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   Mar 18

St John’s wort herbal remedies can block contraceptive implants, warn doctors

Since 2000, 19 cases of interference with contraceptives reported

Herb dilutes the effect of pills and implants which can cause pregnancy

Two women taking herb got pregnant while using implant last year

Drug safety chiefs have issued renewed warnings about the dangers of mixing the herbal remedy St John’s wort with some contraceptives.

The herb dilutes the effect of the pill and implants, which could lead to unplanned pregnancies.

Two women got accidentally pregnant while using implants at the end of last year, said the Medicines and Healthcare products Regulation Agency (MHRA).

Experts have warned that herbal remedies which include St John’s Wort affect contraceptive implants

It received two yellow card reports, which are used for suspected interactions between drugs as well as from taking medicines with herbal medicines and even foods.

‘These women started taking St John’s wort and then had unplanned pregnancies’ said a spokesman.

A total of 19 reports of suspected interactions involving the herb and hormonal contraceptives have been filed since 2000.

Four were for implants and 15 for the pill, with 15 resulting in unplanned pregnancies.

A total of 19 suspected interactions between St John’s wort and contraceptives were reported since 2000, with 15 involving the pill

St John’s wort, which is taken for mild to moderate depression, can also interact with immunosuppressive drugs and potentially lead to transplant rejection.

Oral contraceptives and implants already contain warnings on patient information sheets not to take the herbal remedy because of the risk of reducing their effectiveness. Doctors are meant to reinforce the advice to patients.

Packets of St John’s wort also contain warnings but some unlicensed products or those available online often do not carry the information.

Dr Sarah Branch, MHRA’s deputy director of Vigilance and Risk Management of Medicines said ‘Patient information leaflets for contraceptive pills and implants already contain information on the interaction with St. John’s wort warning that their effectiveness could be reduced.

‘Patients are advised to tell their doctor if they are using St. John’s wort when they are prescribed their contraceptive or receiving their implant.

‘Healthcare professionals should also warn patients of the risk of unplanned pregnancy associated with St. John’s wort when using contraceptives.’

An estimated 10 million Britons take herbal remedies, vitamins and minerals regularly.

Previously, warnings have been issued about the side effects of several herbal supplements and foods when combined with prescription or over-the-counter medicines.

The herbs feverfew, ginger, and gingko can interact with aspirin, which is taken by millions in low doses to ward off heart attacks.

Garlic can interfere with anti-clotting medications and the immunosuppressant drug cyclosporine which prevents transplant rejection, while the sedative valerian can intensify the effect of anaesthetics.

Other plants and herbs also interact with medicines, such as garlic which can affect anti-clotting medication
Herbal products marketed for osteoarthritis also can pose serious risks when combined with prescription medications; for example glucosamine and chondroitin can affect clotting agents.

Black cohosh can interact with the cancer drug tamoxifen and cat’s claw can interact with clotting agents and blood pressure medications.

Research about the interaction of grapefruit juice with drugs suggests that compounds in grapefruit juice may block the enzymes in the intestines that normally break down many drugs.

One glass of grapefruit juice could result in the maximum blocking effect, and the effect may persist for longer than 24 hours.

Since the effects can last for such a prolonged period of time, grapefruit juice does not have to be taken at the same time as the medication in order for the interaction to occur.

Many people are advised not to drink grapefruit juice at all while also taking certain drugs, including statins, anti-hypertensives, psychiatric drugs and Viagra.

Source: Daily Mail

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