Simvastatin and Lopinavir: 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
Simvastatin
Lopinavir
No brand names on record
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 shouldn't be taken together. Lopinavir (usually combined with ritonavir) strongly blocks a liver enzyme called CYP3A4, which is the same enzyme your body uses to break down simvastatin. When that enzyme is blocked, simvastatin can build up to much higher levels than intended.
Too much simvastatin can cause serious muscle problems, including pain, tenderness, weakness, and rarely a dangerous condition called rhabdomyolysis. The good news is your care team has safer options. Please don't stop anything on your own, but do talk with your pharmacist or doctor, because they can switch you to a statin that fits well with lopinavir.
Combination is contraindicated. Lopinavir/ritonavir is a potent CYP3A4 inhibitor; simvastatin is a CYP3A4 substrate (not a prodrug for this pathway). Inhibition markedly reduces simvastatin metabolism, increasing systemic exposure (AUC/Cmax) and the risk of myopathy and rhabdomyolysis.
- Direction: increased simvastatin effect and toxicity
- Onset: delayed
- Evidence: theoretical, but severity is well established mechanistically
- Management: avoid combination; prefer fluvastatin, pitavastatin, or pravastatin (least CYP3A4 dependence). If coadministration is unavoidable, temporarily suspend simvastatin for the duration of lopinavir/ritonavir therapy. Monitor for muscle symptoms and CK if concern arises.
What happens
An increased risk of myopathy or rhabdomyolysis
Interaction Deep Dive
The combination of lopinavir/ritonavir with simvastatin is contraindicated. As a strong CYP3A4 inhibitor, lopinavir/ritonavir reduces the metabolism of simvastatin, which is a CYP3A4 substrate. This reduced metabolism markedly raises the likelihood of myopathy and rhabdomyolysis2. For patients on lopinavir/ritonavir, fluvastatin, pitavastatin, or pravastatin may be considered as alternatives to lovastatin, since these carry the lowest potential for interaction3. Should coadministration become necessary, simvastatin should be discontinued for the duration of lopinavir/ritonavir therapy1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated simvastatin metabolism by lopinavir/ritonavir
How to manage this interaction
This combination is one to avoid. Keep taking your medicines as prescribed and reach out to your pharmacist or prescriber, who can manage this safely.
- Your team may switch you to a statin less affected by lopinavir, such as fluvastatin, pitavastatin, or pravastatin.
- If simvastatin must be used, your team may temporarily pause it during the course of lopinavir/ritonavir treatment.
- Watch for and promptly report any muscle pain, tenderness, or weakness, especially if it comes with dark urine or feeling unwell.
Please don't start, stop, or change either medicine on your own.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Simvastatin and Lopinavir together?
Simvastatin and lopinavir/ritonavir should not be used together because simvastatin can build up and cause serious muscle damage; ask your doctor or pharmacist about a safer statin like pravastatin, pitavastatin, or fluvastatin. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Simvastatin and Lopinavir 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 Simvastatin and Lopinavir interaction managed?
This combination is one to avoid. Keep taking your medicines as prescribed and reach out to your pharmacist or prescriber, who can manage this safely. Your team may switch you to a statin less affected by lopinavir, such as fluvastatin, pitavastatin, or pravastatin. If simvastatin must be used, your team may temporarily pause it during the course of lopinavir/ritonavir treatment. Watch for and pro… Management is individual — always follow your own care team's guidance.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
From our Q&A
Real reader questions about these medications, each personally answered by our pharmacist:
Questions for your pharmacist
- Does my dose of Simvastatin or Lopinavir 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 (3)
- Product Information: ZOCOR(R) oral tablets, simvastatin oral tablets. Organon & Co (per FDA), Jersey City, NJ, 2022. DailyMed
- Product Information: KALETRA(R) oral capsules, solution, lopinavir ritonavir oral capsules, solution. Abbott Laboratories (per manufacturer), North Chicago, IL, 2012. DailyMed
- Panel on Antiretroviral Guidelines for Adults and Adolescents: Guidelines for the use of antiretroviral agents in HIV-1-infected adults and adolescents. AIDSinfo, Department of Health and Human Services. Rockville, MD. 2012.
Keep reading about Simvastatin
Keep reading about Lopinavir
These medications also interact with supplements
Prescription drugs aren't the whole picture — herbal and dietary supplements can interact with them too. From the evidence-graded Natural Medicines database:
major · moderate · minor — check everything you take with our drug–supplement interaction checker.
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