Pralsetinib and Nafcillin Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Pralsetinib
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 pralsetinib exposure and reduced efficacy of pralsetinib
Interaction Deep Dive
Coadministration of pralsetinib (a CYP3A substrate) with a moderate CYP3A inducer may result in decreased pralsetinib exposure, which may decrease the efficacy of pralsetinib. Avoid concomitant use. If coadministration cannot be avoided, increase the starting dose of pralsetinib (i.e., from 400 mg once daily to 600 mg once daily; 300 mg once daily to 500 mg once daily and 200 mg once daily to 300 mg once daily) starting on Day 7 of coadministration with the moderate CYP3A inducer. After the moderate CYP3A inducer has been discontinued for at least 14 days, resume the dose of pralsetinib that was taken prior to initiating the moderate CYP3A inducer1.
Why it happens (mechanism)
Induction of CYP3A-mediated metabolism of pralsetinib
Literature reports
1 report — tap to read
a) Coadministration of multiple doses of efavirenz 600 mg once daily (moderate CYP3A inducer) is predicted to decrease the pralsetinib Cmax by 18% and AUC by 45% 1.
Common questions
Can I take Pralsetinib and Nafcillin Injection together?
Reduced pralsetinib exposure and reduced efficacy of pralsetinib Always confirm with your pharmacist or prescriber before making any change.
How serious is the Pralsetinib 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 Pralsetinib 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 (1)
- Product Information: GAVRETO(TM) oral capsules, pralsetinib oral capsules. Genentech USA Inc (per FDA), South San Fransisco, CA, 2023. DailyMed
Keep reading about Pralsetinib
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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