Nirmatrelvir and Ritonavir
Nirmatrelvir and ritonavir (Paxlovid) is an antiviral combination used to treat mild-to-moderate COVID-19 in adults who are at high risk of becoming seriously ill.
🧬 Where this information comes from Click to expand
The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 1 clinical label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →
⚠️ FDA Boxed Warning — the FDA’s strongest safety alert ▾
Paxlovid can cause dangerous interactions with many common medications. Ritonavir — one of the two ingredients in Paxlovid — is a strong inhibitor of an enzyme (CYP3A) that the body uses to break down many drugs. When Paxlovid is taken alongside certain other medications, those drugs can build up to levels that cause severe, life-threatening, or even fatal reactions. Before starting Paxlovid, your prescriber must review every medication you are taking. Some drugs will need their dose adjusted, some will need to be temporarily stopped, and some cannot be used with Paxlovid at all. The benefit of Paxlovid in reducing COVID-19 hospitalization and death must always be weighed against the risk of these interactions for each individual patient.
📖 Nirmatrelvir and Ritonavir: Patient Information Guide
A plain-language walkthrough of Nirmatrelvir and Ritonavir — what it treats, how it works, how it’s taken, side effects, warnings and interactions. Tap any section to expand it.
🎯What it's used for▾
Paxlovid (nirmatrelvir/ritonavir) is approved for the following use:
- Treatment of mild-to-moderate COVID-19 in adults who are at high risk of progressing to severe disease, including hospitalization or death
- Treatment must be initiated as soon as possible after diagnosis and within 5 days of symptom onset
- Paxlovid is not approved for pre-exposure or post-exposure prevention (prophylaxis) of COVID-19
⚙️How it works▾
Nirmatrelvir targets and blocks a critical enzyme called the main protease (Mpro) that the SARS-CoV-2 virus relies on to replicate. Without this enzyme functioning, the virus cannot make copies of itself, and the infection is brought under control. Ritonavir is included not to fight the virus, but to inhibit the CYP3A enzyme in your liver that would otherwise break nirmatrelvir down too quickly — keeping nirmatrelvir at levels high enough to work.
Ritonavir itself is classified as an HIV-1 protease inhibitor, but it has no meaningful activity against the COVID-19 virus. Its role here is entirely as a pharmacokinetic booster for nirmatrelvir.
💊How it's taken▾
Paxlovid is taken by mouth twice daily for 5 days. The nirmatrelvir tablets and the ritonavir tablet are taken together at the same time each day, with or without food. Treatment should begin as soon as possible after a confirmed COVID-19 diagnosis and within 5 days of when symptoms started.
- People with moderate kidney impairment may require a dose adjustment — follow your prescriber's guidance
- Paxlovid is not approved for use in patients under 18 years of age
- Always follow the exact instructions from your prescriber and on your prescription label
🤒Side effects — in detail▾
The most commonly reported side effects with Paxlovid (occurring in at least 1% of patients and more often than with placebo) are:
- Dysgeusia — an altered or strange taste in the mouth
- Diarrhea
- High blood pressure
- Muscle aches
Serious reactions to watch for include signs of a severe allergic reaction (trouble breathing, swelling, severe rash or skin blistering) and signs of liver problems (yellowing of skin or eyes, dark urine). Stop Paxlovid and seek medical help immediately if any of these occur. Severe, life-threatening adverse reactions have also been reported due to drug interactions with other medications.
⚠️Warnings & precautions▾
- Drug interactions (most critical): Ritonavir dramatically raises blood levels of many other medications. This can cause life-threatening or fatal reactions. The most serious cases reported involved calcineurin inhibitors (tacrolimus, cyclosporine) and calcium channel blockers. A full medication review is mandatory before starting Paxlovid.
- Severe allergic reactions: Anaphylaxis (a life-threatening allergic response), toxic epidermal necrolysis, and Stevens-Johnson syndrome have been reported. Discontinue immediately and get emergency care if signs appear.
- Liver toxicity: Liver enzyme elevations, clinical hepatitis, and jaundice have occurred with ritonavir. Use with extra caution in people with pre-existing liver disease.
- HIV resistance risk: In people with uncontrolled or undiagnosed HIV infection, ritonavir may cause the virus to become resistant to HIV protease inhibitor medications.
