often taking a mild depressant or stimulant does not have much effect on the person who took it. but more serious drugs, substances, or even medications can have a large effect on the person. usually stimulants keep the person awake and energetic. depressants work the opposite way; they decrease the heart rate of the person and relax them. sedatives give the same effect. more of these substances can carry harm or even life-threatening effects, if ingested in large amounts. mixing alcohol with prescription drugs often leads to increased or hastened impairment. alcohol can produce hazardous side effects, reduce heart rate, and drop blood pressure to a dangerous level.