Pharmacology Vocabulary in English

A dose is a single measured quantity of a medicine that you take at one time, such as one tablet or 5 millilitres of liquid. A dosage is broader: it describes the whole pattern of taking the medicine, including how much, how often, and for how long. For example, "one 500 mg tablet" is a dose, while "one 500 mg tablet every six hours for five days" is the dosage. Always read the dosage instructions on the label carefully, because taking too much can be harmful.

A side effect is any effect of a medicine other than the one you want, and it can be mild and even expected, such as feeling slightly drowsy. An adverse reaction is a harmful, unintended response that happens at a normal dose, such as a serious rash or breathing difficulty. In short, all adverse reactions are side effects, but not all side effects are harmful. If you notice a worrying reaction, you should stop and speak to a pharmacist or doctor straight away.

A contraindication is a specific reason why a particular medicine should not be given to a patient, because it could cause harm. For example, a drug might be contraindicated during pregnancy, in people with kidney problems, or alongside another medicine it interacts badly with. Patient information leaflets list contraindications so that doctors and pharmacists can decide whether a medicine is safe for you. Always tell your pharmacist about other conditions and medicines, as this helps them spot any contraindication.

A prescription medicine can only be supplied with written authorisation from a doctor or other prescriber, because it needs medical supervision. An over-the-counter medicine can be bought directly from a pharmacy or shop without a prescription, such as paracetamol or hay-fever tablets. Prescription-only medicines are usually stronger or carry greater risks, while over-the-counter medicines are considered safe for people to choose for minor problems, although the pharmacist can still offer advice.

A generic drug is a medicine sold under its chemical name rather than a brand name. Once a company's patent expires, other manufacturers can make the same medicine, which usually makes it much cheaper. A generic drug contains the same active ingredient at the same strength as the branded version and works in the same way. In the UK, the NHS often dispenses generic drugs to keep costs down, and they are just as safe and effective as branded medicines.

A drug interaction happens when one medicine changes the way another medicine works, or when food, drink, or a health condition affects a medicine. Some interactions make a drug less effective, while others increase the risk of harmful side effects. This is why it is important to tell your pharmacist about everything you take, including supplements and over-the-counter medicines. The pharmacist can then check for any dangerous interaction before you start a new treatment.

An antibiotic is a medicine that kills bacteria or stops them from growing, so it is used to treat bacterial infections such as a chest or urine infection. An analgesic is a painkiller, used to relieve pain from headaches, injuries, or illness. The two do very different jobs: an antibiotic targets the cause of an infection, while an analgesic only eases the symptom of pain. Antibiotics do not work against viruses such as colds, which is why doctors do not prescribe them for every illness.

The half-life is the time it takes for the amount of a drug in the body to fall to half its original level. It helps doctors decide how often a medicine should be taken. A drug with a short half-life leaves the body quickly, so it may need to be taken several times a day to keep the level steady. A drug with a long half-life stays in the body longer and may only need to be taken once a day, which can make it easier to follow the dosage correctly.

A placebo is a dummy treatment that looks like the real medicine but contains no active ingredient. In a clinical trial, some volunteers receive the real drug while others receive a placebo, and neither group knows which they are taking. This lets researchers compare the two and measure the true efficacy of the medicine, separating its real effect from people simply feeling better because they expect to. Without a placebo group, it would be hard to tell whether a new drug actually works.

The most effective way is to connect each word to a real situation. When you read a medicine label, notice the words for the dosage, the active ingredient, and any listed side effects. When you collect a prescription, listen to how the pharmacist uses these terms. Practise the 20 words on this page with Flash Cards on LexFizz, then test yourself with the Quiz. Linking the vocabulary to tasks you actually do, such as taking a tablet at the right time, helps the words stick far faster than memorising a list.