5 April 2001
The Therapeutic Goods Administration (TGA) issued a warning late last year to all doctors regarding the possible interaction between St John’s wort, a popular herbal therapy used for depression, and hormonal preparations such as the contraceptive pill.
St John’s wort is a natural therapy which seems to be effective in the treatment of depression. It appears that preparations containing St John’s wort may well increase the metabolism of many medications by the liver, reducing the level of the medications in the blood and possibly making them less effective. The contraceptive pill is one such medication, and it is known that St John’s wort reduces the effectiveness of some of the drugs used in the treatment of HIV. There is also the suggestion that it can reduce the effectiveness of some of the drugs used in the treatment of heart disease, asthma and epilepsy.
Dr Terri Foran, Medical Director, FPA Health, said that irregular bleeding had been reported overseas in women using hormonal contraception and St John’s wort at the same time.
‘As yet a pregnancy has not been reported but it is possible that the use of St John’s wort may lead to reduced protection,’ Dr Foran said.
‘A similar effect may also occur in those women using hormone replacement therapy (HRT), which again may lead to irregular bleeding, although pregnancy in this instance is not an issue.
‘I would advise any woman using St John’s wort with HRT or hormonal contraception to contact her doctor for further information.'
Last Reviewed: 06 April 2001