Praziquantel and Nafcillin Injection: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Praziquantel
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 praziquantel exposure and reduced efficacy of praziquantel
Interaction Deep Dive
Avoid concomitant administration of praziquantel with moderate CYP3A inducers unless the benefit outweighs the risks as it may decrease praziquantel AUC and Cmax which may reduce the efficacy of praziquantel. In a crossover study among of 20 healthy subjects, administration of single 40 mg/kg oral dose of praziquantel following pretreatment with oral efavirenz (400 mg daily for 13 days) resulted in reduced mean praziquantel AUC and Cmax by 77% (95% CI: 38% to 91%) and 79% (95% CI: 41% to 92%), respectively, when compared to praziquantel given alone. In patients receiving a clinically significant CYP3A inducer drug who need immediate treatment for schistosomiasis, alternative agents for schistosomiasis should be considered, where possible. If praziquantel is necessary immediately, increase monitoring for reduced anthelmintic efficacy associated with praziquantel. In patients receiving a clinically significant CYP3A inducer drug whose treatment could be delayed, discontinue the CYP3A inducer drug at least 2 weeks to 4 weeks before administration of praziquantel and, where possible, consider starting alternative medications that are not CYP3A inducers. The CYP3A inducer drug can be restarted one day after completion of praziquantel treatment, if needed1.
Why it happens (mechanism)
Induction of CYP3A-mediated metabolism of praziquantel
Literature reports
1 report — tap to read
a) In a crossover study among of 20 healthy subjects, administration of single 40 mg/kg oral dose of praziquantel following pretreatment with oral efavirenz (400 mg daily for 13 days) resulted in reduced mean praziquantel AUC and Cmax by 77% (95% CI: 38% to 91%) and 79% (95% CI: 41% to 92%), respectively, when compared to praziquantel given alone 1.
Common questions
Can I take Praziquantel and Nafcillin Injection together?
Reduced praziquantel exposure and reduced efficacy of praziquantel Always confirm with your pharmacist or prescriber before making any change.
How serious is the Praziquantel 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 Praziquantel 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: BILTRICIDE oral tablets, praziquantel oral tablets. Bayer HealthCare Pharmaceuticals Inc (per FDA), Whippany, NJ, 2023. DailyMed
Keep reading about Praziquantel
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.
Check another combination
Our instant two-drug interaction checker is almost here.
Still have questions about this combination?
Every question gets a real answer from a licensed pharmacist — free, and usually within a day.
Ask the pharmacist