Adult

Paxlovid® (Nirmatrelvir/ritonavir)

General Information

Drug class: Antiviral

Nirmatrelvir is a peptidomimetic inhibitor of coronavirus 3C-like protease. Ritonavir inhibits CYP 3A4 mediated metabolism of nirmatrelvir.

Restricted: Treatment of symptomatic COVID-19 in adults who do not require supplemental oxygen and have a high risk of serious illness, as defined in NICE TA878 (see section 5). 

The groups of clinical conditions are as below and details of the risk factors for progression to severe COVID-19 in adults can be found HERE.

  • Down's syndrome and other genetic disorders
  • Solid cancer
  • Haematological diseases and recipients of haematological stem cell transplant (HSCT)
  • Renal disease 
  • Liver diseases 
  • Solid organ transplant recipients
  • Immune-mediated inflammatory disorders (diseases in which autoimmune or autoinflammation-based pathways are implicated in disease, for example, inflammatory arthritis, connective tissue diseases, inflammatory skin diseases, inflammatory gastrointestinal disease)
  • Respiratory
  • Immune deficiencies
  • HIV/AIDS
  • Neurological disorders

Paxlovid® (Nirmatrelvir/ritonavir) can be initiated by all consultants in acute general medicine areas, infectious diseases, respiratory HDU and Critical Care.

A BlueTeq form must be completed. This should be completed by the clinical team or Micro/ID. This can be completed retrospectively.

Dosing

  Oral dose
Standard dose

3 tablets (2 x 150mg nirmatrelvir tablets AND 1 x 100mg ritonavir tablet)

TWICE a day

To be commenced within 5 days of symptom onset.

The recommended course length is 5 days.

Both nirmatrelvir tablet(s) and ritonavir tablet should be taken TOGETHER.

Obesity

No dose adjustment required.

Renal and hepatic impairment

Renal impairment

eGFR (mL/min/1.73m2)

Dose

60 and above 

Dose as in normal renal function

30 upto 60

2 tablets (1 x 150mg nirmatrelvir tablets AND 1 x 100mg ritonavir tablet) TWICE a day*

Less than 30

Day 1: 3 tablets (2 x 150mg nirmatrelvir tablets AND 1 x 100mg ritonavir tablet) ONCE* only

Then

Days 2-5: 2 tablets (1 x 150mg nirmatrelvir tablets AND 1 x 100mg ritonavir tablet) ONCE a day*

Both nirmatrelvir tablet(s) and ritonavir tablet should be taken TOGETHER.

*For patients requiring a dose reduction, the additional nirmatrelvir tablet will be removed by pharmacy at the point of dispensing.

 

Hepatic impairment

  • Mild or moderate hepatic impairment (Child-Pugh class A or B): No dose adjustment is required. Use with caution.
  • Severe hepatic impairment (Child-Pugh class C): No pharmacokinetic or safety data available. Avoid in severe hepatic impairment.

Notable Interactions

Paxlovid® (Nirmatrelvir/ritonavir) has an extensive list of drug-drug interactions.

This includes medications that are dependent on CYP3A for clearance and medications which are potent inducers or inhibitors of CYP3A.

  • Paxlovid® (Nirmatrelvir/ritonavir) should NOT be prescribed and supplied until a FULL drug history (including prescribed medications, clinical trial medications, over the counter and herbal medicines) has been confirmed.
  • All interactions should be checked using The Liverpool COVID-19 Drug Interaction Checker including Resources for Nirmatrelvir/ritonavir (Paxlovid® ; 5 day administration).
  • All RED interactions: Paxlovid® must be avoided. AMBER interactions that suggest dose modification should be discussed with Micro/ID, a pharmacist or the relevant specialist team. 
  • Note, use of Paxlovid® in a patient receiving apixaban requires a risk-based approach and should be discussed with Micro/ID or a pharmacist.

Other useful resources for checking interactions include:

Contraception, pregnancy and breastfeeding

See BNF and Summary of Product Characteristics

A useful additional resource for Breastfeeding is Specialist Pharmacy Services: Managing COVID-19 and breastfeeding – SPS - Specialist Pharmacy Service – The first stop for professional medicines advice

Additional information

  • As nirmatrelvir is co-administered with ritonavir, there may be a risk of HIV-1 developing resistance to HIV protease inhibitors in individuals with uncontrolled or undiagnosed HIV-1 infection. Discuss with Micro/ID.
  • Discharge letters to primary care, and other handovers of clinical care, should explicitly record the treatment that has been given, together with the dose and date of administration.
  • Patients discharged before completing treatment should continue the course on discharge. The patient should be counselled on how to take the medication and on any adjustments made to other medication prior to discharge.

References

  1. Pfizer Limited. Paxlovid 150 mg/100 mg film-coated tablets summary of product characteristics. Electronic medicines compendium. Last revision of the text 09/2026. Accessed via www.medicines.org.uk Accessed 16/10/26.
  2. National Institute for Health and Care Excellence. Nirmatrelvir plus ritonavir, sotrovimab and tocilizumab for treating COVID-19. Technology Appraisal guidance TA878, available at Link. Last updated 26/2/26. Accessed 16/10/26.
  3. British National Formulary. Nirmatrelvir with ritonavir. BNF online accessed via www.medicinescomplete.com Accessed 16/10/26.
  4. Specialist Pharmacy Service. Managing COVID-19 and breastfeeding. Published 6/10/23. Accessed via www.sps.nhs.uk Accessed 16/10/26

Editorial Information

Last reviewed: 16 Oct 2026

Next review date: 15 Oct 2029

Author(s): AMST.