Herbal supplements and mental health medicines: safer choices

Herbal supplements are commonly used for sleep, anxiety and low mood, and many are sold over the pharmacy counter without a prescription. A capsule, tincture or tea may look gentle, yet its active constituents can alter the action of prescribed psychiatric medicines. “Natural” describes the source, not a guarantee of safety when products are combined.

In Australia, most everyday complementary medicines are TGA-listed and carry an AUST L number. That status involves assessment against applicable standards, but it is not an endorsement for use with every prescription medicine. Supplements also usually receive no PBS subsidy, while pharmacies, supermarkets and online marketplaces offer products with widely differing prices and quality. For someone in Sydney or Melbourne, an ordinary routine might include vitamins with breakfast, a calming tea in the evening and a prescription collected after work, with each product treated as a separate health choice.

Herb–medicine interactions can be pharmacodynamic, when two substances produce the same or opposing effects, or pharmacokinetic, when one changes the absorption or metabolism of another. Supplements also vary in dose, extraction method and contaminants. Understanding and managing drug interactions with common herbal supplements for mental health starts with a complete medicines review.

Why herb and medicine interactions matter

St John’s wort is the best-known high-risk example because it can increase serotonergic activity while inducing drug-metabolising enzymes and transporters. With antidepressants, the concern is serotonin toxicity, often called serotonin syndrome; with several other medicines, reduced exposure can make treatment less effective. The affected list extends beyond mental health drugs to contraceptives, anticoagulants, transplant medicines and some HIV treatments.

Other interactions are additive rather than metabolic. Valerian or kava taken with a benzodiazepine, zopiclone, opioid or alcohol may increase drowsiness and impair coordination. A person may consider this harmless because both products cause sleepiness, yet the combined effect can be substantially stronger. Fixed doses cannot account for every factor, including kidney function, frailty, driving and other medicines used at the same time.

A pharmacist can turn this complexity into a practical review by checking prescription records against over-the-counter products, vitamins, teas and traditional remedies. Ask for the original containers, note how long each product has been used and record who prescribed each medicine. Separating doses by a few hours is not a reliable fix for enzyme effects or sustained-release products; the combination itself may need to change under a prescriber’s direction.

These habits are central to the pharmacist’s patient education role, where open questions and confirmation of understanding improve safe use. The communication principles described in patient education role apply equally to supplements, even though the products and risks differ.

Supplements that warrant particular caution

St John’s wort requires the closest review. It can trigger serotonin toxicity when combined with SSRIs, SNRIs, MAO inhibitors, tramadol and certain antidepressants used for anxiety. Symptoms can include agitation, sweating, tremor, rapid pulse, muscle twitching, confusion or fever. It can also reduce the effectiveness of medicines such as the oral contraceptive pill, warfarin, ciclosporin and some antiretroviral drugs. It should not be started without a pharmacist and prescriber reviewing the complete regimen.

Valerian is often promoted for sleep, but its sedative effect may add to benzodiazepines, Z-drugs, antihistamines and alcohol. Kava deserves separate caution because it can cause liver injury and may add to sedation. The TGA has long advised that kava is not approved for therapeutic use in Australia, and imported products should not be treated as automatically safe. Any use warrants discussion with a clinician, especially when liver disease, heavy alcohol use or other sedatives are involved.

Passionflower, lavender and ashwagandha are also sold for anxiety or stress. Passionflower and lavender may increase central nervous system depression; ashwagandha has been associated with liver injury and may affect thyroid or sedative medicines. SAMe can add serotonergic effects when taken with some antidepressants. Although reactions vary, “only a herb” is not an appropriate risk assessment. Background information on names, uses and cautions can be checked through herbal safety information, but it cannot replace an individual interaction check.

If someone develops marked agitation, fever, sweating, tremor, confusion, severe drowsiness or slowed breathing while using a supplement, they should avoid another dose of the suspect product and seek urgent medical help. Symptoms such as yellow skin, dark urine or severe vomiting may signal liver injury and also need prompt assessment. An emergency department or 000 is appropriate for severe or rapidly worsening symptoms.

