Simvastatin and Quinine: 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
Quinine
No brand names on recordSimvastatin
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.
Here's what's going on. Your body uses an enzyme called CYP3A4 to break down simvastatin (Zocor). Quinine can slow that enzyme down, so simvastatin may build up to higher levels than usual in your blood.
When statin levels get too high, the main worry is your muscles. That can show up as unusual muscle pain, tenderness, or weakness. In rare cases it can lead to a serious muscle problem. The good news is this is very manageable. Your care team can use the lowest effective dose of simvastatin and keep a close eye on you, especially early on. Please tell your pharmacist or doctor about any new muscle aches, and don't stop either medicine on your own.
Mechanism/direction: Quinine inhibits CYP3A4, the primary enzyme metabolizing simvastatin (an active drug, not a prodrug). Reduced clearance increases simvastatin exposure (AUC/Cmax), raising risk of myopathy and rhabdomyolysis.
- Evidence: Theoretical; PK data for this pair are lacking, but a case report describes rhabdomyolysis with acute renal failure after a single quinine dose in an atorvastatin patient.
- Onset: Unspecified.
- Management: If used together, employ the lowest effective simvastatin starting/maintenance dose. Monitor for muscle pain, tenderness, weakness and CPK, particularly during initiation. Discontinue simvastatin if myopathy is suspected or CPK exceeds 10x ULN.
What happens
Increased plasma concentrations of simvastatin and increased risk of myopathy or rhabdomyolysis
Interaction Deep Dive
Co-administration of quinine and simvastatin can raise simvastatin plasma levels, thereby heightening the likelihood of myopathy or rhabdomyolysis, because quinine inhibits the CYP3A4-mediated metabolism of simvastatin. The pharmacokinetic effects of giving quinine alongside simvastatin have not been formally investigated; however, one case report documents rhabdomyolysis accompanied by acute renal failure secondary to myoglobinuria in a patient on atorvastatin after that patient received a single dose of quinine. When the anticipated benefits of using these agents together are judged to exceed the possible hazards, the lowest effective starting and maintenance doses of simvastatin should be considered, along with close observation for statin toxicity, especially during the early phase of treatment. Simvastatin should be stopped in patients who show markedly raised creatine phosphokinase (CPK) values, or when myopathy (defined as muscle aches or muscle weakness together with CPK levels exceeding 10 times the ULN) is diagnosed or suspected1.
Why it happens (mechanism)
Inhibition of CYP3A-mediated simvastatin metabolism by quinine
How to manage this interaction
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This interaction is manageable.
- Your care team may use the lowest effective dose of simvastatin, individualized to you.
- They may monitor you more closely, especially when you first start, including watching for muscle symptoms and possibly checking a blood test (CPK).
- Report any new or unexplained muscle pain, tenderness, or weakness to your pharmacist or doctor right away, particularly if it comes with dark urine or feeling unwell.
Ask your pharmacist to review both medicines so the plan fits your situation.
Management is individual — confirm any change with your pharmacist or prescriber.
Common questions
Can I take Simvastatin and Quinine together?
Quinine can raise simvastatin levels and increase the small risk of muscle problems, so your team may use a lower statin dose and watch you closely. Report new muscle pain, tenderness, or weakness and keep taking both unless told otherwise. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Simvastatin and Quinine interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "unspecified". The timing of this interaction is not well characterized.
How is the Simvastatin and Quinine interaction managed?
Keep taking both medicines as prescribed unless your prescriber tells you otherwise. This interaction is manageable. Your care team may use the lowest effective dose of simvastatin, individualized to you. They may monitor you more closely, especially when you first start, including watching for muscle symptoms and possibly checking a blood test (CPK). Report any new or unexplained muscle pain, ten… 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 Quinine 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 anything you'd monitor while I'm on both?
References (1)
- Product Information: QUALAQUIN(R) oral capsules, quinine sulfate oral capsules. AR Scientific, Inc. Philadelphia, PA, 2010. DailyMed
Keep reading about Quinine
Keep reading about Simvastatin
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