Pregnancies prompt herb warning

St John's Wort is taken to relieve depression

A new warning about the effect of the herbal remedy St John's Wort on the contraceptive pill has been issued after two Swedish women had unwanted pregnancies.

The country's pharmaceutical regulator, the Medical Products Agency (MPA), has issued a new warning about the herbal extract.

St John's Wort is often taken to alleviate mild depression.

But it is known to counteract the effect of certain drugs, including hormone-based contraceptives, HIV medicines, blood-thickening drugs, and cyclosporine, a drug used to prevent rejection of organ transplants.

Doctors should question patients about their use of herbal drugs and bear in mind the possibility of herb-drug interactions

Royal College of GPs spokesman

Swedish health experts said the herbal extract contained a substance called hyperfourin, which made the liver work more efficiently, helping it break down the pharmaceutical chemicals.

They suggest some products may have more of an effect on conventional medications than others.

The two Swedish women, aged 28 and 31, became pregnant even though they were taking the pill.

Authorities in the UK have had seven reports since February 2000 of women becoming pregnant while using oral contraceptives and St John's Wort - one had also used emergency contraception.

In a separate case, a woman became pregnant while taking St John's Wort, after taking emergency contraception.

The MPA in Sweden says it now wants a compulsory labelling warning of the interactions of all St John's Wort products, apart from tea.

What is really new is that we have found some products have less of an effect than others

Per Claeson
MPA

Per Claeson, of the MPA, said one problem was that not all women regarded the pill as a pharmaceutical drug.

He said that the emergence of the two unwanted pregnancies had led to the MPA restating advice first given in 1999.

"The evidence has come from clinical interaction studies and also biochemical research.

"What is really new is that we have found some products have less of an effect than others, and these have been allowed a milder form of labelling."

Warnings about the interaction between St John's Wort and some prescription medicines were first issued in the UK in March 2000.

The Medicines Control Agency (MCA) reiterated its advice given then that people who are taking St John's Wort at the same time as a pharmaceutical drug should talk to their doctor.

Women taking the oral contraceptive pill were advised to stop taking the herbal remedy.

Voluntary agreement

A spokesman for the MCA told BBC News Online: "The advice we gave at Easter 2000 still stands."

Since then, there has been a voluntary agreement between manufacturers to provide information about potential interactions with products.

A spokesman for the Royal College of General Practitioners said: "There is a need for better protection and information for the public on herbal medicines and the possible interactions these can have when taken with conventional medicines.

"Doctors should question patients about their use of herbal drugs and bear in mind the possibility of herb-drug interactions."