Paxlovid side effects: 8 key things to know

Key Points

• Paxlovid (nirmatrelvir and ritonavir) is an oral antiviral medicine used to treat mild-to-moderate COVID-19. It’s used in people 12 years of age and older weighing at least 88 pounds (40 kg) with a high risk for severe illness, including hospitalization or death.
• Most people tolerate Paxlovid well. The top 3 most common but usually temporary side effects with Paxlovid are a bitter or metallic taste, diarrhea and an increase in blood pressure.
• Important but less common side effects or warnings can include severe allergies, liver problems and a build up of resistance to HIV medicines.

Most people tolerate Paxlovid well and don’t need to stop treatment because of side effects. In studies, the number of people taking Paxlovid who needed to stop treatment due to a side effect was 2%, but it was even higher in the placebo group (4%). A placebo is a pill that contains no active medicine, and is often used in research to help determine effectiveness of medicines.

If you have tested positive for COVID-19, contact a healthcare provider right away to determine if Paxlovid is right for you. Paxlovid should be taken as soon as possible after diagnosis of COVID-19 in patients at high risk. It's important to take it within 5 days of the onset of your COVID-19 symptoms for the best effect.

If available, bring your latest lab tests (no more than one year old) and medication records when you talk to your healthcare provider. Pharmacists who participate in Paxlovid prescribing will need your kidney and liver lab test results and medication records, as well.

Before you start treatment, be sure to talk to your healthcare provider about possible side effects and drug interactions. Like all medicines, Paxlovid has side effects you should learn how to recognize.

8 key things to know about Paxlovid side effects

The FDA granted approval for Paxlovid in May 2023, for the treatment of mild-to-moderate COVID-19 in adults at high risk for severe COVID-19, including hospitalization or death. Since December 2021, Paxlovid had been available for treatment of COVID under an Emergency Use Authorization (EUA). Paxlovid is still available for eligible children, 12 to 17 years of age (and weighing at least 40 kg), under the existing EUA.

EUA and NDA

Paxlovid has gone through several EUAs and is now fully approved for use in adults 18 years and older by the FDA. In December 2023, Pfizer will begin to fully manage the distribution of Paxlovid as the U.S. government transitions away from distribution of Paxlovid under the EUA.

In addition, on Nov. 1, 2023 the FDA revised the EUA for pediatric patients 12 to 17 years of age to authorize NDA labeled Paxlovid for the treatment of mild-to-moderate COVID-19 in these patients at high risk for progression to severe COVID-19. Either NDA-labeled Paxlovid or EUA-labeled Paxlovid can be used for the treatment of both adults and adolescents consistent with the approved and authorized labeling as appropriate.

Studies

Here, we’ll look at 8 key things you need to know about Paxlovid side effects and how you can best manage them. Always check with your healthcare provider about any side effects that are severe or that don’t go away. Additional side effect information for Paxlovid may become available with more widespread use.

In studies, side effects were evaluated in studies with 2,224 adults who were at high risk of developing severe COVID-19 illness. Patients were assigned to take either Paxlovid or a matching inactive placebo twice daily for 5 days. Adverse events (side effects) were reported from patients who took at least one dose of medicine through Day 34 after starting the study treatment.

1. Taste changes (dysgeusia)

An altered or bad taste in the mouth is the most commonly reported side effect with Paxlovid. People report a bitter or metallic taste (often referred to as “Paxlovid mouth”) that’s hard to get rid of while on treatment. In studies, this side effect was shown to occur in about 6% of people who took Paxlovid (6 out of every 100 people).

The good news is that it’s temporary and harmless. But that does not make it any easier to tolerate. If you can't tolerate the taste at all, or if you have vomited, contact your doctor right away. Don’t stop treatment on your own.

How can you mask the bad taste of Paxlovid?

• Chewing sugar-free gum
• Having a supply of sweet hard candies (sugar-free, if preferred) or mints to help mask the taste
• Sucking on ice
• Brushing your teeth frequently and using mouthwash
• Drink plenty of fluids throughout the day

Why does Paxlovid cause a bad taste in the mouth?

One of the two medicines in Paxlovid, ritonavir, is known to cause a bad taste during treatment. A study has shown that ritonavir, and some other drugs in the protease class, such as indinavir and saquinavir, can cause a bad taste during treatment. In the study, participants reported tastes such as bitter, medicinal, metallic, astringent, sour and burning.

2. Diarrhea

Diarrhea is another side effect you may encounter during treatment with Paxlovid, but it’s also a side effect of COVID-19. For most people, diarrhea due to Paxlovid clears up after treatment and tends to be mild.

Diarrhea with Paxlovid was infrequently reported in studies, occurring in 3% of people taking Paxlovid and 2% of people taking a placebo (an inactive pill).

If you have diarrhea with this treatment, be sure to drink plenty of fluids to replace those you may be losing. Avoid any foods that may upset your stomach, like spicy, fried or fatty foods.

