Medicines derived from plants have been used for centuries. The pragmatic and most definitive classics on Oriental medicine are Shang Han Lung ( Treatise on Febrile Disease) and Chin Kuei Yao Lueh ( Summaries of Household Treatments) described in southern China by Chang Chung-ching in the eastern Han dynasty ( ad 25–220). This empirical system has been followed for the past 2000 years and many of the formulae in these two books are still used today.

Many herbs have found their way into the pharmacopoeias of orthodox medicine, sometimes as the isolated and chemically standardized active ingredient. Drugs such as cocaine, coumarin, curare, digoxin, ephedrine, morphine, quinine and quinidine, reserpine, senna and the ergot and vinca alkaloids entered orthodox medicinal use by this route.

Many other herbal substances are freely available to the public, and in the UK only a small proportion comes under the direct control of the Medicines Act. Individual unprocessed traditional herbs are not considered as medicines and, therefore, do not require product licences in the UK. In Britain alone it has been estimated that 6000–7000 tons of herbs are extracted annually for use as ingredients of herbal remedies.

Medical practitioners rarely prescribe herbal remedies, and medical herbalists, who constitute only a small professional body, are not consulted by most people who purchase herbal products. Consequently, the principal outlets are health food stores or mail order firms advertising in health magazines and brochures. Now herbal products are available at community pharmacies and are stocked by some supermarkets.

In some areas of the UK certain immigrant races have brought their own medical traditions. Oriental medicine in particular has remained the most widely used traditional medicine. Oriental drugs are alleged to have specific characters such as the ‘four properties’ (‘chill’ and ‘cool’ of yin and ‘lukewarm’ and ‘heat’ of yang with ‘intermediate’) and the ‘five flavours’ (‘acrid’, ‘sour’, ‘sweet’, ‘bitter’ and ‘salty’). Drugs are dispensed according to their character (e.g. diseases with fever are treated with chill and cool drugs). Over 500 herbal remedies are used in Chinese medicine and there are about 600 or more varieties of crude drugs.

Asian medicine has also been brought to the UK with the traditional practices of Unani and Ayurvedic medicine. The traditional healer is termed hakim if he practises the Unani system or vaid if he practises the Ayurvedic. Unlike Oriental medicine which follows traditional formulae, the philosophy behind the Asian system is that preparations are not uniform from country to country, i.e. a preparation sold in India under a certain name will differ from the nominally identical product prepared for sale in Britain. The addition or omission of certain herbs is usually explained by reference to different climates or temperaments of the person being treated.

In general, herbal medicines aim to use the patient’s natural resistance and to restore the balance of health. They are commonly used in treating chronic disorders which respond poorly to orthodox remedies, such as the common cold, arthritis, back pain, mental and stress problems and, sometimes, malignant disease. They are being increasingly used to treat intractable diseases such as dementias in the elderly and diseases of obscure aetiology and poor prognosis, such as multiple sclerosis.

Many of the plants used in herbal medicine contain principles whose effects can be demonstrated pharmacologically, and the action of the whole plant extract can usually be related to that of the isolated constituents. However, for some herbal remedies it is not possible to demonstrate or evaluate their pharmacological activity and the situation is further complicated by the concurrent use of a number of drugs, the supposed active ingredients of which have not been identified.

It seems to be a commonly held belief that, by and large, herbal remedies, being natural products, are inherently safer than the potent synthetic drugs of orthodox medicine which sometimes produce undesirable side-effects. However, toxicity from herbal medicines does occur, although it is rarely an acute episode due to accidental consumption of an overdose. Herbal remedies are often taken over long periods and the appearance of toxicity may be considerably delayed and may even appear after the remedy has been discontinued. The quality of the product can be affected by environmental factors, such as climate and growing conditions before harvesting, and toxicity may vary with the part of the plant used, time of harvesting, post-harvest factors and method of preparation.

Concern over the uncontrolled supply and administration of these products has led the Committee on Safety of Medicines (CSM) to remind doctors that the yellow card scheme applies as much to these products as it does to conventional medicines. However, the CSM can take little action as these medicines do not have a product licence.