IGCSE Biology Topic 15: Drugs MCQs – 30 Practice Questions with Answers (Cambridge 0610)

Free practice for Cambridge IGCSE Biology 0610 on drugs, covering what drugs are, medicinal use, antibiotics and antibiotic resistance, and the general effects of drug misuse, with every question followed by a worked explanation.

What Drugs Are and How They Are Used in Medicine

Q1. Which definition best describes a drug?

  • (A) A substance that only ever harms the body and can never be used safely to treat any illness at all
  • (B) Any substance taken into the body that modifies or affects chemical reactions in the body
  • (C) A vitamin that must be taken every day
  • (D) A protein made by the body to fight infection
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Answer: B – A drug is defined by its effect on the body’s chemical reactions, whether that effect is helpful or harmful.

Q2. Which statement best describes a medicinal drug?

  • (A) A drug used to treat or prevent illness, at the right dose for the right condition
  • (B) A drug taken in any amount for any purpose, whether or not a doctor has recommended its use
  • (C) A drug that can only be used once in a lifetime
  • (D) A drug that has no effect on the body at all
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Answer: A – Medicinal drugs are used deliberately to treat or prevent illness, and dose and condition matter for safe use.

Q3. Insulin is prescribed to a patient whose body cannot control blood glucose. Which kind of drug use is this?

  • (A) Drug misuse for a non-medical purpose, taken without any medical reason or supervision
  • (B) An antibiotic treatment for a virus
  • (C) A treatment that only affects the skin
  • (D) Medicinal use to treat a medical condition
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Answer: D – Using insulin to manage a medical condition is medicinal use, not misuse.

Q4. Which example best illustrates drug misuse?

  • (A) Taking a prescribed painkiller exactly as directed for an injury
  • (B) Taking insulin as prescribed to control blood glucose
  • (C) Taking a drug in a harmful way or for a non-medical purpose
  • (D) Taking a vitamin supplement recommended by a doctor
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Answer: C – Misuse means harmful use or use for a non-medical purpose, rather than proper medicinal use.

Q5. Antibiotics are used for the treatment of which type of infection?

  • (A) Bacterial infections
  • (B) Viral infections only
  • (C) Fungal infections only
  • (D) Infections caused by a lack of vitamins
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Answer: A – Antibiotics are medicines used to treat bacterial infections.

Q6. How do antibiotics act on bacteria?

  • (A) They convert bacteria into viruses
  • (B) They kill bacteria
  • (C) They make bacteria grow faster
  • (D) They hide bacteria from the immune system
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Answer: B – Antibiotics kill bacteria, which is why they are effective against bacterial infections.

Q7. A patient has influenza, which is caused by a virus. What effect would an antibiotic have on the virus causing the illness?

  • (A) It would kill the virus immediately
  • (B) It would prevent the virus from spreading to other people
  • (C) It would turn the virus into harmless bacteria
  • (D) It would have no effect on the virus
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Answer: D – Antibiotics kill bacteria but do not affect viruses, so they cannot treat a viral illness such as influenza.

Q8. Which statement about antibiotics and viruses is correct?

  • (A) Antibiotics kill viruses more effectively than bacteria
  • (B) Antibiotics kill bacteria and viruses equally well
  • (C) Antibiotics kill bacteria but do not affect viruses
  • (D) Antibiotics have no effect on bacteria or viruses
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Answer: C – The action of antibiotics is on bacteria; viruses are not affected by them.

Q9. Why might a doctor decide not to prescribe an antibiotic for a common cold?

  • (A) Colds are caused by bacteria that antibiotics cannot reach because they hide inside body cells
  • (B) Colds are usually caused by viruses, which antibiotics do not affect
  • (C) Antibiotics would make the cold virus grow stronger directly
  • (D) Antibiotics are never prescribed for any illness
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Answer: B – Since a cold is viral, an antibiotic would not treat its cause.

Q10. A patient with a confirmed bacterial throat infection is prescribed an antibiotic. What is the expected action of the medicine?

  • (A) It kills the bacteria causing the infection
  • (B) It lowers the patient’s body temperature by stopping sweating
  • (C) It replaces the patient’s white blood cells
  • (D) It prevents all future infections of any kind
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Answer: A – In a bacterial infection, the antibiotic acts by killing the bacteria responsible.

Antibiotic Resistance

Q11. What is meant by antibiotic resistance in bacteria?