3. Blood pressure increase (hypertension)

High blood pressure was listed as a side effect with Paxlovid, but it’s not very common. High blood pressure, also called hypertension, occurred in about 1% of people (1 out of everyone 100) in Paxlovid studies (and less than 1% in the placebo group).

If you already have high blood pressure or heart disease, this might be a serious side effect you need to watch out for more closely.

Talk to your doctor about high blood pressure with Paxlovid. Your doctor may ask you to keep an eye on your blood pressure readings at home during treatment.

4. Muscle aches and pain (myalgia)

Muscle aches (myalgia) occurred in about 1% of people in studies with Paxlovid, and less than 1% of the placebo group. However, muscle aches and pains are a common symptom of COVID-19 and may appear about 2 to 14 days after exposure to the virus.

Most people can treat minor aches and pains during COVID-19 or from Paxlovid treatment with over-the-counter acetaminophen (Tylenol) or ibuprofen (Advil, Motrin). Speak to your doctor about the safest treatment for you.

If your muscles aches seem serious, or continue even after you’ve finished Paxlovid treatment or test negative for COVID-19, contact your healthcare provider for further advice.

5. Severe allergies (anaphylaxis)

A severe allergy with Paxlovid treatment is not a common side effect, but, like any severe allergy it can be serious or even deadly. Rarely, severe allergic reactions (which may include anaphylaxis) can happen in people taking Paxlovid, even after taking only one dose.

If you’ve had a severe allergic reaction to either active ingredient in Paxlovid (nirmatrelvir or ritonavir) or any other components of the product, you should not take it. This includes rare, severe skin allergies known as toxic epidermal necrolysis (TEN) or Stevens-Johnson syndrome. Be sure to let your doctor know if you’ve had any severe allergies to nirmatrelvir or ritonavir (Norvir).

Stop taking Paxlovid and call your healthcare provider or 911 right away if you get any of the following symptoms of an allergic reaction:

• Hives, skin rash, or other skin reaction like skin peeling or redness
• Trouble swallowing or breathing
• Swelling of the mouth, tongue, lips, or face
• Tightness in the throat
• Hoarseness of the voice

6. Liver problems

Paxlovid may cause liver damage, but this has not been reported as a common side effect.

In studies, increases in liver enzymes, hepatitis (inflammation of the liver), and jaundice (yellowing of skin, yellowing of the whites of the eyes) have been reported in patients taking ritonavir (Norvir), one of the active ingredients found in Paxlovid.

If you have a history of liver disease, be sure to tell your healthcare provider before receiving Paxlovid. Paxlovid is not recommended in patients with severe liver disease.

Tell your healthcare provider right away if you have any symptoms of liver problems, which may include:

• Loss of appetite
• Nausea or vomiting that does not stop
• Yellowing of your skin and the whites of eyes (jaundice)
• Dark-colored urine
• Pale-colored stools and itchy skin
• Stomach area (abdominal) pain

7. Kidney problems

Blood levels of nirmatrelvir (one of the antivirals in Paxlovid) may increase in patients with certain levels of kidney disease.

You should not use Paxlovid if you have severe kidney disease. A lower dose of Paxlovid is needed if you have moderate kidney disease. If needed, your doctor can order a simple blood test to determine how well your kidney is working.

Tell your healthcare provider and pharmacist if you have a history of kidney problems before receiving Paxlovid. Bring your latest lab results when you visit your healthcare professional (doctor and / or pharmacist) .

8. Resistance to HIV medicines / Drug interactions

If you have HIV that has not been treated or diagnosed, you may be at risk of developing resistance to HIV protease inhibitor antiviral medicines if you take Paxlovid. These HIV medicines may not work as well if you take them in the future.

Talk to your doctor if you think you've been recently exposed to HIV before taking Paxlovid. You may need to take a different treatment or have additional lab tests.

Drug interactions

There are many drug interactions with Paxlovid, including certain medicines you cannot take with Paxlovid.

This means you need to tell your doctor and pharmacist about all of the medicines you take (prescription, over-the-counter (OTC), vitamins and herbal supplements) so a drug interaction review can be completed before you start treatment. There may be treatments you need to temporarily stop, or you may not be able to take Paxlovid at all. Your healthcare provider can review your medications with you.

• Drug interactions may lead to side effects because levels of drugs may increase. Also, if drug levels go down, your medicine may not work as well.
• You can ask your healthcare provider or pharmacist for a list of medicines that interact with Paxlovid. Do not start or stop any treatments without speaking to your prescriber first while taking Paxlovid.
• Tell your healthcare provider if you are taking combination hormonal contraceptive (estrogen and progestin), as Paxlovid can affect how your birth control pills work. Females who can become pregnant should use another effective alternative form of contraception or an additional barrier method of contraception (such as a condom).

This is not all the information you need to know about Paxlovid or COVID-19 for safe and effective use and does not take the place of your healthcare provider's directions. Review the full product information and discuss this information and any questions you have with your doctor or other health care provider.