15.1 Drugs
- Syllabus
- 0610–2026–2027
- Topic
- 15.1
- Level
- —
Learning objectives
15.1.1Drug as any substance taken into• Describe a drug as any substance taken into the body that modifies or affects chemical reactions in the body15.1.2Use of antibiotics for the treatment• Describe the use of antibiotics for the treatment of bacterial infections15.1.3Some bacteria are resistant• State that some bacteria are resistant to antibiotics which reduces the effectiveness of antibiotics15.1.4Antibiotics kill bacteria but do not• State that antibiotics kill bacteria but do not affect viruses15.1.5Using antibiotics only when essential• Explain how using antibiotics only when essential can limit the development of resistant bacteria such as MRSA
Define a drug
A drug is any substance taken into the body that modifies or affects chemical reactions in the body.
A substance is not defined as a drug merely because it is harmful or addictive; the defining feature is that it changes chemical reactions in the body.
Describe the use of antibiotics
Antibiotics are drugs used to treat bacterial infections.
An effective antibiotic kills bacteria or prevents their growth, allowing the infection to be controlled.
Antibiotics treat infections caused by bacteria; they are not a general treatment for every disease or pathogen.
Explain why bacterial resistance matters
Some bacteria are resistant to an antibiotic, so the antibiotic does not kill them or stop their reproduction.
Resistant bacteria survive treatment, reproduce and can spread, reducing the antibiotic's effectiveness and making the infection harder to treat.
Bacteria become resistant; the patient does not become resistant to the antibiotic.
Distinguish antibiotic effects on bacteria and viruses
Antibiotics kill bacteria but do not affect viruses.
| Pathogen | Antibiotic effect | Reason |
|---|---|---|
| bacterium | may be killed or its growth stopped | has cellular structures or processes targeted by antibiotics |
| virus | not affected | lacks the bacterial cell structures and processes targeted by antibiotics |
Antibiotics do not treat viral infections; using them against a virus gives no antiviral benefit.
Limit the development of antibiotic resistance
Using antibiotics only when essential reduces selection for resistant bacteria such as MRSA.
| Responsible action | Why it helps |
|---|---|
| use antibiotics only for necessary bacterial infections | reduces unnecessary exposure and selection |
| use the appropriate antibiotic | targets the infecting bacterium effectively |
| complete the prescribed course | reduces survival and reproduction of partially treated bacteria |
| avoid routine use in healthy livestock | reduces repeated selection in bacterial populations |
Antibiotics should not be used for viral infections, and stopping a prescribed course early can leave surviving bacteria.