Grazoprevir and Loperamide: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
Loperamide
Grazoprevir
No brand names on record
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
Increased loperamide exposure and an increased risk of loperamide-related adverse reactions
Interaction Deep Dive
Concomitant use of loperamide and CYP3A4 inhibitors may increase the exposure of loperamide and may increase a risk for cardiac adverse reactions. Concomitant administration of multiple doses of 100 mg itraconazole twice daily (CYP3A4 inhibitor) with a single 4 mg dose of loperamide hydrochloride increased the peak plasma concentration and the systemic exposure to loperamide by 2.9-fold and 3.8-fold, respectively. Also, when multiple doses of both 100 mg itraconazole (CYP3A4 inhibitor) and 600 mg gemfibrozil twice daily were administered with a single 4 mg dose of loperamide hydrochloride, the mean peak plasma concentration and the systemic exposure to loperamide was increased by 4.2-fold and 12.6-fold, respectively. Monitor patients for cardiac adverse reactions1.
Why it happens (mechanism)
Inhibition of CYP3A4-mediated metabolism of loperamide
Literature reports
2 reports — tap to read
a) Concomitant administration of multiple doses of 100 mg itraconazole twice daily (CYP3A4 inhibitor) with a single 4 mg dose of loperamide hydrochloride increased the peak plasma concentration and the systemic exposure to loperamide by 2.9-fold and 3.8-fold, respectively 1.
b) When multiple doses of both 100 mg itraconazole (CYP3A4 inhibitor) and 600 mg gemfibrozil twice daily were administered with a single 4 mg dose of loperamide hydrochloride, the mean peak plasma concentration and the systemic exposure to loperamide was increased by 4.2-fold and 12.6-fold, respectively 1.
Common questions
Can I take Grazoprevir and Loperamide together?
Increased loperamide exposure and an increased risk of loperamide-related adverse reactions Always confirm with your pharmacist or prescriber before making any change.
How serious is the Grazoprevir and Loperamide 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 Grazoprevir or Loperamide 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: Loperamide hydrochloride oral capsules, loperamide hydrochloride oral capsules. Mylan Pharmaceuticals Inc (per DailyMed), Morgantown, WV, 2022. DailyMed
Keep reading about Loperamide
Keep reading about Grazoprevir
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