Drug Interaction Report

Nafcillin Injection and Pirtobrutinib: Interaction Details

Name: Nafcillin Injection and Pirtobrutinib Interaction
Creator: Dr. Brian Staiger, PharmD, BCPS

A pharmacist-reviewed analysis of the Nafcillin Injection and Pirtobrutinib interaction: the documented clinical effects, severity rating, onset, mechanism, and management considerations, with cited references throughout.

AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature

Nafcillin Injection

Unipen® Injection

Pirtobrutinib

Jaypirca Jaypirca®

Medically reviewed by

Dr. Brian Staiger, PharmD, BCPS

Updated Aug 8, 2026

Editorial policy · Data sources

Interaction severity

Major

Potentially serious — often needs a change or close monitoring.

Minor

Moderate

Major

Contraindicated

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.

Of 197 documented Nafcillin Injection interactions, 170 are rated major — including this one.

Worried about symptoms right now? Contact your pharmacist or prescriber, or call Poison Control at 1-800-222-1222 (US). Call 911 for an emergency.

Onset

unspecified

Evidence

probable

Severity

Major

What happens

Reduced pirtobrutinib exposure and reduced efficacy of pirtobrutinib

Interaction Deep Dive

Avoid concomitant use of pirtobrutinib with moderate CYP3A inducers. Concomitant use of pirtobrutinib with moderate CYP3A inducers reduces pirtobrutinib exposure which may reduce the efficacy of pirtobrutinib. If concomitant use of a moderate CYP3A inducer is unavoidable, increase the pirtobrutinib dosage. If the current dosage of pirtobrutinib is 200 mg once daily, increase the dose to 300 mg. If the current dosage is 50 mg or 100 mg once daily, increase the dose by 50 mg. Efavirenz and bosentan are predicted to decrease the AUC of pirtobrutinib by 49% and 27% respectively¹.

Why it happens (mechanism)

Induction of CYP3A-mediated metabolism of pirtobrutinib

Literature reports

1 report — tap to read

a) Efavirenz and bosentan (moderate CYP3A inducers) are predicted to decrease the AUC of pirtobrutinib by 49% and 27% respectively ¹.

Common questions

Can I take Nafcillin Injection and Pirtobrutinib together?

Reduced pirtobrutinib exposure and reduced efficacy of pirtobrutinib Always confirm with your pharmacist or prescriber before making any change.

How serious is the Nafcillin Injection and Pirtobrutinib 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 "probable". Good supporting evidence, though not definitively proven.

Questions for your pharmacist

Does my dose of Nafcillin Injection or Pirtobrutinib 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)

Product Information: JAYPIRCA(TM) oral tablets, pirtobrutinib oral tablets. Lilly USA LLC (per FDA), Indianapolis, IN, 2023. DailyMed

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Nafcillin Injection

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All Nafcillin Injection interactions (197) Nafcillin Injection drug information

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Pirtobrutinib

Keep reading about Pirtobrutinib

All Pirtobrutinib interactions (50) Pirtobrutinib drug information

Also serious with: Colchicine Fentanyl Transdermal Patch Nifedipine Doxorubicin

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HelloPharmacist doesn't license one of the big commercial interaction databases, so what you'll find here is not a complete list of every known drug interaction. Instead, each entry is researched, analyzed, and written up individually — documented from the published literature, reviewed by a pharmacist, and cited so you can check every source yourself.

If a combination isn't listed here, it means we haven't documented it yet — never that it's safe. For screening a full medication list, we recommend pairing this site with a comprehensive tool like the Drugs.com Interaction Checker and, most importantly, a review by your own pharmacist. For a deep, plain-English, fully sourced explanation of a specific documented interaction — that's exactly what we built this for.

This information is for education, not a substitute for professional medical advice. Do not start, stop, or change any medication without talking to your pharmacist or prescriber.