Checking a product before use

Choose products with a clear Australian ingredient list, botanical name, extract strength, batch number and expiry date. An AUST L number can be checked in the TGA’s Australian Register of Therapeutic Goods. It confirms the listed product’s regulatory status; it does not establish that the product is effective for a particular mental health symptom or safe with every medicine. Online marketplaces and discount chemist shelves can include counterfeities or products whose actual content differs from the label.

Australian state and territory pharmacy and poisons legislation governs some restricted ingredients, and certain complementary medicines are pharmacist-supply only or prescription-only. Ask the pharmacist to identify the exact category rather than assuming every preparation is available for direct sale. Cost may influence choice because the PBS subsidises many prescription medicines but generally not complementary medicines. A lower-priced product is not automatically inferior, but an unverified product without traceable labelling is difficult to assess.

Before starting anything, make a list of all prescribed medicines, OTC products, vitamins, herbal teas and supplements. Give the pharmacist the list and the reason each product is being used. Useful checks include the intended dose, treatment duration, recent changes, alcohol consumption and other health conditions. National resources such as Healthdirect, the National Poisons Information Service and reputable product monographs can support the conversation, but they should not be used to make changes without professional advice.

Managing a suspected interaction

If someone has already started a supplement, they should not stop or change a prescribed medicine abruptly without advice, especially an antidepressant, antipsychotic or mood stabiliser. Contact a pharmacist or prescriber promptly, describe the exact product and dose, and report symptoms and the time they began. A pharmacist can determine whether the combination needs urgent review, observation, a medicine change or simply closer monitoring.

Triage depends on symptoms rather than the product label. Agitation with fever, shaking and a fast pulse may indicate serotonin toxicity, while unusual drowsiness, poor coordination or slowed breathing suggests excessive sedation. Severe symptoms, rapid deterioration or breathing difficulty require an emergency department and 000. For non-urgent exposure, Australia’s Poison Information Centre on 13 11 26 can provide advice, while Lifeline on 13 11 14 supports people in emotional distress.

When the combination is not causing immediate harm, the pharmacist and prescriber can agree on a plan. This may involve withholding the supplement, changing the time or dose of a suitable medicine, monitoring mood and vital signs, or arranging follow-up. Do not assume that a missed dose or a few hours of separation will correct the problem. Any plan should also account for other people prescribing or supplying the supplement, including family members and traditional practitioners.

The same process applies to medicines with less obvious effects. If an interaction reduces contraceptive, anticoagulant or transplant-drug levels, there may be no early warning symptom, so an early review is safer. Document the interaction, notify relevant prescribers and use one agreed medicines list. This is particularly important when several clinicians are involved, when care is shared across states, or when telehealth makes it easier for two treatment plans to develop separately.

Safer systems for pharmacists and care teams

Community pharmacists often see the whole medication list, including purchases that never appear on a GP record. That position makes them well placed to identify duplicate calming products, ask about alcohol and driving, and refer a person for mental health assessment without making a diagnosis. Counselling should be private and non-judgemental, particularly when a person uses a supplement because standard care has not felt accessible or acceptable to them.

Workload can threaten the quality of that conversation. A practical pharmacist burnout toolkit can help managers improve staffing, protected counselling time, referral pathways and incident follow-up. A supportive process also protects the pharmacist: record significant interactions, seek senior or poison-centre advice when needed, and use a consistent referral pathway rather than resolving every complex case alone.

Patient education is a broader system responsibility. The pharmacist’s role in preventing antibiotic resistance through patient education shows how plain language, teach-back and respectful challenge can reduce unnecessary use; the same methods support honest discussion of supplements. Health professionals should ask what a person hopes the product will do, what they have already tried and whether they wish to continue it. This creates a shared decision without dismissing the person’s distress or implying that natural products are always harmless.

Make the next pharmacy visit a complete medicines review. Bring every supplement bottle, vitamin container and herbal tea blend, plus an up-to-date list of prescribed and OTC medicines. A pharmacist can screen for interactions, explain the options and contact the relevant prescriber where needed.

Start with one specific action: ask for a private interaction check before buying or taking another calming or mood product. A clear medicines list and an honest account of symptoms can prevent a harmful combination and make mental health care safer.