Tacrolimus and Nafcillin Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Tacrolimus
Nafcillin 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 tacrolimus exposure
Interaction Deep Dive
Concomitant use of tacrolimus (a CYP3A substrate) with a weak or moderate CYP3A inducer may increase the metabolism of tacrolimus, leading to lower whole blood trough concentrations12. In a study, tacrolimus coadministered with nafcillin (a moderate CYP3A inducer) resulted in undetectable tacrolimus levels on hospital day 8 3. If tacrolimus is used concomitantly with a weak or moderate CYP3A inducer, monitor tacrolimus blood levels, adjust the tacrolimus dose as needed, and monitor for reduced tacrolimus efficacy 12.
Why it happens (mechanism)
Induction of CYP3A-mediated tacrolimus metabolism
Literature reports
1 report — tap to read
a) A 13-year-old boy with a past medical history significant for cystic fibrosis, liver disease requiring transplantation, type 1 diabetes, and pancreatic insufficiency experienced subtherapeutic levels of tacrolimus (a CYP3A substrate) following therapy with nafcillin (a moderate CYP3A inducer) for a suspected infection. The patient's tacrolimus dose was 1.5 mg orally twice daily with a goal trough of 3 to 5 nanograms/milliliter (ng/mL). Tacrolimus concentration was 2.8 ng/mL 1 week prior to admission; levels were 4.2 ng/mL following 2 doses of nafcillin 2 g, 2 ng/mL following 10 doses of nafcillin, and undetectable (less than 2 ng/mL) on hospital day 8. Tacrolimus levels returned to therapeutic range 5 days after nafcillin discontinuation and remained therapeutic at 2-month follow-up. Similar results were reported when nafcillin was readministered several months later 3.
Common questions
Can I take Tacrolimus and Nafcillin Injection together?
Reduced tacrolimus exposure Always confirm with your pharmacist or prescriber before making any change.
How serious is the Tacrolimus and Nafcillin 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 "unspecified". The timing of this interaction is not well characterized.
How strong is the evidence for this interaction?
The evidence is graded "theoretical". Predicted from the drugs' pharmacology; not yet confirmed in people.
Questions for your pharmacist
- Does my dose of Tacrolimus or Nafcillin 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 (3)
- Product Information: PROGRAF(R) oral capsules, oral granules for suspension, intravenous injection, tacrolimus oral capsules, oral granules for suspension, intravenous injection. Astellas Pharma US Inc (per FDA), Northbrook, IL, 2023. DailyMed
- Product Information: ENVARSUS XR(R) oral extended-release tablets, tacrolimus oral extended-release tablets. Veloxis Pharmaceuticals Inc (per FDA), Cary, NC, 2023. DailyMed
- Wungwattana M & Savic M: Tacrolimus interaction with nafcillin resulting in significant decreases in tacrolimus concentrations: a case report. Transpl Infect Dis 2017; 19(2):e12662. PubMed
Keep reading about Tacrolimus
Keep reading about Nafcillin Injection
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.
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