When amphetamines are used, the neurotransmitters dopamine and norepinephrine are released from nerve endings in the brain and their reuptake is inhibited. This a buildup of these neurotransmitters at synapses in the brain. When nerve cells in the brain and spinal cord are activated by amphetamine, the mental focus, the ability to stay awake, and the ability to concentrate is improved, which is helpful for those with hyperactivity disorders or narcolepsy. Although the physiological experience of using amphetamines and cocaine is almost identical, the effects of amphetamines can last several hours whereas the effects of cocaine generally last less than one hour.15 When mixed with alcohol or other drugs, the effects of prescription amphetamines are enhanced.16 The onset of effects from injecting methamphetamines occurs immediately. When this drug is snorted, effects occur within 3 to 5 minutes; when ingested orally, effects occur within 15 to 20 minutes.17