The Coca plant
Coca is not a drug, it’s food.  

Coca, scientifically known as Erythroxylon Coca  is a medicinal and ceremonial plant traditionally used by Andean cultures.
It is a medium height bush that grows in hot, humid climates on the lower slopes of mountains. Since ancient times coca leaves were, and still are, used due to its medicinal and ritual purposes. They are chewed, ingested or prepared in infusion. 
Coca leaves are actually an essential dietary supplement in the social and ecological conditions of the Andes. They contain a considerable proportion of the requirements of vitamins and minerals.  They also supress hunger, improving life in the jungle and mountain environments where the availability of protein may be limited by local or seasonal factors. Another property of coca, related to its alkaloid content is its stimulating effect, it also facilitates efforts in conditions of the  low oxygen content of the mountain heights.

Coca leaf tea or «mate de coca» is also consumed in Peru and Bolivia to relieve altitude sickness or «altitude sickness» and as a digestive. The medicinal properties of coca resemble to some extent the Mapuche “boldo”.
During colonial times, Spanish authorities used these stimulant and appetite suppressant properties of coca to improve workers performance in the difficult silver miners conditions.
 Coca trade provided considerable income to the colonial authorities. In 1583 more than one millon kilos of coca leaves were brought to the mines of Upper Peru.  
Pictures taken by the author in the Chapare region of Cochabamba.

Coca alkaloids

Coca contains numerous alkaloids which give its known therapeutic properties.
The best known alcaloid is cocaine that has stimulant and digestive effects. Other alkaloids contained in coca include atropine, egnomina, the pecticina, papain, hygrine, globulin, quinoline, conina, cocamine, reserpine, benzoin, inulin and pyridina. Its properties are described in Table 3.2.

Cocaine

Cocaine is structurally to Solanaceae alkaloids such as belladonna, henbane, mandrake and satura. 
Its usual formula is cocaine hydrochloride, and apparently,it prevents the absorption of certain transmitters that have been released by other means. 
 Minimum active dose of nasal application is about 20-30 mg while the lethal dose is 1 to 1.5 grams.  It has a high tolerance and some people have ingested 4-5 grams daily without lethal effects.
This alkaloid was first isolated in 1859 by Florentine Paolo Mantegaza researcher and Austrian Karl Cherence of Austria.
In those days it was considered as an almost miraculous substance.
It was at this time that Dr Frances Angelo Mariani visiting Potosí, Bolivia, observed the natives chewing coca and upon his return to France developed a product which he called Mariani Wine. This “wine” was sold with great success.
In the late nineteenth century, coca and cocaine became popular and prestigious European intellectuals and professional classes became regular consumers..
Sigmond Freud himself stated:
At present it is impossible to assess with certainty the extent to which coca can potentially increase human mental powers.
I have the impression that prolonged use of cocaine can lead to a lasting improvement if the inhibitions expressed before it is consumed only to be physical causes or exhaustion. Of course, the instantaneous effect of a dose of cocaine can not be compared with an injection of morphine; But from the positive point of view, there is no danger of damage to the body generally as is the case with chronic use of morphine. 10   .
Then Freud himself would deny such early claims.
Enthusiasm generated by coca and cocaine in Western society led to their use in medicine and to the preparation of various elixirs which achieved wide acceptance. This habit spread among the population and markets for cocaine expanded.
When the prohibitionist ideology succeeded en the United States. and arguing that cocaine had addictive character and that was potentially harmful (with prolonged administration in high doses) a political movement proposing its banning developed.
In 1906, through the Poor Food and Drug Act, this alkaloid, as well as heroin  poppy, were banned in the United States.
It was the bãeginning of a process that would continue throughout the century. Despite its illegality, cocaine consumption gradually spread. As a result, coca cultivation in their areas of origin as well as clandestine laboratories for the manufacture of cocaine grew in many Latin American countries. Simultaneously  transportation networks for its distribution were organized. The highly unsuccessful war on cocaine had started.
From: "Peoples, Drugs and Serpents", Danilo Anton, Piriguazú Ediciones.