Coca leaves are obtained from two South American plants, Erythroxylum coca and Erythroxylum truxillense, and contain an alkaloid, cocaine. Cocaine has marked effects as a stimulant, and, locally applied, as an anaesthetic by paralysing nerves of sensation. The dried leaves have been used traditionally by indigenous South American people, who chew them mixed with a little lime. Their effect is to dull the mucous surfaces of mouth and stomach, with which the saliva, produced by chewing them, comes into contact – thus blunting, for long periods, all feeling of hunger. The cocaine, being absorbed, stimulates the central nervous system so that all sense of fatigue and breathlessness vanishes for a time. It was by the use of coca that the Indian post-runners of South America were able to achieve their extraordinary feats of endurance. The continued use of the drug, however, results in emaciation, loss of memory, sleeplessness and general breakdown. Dependence on cocaine or a derivative, ‘crack’, is a serious social problem in many countries. (See DEPENDENCE.)
Before the serious effects that result from its habitual use were realised, the drug was sometimes used by hunters, travellers and others to relieve exhaustion and breathlessness in climbing mountains, and to dull hunger. Derivatives of cocaine are used as locally applied analgesics, via sprays or injections, in dentistry and for procedures in the ear, nose and throat. Because of its serious side-effects and the risk of addiction, cocaine is a strictly controlled Class A drug which can be prescribed only by a medical practitioner with a Home Office licence to do so.