Paxlovid interacts with a long list of common medications, including several heart drugs, cholesterol medications, blood thinners, seizure drugs, sedatives, and even herbal supplements like St. John’s Wort. Some of these interactions are dangerous enough that the combination is strictly contraindicated, while others can be managed by temporarily pausing a medication or adjusting the dose during the five-day treatment course.
The reason Paxlovid causes so many problems comes down to one of its two active ingredients: ritonavir. Ritonavir permanently disables the liver enzyme responsible for breaking down a huge number of common drugs. When that enzyme can’t do its job, other medications build up to potentially toxic levels in your bloodstream. Conversely, a few drugs speed up the same enzyme, which can make Paxlovid itself less effective.
Why Paxlovid Causes So Many Interactions
Your liver uses an enzyme called CYP3A4 to process roughly half of all prescription medications. Ritonavir physically attaches itself to this enzyme and shuts it down, one molecule of ritonavir for every molecule of enzyme it destroys. This is actually intentional: ritonavir is included in Paxlovid specifically to keep the antiviral component (nirmatrelvir) circulating in your body longer, making it more effective against COVID-19.
The tradeoff is that every other medication processed by this same enzyme also stays in your system much longer and at much higher concentrations than normal. For some drugs, that elevated level is merely inconvenient. For others, it can cause life-threatening side effects like dangerous heart rhythms, severe drops in blood pressure, or excessive bleeding.
Heart and Blood Pressure Medications
Cardiovascular drugs are the largest category of concern. Several are completely contraindicated, meaning they cannot be taken with Paxlovid at all:
- Amiodarone and dronedarone (heart rhythm drugs). Amiodarone is especially problematic because it stays in the body for weeks, so even stopping it before Paxlovid won’t eliminate the risk.
- Flecainide, propafenone, and quinidine (other heart rhythm drugs)
- Ranolazine (used for chest pain)
- Eplerenone and finerenone (used for heart failure and kidney disease)
- Ivabradine (used to slow heart rate)
- Tolvaptan (used for low sodium levels)
A second group of heart medications isn’t outright banned but requires dose adjustments, temporary holds, or close monitoring. This includes common calcium channel blockers like amlodipine, diltiazem, verapamil, nifedipine, felodipine, and nicardipine. It also includes the blood pressure drug aliskiren and the antianginal disopyramide.
Blood Thinners
If you take a blood thinner, Paxlovid creates a real dilemma because both stopping the blood thinner and increasing its levels carry serious risks. None of the common blood thinners are absolutely contraindicated, but all of them require careful management:
- Apixaban and rivaroxaban can reach dangerously high levels, increasing bleeding risk.
- Dabigatran concentrations may also rise.
- Warfarin levels can shift unpredictably, requiring extra monitoring of clotting times.
- Clopidogrel and ticagrelor (antiplatelet drugs) also interact and need monitoring or adjustment.
Your prescriber will typically weigh the bleeding risk against the benefit of COVID treatment and may adjust doses for the five-day course.
Cholesterol Medications (Statins)
Two statins are contraindicated with Paxlovid: lovastatin and simvastatin. Both are processed almost entirely by the enzyme that ritonavir blocks, so their blood levels can spike to dangerous concentrations, raising the risk of severe muscle breakdown.
The workaround is straightforward. According to the FDA’s prescribing checklist, lovastatin or simvastatin can be held starting 12 hours before the first Paxlovid dose, paused during the entire five-day treatment, and restarted five days after the last dose. That roughly two-week gap without your statin is generally safe for most people.
Atorvastatin also interacts but less severely. It can simply be paused during the five days of treatment and restarted immediately afterward, with no lead-in or washout period needed.
Seizure Medications
Three common anti-seizure drugs are absolutely contraindicated with Paxlovid:
- Carbamazepine
- Phenobarbital
- Phenytoin
These drugs work in the opposite direction from most interactions on this list. Instead of building up to dangerous levels, they are potent “inducers” of the CYP3A4 enzyme, meaning they cause your liver to break down Paxlovid too quickly. The result is that Paxlovid may never reach effective levels in your bloodstream, potentially rendering the treatment useless. Making matters worse, you can’t simply stop these seizure medications to take Paxlovid, since abruptly discontinuing them can trigger breakthrough seizures. For patients on these drugs, an alternative COVID treatment is typically the better option.
