Simvastatin and Ciprofloxacin: 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
Ciprofloxacin
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.
Ciprofloxacin is an antibiotic, and simvastatin (Zocor) is a cholesterol medicine. When you take them together, the antibiotic can slow down how your body breaks down the statin. That means more simvastatin can build up in your body than usual.
The main thing to watch for is muscle trouble. Higher statin levels can cause muscle aches, weakness, or, rarely, more serious muscle breakdown. It can also affect the liver. Please tell your care team about any new muscle pain, tenderness, or dark-colored urine. The good news is this is very manageable. Your doctor or pharmacist can keep an eye on things with simple lab checks and adjust your medicines if needed.
Effect: Ciprofloxacin may increase simvastatin exposure, raising the risk of myopathy, rhabdomyolysis, and hepatic dysfunction.
Mechanism: Weak inhibition of CYP3A4-mediated simvastatin metabolism by ciprofloxacin; simvastatin also acts as substrate/competitive inhibitor of P-gp and MRP efflux of ciprofloxacin. Neither agent is a prodrug relevant here, so inhibition raises the active statin level.
Severity: Major. Evidence: Probable. Onset: Unspecified.
Management:
- Monitor CK and LFTs during concurrent therapy.
- Counsel on myopathy symptoms (myalgia, weakness, dark urine).
- Statin dose may be individualized or a temporary hold/alternative considered by the care team.
What happens
Increased simvastatin exposure and increased risk of myopathy or rhabdomyolysis
Interaction Deep Dive
Taking ciprofloxacin together with simvastatin can lead to myopathy, rhabdomyolysis12, or impaired liver function 2. The proposed mechanism involves weak inhibition by ciprofloxacin of the CYP3A4-mediated metabolism of simvastatin, along with simvastatin acting as a substrate and competitive inhibitor of the p-glycoprotein and multiple drug resistance associated protein efflux pathways for ciprofloxacin 1. Should the two agents be used at the same time, liver function and muscle enzymes should be monitored for any changes 2.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated simvastatin metabolism by ciprofloxacin
How to manage this interaction
If both are needed, this can be managed safely with attention from your care team.
- Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise.
- Your team may monitor your liver function and muscle enzymes with blood tests while you are on both.
- Watch for muscle pain, tenderness, or weakness and unusually dark urine, and report these right away.
- Because ciprofloxacin is often a short course, your team may adjust the timing, tailor your statin dose, or briefly consider an alternative.
Bring any concerns to your pharmacist or prescriber so they can individualize your plan.
Management is individual — confirm any change with your pharmacist or prescriber.
Literature reports
2 reports — tap to read
a) A 77-year-old woman on a maintenance dose of simvastatin 40 mg was admitted to the hospital with severe muscle weakness, widespread muscle aches, and dark-colored urine following the addition of 2 doses of ciprofloxacin to her usual simvastatin regimen. On physical examination she was apyrexial, with a blood pressure (BP) of 197/68 mmHg, a pulse of 68 beats per min, tenderness of the muscles on touch, grade 3 power proximally, grade 4 power distally, and an inability to rise from a chair. Laboratory testing showed the following: reduced hemoglobin (10.2 g/dL), normal WBC (9.3 x 10(3)/mm(3)), normal platelet count (235 x 10(3)/mm(3)), raised erythrocyte sedimentation rate (80 mm/hr), normal creatinine (121 micromol/L), raised C-reactive protein (20 mg/L), raised creatinine kinase exceeding 10 times the ULN (29,980 units/L), normal bilirubin (7 micromol/L), normal alkaline phosphatase (78 units/L), raised alanine transaminase (212 units/L), and a urine dipstick positive for 4 + blood. Serum electrolytes and thyroid function were within normal limits, and autoimmune screening was negative. Following admission, both simvastatin and ciprofloxacin were stopped and the patient received hydration along with high dose methylprednisolone over 3 days. By day 14, creatinine kinase had normalized (166 units/L), and the muscle biopsy showed very few lymphocytes and did not suggest polymyositis, leading to a diagnosis of statin induced rhabdomyolysis possibly attributable to the interaction with ciprofloxacin 1.
b) A systematic review examining drug interactions between statins and quinolones identified 16 case reports that described adverse events including rhabdomyolysis (n=12), muscle weakness (n=1), hip tendinopathy (n=1), myopathy (n=1), and acute hepatitis (n=1). The statin dose and type differed across the case reports and comprised simvastatin (n=10) at doses ranging from 20 to 80 mg/day and atorvastatin (n=4) at 80 mg/day. The coadministered quinolones consisted of ciprofloxacin (n=9) at doses ranging from 800 to 1500 mg/day, levofloxacin (n=6) at doses ranging from 250 to 1000 mg/day, and norfloxacin (n=1) at an unspecified dose range. Roughly 80% of patients were older than 60 years, about 30% had kidney disease, and 62% were taking concurrent CYP3A4 inhibitors, P-gp inhibitors, or OATP1B1 inhibitors. Every case required hospitalization. In seven cases both the statin and quinolone were discontinued; in 4 cases only the statin was stopped, in 2 cases only the quinolone was stopped, and 1 patient was changed to a different statin. Symptoms resolved in all patients within 3 to 28 days. Patients receiving ciprofloxacin or levofloxacin together with simvastatin or high-dose atorvastatin should be monitored for changes in liver function and muscle enzymes, particularly if they are over 60 years of age, have kidney disease, or are taking concurrent CYP3A inhibitors 2.
Common questions
Can I take Simvastatin and Ciprofloxacin together?
Ciprofloxacin can raise simvastatin levels and increase the risk of muscle and liver problems, so watch for muscle pain or dark urine and let your care team monitor your labs. Report new muscle symptoms to your pharmacist or doctor promptly. Always confirm with your pharmacist or prescriber before making any change.
How serious is the Simvastatin and Ciprofloxacin interaction?
It is rated major. Potentially serious — often needs a change or close 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 Ciprofloxacin interaction managed?
If both are needed, this can be managed safely with attention from your care team. Keep taking both as prescribed unless your doctor or pharmacist tells you otherwise. Your team may monitor your liver function and muscle enzymes with blood tests while you are on both. Watch for muscle pain, tenderness, or weakness and unusually dark urine, and report these right away. Because ciprofloxacin is ofte… 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 Ciprofloxacin 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 (2)
- Sawant R: Rhabdomyolysis Due to an Uncommon Interaction of Ciprofloxacin with Simvastatin. Can J Clin Pharmacol 2009; 16(1):e78-e79.
- Zhou J, Yu L, & Xu H: A systematic review of the drug-drug interaction between statins and quinolones. BMC Pharmacol Toxicol 2024; 25(1):39. PubMed
Keep reading about Ciprofloxacin
Keep reading about Simvastatin
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