The kidneys and lungs remove about 10% of the alcohol in the urine and breath, making the breathalyzer test a valid tool to measure a person's blood alcohol level.
Opiate addicted individuals commonly experience bouts of euphoria followed by bouts of depression.
Research has proven that long-term drug use results in changes in the brain that can affect the person long after they have stopped using drugs.
Research indicates that when given a free choice, animals will readily operate pumps that inject them with cocaine or amphetamine. Animals dependent on amphetamines will work hard to get more of the drug.