Sedatives and Sleep Aids
Benzodiazepines and sleep medications are processed by the same liver enzyme, so Paxlovid can amplify their sedating effects. Alprazolam interacts significantly enough that alternatives should be considered during treatment. Clonazepam levels may rise, requiring a dose reduction and close monitoring for excessive drowsiness or impaired coordination.
Zolpidem (a common sleep aid) has a milder interaction. Studies show ritonavir increases zolpidem exposure by roughly 28%, which may not require a dose change for most people, though you should expect somewhat stronger sedation than usual.
Psychiatric Medications
Several commonly prescribed psychiatric drugs interact with Paxlovid, though most can be managed rather than completely avoided.
Trazodone is one of the more concerning. In studies with healthy volunteers, ritonavir more than doubled trazodone levels, which can cause nausea, dizziness, dangerously low blood pressure, and abnormal heart rhythms. A dose reduction is typically needed if trazodone can’t be paused. Quetiapine also requires dose reduction or a temporary switch, since elevated levels can cause excessive sedation and other side effects. Risperidone exposure increases as well, raising the risk of movement disorders and other adverse reactions.
Mirtazapine levels may climb, and because this drug can affect heart rhythm at higher concentrations, extra cardiac monitoring may be warranted. Bupropion, on the other hand, is one of the safer psychiatric medications to continue. Ritonavir is expected to decrease bupropion levels slightly, but because Paxlovid treatment is only five days, the effect is limited and no dose change is typically needed.
Erectile Dysfunction and Pulmonary Hypertension Drugs
PDE5 inhibitors like sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra) all interact with Paxlovid, but the severity depends on why you’re taking them. When sildenafil is used for pulmonary hypertension (under the brand name Revatio), it is completely contraindicated with Paxlovid because of the risk of severe low blood pressure and other dangerous side effects. Tadalafil for pulmonary hypertension (Adcirca) should also be avoided.
When these same drugs are used for erectile dysfunction, the interaction is manageable with significant dose reductions. Avanafil is the exception: no safe dosing regimen has been established, so it should not be used with Paxlovid at all.
Herbal Supplements: St. John’s Wort
St. John’s Wort is one of the most powerful over-the-counter enzyme inducers available, and it is completely contraindicated with Paxlovid. Like the seizure medications above, it revs up the liver enzyme that breaks down Paxlovid, potentially dropping the antiviral to ineffective levels. The FDA’s fact sheet specifically warns that Paxlovid cannot be started immediately after stopping St. John’s Wort because the enzyme-inducing effect lingers for days after the last dose.
Kidney Function and Dose Adjustments
Paxlovid dosing depends heavily on how well your kidneys are working, measured by a blood test called eGFR. Patients with normal kidney function or mild impairment (eGFR of 60 or above) receive the standard dose: two nirmatrelvir tablets plus one ritonavir tablet, twice daily. Moderate kidney impairment (eGFR between 30 and 60) cuts the nirmatrelvir dose in half. Severe impairment (eGFR below 30) requires a different regimen altogether: a loading dose on day one followed by a reduced once-daily dose for the remaining four days. On days when hemodialysis is scheduled, the dose should be taken after the session.
Holding and Restarting Medications
For drugs that can be temporarily paused, the timeline matters. Paxlovid’s effect on your liver enzymes doesn’t disappear the moment you take the last pill. The general pattern for statins, which is representative of many held medications, is to stop the drug before starting Paxlovid and wait about five days after finishing the course before restarting. For lovastatin and simvastatin specifically, the FDA recommends holding the statin 12 hours before Paxlovid, continuing the hold through all five treatment days, and waiting five additional days after the last Paxlovid dose before resuming.
Drugs that induce the enzyme (like St. John’s Wort or certain seizure medications) have the opposite problem: their effects linger even after you stop taking them, so Paxlovid can’t simply be started the next day. This delayed offset makes the timing trickier and often rules out Paxlovid as a practical option for people on those medications.
Because the list of interactions is so extensive, prescribers typically run your full medication list through a drug interaction checker before writing a Paxlovid prescription. If you’re prescribed Paxlovid, make sure every provider involved knows about all your current medications, including over-the-counter supplements, so the right ones can be held, adjusted, or flagged as a reason to consider a different COVID treatment.