Kratom 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
Kratom
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.
Your body uses an enzyme called CYP3A to break down simvastatin (Zocor). Kratom appears to slow that enzyme down, so simvastatin can build up in your blood higher than usual. This is more likely with higher kratom doses or regular, daily use.
Too much simvastatin can raise your risk of side effects like muscle aches, muscle weakness, or (rarely) liver problems. This doesn't mean anything bad will happen, but it's worth knowing. Please don't stop either one on your own. Just let your pharmacist or doctor know you use kratom so they can watch for symptoms and keep your dose right for you.
Effect: Increased simvastatin exposure. Kratom is a probable CYP3A inhibitor, and simvastatin is a sensitive CYP3A4 substrate, so inhibition reduces its metabolism and raises AUC/Cmax of the active moiety.
- Direction: Increased statin exposure, greater myopathy/rhabdomyolysis and hepatotoxicity risk.
- Magnitude: Not quantified; dose- and duration-dependent (higher/chronic kratom use).
- Onset: Unspecified.
- Evidence: Probable.
- Management: Monitor for muscle pain/weakness and check CK and LFTs if symptomatic. Dose may need individualizing by the care team.
What happens
Increased CYP3A substrate exposure
Interaction Deep Dive
When kratom, which inhibits CYP3A, is taken together with a substrate of CYP3A, the resulting exposure to that CYP3A substrate can rise, particularly when kratom is used at elevated doses or over a prolonged period1. Careful monitoring is advised2.
Why it happens (mechanism)
Inhibition of CYP3A-mediated metabolism by kratom
How to manage this interaction
This interaction is usually manageable when your care team knows about it.
- Keep taking both as prescribed unless your prescriber tells you otherwise. Don't stop or change doses on your own.
- Tell your pharmacist and doctor you use kratom, including how much and how often, since higher or daily use matters more.
- Your team may monitor you more closely and your simvastatin dose may need to be adjusted and individualized.
- Report right away: unexplained muscle pain, tenderness, or weakness, dark urine, or yellowing of the skin or eyes.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) An open-label crossover study in healthy adults (N=12) assessed the effect of taking a single low dose of kratom tea (2 g) along with oral midazolam (a CYP3A probe substrate; 2.5 mg) and oral dextromethorphan (a CYP2D6 probe substrate; 30 mg). Kratom produced a modest rise in the midazolam geometric mean AUC (1.39; 90% CI, 1.23 to 1.57) and Cmax (1.5; 90% CI, 1.32 to 1.7); dextromethorphan AUC and Cmax showed no effect. The half life of midazolam was not significantly changed when kratom was used concurrently, indicating inhibition of first-pass metabolism, mainly intestinal CYP3A. The participants (median age, 30 years) had prior exposure to kratom and agreed to refrain from concomitant medications and botanical or other natural products (including kratom) for the duration of the study 1.
Common questions
Can I take Kratom and Simvastatin together?
Kratom can slow how your body clears simvastatin, raising its levels and the chance of muscle or liver side effects, so tell your care team you use kratom and report any muscle pain or weakness. Keep taking both as prescribed unless your doctor advises a change. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Kratom and Simvastatin 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 Kratom and Simvastatin interaction managed?
This interaction is usually manageable when your care team knows about it. Keep taking both as prescribed unless your prescriber tells you otherwise. Don't stop or change doses on your own. Tell your pharmacist and doctor you use kratom, including how much and how often, since higher or daily use matters more. Your team may monitor you more closely and your simvastatin dose may need to be adjusted… 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 Kratom 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 anything you'd monitor while I'm on both?
References (2)
- Tanna RS, Nguyen JT, Hadi DL, et al: Clinical assessment of the drug interaction potential of the psychotropic natural product kratom. Clin Pharmacol Ther 2023; 113(6):1315-1325. PubMed
- Dhoble LR, Gour A, McCurdy CR, et al: Evaluating the drug interactions in kratom usage: clinical application. Expert Opin Drug Metab Toxicol 2025; 21(8):949-959. PubMed
Keep reading about Kratom
Keep reading about Simvastatin
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist