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Nirmatrelvir and ritonavir oral

Updated 2 Feb 2023 | Other antivirals


Oral formulation of nirmatrelvir and ritonavir.

Drugs List

  • nirmatrelvir 150mg and ritonavir 100mg tablets
  • PAXLOVID 150mg+100mg tablets
  • Therapeutic Indications


    Coronavirus disease 2019 (COVID-19) - treatment

    Treatment of COVID-19 in adults who do not require supplemental oxygen and who are at increased risk for progression to severe COVID-19.


    Nirmatrelvir must be co-administered with ritonavir.

    Treatment should be given as soon as possible after positive results of direct SARS-CoV-2 viral testing and within 5 days of onset of symptoms. If a patient requires hospitalisation due to severe or critical COVID-19 after starting treatment with nirmatrelvir and ritonavir, the patient should complete the full 5-day treatment course at the discretion of the patients healthcare provider.


    300mg (two 150mg tablets) of nirmatrelvir with 100mg (one 100mg tablet) ritonavir taken together twice daily for 5 days.

    Patients with Renal Impairment

    Moderate renal impairment
    150mg/100mg (one tablet of each) twice daily for 5 days.

    Additional Dosage Information

    Missed dose
    A missed dose should be taken as soon as possible and within 8 hours of the scheduled time, and the normal dosing schedule should be resumed. If more than 8 hours has elapsed, the missed dose should not be taken and the treatment should resume according to the normal dosing schedule.


    Children under 18 years
    Chronic renal failure
    Severe hepatic impairment
    Severe renal impairment

    Precautions and Warnings

    Females of childbearing potential
    Active liver disease
    Glucose-galactose malabsorption syndrome
    Hepatic enzymes abnormalities
    Lactose intolerance
    Moderate renal impairment

    Reduce dose in patients with moderate renal impairment
    Contains polysorbate
    Some formulations contain lactose
    Monitor patients receiving concurrent anticoagulants
    Advise patient to seek advice at first indications of pregnancy
    Advise patient not to take St John's wort concurrently
    Female: Ensure adequate contraception during treatment
    Female: Use barrier contraception during and for 1 month after treatment
    Breastfeeding: Do not breastfeed during & for 1 week after treatment

    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.

    Pregnancy and Lactation


    Nirmatrelvir and ritonavir is contraindicated during pregnancy.

    The manufacturer advises that nirmatrelvir and ritonavir is not recommended during pregnancy and in women of childbearing potential not using effective contraception. At the time of writing there is no data from the use of nirmatrelvir and ritonavir during pregnancy. In animal studies there was no nirmatrelvir-related effect on foetal morphology or embryo-foetal viability at any dose.

    A large number of pregnant woman were exposed to ritonavir during pregnancy (in combination therapy and not at therapeutic ritonavir dose used with nirmatrelvir). The data indicate no increase in the rate of birth defects compared to rates observed in population-based birth defect surveillance systems. Animal data with ritonavir have shown reproductive toxicity.


    Nirmatrelvir and ritonavir is contraindicated during breastfeeding.

    The manufacturer recommends that breastfeeding should be discontinued during treatment with nirmatrelvir and ritonavir and for 7 days after the last dose. At the time of writing there is no human data on the use of nirmatrelvir and ritonavir during breastfeeding. It is unknown whether nirmatrelvir is excreted in human or animal breast milk. Effects on the breastfed newborn or infant is unknown. Limited published data reports that ritonavir is present in human milk.

    Side Effects

    Increase of liver transaminases


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: January 2022

    Reference Sources

    Summary of Product Characteristics: Paxlovid 150mg/100mg film-coated tablets. Pfizer Limited. Revised January 2022.

    NICE Evidence Services Available at: Last accessed: 27 April 2022

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