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A drug is any substance which when taken will change the chemical processes in the body. It may change how you feel, act and behave.

Types of drugs

When the word drug is mentioned, many people may just jump and think 'cocaine, weed' etc. There are more drugs than these, lets get this clarified.

1. Classes based on the use of the drug

Medical drugs: These are drugs used to treat an illness. There many classes under this group, for example:

  • Antibiotics- Kill bacteria
  • Painkillers- reduce the feeling of pain
  • Statins- used to reduce blood cholesterol levels and prevent heart disease
  • Steroids- Build up muscle

Recreational drugs: These are drugs that people use for pleasure. they include both legal and illegal drugs, for example:

  • Cannabis (weed)
  • Alcohol
  • Tobacco (Nicotine)
  • Cocaine
  • Heroin
  • Ecstacy
  • Caffeine (tea, coffee)


2. Classes based on perceived harm to health

Governments and the international community have asked scientists to classify drugs according to how much damage they cause to human health. This had led to the classification of drugs into legal and illegal drugs

Legal drugs - e.g. alcohol (in many countries), caffeine, tobacco (nicotine)

Illegal drugs- cause major harm to health in the short term. They are classified into classes A, (very harmful), B, C, D (less harmful).

  • These include cocaine, amphetamines, ecstacy, heroin, cannabis etc.

3. Classes based on their effect on the body

Stimulants- Speed up reactions, for example, caffeine, ecstacy, nicotine

Depressants- Slow down responses, for example, alcohol

Hallucinogens- Confuse senses, for example cannabis

Narcotics- Sleep inducing, for example cocaine, heroin


Effects of smoking

Tobacco smoke contains 3 harmful substances:

Nicotine- Is addictive, also affects blood vessels

Carbon monoxide: Is produced by incomplete burning of tobacco. It binds to red blood cells and reduces their ability to carry oxygen. It affects the cardiovascular system (heart and circulation).

Tar- A mixture of hundreds of chemicals, some of them are carcinogenic= They cause cancer of the lungs.


Effects of alcohol

Alcohol is a depressant, it slows down reactions

Short term effects: Speech becomes slurred, causes loss of balance, poor judgement.

Long term effects: Long term overconsumption of alcohol my lead to : High blood pressure, liver cirrhosis (hardening of the liver).



 Challenge yourself:

Find out about doping. Why is it done?


What kind of drugs can be abused by athletes?

Doctors will not give you antibiotics for flu, why?

What is a gateway drug? Give an example.

Alcohol and tobacco kill millions of people every year worldwide. Find out as many reasons why they are still legal in many countries.