One herbal drug which has been adulterated is Tian Ma, used to treat high blood pressure and headaches. In one batch, dried dahlia tubers had been substituted for the herb Gastrodia elata. However, when used in conjunction with warfarin, it can cause bleeding, thus presenting a serious risk for coronary heart disease patients. Without informing her doctors, she took ginkgo biloba along with her prescribed drugs and suffered a brain haemorrhage. Garlic, ginseng, danshen, devil's claw and ginger may also increase the effects of conventional blood-thinning agents.
Some herbs clearly carry risks.
Yet at the moment few GPs or pharmacists are adequately trained about dosages or side effects. Meanwhile, for the hapless consumer walking into a high street shop, the labels on herbal products are confusing and limited. The only way of knowing whether a herbal product is medically licensed is a small, unclear number on the packet. Dr Ann Walker at Reading University's School of Food and BioSciences. The consumer, faced with a choice, will often go for the cheaper brand, but may get an ineffective product.