Nafcillin Injection and Lonafarnib: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Lonafarnib
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 lonafarnib exposure and reduced efficacy of lonafarnib
Interaction Deep Dive
Concomitant use of lonafarnib and a strong or moderate CYP3A inducer is contraindicated as it may reduce lonafarnib exposure, which may reduce lonafarnib efficacy. In a clinical study, with coadministration of a single oral dose of 50 mg lonafarnib (combined with a single oral dose of 100 mg ritonavir) following 600 mg rifAMPin (a strong CYP3A inducer) once daily for 8 days, the Cmax of lonafarnib was reduced by 92% and the AUC was reduced by 98%, as compared to without rifAMPin coadministration in healthy subjects1.
Why it happens (mechanism)
Induction of CYP3A-mediated metabolism of lonafarnib
Literature reports
1 report — tap to read
a) In a clinical study, with coadministration of a single oral dose of 50 mg lonafarnib (combined with a single oral dose of 100 mg ritonavir) following 600 mg rifAMPin (a strong CYP3A inducer) once daily for 8 days, the Cmax of lonafarnib was reduced by 92% and the AUC was reduced by 98%, as compared to without rifAMPin coadministration in healthy subjects 1.
Common questions
Can I take Nafcillin Injection and Lonafarnib together?
Reduced lonafarnib exposure and reduced efficacy of lonafarnib Always confirm with your pharmacist or prescriber before making any change.
How serious is the Nafcillin Injection and Lonafarnib interaction?
It is rated contraindicated. These should generally not be used together.
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 Lonafarnib 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: ZOKINVY(TM) oral capsules, lonafarnib oral capsules. Eiger BioPharmaceuticals Inc (per FDA), Palo Alto, CA, 2024. DailyMed
Keep reading about Lonafarnib
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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