One in 20 people are taking potentially dangerous combinations of herbal and prescription medicines, said researchers speaking at the British Pharmaceutical Conference this week.
The researchers urged health professionals to increase their knowledge of complementary medicines so that they can better advise patients on the side effects.
A study, carried out by the Department of Pharmacy at Kings College, London, found that 62 per cent of those surveyed were taking one or more unreported alternative medicine when they collected a prescription from a pharmacy.
The researchers found that - even when respondents were asked what medicines they were taking - a staggering 41 per cent did not mention complementary medicines (CAMs) as they did not categorise them as medicines. Of these, about one in 20 were taking potentially dangerous combinations of CAMs and prescription medicines, said the researchers.
The most common herb drug interaction in the study was St Johns Wort with selective serotonin re-uptake Inhibitors, taken by 30 per cent of those surveyed. St John's Wort is taken for mild to moderate depression and should not be taken with prescribed antidepressants.
Other potentially dangerous interactions include taking gingko with aspirin , which can lead to haemorrhage and taking St Johns Wort with the contraceptive pill, which can cause nausea, vomiting, headaches and anxiety. Ginseng can also be dangerous when taken with the blood thinning drug Warfarin.
Study author Swati Patel said: "The results clearly show that many patients on prescribed medicines perceive CAMs to be natural and safe and do not associate any adverse drug problems when both are taken together."
Health professionals need to be more aware of CAMs taken by patients and be able to advise them on the possible side effects, he added.
He also said that it was important for professionals to understand the health trends of their local population. "This study identified, for example, that people of Asian origin took the largest amount of CAMs (32 per cent), many of which were Ayurvedic medicines. A health professional based in an area with a high Asian mix should be ready to ask the appropriate questions when people come in with a prescription," claimed Patel.
BPC 2003 opened on Monday and closes today at the Harrogate International Centre.