Amphetamines are all based on the naturally occurring chemical, ephedrine, found in the herb Ephreda vulgaris. Chinese people have used this plant for over 5000 years to treat asthma. In 1887, chemists made amphetamine, a synthetic substitute for ephedrine. They found that amphetamine affects the brain, increasing alertness and decreasing appetite. It increases the levels of two of the brain's chemicals, noradrenaline and dopamine.