Nafcillin and Cyclosporine Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Nafcillin
No brand names on recordCyclosporine Injection
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.
What happens
Reduced cycloSPORINE exposure
Interaction Deep Dive
Concomitant use of cycloSPORINE and nafcillin may result in decreased cycloSPORINE plasma concentrations. If concurrent therapy is required, monitor circulating cycloSPORINE levels and make appropriate dosage adjustments as necessary12. Nafcillin appears to decrease cycloSPORINE serum concentrations or interfere with the cycloSPORINE assay 34. If cycloSPORINE dosing is increased to compensate for nafcillin's effect on cycloSPORINE plasma levels, the risk of nephrotoxicity may be increased 4.
Why it happens (mechanism)
Induction of CYP3A-mediated metabolism of cycloSPORINE
Literature reports
2 reports — tap to read
a) Nafcillin can apparently cause a lowering of cycloSPORINE levels. CycloSPORINE trough levels fell from 229 ng/mL to 68 ng/mL, and 272 ng/mL to 42 ng/mL in two separate episodes when nafcillin was administered. Upon discontinuation of nafcillin, cycloSPORINE trough levels rose to 205 ng/mL and 296 ng/ml respectively. This lowering may result in subsequent acute allograft rejection. The mechanism is most likely enhanced hepatic clearance due to cytochrome P450 enzyme induction. Cautious monitoring of cycloSPORINE levels is advised when any drug which can induce hepatic enzymes is given concurrently 3.
b) In a retrospective study of lung transplant patients whose therapy included cycloSPORINE with nafcillin (9 patients) or cycloSPORINE without nafcillin (10 patients), significantly higher doses of cycloSPORINE were required in the nafcillin group to maintain therapeutic serum levels of cycloSPORINE. The nafcillin group developed higher creatinine concentrations and more renal dysfunction (three patients required dialysis compared with none in the non-nafcillin group). Nafcillin may interfere with the cycloSPORINE assay so that actual cycloSPORINE concentrations would be higher than measured 4.
Common questions
Can I take Nafcillin and Cyclosporine Injection together?
Reduced cycloSPORINE exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Nafcillin and Cyclosporine Injection 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 strong is the evidence for this interaction?
The evidence is graded "probable". Good supporting evidence, though not definitively proven.
Questions for your pharmacist
- Does my dose of Nafcillin or Cyclosporine Injection 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 (4)
- Product Information: NEORAL(R) oral soft gelatin capsules oral solution, cyclosporine modified oral soft gelatin capsules oral solution. Novartis Pharmaceuticals Corporation (per FDA), East Hanover, NJ, 2023. DailyMed
- Product Information: SANDIMMUNE(R) oral capsules, oral solution, intravenous injection, cyclosporine oral capsules, oral solution, intravenous injection. Novartis Pharmaceuticals Corporation (per FDA), East Hanover, NJ, 2023. DailyMed
- Veremis SA, Maddux MS, Pollak R, et al: Subtherapeutic cyclosporine concentrations during nafcillin therapy. Transplantation 1987; 43:913-915. DOI
- Jahansouz F, Kriett JM, Smith CM, et al: Potentiation of cyclosporine nephrotoxicity by nafcillin in lung transplant recipients. Transplantation 1993; 55:1045-1048. PubMed
Keep reading about Nafcillin
Keep reading about Cyclosporine Injection
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