This guide covers IGCSE Biology topic 15: drugs. You will revise medicinal drugs (antibiotics, painkillers), antibiotic resistance, and misuse of drugs (alcohol, smoking, illegal drugs) and their effects on health and society.

Key concepts to revise

• Antibiotics – Kill bacteria (not viruses). Overuse leads to antibiotic-resistant bacteria; finish the course.
• Painkillers – Relieve symptoms; do not kill pathogens (e.g. viruses).
• Alcohol – Depressant; affects brain (judgement, coordination); long-term: liver damage.
• Smoking – Nicotine (addictive); tar (carcinogen, damages lungs); carbon monoxide (reduces oxygen carrying capacity of blood).

Exam tips and command words

• State – What antibiotics kill (bacteria); why antibiotics do not work against viruses.
• Describe – The effect of alcohol on the nervous system; the effect of smoking on gas exchange (tar, cilia).
• Explain – Why antibiotic resistance develops (overuse; bacteria with mutation survive and reproduce); why finishing a course is important.
• Compare – Antibiotic vs painkiller (kill pathogen vs relieve symptom).

Common mistakes

• Saying antibiotics kill viruses (they do not; they kill bacteria).
• Confusing nicotine (addictive) with tar (carcinogen; damages lungs).
• Not stating that antibiotic resistance is a result of natural selection (resistant bacteria survive and pass on resistance).

Revision checklist

• State what antibiotics do and why they do not work against viruses.
• Explain how antibiotic resistance develops and how to reduce it (finish course; avoid overuse).
• Describe the effects of alcohol on the body (short-term and long-term).
• Describe the effects of smoking (nicotine, tar, carbon monoxide) on health.

Next steps

Book a free trial with an IGCSE Biology tutor to practise drugs and health questions, or explore Tutopiya’s learning portal for more revision resources.