While St John's Wort is not a ‘drug’ regulated and approved by the Medicines and Healthcare Regulatory Agency (MHRA), it is popular for its perceived antidepressant effects and is easily accessible in many health food and alternative medicine shops. Research encapsulating exactly what this powerful herbal remedy does has been sparse but there is some evidence to show how the compound works and that significant drug interactions can occur. Herbal remedies should always be considered when reviewing patients' medications and knowledge of this supplement is important among prescribers in order to explain not only its properties, but also the potential interactions patients may experience with their other medications.
An overview of St John's Wort
St John's Wort is a herbal remedy that has been around for hundreds of years to treat mental health problems, and currently is bought over the counter for mild-to-moderate depression, as well as for seasonal affective disorder (SAD), mild anxiety, and sleep disturbances (Mind, 2020). The compound's botanical name is Hypericum perforatum and contains many active substances such as hypericin and hyperforin, which are the substances thought to have an effect on mood. Current understanding of the pharmacokinetics of these substances are that they work in the same way as standard antidepressant medication, increasing the activity of serotonin and noradrenaline to help regulate mood (Mind, 2020). While available without prescription, St John's Wort should not be used to self-medicate if experiencing struggles with mental health without talking to a doctor first, as this may be dangerous and may not be the right drug for the patient. It may interact with a medication they currently take (for example, the combined pill) and it may also have an adverse effect if the person has a diagnosis of bipolar disorder (Mind, 2020), potentially leading to hypomania.
Understanding the antidepressant effect of St John's Wort
Barnes et al (2021) note that the chemical composition of St John's Wort has been well studied, yet the constituents of the substance that actually induce the antidepressant effect are unknown, apart from hypericum and hyperforin being known to have this effect. Documented pharmacological effects of the compound also include antiviral and antibacterial effects, which have received more attention in past research, supporting the traditional use of the remedy (Barnes et al, 2021). Many pharmacological activities appear to be attributable to hypericin and to the flavonoid constituents, and hypericin has been reported to be responsible for the photosensitive reactions that have been documented for St. John's Wort (Barnes et al, 2021). Hyperforin, rather than hypericin as originally thought, has been shown to be one of the major constituents responsible for antidepressant activity, but further research is required to determine which other constituents may also contribute to the remedy's antidepressant effect.
Effectiveness
The authors reviewed randomised controlled trials to confirm the efficacy of St John's Wort extracts over placebo, in the treatment of mild-to-moderately severe depression (Barnes et al, 2021). It has already been noted to be ineffective for severe depression (Mind, 2020). Other randomised controlled studies have provided some evidence that St John's Wort extracts are as effective as some standard antidepressant medications for in mild-to-moderate depression, but the researchers emphasise the need for further trials to assess the efficacy of St John's Wort extracts, in comparison with that of standard antidepressants, especially in the case of the newer antidepressant drugs, such as selective serotonin reuptake inhibitors (SSRIs). Further research is needed for well-defined groups of patients suffering from different types of depression, and conducted over longer periods in order to determine long-term safety.
In their literature review, Barnes et al (2021) found that St John's Wort does appear to have a more favourable short-term safety profile than do standard antidepressants, which is an important factor. The authors also raise concerns over the multiple interactions that can occur between St John's Wort and certain prescribed medications.
Concerns about interactions
Concerns have been raised over interactions between St John's Wort and certain prescribed medicines. The ones to be aware of are: warfarin, ciclosporin, theophylline, digoxin, HIV protease inhibitors, anticonvulsants, selective serotonin reuptake inhibitors, triptans and oral contraceptives. The authors advise that where it can be seen that a patient is taking any of these medications, the patient should be advised to cease taking St John's Wort (Barnes et al, 2021). However, it would be best practice to contact the patient's GP and explain the issue as they may need a full medication and mental health review, so they do not abruptly stop taking something that is helping their mental health, but so that they also receive the appropriate medication for their physical health. It may be a case that they should have an alternative to one of the medications they are currently taking if there is an option, or it may be safer if the priority is their physical condition, to be prescribed a safer antidepressant at low dose as an alternative to St John's Wort.
The National Center for Complementary and Integrative Health (NCCIH) (2017) notes how vital it is to seek the right help for depression. If a patient has been self-medicating for depression and their GP was not aware, it would be important to seek a review for them as soon as possible to consider other lifestyle factors and advice they may need, as well as potential referrals to talking therapies if required. More severe forms of depression can lead to an increased risk of suicide (NCCIH, 2017). There should therefore be no delay in seeking assistance from a healthcare provider for a mental health issue, and the herbal remedy should not replace conventional care. The NCCIH (2017) also notes the importance of a medication review due to the compound in St john's Wort interacting with so many other drugs, and emphasises the importance of understanding that it may not be suitable for pregnant or breastfeeding women to be taking St John's Wort as a remedy.
Conclusion
Overall, it appears that this popular herbal remedy has some benefits for those with mild depression, but in cases where there is concern regarding depression, a discussion with the patient and GP would be required in order to work out what action is required, as they may need therapeutic input or a more effective antidepressant. Awareness between the patient, prescriber and GP that depressive symptoms have been an issue are essential in order that this is monitored as depression should not be managed alone by the patient. If the patient finds St John's Wort effective and they do not take other medication, it may be decided that they simply continue with it. However, for many patients, there may be significant interactions between the drugs they already take and this remedy, reducing the effectiveness of the other drugs they take, and inducing poor health. A comprehensive review of patients' medication is always required, and the importance of checking if they take herbal remedies should never be underestimated.