10 Common Ritonavir Interactions to Be Aware of (Plus Other Medications to Avoid)

Ritonavir (Norvir) is an oral antiretroviral medication. It was originally developed to treat HIV. But today, it’s not prescribed by itself for this health condition. It acts like a sidekick. Ritonavir slows the metabolism (breakdown) of other medications. This often causes higher levels of other medications in the body. Because of this, ritonavir is often used as a “booster” to help other medications be more effective.

Ritonavir is part of some combination HIV treatments, such as Kaletra (lopinavir / ritonavir). It’s also part of an oral COVID-19 treatment, Paxlovid (nirmatrelvir / ritonavir).

Ritonavir is notorious for having many interactions. If you take a medication containing ritonavir, you’ll want to make sure of what other medications you can safely take. In some cases, you may need to stop a medication or take a different dose.

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Here are 10 important ritonavir interactions to know about. But keep in mind these aren’t the only possible ones. Ritonavir interacts with hundreds of medications. So it’s important to share a complete medication list with your healthcare provider and pharmacist.

1. Heart rhythm medications

Certain heart rhythm medications (antiarrhythmics) can build up in the body when combined with ritonavir. This can lead to side effects like palpitations, abnormal heart rhythms, and even a heart attack. Digoxin (Lanoxin) is one example of an antiarrhythmic that interacts with ritonavir. Your healthcare provider may recommend a lower dose of digoxin to continue taking it safely.

Antiarrhythmics that should be avoided when taking ritonavir include:

• Amiodarone (Pacerone)

• Dronedarone (Multaq)

• Flecainide

• Propafenone (Rythmol)

• Quinidine

2. Statins

Statin medications are used to treat high cholesterol. When combined with ritonavir, statins can build up in the body. Higher statin levels can raise the risk of side effects, such as severe muscle pain.

Not all statins interact with ritonavir. Some medications in this class can be combined with ritonavir when prescribed at lower doses:

• Atorvastatin (Lipitor)

• Rosuvastatin (Crestor)

And some statins should be avoided if you also take ritonavir, including:

• Simvastatin (Zocor)

• Lovastatin (Altoprev)

If you’re taking a medication containing ritonavir for a short amount of time (such as with Paxlovid), you may need to temporarily stop your statin. You’d then restart your statin after finishing ritonavir. If you’re taking ritonavir long term, your healthcare provider may suggest lowering your statin dose or switching statins.

3. Blood thinners

Blood thinners, such as anticoagulants and antiplatelet medications, prevent and treat blood clots. Many of them interact with ritonavir. In most cases, ritonavir causes blood thinners to build up in the body. This can raise your risk for serious bleeding. For example, if you’re taking warfarin (Coumadin, Jantoven), you may need to have your dose adjusted, depending on how your blood tests are affected.

Your dose of these blood thinners may need to be lowered if you take ritonavir:

• Apixaban (Eliquis)

• Dabigatran (Pradaxa)

• Edoxaban (Savaysa)

These blood thinners should be avoided:

• Rivaroxaban (Xarelto)

• Clopidogrel (Plavix)

• Ticagrelor (Brilinta)

It’s important to discuss the best way to manage this ritonavir interaction with your healthcare provider. Depending on your unique health history and risk factors, changes to your blood thinner or antiviral treatment might be needed. But don’t stop any of your medications without your provider’s OK.

4. Blood pressure medications

Certain blood pressure medications can build up in the body when combined with ritonavir. This may result in blood pressure that goes too low.

Some beta blockers like metoprolol (Lopressor, Toprol XL) might need a dose reduction while taking ritonavir. And you might also need lower doses of calcium channel blockers like:

• Amlodipine (Norvasc)

• Diltiazem (Cardizem)

• Felodipine

• Nifedipine (Procardia)

• Verapamil

5. Seizure medications

Seizure medications are used to treat and prevent seizures. When certain seizure medications are taken with ritonavir, they can lower the level of ritonavir in the body, potentially making it less effective. This includes primidone (Mysoline) and phenobarbital. You may need your dose of ritonavir raised when taking these medications.

With other seizure medications, ritonavir can increase their levels in the body, raising the risk for side effects. Examples include carbamazepine (Tegretol) and ethosuximide (Zarontin). You might need a lower dose of these medications if you also take ritonavir.

Taking ritonavir can also result in lower levels of certain seizure medications, possibly reducing their effectiveness. Examples include lamotrigine (Lamictal) and divalproex (Depakote). You may need to take a higher dose of these medications while taking ritonavir.

