St John’s wort, depression and #diabetes

Am putting together a brief document on the use of St John’s Wort in people who have diabetes and depression. What have I missed? Does anything sound ridiculous, poorly argued or plain ignorant? Rip it to shreds so that it’s better when I share the final version with my colleagues (ie, please do a little bit of my work for me ho ho) 😉

I’ve not found information about any possible effect of SJW on insulin metabolism – I’ve assumed that this is because insulin is largely metabolised by the kidney whereas some of the other diabetes drugs are dealt with more by the liver…?? I might be wrong. I have enough knowledge of pharmacology to be aware of the possibilities but insufficient knowledge to deal with it effectively!


St John???s wort, depression and diabetes

St John’s Wort (Hypericum perforatum) is a flowering herb popularly used in treating depression (Linde 2009). A Cochrane review of 29 trials, with over 5,000 participants, found that extracts of St John’s Wort were more effective than placebo in treating mild to moderate pervasive depression, however the effects are relatively small (Linde 2009). The studies also showed that St John???s wort is similar in effectiveness to antidepressants but has fewer side effects.

The authors of this review concluded that the use of St John???s wort may be justified but only on the advice of a healthcare professional. While side-effects from the plant are minimal there can be problematic interactions with other medications that people may be taking.

People with diabetes are at greater risk of developing depression (Diabetes UK) and they may also be taking medication for other health conditions in addition to any medication for diabetes.

Preparation used

The flowering tops of the plant are used and the resulting extract (which can vary considerably in quality) is sold in tablet or capsule form. The plant contains a variety of bioactive compounds such as hypericin and hyperforin however the exact mechanism of action is not known. Hyperforin is considered to be more active than hypericin (Shane-McWhorter 2007) however the total plant extract is more effective (Linde 2009).

Adverse effects and interactions with prescribed medication

Taken in isolation St John???s wort generally has some minor side effects including photosensitivity (skin sensitivity to light) in some people, cause gastric upset, sleeping disturbances and withdrawal-like symptoms if stopped suddenly (Shane-McWhorter 2007).

When taken with other prescribed medications St John???s wort preparations can alter the effectiveness of these drugs and should not be taken in combination (Barnes 2008). People taking St John???s wort should be advised to gradually taper the dose of St John???s wort rather than stopping suddenly.


Medications that can be affected by St John???s wort include oral contraceptives, warfarin, triptans (sumatriptan, naratriptan, rizatriptan and zolmitriptan) and Selective Serotonin Reuptake Inhibitors (citalopram, fluoxetine, fluvoxamine, paroxetine and sertraline).

People who treat their diabetes with gliclazide (Xu 2008) or rosiglitazone (Hruska 2005) should take particular care if they are also using St John???s wort as it can reduce the effectiveness of these prescribed medications.

Use in women who are pregnant or breastfeeding

There is a lack of toxicity data for St John???s wort and therefore its use is not recommended in pregnancy or when breastfeeding (Barnes 2008).

Recommendations for people wanting to use St John???s Wort

Depression is serious and may need to be monitored. People with depression and diabetes should seek professional advice and discuss with their doctor any other medications that are currently being taken before considering using St John???s wort. The use of the herbal remedy for mild to moderate depression is justified but only when high quality extracts are used, on the advice of a healthcare professional (Linde 2009).


Barnes J, Anderson L and Phillipson JD (2008) Herbal Medicines on Medicines Complete [online]

Hruska MW, Cheong JA, Langaee YT et al (2005) Effect of St. John???s Wort administration on CYP2C8 mediated rosiglitazone metabolism. Clinical Pharmacology & Therapeutics; 77:

Linde K, Berner MM and Kriston L (2009) St John’s wort for major depression, Cochrane Database of Systematic Reviews, issue 4. Available from web

Shane-McWhorter, L (2007) Complementary & Alternative Medicine (CAM) supplement use in people with diabetes: a clinician???s guide. American Diabetes Association, Canada.

Xu H, Williams KM, Liauw WS et al (2008) Effects of St John???s wort and CYP2C9 genotype on the pharmacokinetics and pharmacodynamics of gliclazide. British Journal of Pharmacology; 153 (7): 1579-1586.

Further reading

Diabetes UK [online] Depression and diabetes.


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