Nirmatrelvir and ritonavir

Paxlovid is used to treat people who have moderate COVID-19 infection. Paxlovid comprises two antiviral medicines – nirmatrelvir and ritonavir.

What is Paxlovid?

Paxlovid is given to some people to help fight a COVID-19 virus infection. It may help you get better faster and stay out of hospital. 

Paxlovid consists of two antiviral medicines – nirmatrelvir (150mg) and ritonavir (100 mg). When taken together, they reduce the amount of virus in your body. Paxlovid is only useful when given within 5 days of the start of your COVID-19 illness so your doctors will decide whether you need this. 

How to take Paxlovid

Paxlovid consists of 2 medicines – nirmatrelvir (pink tablet) and ritonavir (white tablet). It's important to take these tablets as directed below.

  • Timing:  Try to space the doses evenly throughout the day such as the first thing in the morning and at bedtime. Ideally these times should be 12 hours apart. 
  • Food: You can take your tablets with or without food. If Paxlovid gives you nausea (feeling sick), try taking it with food.
  • Swallow the tablets whole with a glass of water (200–250 mLs). Do not chew, break, or crush them.
  • Missed dose: If you miss a dose of Paxlovid but remember within 8 hours of the time it is usually taken, take it as soon as you remember.
    If you miss a dose by more than 8 hours, skip the missed dose and take the next dose at your regular time. Do not take extra doses of Paxlovid to make up for a forgotten dose. If you are not sure what to do, ask your healthcare provider.
  • Complete the course. Do not stop taking Paxlovid without talking to your healthcare provider, even if you feel better. A course of treatment lasts 5 days.

Precautions before taking Paxlovid

Tell your healthcare provider about all the medicines you take.

There are some medicines that may not mix with Paxlovid and when taken together may cause serious side effects.

  • Tell your doctor or pharmacist if you are taking or have recently taken any other medicines, including prescription and over the counter medicines, vitamins and herbal supplements (for example, St. John’s Wort).
  • Do not start taking a new medicine without telling your healthcare provider. Your healthcare provider can tell you if it is safe to take Paxlovid with other medicines.

Are you pregnant or trying for a baby?

If you are pregnant, think you may be pregnant, or are planning to have a baby, do not take Paxlovid. Ask your doctor for advice as Paxlovid is not recommended during pregnancy. Women should avoid becoming pregnant (eg, use contraception or abstain from sexual activity) while taking Paxlovid and for 7 days after treatment ends.

Contraception is very important

If you are taking birth control pills, extra care is needed as Paxlovid may affect how they work. It is recommended that you don’t have sexual activity, or use condoms as well as your usual contraception, while taking Paxlovid and for 7 days after treatment ends. Ask your doctor or pharmacist for advice.  

Are you breastfeeding?

Breastfeeding is not recommended during treatment and for 7 days after the last dose of Paxlovid. This is because it is not known if Paxlovid gets into breast milk and will be passed to the baby. Tell your healthcare provider you are breastfeeding BEFORE taking this medicine.

Possible side effects 

As Paxlovid is a new medicine, it is possible that we do not know all of the side effects yet. However, many people in clinical trials have been treated with Paxlovid for COVID-19.

Common side effects

These are usually mild and go away with time or when the medicine is stopped. Tell your doctor if these side effects cause you problems or don’t go away:

  • runny poo (diarrhoea)
  • being sick (vomiting)
  • changes in your sense of taste. 

Rare, serious side effects

Contact your healthcare team or Healthline on 0800 611 116 immediately if you notice these side effects and tell them you are taking Paxlovid.

  • Signs of an allergic reaction such as skin rash, puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue, chest tightness and trouble breathing.
  • Signs of liver problems such as yellow eyes or skin, dark urine (pee), or pain or discomfort in the upper stomach area.

For more information on side effects, see the Medsafe consumer information leaflet below.

Did you know that you can report a side effect to a medicine to CARM (Centre for Adverse Reactions Monitoring)? 
Report a side effect to a product.

Learn more

Paxlovid Consumer Medicine Information Medsafe, NZ


  1. Paxlovid Medsafe datasheet
  2. Nirmatrelvir and ritonavir NZ Formulary
Credits: Health Navigator Pharmacists. Reviewed By: Maya Patel, MPharm PGDipClinPharm, Auckland Last reviewed: 04 Apr 2022