Drugs In Medicine

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Notes

What is a Drug?

A **drug** is a substance taken into the body that modifies or affects chemical reactions in the body.
Some drugs are **medicinal drugs** used to treat the symptoms or causes of a disease.
Examples of medicinal drugs include **painkillers** and **antibiotics**.

Antibiotics

**Antibiotics** are chemical substances that can kill bacterial cells, useful for treating bacterial infections.
They target processes and structures specific to bacterial cells, so they do not harm animal cells.
Antibiotics have **no effect on viruses**, so they are never used to treat viral infections.
Bacteria can develop **antibiotic resistance**, meaning the antibiotic no longer kills them.

How Antibiotics Work

Antibiotics kill bacteria by damaging bacterial cell walls or interfering with bacterial metabolism.
They exploit differences between bacterial and human cells to selectively target bacteria.

Antibiotic Resistance

**Antibiotic resistance** becomes widespread when bacteria are exposed to antibiotics: non-resistant bacteria die, but resistant ones survive and reproduce.
Reducing antibiotic use can slow the spread of resistance.
Doctors prescribe antibiotics only when essential, and never for viral infections.
**MRSA** (methicillin-resistant×Staphylococcus aureus×) is a dangerous antibiotic-resistant strain.

Preventing Antibiotic Resistance

Use antibiotics only when prescribed by a doctor.
Complete the full course of antibiotics as directed.
Do not use antibiotics for viral infections like colds or flu.
Good hygiene and vaccination help reduce the need for antibiotics.

Diagram of a bacterium showing structures targeted by antibiotics (e.g., cell wall) and where resistance genes may be located (plasmids).

Practice questions

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1.Which of the following best defines a drug?
Easy
- AA substance taken into the body that modifies or affects chemical reactions in the body
- BA substance that only kills bacteria
- CA substance that only treats symptoms of disease
- DA substance that is always harmful to the body
2.Antibiotics are effective against which type of pathogen?
Easy
- AViruses
- BBacteria
- CFungi
- DProtozoa
3.Antibiotics can be used to treat viral infections.
Easy
True or false?
4.State one reason why antibiotics do not harm human cells.
Medium
5.What is antibiotic resistance?
Medium
- AThe ability of bacteria to produce antibiotics
- BThe ability of bacteria to survive exposure to an antibiotic
- CThe ability of viruses to survive antibiotics
- DThe ability of human cells to resist antibiotics
6.Name the antibiotic-resistant strain of bacteria mentioned in the syllabus.
Medium
7.Complete the sentence.
Medium
Antibiotics kill bacteria but have no effect $on ____$ .
8.Arrange the following events in the correct order to show how antibiotic resistance becomes widespread in a bacterial population.
Hard
- Resistant bacteria survive and reproduce
- Exposure to antibiotic kills non-resistant bacteria
- Resistant strain becomes more common
- Some bacteria have a mutation that makes them resistant

Slides

What is a Drug?

A drug is a substance taken into the body that modifies or affects chemical reactions in the body.
Medicinal drugs are used to treat symptoms or causes of disease.
Examples include painkillers and antibiotics.

Which of the following best defines a drug?

A substance that provides energy
A substance that modifies chemical reactions in the body
A substance that only kills bacteria
A substance that is always harmful

Antibiotics

Antibiotics are chemicals that kill bacterial cells.
They target processes and structures specific to bacteria, so they do not harm animal cells.
Antibiotics have no effect on viruses, so they are not used for viral infections.

Antibiotics kill ____ cells but have no effect $on ____$ cells.

Antibiotic Resistance

Bacteria can develop resistance to antibiotics, meaning the antibiotic no longer kills them.
Resistance spreads when non-resistant bacteria are killed, and resistant ones survive and reproduce.
Reducing antibiotic use helps limit the spread of resistance.

Which of these are true about antibiotic resistance?

Antibiotic resistance can spread among bacteria.
Antibiotics are effective against viruses.
Reducing antibiotic use helps prevent resistance.
All bacteria are resistant to antibiotics.

MRSA – A Resistant Strain

MRSA stands for methicillin-resistant Staphylococcus aureus.
It is a strain of bacteria that is resistant to many antibiotics.
Reducing antibiotic use is a key strategy to combat MRSA.

What does MRSA stand for?

Multiple Resistant Staphylococcus Aureus
Methicillin Resistant Staphylococcus Aureus
Methicillin Resistant Streptococcus Aureus
Multiple Resistant Streptococcus Aureus

Why Antibiotics Don't Work on Viruses

Viruses have different structures and replication methods compared to bacteria.
Antibiotics target bacterial-specific processes (e.g., cell wall synthesis).
Viruses do not have these targets, so antibiotics are ineffective.

Antibiotics are not used to treat ____ infections because they target ____ cells.

Responsible Use of Antibiotics

Doctors prescribe antibiotics only when essential.
Patients should complete the full course even if symptoms improve.
Overuse and misuse accelerate resistance.

Which practices help reduce antibiotic resistance?

Taking antibiotics for a cold.
Completing the full prescribed course.
Using antibiotics only when necessary.
Sharing antibiotics with family members.

Summary: Drugs in Medicine

Drugs modify chemical reactions in the body.
Antibiotics kill bacteria but not viruses.
Antibiotic resistance is a growing problem; responsible use is essential.

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