  • (A) Bacteria that can only survive inside a hospital
  • (B) Bacteria that are killed by every antibiotic, including antibiotics they have never been exposed to
  • (C) Bacteria that have changed into viruses
  • (D) Bacteria that are not killed by an antibiotic, so the antibiotic becomes less effective
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Answer: D – Some bacteria are resistant to antibiotics, which reduces the effectiveness of those antibiotics against them.

Q12. A doctor suspects a sore throat is viral and explains that an antibiotic would not help. Which reason best supports this decision?

  • (A) The antibiotic would have no effect on a virus
  • (B) The antibiotic would cure the virus but damage the throat
  • (C) The antibiotic would only work if taken with food
  • (D) The antibiotic would work, but too slowly to matter
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Answer: A – Antibiotics do not affect viruses, so prescribing one for a viral infection would not treat the cause.

Q13. Why does antibiotic resistance make a bacterial infection harder to treat?

  • (A) The resistant bacteria grow too large to see under a microscope or to be attacked by white cells
  • (B) The patient’s immune system stops working entirely
  • (C) Fewer antibiotics remain effective against the resistant bacteria
  • (D) The bacteria leave the body and cannot be found
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Answer: C – When bacteria resist an antibiotic, that medicine can no longer be relied on to kill them, narrowing treatment options.

Q14. MRSA is mentioned in the syllabus as an example of what?

  • (A) A virus that antibiotics can kill quickly and completely in every patient who is treated with them
  • (B) A resistant bacterium, such as one against which antibiotics have lost effectiveness
  • (C) A medicinal drug used to treat viruses
  • (D) A vitamin that prevents bacterial infection
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Answer: B – MRSA is given as an example of resistant bacteria, where antibiotic effectiveness is reduced.

Q15. How can using antibiotics only when essential help to limit the development of resistant bacteria?

  • (A) It makes all bacteria weaker immediately
  • (B) It prevents bacteria from ever entering the body by strengthening the skin and the mucous membranes against infection
  • (C) It replaces antibiotics with the immune system entirely
  • (D) It gives resistant bacteria fewer opportunities to survive and spread when antibiotics are used unnecessarily
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Answer: D – Limiting antibiotic use to essential cases reduces the chances for resistant bacteria to be selected and spread.


Q16. Which practice is most likely to encourage the development of antibiotic resistance in a population?

  • (A) Using antibiotics widely and unnecessarily, including for conditions they cannot treat
  • (B) Using antibiotics only when essential for bacterial infections, after checking what is causing the illness
  • (C) Avoiding antibiotics entirely, even for serious bacterial infections
  • (D) Testing whether an infection is bacterial before prescribing
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Answer: A – Unnecessary and widespread use increases the opportunities for resistant bacteria to survive and spread.

Q17. A student says antibiotics should be taken for every cough and cold, just in case. What is the best response?

  • (A) This is sensible, because antibiotics prevent all infections, including those caused by viruses and fungi
  • (B) This is sensible, because antibiotics kill viruses as well as bacteria
  • (C) This is unwise, because many coughs and colds are viral and unnecessary use encourages resistance
  • (D) This is unwise, because antibiotics cause coughs and colds
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Answer: C – Antibiotics do not affect viruses, and using them when they are not essential helps resistant bacteria develop.

Q18. Two patients have infections: one bacterial and one viral. For which patient is an antibiotic an appropriate treatment, and why?

  • (A) The viral patient, because antibiotics kill viruses
  • (B) The bacterial patient, because antibiotics kill bacteria
  • (C) Both patients, because antibiotics work on all microbes
  • (D) Neither patient, because antibiotics never kill any microbes
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Answer: B – Only the bacterial infection matches the action of antibiotics, which kill bacteria and do not affect viruses.

Q19. Over time, what is the likely result if antibiotics are used far more often than essential?

  • (A) Bacteria become easier to kill with every antibiotic, so infections become simpler to treat over time
  • (B) Viruses disappear from the population
  • (C) Antibiotics become effective against viruses too
  • (D) Resistant bacteria become more common, and antibiotics become less effective
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Answer: D – Repeated unnecessary use favours the survival and spread of resistant bacteria, reducing antibiotic effectiveness.

Q20. Why is it important to know whether an infection is bacterial or viral before prescribing an antibiotic?

