken.
nirmatrelvir + ritonavir interactions
Ritonavir strongly affects CYP3A and other pathways. Check every prescribed, non-prescription and herbal product before treatment; the examples below are not exhaustive.
Amiodarone and several other antiarrhythmics
Concentrations may rise substantially, creating a risk of serious arrhythmias; listed combinations are contraindicated.
Simvastatin and lovastatin
Concentrations may rise and cause severe muscle toxicity, including rhabdomyolysis; concomitant use is contraindicated.
Carbamazepine, phenytoin, phenobarbital and primidone
Strong enzyme induction can lower antiviral exposure, risking loss of effect and resistance; concomitant use is contraindicated.
Common questions about nirmatrelvir + ritonavir
Answers are fully visible for fast scanning and source review.
What does each part of nirmatrelvir + ritonavir do?
Nirmatrelvir directly blocks a protease needed for SARS-CoV-2 replication. Ritonavir slows nirmatrelvir's breakdown and increases its exposure.
Can nirmatrelvir + ritonavir be taken with food?
Yes. The tablets may be taken with or without food.
Can nirmatrelvir + ritonavir tablets be crushed?
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.