CIE Categories Archives: 15. Drugs

15.3) Misused drugs

15.3) Misused drugs


Effects of excessive alcohol consumption and abuse of heroin:

  • Powerful depressant drugs
  • Effect on reaction times and self-control
  • Addiction and withdrawal symptoms
  • Negative social implications, eg. crime


How heroin affects the nervous system:

  • Produces it effects by interacting with receptor molecules at synapse.
  • Heroin mimics the transmitter substances in synapses in the brain, causing the release of dopamine (a neurotransmitter), which gives a short lived ‘high’.


  • Injecting heroin can cause infections such as HIV.
  • Excessive alcohol consumption can cause liver damage.
  • Tobacco smoking can cause chronic obstructive pulmonary disease (COPD), lung cancer and coronary heart disease.
  • Liver is the site of breakdown of alcohol and other toxins.


Evidence for a link between smoking and lung cancer:

There are at least 17 substances in tobacco smoke known to cause cancer in experimental animals, and it is now thought that 90% of lung cancer is caused by smoking.


  • Nicotine, the addictive component of tobacco smoke, produces an increase in the rate if the heartbeat and a rise in blood pressure and can cause an erratic and irregular heart beat.
  • Tar in cigarette smoke is thought to be the main cause of lung cancer in smokers.
  • Carbon monoxide permanently binds with haemoglobin in red blood cells, reducing the smoker’s ability to provide oxygen to respiring cells. This results in a smoker getting out of breath more easily and it reduces physical fitness.


The nicotine and carbon monoxide increase the tendency for the blood to clot and so block the coronary arteries.


Performance-enhancing hormones:


  • Is made in the testes of males and is responsible for promoting male primary and secondary sexual characteristics.
  • Taking testosterone supplements (known as ‘doping’) leads to increased muscle and bone mass.
  • Which can enhance a sports person’s performance.

Anabolic steroids

  • Are synthetic derivatives of testosterone.
  • They affect protein metabolism, increasing muscle development and reducing body fat.
  • Athletic performance is thus enhanced.
  • There are serious long-term effects of taking anabolic steroids: sterility, masculinisation in women, and liver and kidney malfunction.
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15.2) Medicinal drugs

15.2) Medicinal drugs



Antibiotics attack bacteria in a variety of ways

  • Disrupt the production of the cell wall and so prevent the bacteria from reproducing, or even cause them to burst open.
  • Interfere with protein synthesis and thus arrest bacterial growth.


Animal cells do not have cell walls, and the cell structures involved in protein production are different. Consequently, antibiotics do no damage human cells although they may produce some side effects such as allergic reactions.


Development of resistant bacteria:

  • If a course of antibiotics is not completed, some of the bacteria it is being used to destroy will not be killed, but will have been exposed to the drug..
  • Some of the survivors may be drug-resistant mutants. When they reproduce, all their offspring will have the drug resistance, so the antibiotic will become less effective.
  • MRSA (methicillin-resistant Staphylococcus aureus). A type of bacteria that has developed resistance to a number of widely used antibiotics.
  • Development of this can be minimised by using antibiotics only when essential and ensuring treatment is completed.


Antibiotics and viral diseases:

  • Antibiotics are not effective against viral diseases.
  • This is because antibiotics work by disrupting structures in bacteria such as cell walls and membranes, or processes associated with protein synthesis and replication of DNA.
  • Viruses have totally different characteristics to bacteria, so antibiotics do not affect them.
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