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Letters to the Editor
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St John's wort
Continuing awareness of serotonin syndrome needed
From Dr D. Witharana and others
A middle aged woman with a history of post-partum depression was admitted,
under Section 2 of the Mental Health Act, to the acute psychiatric ward
at Worcestershire Mental Health Partnership NHS Trust. She was extremely
agitated, with unusual behaviour, and was expressing suicidal thoughts.
She had been prescribed citalopram, 20mg od, by her GP two months before.
On admission to hospital she was also perspiring and complained of nausea
and abdominal discomfort. A physical examination revealed a tachycardia
of 120 beats per minute and her blood pressure was fluctuating. The clinical
picture was suggestive of serotonin syndrome. However, she had previously
taken selective serotonin reuptake inhibitors (SSRIs) without any complications.
Further investigation revealed that she had been taking St John’s
wort for three weeks. Apparently, her husband had bought it from a high
street pharmacy. Although he had told the pharmacist that his wife was
taking citalopram he was provided with the herbal product and a reassurance.
A possible interaction between St John’s wort and SSRIs, leading
to serotonin syndrome, has been known for a long time.1 The excess serotonin
is believed to be due to common pharmacological mechanisms of action on
serotonin, particularly in the brain, of both St John’s wort and
conventional antidepressants.2 Continuing awareness of the risk needs to
be maintained.
Dumindu Witharana
Senior House Officer in Psychiatry
Alan Pollard
Chief Pharmacist
John Vaughan
Consultant Psychiatrist
Worcestershire Mental Health Partnership NHS Trust, Worcester
References
1. Lantz MS, Buchalter E, Giambanco V. St John's wort and antidepressant
drug interactions in the elderly. Journal of Geriatric Psychiatry and
Neurology 1999;12:7–10.
2. Henderson L, Yue Q.Y, Bergquist C, Gerden B, Arlett P. St John's wort
(Hypericum perforatum): drug interactions and clinical outcomes. British
Journal of Clinical Pharmacology 2002;544:349–56. |
The
Pharmaceutical Journal