Pronunciation: pax-LO-vid
Generic name: nirmatrelvir and ritonavir
Dosage form: tablets, co-packaged for oral use
Drug class: Antiviral combinations

Medically reviewed by Melisa Puckey, BPharm. Last updated on Nov 14, 2024.

What is Paxlovid?

Paxlovid is an antiviral treatment for COVID-19 used to lower the risk of severe COVID-19, including hospitalization or death. Paxlovid contains nirmatrelvir tablets and ritonavir packaged together. 

Paxlovid is an FDA-approved medicine for adults with mild-to-moderate COVID-19 patients who are at high risk of severe COVID-19, including hospitalization or death.

Paxlovid has Emergency Use Authorisation (EUA) to treat patients 12 to 18 years old for mild-to-moderate COVID-19 who are at high risk for progression to severe COVID-19, including hospitalization or death.

People who are at high risk of severe COVID-19 are patients with:

• heart disease, diabetes, lung disease, cancer, blood disorders, immune disorders, mental health conditions, disabilities or other conditions
• being overweight or obese
• 50 years or older
• lifestyle factors, such as smoking
• physical, mental, and developmental disabilities.

Paxlovid works as nirmatrelvir blocks an enzyme (SARS-CoV-2-3CL protease) that the coronavirus needs to replicate. By preventing the virus from reproducing itself, nirmatrelvir reduces the severity of symptoms and decreases the number of hospitalizations and deaths in high-risk patients. Ritonavir is a medication that helps nirmatrelvir stay in the body longer and at a higher concentration, making nirmatrelvir a more effective antiviral.

You should start taking Paxlovid as soon as possible after COVID diagnosis and within the first 5 days that you have had symptoms. The usual Paxlovid dose is two nirmatrelvir tablets and one ritonavir tablet taken together twice daily for 5 days. The dose needs to be changed if you have kidney problems, and if you are taking certain medicines, Paxlovid is not suitable for some patients.

Paxlovid is not approved for use as a pre-exposure or post-exposure prophylaxis to prevent COVID-19 or for the prevention of long COVID.

Paxlovid may be prescribed for an individual patient by physicians, advanced practice registered nurses, and physician assistants licensed or authorized under state law to prescribe drugs. It may also be prescribed for an individual patient by a state-licensed pharmacist under specific conditions.

Paxlovid side effects

Common Paxlovid side effects

Common Paxlovid side effects include a bad taste or change in taste (5%) and diarrhea (3%) in the EPIC-HR clinical trial. Other Paxlovid side effects, including abdominal pain, nausea, vomiting, high blood pressure, headache, generally feeling unwell (malaise), allergic reaction, and hypersensitivity reactions, occurred in Paxlovid Emergency Use Authorization Experience. 

The Paxlovid side effect of bad taste or change in taste (dysgeusia) is the most common side effect, it is often described as a metallic taste or bitter taste and usually goes when you have finished the course. If you get this side effect, you may want to try gum, mints, or mouthwash for temporary relief.

Serious Paxlovid side effects

Paxlovid may cause serious side effects, including allergic reactions, hypersensitivity reactions, and liver problems.

Allergic reactions: Get emergency medical help if you have signs of an allergic reaction (hives, difficulty 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).

Liver problems: Call your doctor at once if you have:

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

Ritonavir side effects

Ritonavir, one of the active ingredients in Paxlovid, 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.

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.

Related/similar drugs

Warnings

Paxlovid Drug Interactions: Paxlovid can interact with other medicines, causing severe or life-threatening side effects or death. It is important to know the medicines that should not be taken with Paxlovid. See the Interactions section below and check the interactions checker.

Hypersensitivity Reactions: Anaphylaxis, serious skin reactions (including toxic epidermal necrolysis and Stevens-Johnson syndrome), and other hypersensitivity reactions have been reported with this medicine. Do not take this medicine if you are allergic to nirmatrelvir, ritonavir, or any of the ingredients in Paxlovid. If signs and symptoms of a clinically significant hypersensitivity reaction or anaphylaxis occur, immediately stop taking Paxlovid and start appropriate medications and/or supportive care. 

Hepatotoxicity: Hepatic transaminase elevations, clinical hepatitis, and jaundice have occurred in patients receiving ritonavir, one of the active ingredients in Paxlovid.

HIV-1 Drug Resistance: Using Paxovid may lead to a risk of HIV-1 developing resistance to HIV protease inhibitors if you have uncontrolled or undiagnosed HIV-1 infection. 

Paxlovid rebound and COVID rebound

COVID rebound is when COVID symptoms return between 2 and 8 days after finishing treatment; symptoms are mild, transient, and usually clear up in 1 to 3 days. COVID rebound can happen in some people who are vaccinated, unvaccinated, Paxlovid treated, and people who have not been treated with Paxlovid. When COVID-19 symptoms return in Paxlovid-treated patients, some people have called it Paxlovid rebound.

The CDC states that “There is currently no evidence that additional treatment is needed with Paxlovid or other anti-SARS-CoV-2 therapies in cases where COVID-19 rebound is suspected.”

Before taking this medicine

You should not use Paxlovid if you are allergic to the active ingredients nirmatrelvir and ritonavir or any of the inactive ingredients. A list of ingredients is at the bottom of this page.

Some drugs have drug interactions with Paxlovid, and they should not be used with Paxlovid, such as those listed below.

• alfuzosin, colchicine;
• sildenafil (Revatio) when used to treat pulmonary arterial hypertension (PAH);
• pain medicine - pethidine, piroxicam, propoxyphene;
• heart medicine - amiodarone, dronedarone, flecainide, propafenone, quinidine, ranolazine;
• antipsychotic medicine - lurasidone, pimozide, clozapine;
• ergot medicine - dihydroergotamine, ergotamine, methylergonovine;
• cholesterol-lowering medicine - lovastatin, simvastatin; or
• a sedative - riazolam, oral midazolam.

