Heroin belongs to a class of drugs called opioids, which also includes the painkillers codeine and morphine. Heroin comes from a natural substance extracted from the seedpod of the Asian poppy plant. It usually appears as a white or brown powder.
Heroin is usually injected, sniffed, snorted, or smoked. Injection of the drug provides the greatest intensity and most rapid onset of symptoms. Almost immediately upon injection, the user is relieved of physical pain and discomfort and experiences pleasurable feelings. This false sense of well-being plays a part in the addiction to heroin. The drug “rush” is accompanied by a flushing of the skin.
Less pleasant aftereffects of heroin use include a dry mouth and heavy feeling in the limbs, which may be accompanied by nausea, vomiting, and severe itching. Abusers are generally drowsy for several hours. When heroin is used, mental functioning becomes clouded as the central nervous system, heart, and breathing slow down. In the case of overdose, this decrease in functioning can cause death.
Heroin and Neurotransmitters
The brain naturally contains receptors for opioids that are involved in breathing, perception of pain, emotion, and reward. When a person abuses heroin, the drug travels quickly to the brain and activates these receptors. Research suggests that this causes greater amounts of dopamine to be released into the reward system, resulting in an intense, short-lived rush. Long-term use of heroin can decrease the number of receptors and their sensitivity to the drug, so that users must use more and more heroin just to feel like they are functioning normally. This is addiction. The receptors that are sensitive to heroin are located in several parts of the brain, including the cerebral cortex and brain stem.
Long-term Effects, Addiction, and Withdrawal
Long-term effects of heroin abuse include addiction, infection of the heart lining and valves, and liver disease. For those users who inject the drug, there is a high risk of infectious diseases, including HIV/AIDS, collapsed lungs, and hepatitis B and C. Lung complications, including various types of pneumonia, may result from the overall poor health of the abuser as well as from heroin’s effects on respiration. Death by overdose is not uncommon.
When addicted users stop taking the drug, they go through a severe withdrawal. Symptoms of withdrawal include restlessness, muscle and bone pain, inability to sleep, diarrhea, vomiting, cold flashes with goose bumps (“cold turkey”), and involuntary leg movements. A person who is going through withdrawal craves the drug and will do just about anything to get it.
Cocaine is a very addictive stimulant that is made from the leaves of the coca plant. It comes in two forms: powder and crystal (“crack”). Cocaine can be snorted, injected, or smoked. Immediately after use, cocaine produces feelings of happiness, increased energy, and alertness. This “high” is followed by feelings of depression, edginess, and a craving for more of the drug. People who use cocaine often don’t eat or sleep regularly and may feel paranoid, angry, hostile, and anxious. Cocaine use can cause an increase in heart rate, muscle spasms, and convulsions. Breathing becomes faster. Users may sweat and have dilated pupils. Long-term health risks of cocaine use include damage to the nasal tissue, seizures, stroke, heart attack, and sudden death from overdose.
Cocaine and Neurotransmission
Normally, dopamine is reabsorbed into the neuron that released it after stimulating the neighboring neuron. Cocaine acts on the reward system by preventing this reabsorption of dopamine, resulting in a buildup of dopamine in the synapse. The excess dopamine continues to stimulate the neighboring neuron, producing strong feelings of pleasure. Because there is excess dopamine present in the synapse, the neighboring neuron eventually decreases the number of dopamine receptors. As a result, the cocaine abuser needs more and more of the drug to achieve a high.
When cocaine is no longer taken, dopamine levels return to their normal lower concentration. Because there are now fewer dopamine receptors available, the dopamine is unable to fully activate nerve cells. At this point, a person is addicted to cocaine and experiences intense craving and withdrawal. Damage to the neurons and the process of neurotransmission can lead to many problems, including problems with memory and a disruption in the rate of learning. Cocaine is very addictive; withdrawal is very hard.
Long-term Effects, Addiction, and Withdrawal
Cocaine abusers eventually are unable to achieve the same effects from the drug as they did from their first experience. This is because they have developed a tolerance to the drug. At this point, they must repeatedly increase their doses in an attempt to obtain those initial effects again. When cocaine use is stopped, the person may feel a strong craving for more cocaine, accompanied by feelings of depression, anxiety, irritability, and paranoia.
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As a result of scientific research, we know that addiction is a disease that affects both brain and behavior.