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What is a drug?

A drug is a chemical which changes the chemical reactions of cells if taken in.

There are a variety of groups of drugs, but what we are interested in here are recreational and medical drugs.

  • Drugs can grouped according to their uses i.e. medical and recreational drugs.
  • They can also be grouped according to their perceived harm i.e.illegal drugs Class A, B, C and legal drugs.
  • They can also be classified by the effects they cause in the body i.e. Stimulants, Depressants and Hallucinogens.

Recreational drugs

Reacreational drugs are drugs which people take for pleasure. They may be legal, for example, alcohol, caffeine and smoking (nicotine) or illegal, for example Cannabis, Heroin and Cocaine

Why do people use recreational drugs?

There are many reasons, including:

  • Cultural reasons, for example alcohol is a widely acceptable drink in the western world.
  • Peer pressure
  • Stress- to escape the troubles of the world


Alcohol is mainly the chemical ethanol. It is sold in a variety of drinks, ranging from lager, spirits to whisky.

Short term effects

Alcohol is a depressant which affects the Brain and nervous system.

It slows down the ability to react by slowing down impulses at synapses.

It therefore results in loss of balance and slurred speech.

This may also impaire judgement making the person engage in unneccessary risk taking.

Long term effects

Alcohol is metabolised (broken down) by the liver. Abuse of alcohol may result in the death of liver cells, leading to their replacement by scar tissue. This is called Liver Cirrhosis. It may result in death or the person may require a liver transplant.

The liver may also accumulate a lot of fat. This is fatty liver disease.



Nicotine is available from cigarette smoking. It is a stimulant which affects the brain and nervous system. Nicotine is very addictive as it mimics neurotransmitters at the synapse. This makes people unable to give up smoking.

Cigarette smoking also carries with it other substances like carbon monoxide and tar.

Carbon monoxide- binds to red blood cells reducing their ability to carry oxygen. This affects the cardiovascular system and makes smokers easily become breathless.

Tar- is a mixture of hundreds of different chemicals. These chemicals are carcinogenic, they cause cancer of the lungs.


Cannabis is a hallucinogenic Class B substance. Its active ingredient are chemicals called cannabinoids which cause feelings of euphoria and invincibility.

Cannabis is not addictive and affects the brain and nervous system. Prolonged use may result in mental illness.


Impact of legal drugs and Gateway drugs

Legal recreational drugs seem to cause higher deaths than illegal drugs. This could be because:

  • They are cheap
  • They are available to everyone so people can take them in large amounts.

Some drugs like cannabis have been linked to the progression to hard drugs like Heroin and cocaine. They are called 'gateway drugs'. Why is this so?

Performance enhancing drugs

Some athletes take drugs which:

  • Increase the building up of muscle- Anabolic Steroids
  • Increase their metabolic rate- Stimulants
  • Increase Respiration

What are the ethical and medical issues associated with this practice?


Medical drugs

Medical drugs are drugs that are taken to treat a disease or to reduce pain.

Painkillers- reduce the sensation of pain. Most do this by blocking pain impulses in the nervous system. Examples include paracetamol, asprin and ibuprofen. These are mild painkillers. Stronger painkillers include morphine.

Although painkillers stop us feeling pain, they do not kill any pathogens or treat the disease affecting us.

Antibiotics- These are drugs that kill bacteria. They do not kill viruses because viruses live inside the host cells. It would be difficult to kill the virus without damaging the host cell. Examples include penicillin and amoxycillin. Penicillin works by inhibiting cell wall formation in bacteria, meaning that they can't divide (reproduce), they just die.

Statins: These are drugs which lower cholesterol (LDL) levels in the blood, reducing chances of a stroke and heart attack. They do this by inhibiting cholesterol production by the liver, which means there will be less of it circulating around.



MRSA stands for Methicillin Resistant Staphylococcus Aureus. This is a bacteria that is resistsnt to Methicillin, an antibiotic that is similar to penicillin.

Antibiotic resistance is a situation whereby a bacteria is not affected by a particular antibiotic. Resistance arises in many ways but most importantly because of:

  • Careless use of antibiotics such as prescribing them for viral infections.
  • Not finishing the course of prescribed antibiotics.

The stages involved in antibiotic resistance are similar:

  • Initially there is a wide variety of bacteria, weak and strong, infectious and non-infectious.
  • Taking antibiotics begins to kill the bacteria and signs of infection start to disappear within a few days. This may tempt the person to stop taking antibiotics.
  • The surviving (strong) bacteria mutate (change their DNA) and change their antigens, so that the antibiotic may not affect them anymore.
  • These mutant bacteria reproduce/multiply and may cause worse infection.

This is an example of natural selection.


Bloody Thalidomide

Thalidomide is a drug that was first used in the 1950s in Germany using the trade name Distaval. Initially it was used to treat sleep disorders like Insomnia then it was realised that it could also treat morning sickness in pregnant mothers. However, Thalidomide had not been tested in pregnant mothers or even animals. It was also unstable, meaning that it broke down in the body releasing a host of other chemicals which resulted in a large number of children born with limb deformities.

But thalidomide is still being used in some cases today:

To treat leprosy

To treat HIV


No other drugs available.

Thalidomide seems like miracle drug: It seems to have the potential to treat many new diseases.