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Nirmatrelvir and ritonavir

Generic name: nirmatrelvir and ritonavir
Brand name: Paxlovid
Dosage forms: oral tablet (150 mg-100 mg (150 mg-100 mg Dose), 150 mg-100 mg (300 mg-100 mg Dose))
Drug class: Antiviral combinations

Medically reviewed by on Feb 3, 2023. Written by Cerner Multum.

What is nirmatrelvir and ritonavir?

Nirmatrelvir in combination with ritonavir is an experimental medicine being studied for the treatment of mild-to-moderate COVID-19. This drug is still being studied and all of its risks are not yet known.

The US Food and Drug Administration (FDA) has authorized emergency use of nirmatrelvir in combination with another medicine called ritonavir for the treatment of mild-to-moderate COVID-19 in adults and people 12 years of age and older (weighing at least 40 kg or 88 lbs) who are at high risk for progression to severe COVID-19, including hospitalization or death.

Nirmatrelvir and ritonavir is not authorized for use:

  • for initiation of treatment in people needing hospitalization due to COVID-19;

  • for prevention before or after exposure of COVID-19; or

  • longer than 5 consecutive days.

Nirmatrelvir and ritonavir may also be used for purposes not listed in this medication guide.

Nirmatrelvir and ritonavir side effects

Get emergency medical help if you have signs of an allergic reaction (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning eyes, skin pain, red or purple skin rash with blistering and peeling).

Nirmatrelvir and ritonavir may cause serious side effects. Call your doctor at once if you have:

  • liver problems--loss of appetite, stomach pain (upper right side), tiredness, itching, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Ritonavir affects your immune system, which may cause certain side effects (even weeks or months after you've taken nirmatrelvir and ritonavir). Tell your doctor if you have:

  • signs of a new infection--fever, night sweats, swollen glands, cold sores, cough, wheezing, diarrhea, weight loss;

  • trouble speaking or swallowing, problems with balance or eye movement, weakness or prickly feeling; or

  • swelling in your neck or throat (enlarged thyroid), menstrual changes, impotence.

Common side effects of nirmatrelvir and ritonavir may include:

  • changes in your sense of taste;

  • diarrhea;

  • elevated blood pressure; or

  • muscle pain.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.


The US Food and Drug Administration (FDA) has authorized emergency use of nirmatrelvir in combination with another medicine called ritonavir for the treatment of mild-to-moderate COVID-19 in adults and people 12 years of age and older (weighing at least 40 kg or 88 lbs).

Before taking this medicine

You should not use nirmatrelvir and ritonavir if you are allergic to it.

Some drugs should not be used with nirmatrelvir and ritonavir, such as those listed below.

Nirmatrelvir and ritonavir should not be started immediately after discontinuation of any of the following drugs:

Tell your doctor if:

  • you have liver problems or a liver disease such as hepatitis;

  • you have kidney problems;

  • you have an HIV-1 infection;

  • you are pregnant or breastfeeding; or

  • you have any serious or chronic disease.

COVID-19 is more likely to cause serious illness or death in a pregnant woman. Not all risks are known yet, but being treated with nirmatrelvir and ritonavir is likely to be less harmful than being infected with COVID-19 during pregnancy.

Ritonavir can make birth control pills or skin patches less effective. Ask your doctor about other birth control options such as an injection, implant, vaginal ring, condom, diaphragm, cervical cap, or contraceptive sponge.

How should I take nirmatrelvir and ritonavir?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Take nirmatrelvir together with ritonavir (two tablets of nirmatrelvir and one tablet of ritonavir) twice a day for 5 consecutive days.

Take nirmatrelvir and ritonavir as soon as possible after diagnosis of COVID-19 and within 5 days of when symptoms first appear.

You may take nirmatrelvir and ritonavir with or without food.

Swallow the tablets whole and do not crush, chew, or break them.

You may need frequent blood tests to check your liver function.

Being treated with nirmatrelvir and ritonavir will not make you less contagious to other people. Keep using infection control methods such as self-isolation, social distancing, hand-washing, using protective face covering, disinfecting surfaces you touch a lot, and not sharing personal items with others.

Nirmatrelvir and ritonavir are still being studied and all of the risks are not yet known.

What happens if I miss a dose?

Use the medicine as soon as you can, but skip the missed dose if you are more than 8 hours late for the dose. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222.

What should I avoid while taking nirmatrelvir and ritonavir?

Follow your doctor's instructions about any restrictions on food, beverages, or activity.

What other drugs will affect nirmatrelvir and ritonavir?

Sometimes it is not safe to use certain medicines at the same time. Some drugs can affect your blood levels of other drugs you use, which may increase side effects or make the medicines less effective.

Many drugs can affect nirmatrelvir and ritonavir, and some drugs should not be used at the same time. Tell your doctor about all other medicines you use. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here.

Frequently asked questions

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.