3 Clinical psychopharmacology3.3 Pharmacodynamics
3.3.8 Herbal remedies in psychiatry
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Written by Resident Doctor Committee · Published
New in the 2027 syllabus
The College added this topic for exams from January 2027.
Why herbal remedies matter
Herbal products contain biologically active substances. They can cause adverse effects of their own, and they can interact with prescribed medicines.
The contents of a product can vary from one preparation to another. A finding for one standardised extract does not automatically apply to a different product.
Taking a medication history
Ask about everything the person takes, not only prescribed medicines. This includes:
teas and extracts
products bought online
remedies bought without a prescription.
For each one, record the brand, the ingredients, the dose and the reason the person takes it.
Talk it through together. This helps you understand why the person prefers a remedy, and it prevents combinations with prescribed treatment that nobody has been told about.
Common preparations
Preparation | Why people use it | Concern in psychiatry |
|---|---|---|
St John's wort | Low mood | Induces drug-metabolising enzymes and has serotonergic interactions |
Valerian | Sleep problems | Sedation, and the benefit is uncertain |
Kava | Anxiety | Severe liver injury has been reported |
Ginkgo | Memory complaints | Bleeding risk, especially with anticoagulants |
St John's wort
St John's wort (Hypericum perforatum) is the herbal remedy most likely to cause problems alongside psychiatric drugs.
Enzyme induction. It can induce drug-metabolising enzymes and P-glycoprotein, a transporter protein that moves drugs out of cells. This lowers the levels of susceptible medicines.
Hormonal contraception may become less effective, and this includes implants. The result can be an unintended pregnancy.
Serotonergic antidepressants can interact with it pharmacodynamically, meaning their effects on the body add together. This raises the risk of serotonin toxicity.
Stopping it needs review too. Once an enzyme-inducing product is stopped, the levels of another medicine can rise again.
Safety and evidence
Additive sedation is a risk when a sedating herbal preparation is taken with alcohol, hypnotics or other central nervous system depressants.
A traditional herbal registration means the product meets set requirements for quality, safety and traditional use. It is not the same as proof from modern clinical trials that the product works.
Suspected adverse reactions to herbal medicines can be reported through the Yellow Card scheme. This includes reactions to products bought online.
Pregnancy and breastfeeding need particular caution, because evidence on exposure and on what a product contains may be limited.