Drug interactions
Morphine + St john's wort
Severity: Moderate
Morphine and St john's wort: moderate interaction.
Last updated
For healthcare professionals — reference only. This page is a brief summary, not medical advice and not a substitute for official labeling or clinical judgement. Always verify before prescribing or dispensing.
Summary
St John's wort has serotonergic activity and may add to opioid serotonergic effects, though morphine rarely causes serotonin syndrome. It may also modestly lower morphine exposure through P-gp induction.
What this interaction means in plain words
Morphine and St john's wort can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken.
Why it happens
Additive serotonergic effects and possible P-glycoprotein induction by St John's wort.
What to do
Monitor for serotonin toxicity symptoms and for changes in analgesic response. Consider stopping St John's wort if adverse effects occur.
What to ask your pharmacist
- Should I take them at different times of day?
- Does the dose of either medicine need to change?
- Is there anything I should avoid, such as alcohol or certain foods, while on both?
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Other interactions of Morphine
- Alvimopan + Morphine Contraindicated
- Isocarboxazid + Morphine Contraindicated
- Morphine + Olanzapine / samidorphan Contraindicated
- Morphine + Phenelzine Contraindicated
- Morphine + Tranylcypromine Contraindicated
- Alfentanil + Morphine Major
Frequently asked questions
Can I take Morphine with St john's wort?
MediHelp rates the interaction as moderate. Morphine and St john's wort can affect each other. The combination is often manageable, but it may need a change of dose, a change of timing, or extra checks while both are taken. St John's wort has serotonergic activity and may add to opioid serotonergic effects, though morphine rarely causes serotonin syndrome. It may also modestly lower morphine exposure through P-gp induction.
How serious is the interaction between Morphine and St john's wort?
MediHelp rates it moderate, on a four-level scale (minor, moderate, major, contraindicated) based on published labels and references. What to do, in brief: Monitor for serotonin toxicity symptoms and for changes in analgesic response. Consider stopping St John's wort if adverse effects occur.
What other medicines interact with Morphine?
MediHelp also lists interactions of Morphine with, for example, Alvimopan, Isocarboxazid, Olanzapine / samidorphan. The full list is on the Morphine page.
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