Loperamide and St John's Wort: Interaction Details
AI-assisted, pharmacist-reviewed · Source data updated Aug 8, 2026 · Sources: FDA labeling, DDInter 2.0, cited literature
St John's Wort
No brand names on recordLoperamide
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
Delirium with symptoms of confusion, agitation, and disorientation
Interaction Deep Dive
A case of delirium in a patient taking St. John's Wort, valerian, and loperamide has been reported1. It is unclear whether this was an interaction between St. John's Wort and loperamide, St. John's Wort and valerian, valerian and loperamide, or a combination of all three agents. Until the potential interaction is understood, caution is advised if St. John's Wort and loperamide are taken together.
Why it happens (mechanism)
Unknown
Literature reports
1 report — tap to read
a) A 39 year-old female was hospitalized with disorientation, agitation, and confusion. She had been taking St. John's Wort and valerian (dosage unspecified) daily for 6 months, with recent use of loperamide (dosage and exact timing not specified). On admission, blood pressure was 140/100 mmHg, pulse 140 beats per minute, respiratory rate 24 breaths per minute. Pupils were dilated to 6 millimeters. Glucose was elevated at 139 milligrams/deciliter (mg/dL), potassium was 2.9 millimoles/liter (mmol/L) (lab reference values not specified), and toxicology screen was positive for opioids (explained by the recent use of loperamide). The patient's medical history included depression and migraine headaches. Treatment consisted of charcoal (routine treatment for toxicity), thiamine 100 mg (for vitamin deficiency and neuroprotective purposes), naltrexone 2 mg (to counteract opioid effect), ceftriaxone 1 gram (for possible infection), and lorazepam 8 mg (to calm the patient). Intubation was required briefly. The patient recovered from delirium within 2 days. The symptoms may have resulted from an interaction of St. John's Wort with loperamide or valerian, or a combination of all three agents. Monoamine oxidase inhibitory activity of St. John's Wort in combination with loperamide was postulated to have caused the symptoms 1.
Common questions
Can I take Loperamide and St John's Wort together?
Delirium with symptoms of confusion, agitation, and disorientation Always confirm with your pharmacist or prescriber before making any change.
How serious is the Loperamide and St John's Wort interaction?
It is rated moderate. Can be significant — usually manageable with monitoring.
How quickly could this interaction happen?
The documented onset is "delayed". Effects tend to build up gradually over days to weeks.
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 Loperamide or St John's Wort 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 anything you'd monitor while I'm on both?
References (1)
- Khawaja IS, Marotta RF, & Lippmann S: Herbal medicines as a factor in delirium (letter). Psych Serv 1999; 50(7):969-970. PubMed
Keep reading about St John's Wort
Keep reading about Loperamide
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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