  • (A) So the antibiotic can be given at exactly the right time of day for the best possible effect
  • (B) So the patient can be told to rest for longer
  • (C) So a stronger painkiller can be chosen instead
  • (D) Because the antibiotic will only help if bacteria are causing the infection
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Answer: D – Knowing the cause matters because an antibiotic only helps when bacteria are responsible; it will not treat a viral infection.

Drug Misuse: General Effects on the Body and Society

Q21. What is the general effect of a depressant drug on the nervous system?

  • (A) It has no effect on reaction speed at all, leaving coordination and judgement completely unchanged
  • (B) It improves coordination and judgement
  • (C) It slows down nervous activity, reactions and coordination
  • (D) It only affects the muscles, never the brain
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Answer: C – A depressant slows the nervous system, so reactions become slower and coordination and judgement are impaired.

Q22. Alcohol is described as a depressant. Which effect on behaviour follows from this?

  • (A) Faster reactions and sharper judgement
  • (B) Improved balance and steadier walking
  • (C) No change in how a person thinks or moves
  • (D) Slower reactions with impaired judgement and coordination
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Answer: D – As a depressant, alcohol slows reactions and impairs judgement and coordination, making tasks such as driving unsafe.

Q23. What is the general effect of a stimulant drug on the nervous system?

  • (A) It slows all nervous activity to a standstill
  • (B) It overstimulates the nervous system, increasing activity and alertness in a way that can become unsafe
  • (C) It blocks all signals between neurones permanently
  • (D) It has exactly the same effect as a depressant
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Answer: B – Stimulants overstimulate the nervous system, in contrast to depressants, which slow it down.

Q24. Which statement best describes addiction?

  • (A) A person feels unable to stop using a drug, even though it is causing harm
  • (B) A person uses a drug once and never thinks about it again
  • (C) A person takes a prescribed medicine exactly as directed
  • (D) A person avoids all medicines for the rest of their life
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Answer: A – Addiction means continued use that the person feels unable to stop, despite harmful effects.

Q25. What are withdrawal symptoms?

  • (A) Pleasant effects felt while a drug is working
  • (B) Symptoms of the original illness returning after treatment ends
  • (C) Unpleasant symptoms that can appear when a person stops using a drug they have become dependent on
  • (D) Side effects that only occur before a drug is first taken
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Answer: C – When use stops, a dependent person may experience withdrawal symptoms as the body adjusts.

Q26. Beyond harm to health, which social cost is linked to drug misuse?

  • (A) Improved performance at school and work
  • (B) Stronger family relationships in every case
  • (C) A reduced risk of accidents on the road
  • (D) Accidents, broken relationships and crime
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Answer: D – Drug misuse carries social costs as well as health costs, including accidents, damaged relationships and crime.

Q27. Why is driving after taking a depressant drug particularly unsafe?

  • (A) The driver becomes more alert than usual
  • (B) Slowed reactions and impaired judgement make it harder to respond to hazards in time
  • (C) The driver’s eyesight improves temporarily
  • (D) The car becomes harder to steer mechanically
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Answer: B – Driving needs fast reactions and sound judgement, both of which a depressant impairs.

Q28. What is the key difference between medicinal use and misuse of the same drug?

  • (A) Medicinal use treats or prevents illness at a suitable dose, while misuse is harmful use or use for a non-medical purpose
  • (B) Medicinal use always involves a larger dose than misuse
  • (C) Misuse is always safer than medicinal use
  • (D) There is no difference between the two
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Answer: A – Purpose and manner of use separate medicinal use from misuse, not the name of the substance alone.

Q29. What is meant by tolerance in the context of repeated drug misuse?

  • (A) The body becomes completely immune to all drugs
  • (B) A person no longer needs any medical treatment
  • (C) A larger dose is needed over time to produce the same effect
  • (D) The drug stops having any effect on the first use
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Answer: C – With repeated misuse, tolerance can develop, so a larger dose may be taken to achieve the same effect.

Q30. Which long-term health effect is linked to heavy alcohol use?

  • (A) Improved liver function over time
  • (B) Damage to the liver
  • (C) No lasting effect on any organ
  • (D) Stronger coordination and faster reactions
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Answer: B – Long-term heavy alcohol use damages the liver, in addition to its short-term depressant effects.

Revisit any questions you missed, especially why antibiotics do not treat viruses and how essential-only use limits resistance.