🔀What it interacts with▾
Paxlovid has a large number of significant drug interactions because ritonavir is a strong CYP3A inhibitor and also affects CYP2D6, P-gp, and OATP1B1 enzymes. Key interactions include:
- Contraindicated combinations (must NOT be used together): Certain heart rhythm drugs (amiodarone, dronedarone, flecainide, quinidine), the sedatives triazolam and oral midazolam, lovastatin and simvastatin (cholesterol drugs), lurasidone, pimozide, sildenafil (when used for pulmonary arterial hypertension), alfuzosin, ranolazine, and others — elevated levels can cause life-threatening reactions
- Strong CYP3A inducers: Rifampin, carbamazepine, phenytoin, phenobarbital, St. John's Wort, and others — these lower Paxlovid levels and can make it stop working; they are contraindicated
- Blood thinners: Warfarin (INR monitoring needed), rivaroxaban (avoid), apixaban (dose-dependent guidance), dabigatran (possible dose reduction needed) — bleeding risk may increase
- Calcium channel blockers (amlodipine, diltiazem, verapamil, others) — levels increase; monitoring and possible dose reduction needed
- Hormonal contraceptives: Combined hormonal birth control may be less effective — use an alternative or additional barrier method
- Immunosuppressants like tacrolimus and cyclosporine — levels can rise dangerously; close monitoring required
- Other anticancer, antifungal, antipsychotic, and anti-HIV medications — many require dose adjustments or avoidance; always review with a pharmacist or prescriber
This is not a complete list of interactions. Always talk with your doctor or pharmacist before starting, stopping, or changing any medication.
📋Before taking it▾
- People with kidney disease: Paxlovid exposure increases with worsening kidney function; a dose adjustment is needed for moderate impairment and specific guidance applies for severe impairment
- People with liver disease or hepatitis: Use with caution; ritonavir has been associated with liver toxicity
- People who are pregnant: Insufficient data exist on nirmatrelvir in pregnancy; untreated COVID-19 also carries fetal risks — discuss with your doctor
- People who are breastfeeding: Small amounts of both nirmatrelvir and ritonavir pass into breast milk; discuss risks and benefits with your doctor
- People using combined hormonal contraceptives: Use an alternative or additional barrier method during treatment
- People with undiagnosed or uncontrolled HIV: Ritonavir may cause HIV resistance to protease inhibitors
- Children under 18: The correct dose has not been established; Paxlovid is not approved for pediatric patients
- Older adults: Used safely in people 65 and older, but careful drug interaction review is especially important in this group
- Anyone with a prior serious allergic reaction to nirmatrelvir or ritonavir must not take Paxlovid
🚑If you take too much▾
There is no specific antidote for a Paxlovid overdose. If too much is taken, treatment focuses on supportive care — monitoring vital signs and watching for symptoms. If you suspect an overdose, contact a poison control center or seek emergency medical care right away.
📡Pharmacodynamics — effects in the body▾
At doses three times higher than the recommended level, nirmatrelvir does not cause any clinically meaningful changes to the heart's electrical activity (specifically, it does not prolong the QTc interval, which is a measure of heart rhythm). This means Paxlovid is not expected to cause dangerous heart rhythm problems at normal therapeutic doses.
🔬Pharmacokinetics — how your body processes it▾
After oral dosing, nirmatrelvir reaches peak blood levels in about 3 hours and ritonavir in about 4 hours. Nirmatrelvir is primarily cleared through the kidneys, while ritonavir is mainly broken down by the liver. Both have a half-life of roughly 6 hours, meaning the body eliminates about half of each drug in that time. Because ritonavir inhibits the breakdown of nirmatrelvir, steady therapeutic levels of nirmatrelvir are reached by the second day of treatment. Nirmatrelvir exposure increases substantially in people with moderate-to-severe kidney impairment, which is why dose adjustments are required in those patients.
📦How to store it▾
Store at USP controlled room temperature 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C to 30°C (59°F to 86°F).
📄 Written from Nirmatrelvir and Ritonavir’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Every point is grounded in that labeling — nothing is invented. How we use AI →
Supplements & herbs that interact with Nirmatrelvir and Ritonavir
176 supplements and herbal products have documented interactions with Nirmatrelvir and Ritonavir in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.
- Major · 6
- Moderate · 134
- Minor · 36
Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.
🩺 Pharmacist Counseling Corner
Quick, plain-English answers to the questions patients ask most about Nirmatrelvir and Ritonavir — the kind of thing our pharmacy team would talk through with you at the counter.
What exactly is Paxlovid and why was it prescribed to me? ▾
Does it matter if I take Paxlovid with food or on an empty stomach? ▾
Why is it so important to tell my pharmacist about all my other medications? ▾
What side effects should I expect, and when should I actually call my doctor? ▾
I'm pregnant — is Paxlovid safe for my baby? ▾
I'm on birth control pills — do I need to worry about that? ▾
Is Nirmatrelvir and Ritonavir available over the counter? ▾
When was Nirmatrelvir and Ritonavir first available? ▾
💬 Answers drafted from Nirmatrelvir and Ritonavir’s FDA-approved label information, summarized in plain language with AI, and reviewed by our pharmacy team before publication. Grounded in that labeling — nothing is made up. How we use AI →
🧰 Keep exploring
📊 Nirmatrelvir and Ritonavir across the U.S. market
How Nirmatrelvir and Ritonavir appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.
