Drug Interaction Report

Tezacaftor and Nafcillin Injection: Interaction Details

A pharmacist-reviewed analysis of the Tezacaftor and Nafcillin Injection 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
+

Tezacaftor

No brand names on record
Dr. Brian Staiger, PharmD, BCPS
Medically reviewed by
Dr. Brian Staiger, PharmD, BCPS
Updated Aug 8, 2026
Editorial policy · Data sources
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Interaction severity
Major
Potentially serious — often needs a change or close monitoring.
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 15 documented Tezacaftor interactions, 15 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 tezacaftor exposure and reduced efficacy of tezacaftor

Interaction Deep Dive

Coadministration of tezacaftor-containing products with strong or moderate CYP3A inducers is not recommended as it may significantly reduce tezacaftor exposure and reduce its efficacy1. Coadministration of ivacaftor with strong inducer rifAMPin, exposure to ivacaftor was decreased by 89%. Similar significant reductions in exposure to tezacaftor can be expected 23.

Why it happens (mechanism)

Induction of CYP3A-mediated metabolism of tezacaftor

Literature reports

2 reports — tap to read

a) Coadministration of ivacaftor (CYP3A substrate) 150 mg orally as a single dose with the strong CYP3A inducer rifAMPin 600 mg orally once daily significantly decreased AUC of ivacaftor by 89% 23.

b) In a drug interaction study, coadministration of vanzacaftor/tezacaftor/deutivacaftor combination (20/100/250 mg once daily) with the strong CYP3A inducer rifAMPin 600 mg once daily significantly reduced vanzacaftor AUC by 18% and Cmax of by 22%, it also reduced deutivacaftor AUC by 10% and Cmax by 20% 1.

Common questions

Can I take Tezacaftor and Nafcillin Injection together?

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

How serious is the Tezacaftor 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 "probable". Good supporting evidence, though not definitively proven.

Questions for your pharmacist

  • Does my dose of Tezacaftor 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)

  1. Product Information: ALYFTREK(R) oral tablets, vanzacaftor, tezacaftor, and deutivacaftor oral tablets. Vertex Pharmaceuticals Incorporated (per FDA), Boston, MA, 2024. DailyMed
  2. Product Information: SYMDEKO(TM) oral tablets, tezacaftor ivacaftor oral tablets and ivacaftor oral tablets. Vertex Pharmaceuticals Incorporated (per manufacturer), Boston, MA, 2019. DailyMed
  3. Product Information: TRIKAFTA(R) oral tablets oral granules, elexacaftor, tezacaftor, ivacaftor oral tablets oral granules; ivacaftor oral tablets oral granules. Vertex Pharmaceuticals Incorporated (per FDA), Boston, MA, 2024. DailyMed
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Nafcillin Injection

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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.