How Does Paxlovid Work? (Nirmatrelvir/Ritonavir)

How Does Paxlovid Work (NirmatrelvirRitonavir)

Paxlovid (nirmatrelvir/ritonavir) is a prescribed antiviral medication administered orally, designed to combat the symptoms of COVID-19, a viral respiratory illness caused by the SARS-CoV-2 virus. It’s a branded medication that combines two antiviral drugs, namely nirmatrelvir and ritonavir. Paxlovid is available in the form of swallowable tablets, which impede the replication of the COVID-19 virus and prevent it from progressing to a severe state.

Recently, the Food and Drug Administration (FDA) granted approval for Paxlovid to treat mild to moderate COVID-19 in adults aged 18 and above who are at a high risk of developing severe illness. Additionally, Paxlovid received Emergency Use Authorization (EUA) in December 2021 for specific high-risk pediatric cases (individuals under 18), effectively reducing the risk of COVID-19-related hospitalization or death.

In this article, we at TGH Urgent Care powered by Fast Track aim to provide our patients and readers with comprehensive information about Paxlovid, covering essential topics like how it works, potential side effects, and more, to ensure you have a clear understanding of this medication.

How Does Paxlovid Work?

Paxlovid contains two distinct antiviral drugs: nirmatrelvir and ritonavir. Nirmatrelvir halts the viral replication of SARS-CoV-2, a type of coronavirus, by obstructing the virus’s ability to copy its DNA during multiplication. Administering Paxlovid early in a COVID-19 infection can prevent the infection from becoming severe.

Ritonavir, while not directly active against SARS-CoV-2, enhances the effectiveness of nirmatrelvir by extending its duration and potency in the body. Together, ritonavir and nirmatrelvir form an effective combination against COVID-19.

Studies have shown that Paxlovid can reduce the risk of COVID-19-related hospitalization or death by 89%. In a comparison study with a placebo, only 9 out of 1,039 individuals taking Paxlovid succumbed to COVID-19, compared to 66 out of 1,046 people taking a placebo.

Paxlovid Approval

Paxlovid has been available for healthcare providers to prescribe for COVID-19 since December 2021. Similar to the process for COVID-19 vaccines, it initially received FDA authorization through an EUA. While EUAs do not follow the same approval process as regular FDA reviews, they still require safety testing before emergency use.

On May 25, 2023, Paxlovid obtained full FDA approval for treating mild to moderate COVID-19 in high-risk adults, while the EUA remains in place for pediatric cases.

In a significant development in July 2022, pharmacists were authorized to prescribe Paxlovid in specific situations, allowing eligible patients to access timely treatment within five days of symptom onset.

When to Use Paxlovid

Paxlovid treatment should commence as soon as possible following a positive COVID-19 test result or within five days of symptom onset. Common COVID-19 symptoms include cough, fever, chills, sore throat, shortness of breath, muscle aches, fatigue, and headache.

Paxlovid is authorized for high-risk pediatric individuals aged 12 and older, weighing at least 88 pounds, and at risk of developing severe COVID-19 due to various factors such as age, underlying health conditions, and more. It is not approved or authorized for prevention in individuals who may have been exposed to the virus; its use is specifically intended after a confirmed COVID-19 diagnosis.

Alternative Uses of Paxlovid

Paxlovid is primarily prescribed for COVID-19 treatment. However, one of its components, ritonavir, has been used in combination with other drugs to treat different viral illnesses like hepatitis C and HIV/AIDS. While Paxlovid is not approved for treating long COVID, some evidence suggests it may help alleviate its symptoms. Additionally, taking Paxlovid during the acute phase of COVID-19 may reduce the risk of developing long COVID. Nevertheless, more clinical trials are required to confirm these potential benefits.

Side Effects & Safety

As with any medication, Paxlovid carries the potential for side effects. Common side effects include dysgeusia (an altered taste sensation) and diarrhea. Other possible side effects encompass high blood pressure, muscle aches, abdominal pain, nausea/vomiting, increased liver enzyme levels, and, rarely, severe allergic reactions like anaphylaxis.

Severe skin reactions such as Stevens-Johnson syndrome and toxic epidermal necrolysis have been reported but are rare. Certain individuals may be at higher risk for Paxlovid’s side effects, particularly those with pre-existing liver or kidney issues or HIV infection.

Paxlovid is not recommended for individuals with known allergies to its components, specific drug interactions, or certain medical conditions. It is generally a five-day treatment with side effects expected to resolve after the last dose, with no known long-term side effects.

