A medicine that cures an infection and a substance that damages your lungs can both be called drugs. In biology a drug has a precise meaning, and the same molecule can heal or harm depending on how it is used. This topic looks at useful drugs like antibiotics, the growing problem of resistance, and the serious effects of two widely used legal drugs – alcohol and the chemicals in tobacco smoke.
A drug is any substance taken into the body that modifies or affects chemical reactions in the body. This definition covers helpful medicines as well as harmful or addictive substances.
The key idea is that drugs change how the body works at a chemical level – the effect may be beneficial, harmful, or both.
Antibiotics are drugs that kill bacteria or stop them growing, used to treat bacterial infections. They do not work against viruses, so they cannot cure illnesses like the common cold or flu.
To slow this, patients should complete the full course of antibiotics and doctors should avoid prescribing them unnecessarily.
Two legal but harmful drugs are tested often in exams.
Smoking also damages the cilia and the alveoli, leading to bronchitis and emphysema and increasing the risk of coronary heart disease.
Practise exam-style questions on this topic.