herbs can be dangerous when mixed with drugs

Beware: the innocent herbal remedies we take to ward off colds or lift our spirits could cause problems with our prescription medicines, says Anne Woodham

Herbal medicine is increasingly popular (some estimate annual sales of products are as high as £240 million a year) and evidence is building that certain herbs are effective for specific conditions. Research has shown that St John's Wort can help people with mild to moderate depression, for example, or that saw palmetto does as good a job of relieving prostate problems as prescription drugs.

But little is really known about how some of the remedies work. Plants contain a wide range of chemical components and it doesn't take a lot of imagination to realise that their actions might interfere with pharmaceutical chemicals. The dossier is growing. Patients and doctors have reported a number of interactions and chemists are advising about potential contraindications. It seems that herbs can affect a drug's action either by decreasing or increasing the amount absorbed, or by altering the way the drug works in the body.

Combinations to watch

Echinacea

This could potentially damage the liver if used for more than eight weeks, especially if used with other liver-toxic drugs such as anabolic steroids. Limiting your alcohol intake would also be sensible. Because echinacea stimulates the immune system, it could offset the effects of immunosuppressant drugs like cyclosporine and corticosteroids.

Ephedra

Taking this stimulant with other stimulants like caffeine could increase the risk of high blood pressure, irregular heartbeat or even heart attack or stroke. Don't take it with decongestants containing phenylpropanolamine or pseudoephedrine, or with dexamethasone, oxytocin, digoxin, theophylline or diabetes medications. Although banned in the UK, it can be bought over the counter in the US.