Simvastatin and Risperidone: 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
Risperidone
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.
Taking simvastatin (Zocor) and risperidone (Risperdal) together needs a little extra care. Both are broken down by the same liver pathway. In some people, risperidone can slow down how the body clears simvastatin, so the statin can build up to higher levels than expected.
When simvastatin levels rise, the main worry is a muscle problem. This can show up as muscle pain, tenderness, or unusual weakness. In rare cases it becomes serious. The good news is your care team can manage this by watching you closely and checking a muscle blood test if needed. Please tell your pharmacist or doctor if you notice new or unexplained muscle aches.
Effect: Increased simvastatin serum concentrations with elevated risk of myopathy/rhabdomyolysis.
Mechanism: Competitive inhibition of CYP3A4-mediated simvastatin metabolism. Risperidone is predominantly a CYP2D6 substrate, but in CYP2D6 poor metabolizers CYP3A4 becomes the primary route, allowing competition with simvastatin (itself a CYP3A4 substrate). Neither is an active-metabolite-dependent prodrug relevant here, so higher simvastatin exposure means increased effect and toxicity.
- Direction: Increased simvastatin exposure
- Onset: Delayed
- Evidence: Probable (case report of rhabdomyolysis with compartment syndrome)
- Management: Concurrent use not recommended; if used, monitor for muscle symptoms and CK, discontinue if myopathy suspected.
What happens
Increased simvastatin serum concentrations with an increased risk of myopathy or rhabdomyolysis
Interaction Deep Dive
Taking risperiDONE together with simvastatin may raise simvastatin's bioavailability. Both risperiDONE and simvastatin undergo metabolism via cytochrome P450-3A4 (CYP3A4). RisperiDONE is chiefly metabolized by CYP2D6; however, in people with a slow metabolizer phenotype stemming from a CYP2D6 polymorphic genotype, CYP3A4 may become the main isoform responsible for risperiDONE metabolism. Consequently, risperiDONE can competitively inhibit the metabolism of simvastatin, which in turn elevates the likelihood of myopathy and rhabdomyolysis. One case report described a patient who experienced rhabdomyolysis that was further complicated by acute compartment syndrome following the combined administration of simvastatin and risperiDONE1.
Why it happens (mechanism)
Competitive inhibition of cytochrome P450-3A4-mediated simvastatin metabolism
How to manage this interaction
Keep taking both medications as prescribed unless your prescriber tells you otherwise. This combination is generally not recommended, so your care team may consider whether an alternative is appropriate for you.
If you continue both, your team will typically:
- Watch for muscle pain, tenderness, or weakness
- Check a blood test called creatine kinase (CK) if muscle symptoms appear
- Adjust or stop the statin if a muscle problem is found or suspected
What to do: Report any new or unexplained muscle aches, especially with dark urine, to your pharmacist or doctor promptly.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
1 report — tap to read
a) A 22-year-old man developed rhabdomyolysis after simvastatin 10 milligrams (mg) daily was introduced to a stable regimen consisting of clonazepam 2 mg and risperiDONE 4 mg daily. About 5 days after starting simvastatin, the patient reported pain in the right ankle and heel. During the following 24 hours, the pain moved proximally and worsened, and the limb displayed warmth, erythema, rash, and marked tenseness of the distal muscle compartments. Serum creatine kinase (CK), aspartate aminotransferase, and alanine aminotransferase levels were 12, 408 units/liter (L), 296 International Units (IU)/L, and 97 IU/L, respectively. CK levels reached a maximum of 25, 498 units/L. Simvastatin was discontinued, and the patient needed emergency decompression fasciotomies because of acute compartment syndrome of the right lower extremity. RisperiDONE and clonazepam were maintained without any problem 1.
Common questions
Can I take Simvastatin and Risperidone together?
Risperidone can raise simvastatin levels and increase the risk of muscle injury, so this combination is generally avoided; if you take both, watch for muscle pain or weakness and check with your care team. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Simvastatin and Risperidone interaction?
It is rated major. Potentially serious — often needs a change or close monitoring.
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 Risperidone interaction managed?
Keep taking both medications as prescribed unless your prescriber tells you otherwise. This combination is generally not recommended, so your care team may consider whether an alternative is appropriate for you. If you continue both, your team will typically: Watch for muscle pain, tenderness, or weakness Check a blood test called creatine kinase (CK) if muscle symptoms appear Adjust or stop the s… 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 Simvastatin or Risperidone 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 (1)
- Webber MA, Mahmud W, Lightfoot JD, et al: Rhabdomyolysis and compartment syndrome with coadministration of risperidone and simvastatin. J Psychopharmacol 2004; 18(3):432-434. PubMed
Keep reading about Simvastatin
Keep reading about Risperidone
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