How to Take Paxlovid

Paxlovid treatment should commence as soon as possible after a COVID-19 diagnosis, within five days of symptom onset. It can be taken with or without food. Each dose comprises three tablets: two 150 mg nirmatrelvir tablets (300 mg total) and one 100 mg ritonavir tablet. These tablets are taken orally twice daily for five days and come in a dose card to help track the regimen. Adjusted doses may be prescribed for individuals with reduced kidney function.

Paxlovid Interactions

Before taking Paxlovid, inform your healthcare provider about your current medications, herbs, or supplements. Paxlovid interacts with certain drugs and can affect their effectiveness. The enzyme CYP3A processes Paxlovid, and using specific medications during Paxlovid treatment may result in either excessive or inadequate drug levels in your body.

Some drugs and supplements can reduce Paxlovid’s effectiveness, such as certain seizure medications, rifampin, and St. John’s wort. Paxlovid can also interact with other drugs, potentially increasing their side effects, including alfuzosin, antiarrhythmic medications, lurasidone, atorvastatin, colchicine, dihydroergotamine, and certain migraine medications.

This is not an exhaustive list of Paxlovid’s interactions, so it’s essential to consult your pharmacist or healthcare provider for comprehensive information on drug interactions with Paxlovid.


The FDA initially granted Emergency Use Authorization (EUA) for Paxlovid as a treatment for COVID-19. It has since received full approval for use in high-risk adults with mild to moderate COVID-19, aimed at preventing the progression to severe illness.

Paxlovid is an antiviral medication designed for the treatment of COVID-19 and should ideally be initiated within five days of the onset of symptoms. Each dose of Paxlovid comprises three oral tablets, consisting of two 150 mg nirmatrelvir tablets and one 100 mg ritonavir tablet.

Before starting Paxlovid, it’s important to discuss your current medications with your healthcare provider.

In summary, it is imperative to remain vigilant and prepared for the potential increase in COVID-19 cases during the fall and winter months. If you experience symptoms, do not hesitate to visit one of our conveniently located TGH Urgent Care walk-in centers for COVID-19 testing. Additionally, ensure that you are up to date with your vaccinations if you haven’t already done so.

TGH Urgent Care, powered by Fast Track, is committed to delivering high-quality care for non-life-threatening medical issues, catering to patients aged 3 months and older. Our services encompass the management of various ailments, including urinary tract infections, ear infections, and influenza. With our in-house laboratory testing and advanced imaging capabilities, we can provide prompt and comprehensive diagnoses. Moreover, we have an on-site pharmacy to efficiently fulfill any necessary prescriptions.

Our extensive network of 15+ TGH Urgent Care locations operates from 8 a.m. to 8 p.m., seven days a week, ensuring access to COVID-19 treatment when you need it most. For additional information regarding the range of treatments we offer, please feel free to contact us. If you plan to visit, you can expedite your wait time by using our convenient On My Way system to check in ahead of your arrival. Your health and well-being are our utmost priorities.


  • Are there alternative treatments available for COVID-19?

There are other FDA-approved treatment options for COVID-19, including Lagevrio (molnupiravir) and Veklury (remdesivir). Lagevrio is an oral medication typically administered for a five-day course, while Veklury is an intravenous (IV) infusion primarily used in hospitalized individuals with severe COVID-19 for up to seven days.

It’s important to note that hydroxychloroquine is not recommended for the treatment of COVID-19. Initially granted an Emergency Use Authorization (EUA) for COVID-19, the FDA later revoked this authorization and issued warnings against its use.

  • Can Paxlovid be used to treat severe COVID-19 symptoms?

Paxlovid is effective in treating mild to moderate COVID-19 in individuals at a high risk of progressing to severe COVID-19.

Severe COVID-19 symptoms, such as difficulty breathing, can lead to hospitalization and other critical complications. Paxlovid has significantly reduced the risk of COVID-related hospitalization and mortality.


TGH Urgent Care powered by Fast Track, uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles.

  1. Nirmatrelvir and ritonavir.
  2. Fact sheet For healthcare providers: emergency use authorization for Paxlovid.
  3. Food and Drug Administration. Paxlovid (nirmatrelvir tablets; ritonavir tablets) prescribing information.
  4. Wong LH, Edgar JR, Martello A, Ferguson BJ, Eden ER. Exploiting connections for viral replication. Front Cell Dev Biol. 2021;9:640456. doi:10.3389/fcell.2021.640456
  5. Najjar-Debbiny R, Gronich N, Weber G, et al. Effectiveness of Paxlovid in reducing severe coronavirus disease 2019 and mortality in high-risk patients [published correction appears in Clin Infect Dis. 2023;76(6):1158-1159]. Clin Infect Dis. 2023;76(3):e342-e349. doi:10.1093/cid/ciac443
  6. Food and Drug Administration. Norvir (ritonavir) prescribing information.
  7. Hammond J, Leister-Tebbe H, Gardner A, Abreu P, Bao W, Wisemandle W, Baniecki M, Hendrick VM, Damle B, Simón-Campos A, Pypstra R. Oral nirmatrelvir for high-risk, nonhospitalized adults with Covid-19.N Engl J Med. 2022 Apr 14;386(15):1397-408. doi: 10.1056/NEJMoa2118542
  8. Pfizer’s Paxlovid™ receives FDA approval for adult patients at high risk of progression to severe COVID-19.
  9. Food and Drug Administration. Emergency Use Authorization.
  10. Food and Drug Administration. Coronavirus (COVID-19) update: FDA authorizes pharmacists to prescribe Paxlovid with certain limitations.
  11. Centers for Disease Control and Prevention. COVID-19.
  12. Centers for Disease Control and Prevention. COVID-19: Underlying Medical Conditions.
  13. Centers for Disease Control and Prevention. Long COVID or post-COVID conditions.
  14. Peluso MJ, Anglin K, Durstenfeld MS, et al. Effect of oral nirmatrelvir on long COVID symptoms: 4 cases and rationale for systematic studies.Pathog Immun. 2022;7(1):95-103. doi:10.20411/pai.v7i1.518
  15. Xie Y, Choi T, Al-Aly Z. Association of treatment with nirmatrelvir and the risk of post-COVID-19 condition [published online ahead of print, 2023 Mar 23].JAMA Intern Med. 2023;e230743. doi:10.1001/jamainternmed.2023.0743
  16. United States Department of Health and Human Services. What are the possible treatment options for COVID-19?
  17. Food and Drug Administration. FDA cautions against use of hydroxychloroquine or chloroquine for COVID-19 outside of the hospital setting or a clinical trial due to risk of heart rhythm problems.


Read more: Walk-In Clinic near Seminole, Florida


The blogs presented by TGH Urgent Care in partnership with Fast Track are not a replacement for medical care and are exclusively intended for educational purposes. The content provided here should not be construed as medical guidance. If you are encountering any symptoms, we strongly recommend that you seek an appointment with a duly qualified medical practitioner at our nearest facility.

Employer Solutions

Our goal is to provide exceptional patient care with a strong return-to-work philosophy. We can help you control your healthcare costs by reducing emergency room visits. We are here to give you and your employees a convenient, quality-focused choice for all your occupational health and work injury management needs.


Available Positions

  • X-Ray Tech
  • MA
  • LPN
  • NP/PA
  • Medical Receptionist
  • Admin Support and more!


Commitment to Responsible Prescribing Practices

We are committed to responsible antibiotic prescribing practices. Our goal is to adequately treat infections while protecting our community from the harmful effects of antibiotic resistant infections. TGH Urgent Care has earned the Antibiotic Stewardship Commendation Award from the Urgent Care Association due to our ongoing commitment to this goal.

The entire staff was so friendly & helpful. Our first visit here was quick, the office was very clean & they were great with my kids. We will be back for sure!

Sandra P.
See more reviews from others like Sandra P.

By far the nicest urgent care I've had the unfortunate opportunity to experience. The cleanliness and friendliness of this clinic are unmatched. - Sara S.

Sara S.
See more reviews from others like Sara S.

You dealt with my issue promptly and efficiently and i was on my way.

Stephen S.
See more reviews from others like Stephen S.

The wait was minimum and the PA was very understanding. The staff at the front desk could be a bit more friendly. Other than that, good overall experience.

Alexander C.
See more reviews from others like Alexander C.

Fast, quick, responsive, professional and courteous.

Melanie G.
See more reviews from others like Melanie G.

CLEAN, CLEAN, CLEAN and very friendly!!!

Rosaria F.
See more reviews from others like Rosaria F.

The staff was wonderful, very caring and truly cared about how I was.

Brandy P.
See more reviews from others like Brandy P.

See more reviews from others like Brandy P. See more reviews
Now Hiring for Pasco, Pinellas, and Hillsborough Counties
This is default text for notification bar