Cocaine is a drug found in leaves of the shrub Erythroxylon coca. It exaggerates changes caused by at least two brain chemicals, noradrenaline and dopamine, increasing alertness and causing euphoria. Pure cocaine was prepared in 1860 and was hailed as a cure-all. Doctors used it to treat anxiety and depression until they realised it was addictive. Dentists also used cocaine to numb their patients' mouths. But, because it damages living tissues, it has been replaced by drugs such as lignocaine.