Ritonavir and Simvastatin: Interaction Details
AI-assisted, pharmacist-reviewed · AI content regenerated Jul 11, 2026 · Source data updated Jul 4, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Ritonavir
Simvastatin
How we grade severity & evidence
Severity levels
- Contraindicated: These should generally not be used together.
- Major: Potentially serious — often needs a change or close monitoring.
- Moderate: Can be significant — usually manageable with monitoring.
- Minor: Usually limited clinical impact.
Evidence grades
- Established: Well documented — supported by controlled studies or strong clinical data.
- Probable: Good supporting evidence, though not definitively proven.
- Suspected: Some evidence suggests this interaction, but it is not well established.
- Possible: Limited or conflicting evidence; the interaction may occur.
- Theoretical: Predicted from the drugs' pharmacology; not yet confirmed in people.
Ratings come from the documented interaction literature and are reviewed by a pharmacist. They describe the documented risk of the combination, not what will necessarily happen to you — your dose, timing, and health picture all matter.
These two medicines should not be taken together. Ritonavir (Norvir) slows down the way your body breaks down and clears simvastatin (Zocor). That means the statin can build up to much higher levels than normal.
When simvastatin gets too high, it raises the risk of serious muscle problems, including unexplained muscle pain, weakness, or tenderness. In rare cases this muscle damage can become severe (a condition called rhabdomyolysis) and affect the kidneys. The good news is that this is very manageable. Your care team can pause the statin or switch you to a different one that works safely with ritonavir. Please talk with your pharmacist or doctor before taking both.
Contraindicated combination. Ritonavir inhibits both CYP3A4-mediated metabolism and OATP1B1 transport of simvastatin, markedly increasing simvastatin exposure (AUC/Cmax) and the risk of myopathy and rhabdomyolysis. Onset is delayed; evidence is rated probable.
- Direction: increased simvastatin effect/toxicity (simvastatin is the affected substrate).
- Management: Avoid concurrent use. If ritonavir is required, suspend simvastatin for the treatment duration.
- Nirmatrelvir/ritonavir (Paxlovid): stop simvastatin at least 12 hours before, throughout the 5-day course, and for 5 days after.
- Alternatives: pravastatin or fluvastatin have less CYP3A4 dependence.
- Monitor for muscle pain, weakness, and CK/renal changes.
What happens
Increased simvastatin exposure and an increased risk of myopathy or rhabdomyolysis
Interaction Deep Dive
The joint administration of ritonavir and simvastatin is contraindicated, because it can raise simvastatin exposure2 and because of the possibility of a heightened risk of myopathy, potentially including rhabdomyolysis 34. Should coadministration become necessary, simvastatin should be held for the duration of ritonavir treatment 1. When nirmatrelvir/ritonavir is judged to be medically required, stop simvastatin at a minimum of 12 hours before starting nirmatrelvir/ritonavir, throughout the 5 days of nirmatrelvir/ritonavir therapy, and for a further 5 days once nirmatrelvir/ritonavir has been finished 2.
Why it happens (mechanism)
Inhibition of OATP1B1-mediated efflux transport of simvastatin; inhibition of CYP3A4-mediated simvastatin metabolism
How to manage this interaction
This combination is generally avoided. Your care team has clear ways to manage it safely:
- They may pause simvastatin for the whole time you are on ritonavir.
- They may switch you to a different statin, such as pravastatin or fluvastatin, which fit better with ritonavir.
- If you are prescribed nirmatrelvir/ritonavir (Paxlovid), simvastatin is typically stopped at least 12 hours before, during the 5-day course, and for 5 days afterward.
What you should do: Do not start or stop either medicine on your own. Tell your pharmacist and prescriber you take both, and report any muscle pain, weakness, tenderness, or dark urine right away.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) A report described a case of rhabdomyolysis attributed to a probable interaction between simvastatin and ritonavir. A 51-year-old woman was admitted to the hospital after experiencing weakness in her upper and lower extremities along with body aches lasting 4 days. Her medical history was notable for type 2 diabetes mellitus, HIV infection acquired through a blood transfusion, gastroesophageal reflux disease, and hypercholesterolemia. At the time, her medications included zidovudine, lamiVUDine, indinavir, ritonavir, simvastatin, omeprazole, isophane insulin, metFORMIN, meclizine, conjugated estrogens, and medroxyPROGESTERone. Ritonavir had been started one week prior to her admission. Upon admission, her serum levels of creatine kinase (CK), CK-MB isoenzyme, LDH, AST, and ALT were raised. Urinalysis showed positive results for hemoglobin and some crystals. She was treated with intravenous fluids and sodium bicarbonate to alkalinize her urine. By the third day in the hospital, her muscle and liver enzyme levels reached their highest point. At that stage she was unable to raise her upper or lower extremities. By hospital day 6 she regained the ability to walk and to move her upper extremities. She was discharged with a serum CK level of 8223 international units/liter. Her liver and muscle enzymes returned to normal ten days following discharge. Clinicians should remain alert to identifying this potentially serious interaction and, where feasible, should avoid administering statins to patients taking protease inhibitors 5.
Common questions
Can I take Ritonavir and Simvastatin together?
Ritonavir and simvastatin should not be taken together because ritonavir raises simvastatin levels and the risk of serious muscle damage. Your care team will pause the statin, adjust timing, or switch you to a safer statin like pravastatin or fluvastatin. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Ritonavir and Simvastatin interaction?
It is rated contraindicated. These should generally not be used together.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
How is the Ritonavir and Simvastatin interaction managed?
This combination is generally avoided. Your care team has clear ways to manage it safely: They may pause simvastatin for the whole time you are on ritonavir. They may switch you to a different statin, such as pravastatin or fluvastatin, which fit better with ritonavir. If you are prescribed nirmatrelvir/ritonavir (Paxlovid), simvastatin is typically stopped at least 12 hours before, during the 5-d… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Ritonavir or Simvastatin need adjusting while I take them together?
- What symptoms should prompt me to call you or my prescriber right away?
- Does the timing of my doses matter for this combination?
- Is there a safer alternative to one of these medications for me?
References (5)
- Product Information: ZOCOR(R) oral tablets, simvastatin oral tablets. Organon & Co (per FDA), Jersey City, NJ, 2022. DailyMed
- Product Information: PAXLOVID(TM) oral tablets, nirmatrelvir oral tablets, ritonavir oral tablets. Pfizer Labs (per FDA), New York, NY, 2025. DailyMed
- Product Information: NORVIR(R) oral capsules, oral solution, ritonavir oral capsules, oral solution. Abbott Laboratories, North Chicago, IL, 2009. DailyMed
- Product Information: KALETRA(R) film coated oral tablets, oral solution, lopinavir and ritonavir film coated oral tablets, oral solution. Abbott Laboratories, North Chicago, IL, 2009.
- Cheng CH, Miller C, Lowe C, et al: Rhabdomyolysis due to probable interaction between simvastatin and ritonavir. Am J Health Syst Pharm 2002; 59(8):728-730. PubMed
Keep reading about Ritonavir
Keep reading about Simvastatin
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