Paxlovid should not be started immediately after discontinuation of any of the following drugs:

• rifampin;
• St. John's Wort;
• a cancer medicine - apalutamide; or
• seizure medicine - carbamazepine, phenobarbital, phenytoin.

Not all possible interactions are listed here. Also, see the Interactions section below and check the interactions checker.

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.

Pregnancy

Tell your healthcare provider right away if you are or if you become pregnant. It is not known if Paxlovid can harm your unborn baby. Ritonavir can make birth control pills or birth control 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.

Breastfeeding

Tell your healthcare provider you are breastfeeding or plan to breastfeed. It is not known if Paxlovid can pass into your breast milk. Talk to your healthcare provider about the best way to feed your baby during treatment with this medicine.

How should I take Paxlovid?

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

Paxlovid Instructions

Take nirmatrelvir together with ritonavir (two tablets of nirmatrelvir and one tablet of ritonavir) twice a day for 5 consecutive days. If you have kidney disease, talk to your healthcare provider, as you may need to take a different dose.

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

You may take Paxlovid with or without food.

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

General Information

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

If you are taking a ritonavir- or cobicistat-containing medicine to treat hepatitis C or Human Immunodeficiency Virus (HIV), you should continue to take your medicine as prescribed by your healthcare provider.

Talk to your healthcare provider if you do not feel better or if you feel worse after 5 days.

If you have kidney disease, your prescriber may prescribe you a lower dose. Talk to your healthcare provider to make sure you receive the correct Dose Pack.

Paxlovid Dosage information

Usual Paxlovid Dosing for Adult COVID-19 (FDA-approved)

Nirmatrelvir: 300 mg orally twice a day for 5 days
Ritonavir: 100 mg orally twice a day for 5 days

Usual Paxlovid Dosing for 12 to 18 Year Old COVID-19 (EUA)

For investigational use only
Use: Patients 12 to 18 years old weighing at least 40 kg:
Nirmatrlvir 300 mg orally twice a day for 5 days
Ritonavir 100 mg orally twice a day for 5 days

Usual Paxlovid Dosing for Renal Impairment

Use: Patients with moderate renal impairment (eGFR ≥30 to <60 mL/min)
Nirmatrelvir 150 mg twice daily for 5 days
Ritonavir 100 mg twice daily for 5 days 
No dosage adjustment is recommended in patients with mild renal impairment (eGFR ≥60 to <90 mL/min)

General Paxlovid Dosing information:

• If you have kidney disease, your healthcare provider may prescribe a lower dose. Talk to your healthcare provider to make sure you receive the correct Dose Pack.
• Nirmatrelvir must be coadministered with ritonavir. Prescriptions should specify the numeric dose of each active component within this product.
• This product should be started as soon as possible after COVID-19 has been diagnosed and within 5 days of symptom onset.
• If hospitalization is required due to severe/critical COVID-19 after starting treatment with this product, the patient should complete the full 5-day treatment course per health care provider's discretion.

What happens if I miss a dose?

If you miss a dose of Paxlovid 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 2 doses of Paxlovid at the same time.

What happens if I overdose?

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

What other drugs will affect Paxlovid?

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 Paxlovid and some drugs should not be used at the same time. Paxlovid can interact with other medicines causing severe or life-threatening side effects or death. 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.

Paxlovid Drug Interactions

Do not take Paxlovid if you are taking any of the following medicines: alfuzosin, amiodarone, apalutamide, carbamazepine, colchicine, dihydroergotamine, dronedarone, eletriptan, eplerenone, ergotamine, finerenone, flecainide, flibanserin, ivabradine, lomitapide, lovastatin, lumacaftor/ivacaftor, lurasidone, methylergonovine, midazolam (oral), naloxegol, phenobarbital, phenytoin, pimozide, primidone, propafenone, quinidine, ranolazine, rifampin, rifapentine, St. John’s Wort (hypericum perforatum), sildenafil (Revatio®, Liqrev®) for pulmonary arterial hypertension, silodosin, simvastatin, tolvaptan, triazolam, ubrogepant, voclosporin.

These are not the only medicines that may cause serious or life-threatening side effects if taken with Paxlovid. It is very important to tell your healthcare provider about all of the medicines you are taking because additional laboratory tests or changes in the dose of your other medicines may be necessary during treatment with this Paxlovid. Your healthcare provider may also tell you about specific symptoms to watch out for that may indicate that you need to stop or decrease the dose of some of your other medicines.

Not all possible interactions are listed in this medication guide. Use the Paxlovid interaction checker below to check for more interaction information.

Ingredients

Nirmatrelvir 150 mg tablets

Active ingredient: nirmatrelvir
Inactive ingredients: colloidal silicon dioxide, croscarmellose sodium, lactose monohydrate, microcrystalline cellulose, and sodium stearyl fumarate. The following are the ingredients in the film coating: hydroxy propyl methylcellulose, iron oxide red, polyethylene glycol, and titanium dioxide.

Ritonavir 100 mg tablets

Active ingredient: ritonavir
Inactive ingredients: anhydrous dibasic calcium phosphate, colloidal silicon dioxide, copovidone, sodium stearyl fumarate, and sorbitan monolaurate. The following are the ingredients in the film coating: colloidal silicon dioxide, hydroxypropyl cellulose, hypromellose, polyethylene glycol 400, polyethylene glycol 3350, polysorbate 80, talc, and titanium dioxide.

Storage

Store at room temperature temperature 20°C to 25°C (68°F to 77°F).

Company

Paxlovid Pfizer Labs, Division of Pfizer Inc. New York, NY 10001.

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