6. Antidepressants

Antidepressants treat conditions like depression and anxiety. When certain antidepressants are taken with ritonavir, side effects are more likely. This is because antidepressant levels can build up in the body.

Antidepressants that have this interaction with ritonavir include:

• Fluoxetine (Prozac)

• Paroxetine (Paxil)

• Amitriptyline

• Nortriptyline (Pamelor)

• Trazodone

One antidepressant, bupropion (Wellbutrin XL, Wellbutrin SR), may have lower levels when combined with ritonavir. So bupropion may be less effective.

7. Antipsychotics

Antipsychotics treat mental health conditions like bipolar disorder and schizophrenia. Some antipsychotics build up in the body when taken with ritonavir. This can raise the risk of side effects.

Typically, lower doses of antipsychotics will help manage this interaction. But certain antipsychotics shouldn’t be combined with ritonavir, including:

• Quetiapine (Seroquel)

• Lurasidone (Latuda)

• Pimozide.

8. Migraine medications

Several types of medications can help treat migraine headaches. But certain ones can build up when combined with ritonavir, possibly leading to more side effects.

Examples of migraine medications that should be avoided due to this ritonavir interaction include:

• Ergot medications, such as ergotamine (Ergomar)

• Eletriptan (Relpax)

• Rimegepant (Nurtec ODT)

• Ubrogepant (Ubrelvy)

9. Erectile dysfunction medications

Sildenafil (Viagra), tadalafil (Cialis), and vardenafil can help with erectile dysfunction. Avanafil (Stendra) is another example. But when combined with ritonavir, they build up in the body. This can worsen side effects like low blood pressure and passing out. Depending on your situation, it may be recommended to limit or avoid these medications while taking ritonavir.

10. Hormonal birth control medications

When certain hormonal birth control medications are combined with ritonavir, they can be less effective. Medications that contain ethinyl estradiol, including pills, patches, and vaginal rings, are susceptible to this interaction.

If you’re using ethinyl estradiol-containing birth control, you should use a backup method, like condoms, while taking ritonavir. You can also discuss birth control methods that don’t contain this hormone with your healthcare provider.

Other ritonavir interactions you should be cautious of

The list above is not an exhaustive list of ritonavir interactions. There are many more medications that can interact with ritonavir. Other commonly used medications that you may need to stop or adjust the dose are listed below:

• Alfuzosin (Uroxatral)

• Alprazolam (Xanax)

• Clonazepam (Klonopin)

• Colchicine (Colcrys)

• Diazepam (Valium)

• Erythromycin (Ery-Tab)

• Glecaprevir/pibrentasvir (Mavyret)

• Rifampin

• Oxybutynin (Ditropan)

• Ranolazine (Ranexa)

• Salmeterol-containing inhalers, such as Advair (fluticasone / salmeterol)

• Saxagliptin (Onglyza)

• Solifenacin (Vesicare)

• St. John’s wort

• Tamsulosin (Flomax)

• Theophylline (Theo-24)

• Triazolam (Halcion)

• Zolpidem (Ambien)

• Certain HIV medications

• Many cancer medications

• Transplant medications like tacrolimus (Prograf)

When should you contact my healthcare provider about a ritonavir interaction?

Your healthcare provider that prescribes ritonavir should be aware of possible interactions. Ideally, potential interactions should be addressed upfront, before starting treatment. But if you have questions, it’s best to check with your provider.

It’s also possible that you might start an interacting medication while you’re taking ritonavir. This is why it’s important to share your list of medications with your provider at each visit.

You can also use the University of Liverpool’s HIV medication interaction checker to help guide your discussion with your healthcare team. But even if you do discover a potential ritonavir interaction, don’t stop taking your medication without your provider’s OK. This is because some interactions only require dosage changes to manage them.

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Written by:

Austin Ulrich, PharmD, BCACP

Austin Ulrich, PharmD, BCACP, is a board-certified ambulatory care clinical pharmacist. In his early career, he provided direct patient care in a variety of settings, including hospital and community pharmacies, and in a primary care clinic as a clinical pharmacist.

Edited by:

Christina Aungst, PharmD

Christina Aungst, PharmD, is a pharmacy editor for GoodRx. She began writing for GoodRx Health in 2019, transitioning from freelance writer to editor in 2021.

Reviewed by:

Joshua Murdock, PharmD, BCBBS

Joshua Murdock, PharmD, BCBBS, is a licensed pharmacist in Arizona, Colorado, and Rhode Island. He has worked in the pharmacy industry for more than 10 years and currently serves as a pharmacy editor for GoodRx.

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