There are many types of drugs available through both legal and illegal means in the world. For the purposes of this lecture we are going to focus on those chemicals that would be classified as "illegal drugs".
An illegal drug is a chemical substance that people of any age may not lawfully manufacture, possess, buy, or sell.
The improper use of medicines - either prescription or over-the-counter drugs - is called drug misuse. It is their use that is illegal, not the drug itself.
We are all probably guilty of some form of drug misuse during our lifetime but that does not necessarily make us criminals. Take cough syrup for instance. If you read the instructions, it says to take 20 mL every 8 hours. But how many of us really note the exact time we took the medication? We normally take the cough syrup again when the cough starts coming back, so we would then be guilty of misuse of the drug.
Now if we were to take the cough syrup when we didn�t need it just because of the way it made us feel, then we would be guilty of drug abuse. The important thing to note here are that not all drugs that are abused are illegal.
Before we get to the different types of drugs and their abuse, we need to discuss why they are abused.
Drug Abuse and the Brain
A mood-altering drug, also called a psychoactive drug, is a chemical that affects brain activity. Almost all of the drugs that are commonly abused are psychoactive; their effect being referred to as a "high". Psychoactive drugs may be legal or illegal but almost all of them are also addictive.
Mechanism of Drug Addiction in the Brain
Alila Medical Media (YouTube)
Addiction can be defined in two ways:
- The compulsive use of a drug, despite any cost to health, family, or social standing.
- A disease that changes the structure and chemistry of the brain.
It is the second definition that concerns chemists the most. How and why do certain chemicals (drugs) affect the chemical and structural make-up of the brain? How do we detect these changes and/or counteract them?
We have all seen people who are addicted to drugs. They are generally thin to the point of emaciation, their skin is sallow and their eyes are glazed. Based on this description it becomes difficult to understand why they don't just quit. But there is a good reason for their refusal or inability to quit: Withdrawal.
Withdrawal
Once the brain becomes accustomed to the abuse of a drug (legal or illegal), quitting becomes both mentally and physical difficult to the point of pain in some instances. Think about how hard it is to diet or quit smoking. These are both types of addiction to legal drugs (food and cigarettes). If a person who is dependent on a psychoactive drug stops taking the drug, that person will experience severe withdrawal symptoms that include:
- Headaches and muscle aches
- Fever
- Nausea and vomiting
- Dizziness
- Paranoia
- Seizures and tremors
- Death
So how do the chemicals in drugs "hook" you?
Many psychoactive drugs trigger activity along a pathway of cells in the brain called the "reward pathway." Brain cells along the activated reward pathway release a chemical called dopamine.
Dopamine
Dopamine and the Brain
Bryce Wylde (YouTube)
Dopamine is a neurotransmitter that helps control the brain's reward and pleasure centers. Dopamine also helps regulate movement and emotional responses, and it enables us not only to see rewards, but to take action to move toward them. The extra dopamine released during drug use can cause the user to ignore the harmful effects of the drug and want to continue using it. Flooding the reward pathway with dopamine may lead to intense cravings for the drug. After a time, drug abuse can dull the brain's reactions to natural levels of dopamine. This means that the only way for the user to get the "high" naturally afforded by dopamine is to use more and more of the drug.
There are many categories of drugs but for the sake of this lecture we will focus on the following seven: Narcotics, Stimulants, Depressants, Hallucinogens, Cannabis, Steroids and Inhalants.