Medicines (AQA GCSE Combined Science: Synergy: Life & Environmental Sciences): Revision Note

Antibiotics & Painkillers

• When treating a disease there are two types of medication that an individual can take:

  • Medicines that treat the cause of the disease – antibiotics

  • Medicines which treat the symptoms of the disease – eg. painkillers

• Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body

• The use of antibiotics has greatly reduced the deaths from infections in the last century

• Only certain antibiotics will work on certain diseases, however, so a doctor will prescribe different antibiotics depending on the type of infection (see Culturing Microorganisms)

• It is important that specific bacteria should be treated by specific antibiotics that are known to work against them

• Antibiotics work by stopping bacteria cellular processes such as the production of the cell wall – they affect processes usually only in bacteria so are not harmful to animal cells

Penicillin was the first antibiotic to be discovered and is widely used, although resistance is a problem

• Antibiotics will not work against viruses, as viruses reproduce inside cells. It is difficult to develop drugs that kill viruses without also damaging the body’s tissues

• Painkillers and other medicines are used to treat the symptoms of disease but do not kill pathogens (eg. ibuprofen can reduce pain and inflammation)

Antibiotic Resistance

• The use of antibiotics has increased exponentially since they were first introduced in the 1930s

• In that time they have saved millions of lives

The introduction of antibiotics has had one of the largest impacts on global health, shown by this example in the USA

• However, since their discovery and widespread use, antibiotics have been overused and antibiotic resistance has developed in many different types of bacterial species

  • Bacteria, like all organisms, have random mutations in their DNA

  • One of these mutations may give them resistance to an antibiotic

  • If an organism is infected with bacteria and some of them have resistance, they are likely to survive treatment with antibiotic

  • The population of the resistant bacteria will increase

  • If the resistant strain is causing a serious infection then another antibiotic will be needed

  • A strain of Staphylococcus aureus has developed resistance to a powerful antibiotic methicillin, this is known as MRSA (Methicillin resistant Staphylococcus aureus)

  • MRSA can infect wounds and is difficult to treat without antibiotics

Bacteria evolve rapidly as they reproduce quickly and acquire random mutations – some of which confer resistance

Reducing the risks of antibiotic resistance

• Overuse of antibiotics should be avoided

• Antibiotics should only be prescribed when necessary and matched to the correct bacterium

• Antibiotics should not be used for viral or mild infections that the immune system can clear

• Patients must complete the full course of antibiotics to prevent survival of resistant bacteria

• Antibiotic use in agriculture should be reduced and tightly controlled

• Good hygiene practices reduce the spread of resistant strains such as MRSA

• Infected patients should be isolated to prevent transmission, especially in hospitals

Medicines as Mixtures

• Most medicines are mixtures rather than pure substances

• Medicines are formulated by mixing ingredients in carefully measured quantities

• Formulations are designed to give the medicine the required properties

• One or more ingredients may be the active drug, such as aspirin

  • Other ingredients help make the medicine easier to take

  • Some ingredients improve taste, stability or absorption

• Medicines can be taken as solutions, tablets or capsules