Since the 1930s, amphetamines have been used to improve alertness in narcolepsy and other conditions. These medications are among the most effective for reducing sleepiness, but side effects are moderately common.
A large variety of amphetamines are clinically available, and individuals may respond better to one than to another. Some of the most common are dextroamphetamine (Dexedrine) and a mixture of amphetamines and dextroamphetamine (Adderall). Methylphenidate (Ritalin, Concerta, Metadate, and Methylin) is closely related to the amphetamines and has similar benefits and side effects.
All these medications improve alertness by increasing brain levels of dopamine. To a lesser degree they can also increase brain levels of two other wake-promoting chemicals, serotonin and norepinephrine.