Also listed with the FDA, not a patient dose form: Kit (14) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.
📈 How widely Nirmatrelvir and Ritonavir is used
A general measure of how commonly Nirmatrelvir and Ritonavir is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.
Think of this as a proxy for how widely Nirmatrelvir and Ritonavir is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.
How commonly is Nirmatrelvir and Ritonavir prescribed? Of the 1,597 medications we measure, Nirmatrelvir and Ritonavir ranks #433 by Medicaid prescriptions — more than 73% of them.
Utilization by Nirmatrelvir and Ritonavir product
Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.
Other Nirmatrelvir and Ritonavir products — combination packs and listings not yet matched to a specific clinical product (kept visible so every prescription is accounted for)
Summed across the 5 of 9 listed NDC products with Medicaid activity.
Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.
Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Nirmatrelvir and Ritonavir, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 5 of 9 listed Nirmatrelvir and Ritonavir NDCs with Medicaid activity.
🔍 Compare Nirmatrelvir and Ritonavir products
A representative set of FDA-listed product records for Nirmatrelvir and Ritonavir — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)
| Manufacturer / Labeler | Category ⓘ | Details |
|---|---|---|
| 💊Kits | ||
| Pfizer Laboratories Div Pfizer Inc × 8 listings | NDA | View NDC → |
| Pfizer Laboratories Div Pfizer Inc × 6 listings | EMERGENCY USE AUTHORIZATION | View NDC → |
Showing 14 of 14 products — FDA National Drug Code Directory. See every product, package size and price: browse all 14 Nirmatrelvir and Ritonavir NDCs →
📈 What people report — real-world data (FDA FAERS)
After a medicine reaches the market, patients, doctors and drugmakers can send the FDA reports of problems they think may be linked to it. Here’s what’s been reported for Nirmatrelvir and Ritonavir — a signal of what to watch for, not proof the drug caused it.
Source: openFDA, from the FDA Adverse Event Reporting System (FAERS). These are voluntary reports — they don’t prove the drug caused the effect, and counts reflect how often something was reported, not how often it actually happens. Reports also often name the very problem the medicine is taken for — a common reason to file one is that the drug didn’t help — so for a pain reliever you may see “pain” high on the list; that points to why the report was filed, not to the drug causing the symptom. This counts every report that lists Nirmatrelvir and Ritonavir in any role, so the total runs higher than the FDA’s official dashboard, which counts only cases where the drug is the suspect. For the authoritative figures, see the FDA FAERS Public Dashboard. Always talk to your pharmacist or doctor.
🏛️ The road to your pharmacy
How Nirmatrelvir and Ritonavir went from FDA review to the pharmacy shelf — the key milestones in its regulatory journey.
Source: Drugs@FDA.
🚨 Recall history
A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.
Source: openFDA drug enforcement (recall) reports.
📦 Supply & shortage status
Whether Nirmatrelvir and Ritonavir is in short supply in the U.S. right now, plus any shortage history the FDA has on record. A shortage usually reflects a manufacturing or demand issue — not a safety problem with the drug.
Source: openFDA, from the FDA Drug Shortages database.
🏷️ Sold under these brand names
🏭 Manufacturers & labelers
🔬 Where this comes from
Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.
How we combine label and product data
HelloPharmacist combines public FDA and NLM records; we don’t author the underlying clinical facts. We identified 1 FDA-filed SPL label set within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. The representative label is the starting point for the displayed reference monograph; the 12 largest stored in-scope SPL records, which may include that representative, are compared section by section, and the longest available version of each section is retained. Forms, routes, brands, labelers, product-listed strengths, and product-record counts are aggregated separately from ingredient-matched FDA NDC Directory records; package records listed above are associated with the linked SPL; and the normalized concept hierarchy comes from NLM RxNorm.
For canonical ingredient pages, bounded product-attributed indication and administration excerpts may be added to the AI evidence, and the generator is instructed to preserve available product, brand, route, and form qualifiers instead of treating one label as universal. Where a section is identified as AI-written, its plain-language text is generated from bounded label evidence. New draft drug pages remain in the admin review queue before first publication. Pfizer Laboratories Div Pfizer Inc is the representative DailyMed label linked for verification and dates; it is not the sole source used for the page.
This is general education, not medical advice — always consult your doctor or pharmacist about your medications and any medical condition. For the exact wording of the linked representative label, view that label on DailyMed; some displayed composite sections may come from other in-scope SPL labels. Learn how we use AI and our data sources & update cadence.