Pharmacology Vocabulary in English
20 essential pharmacology words with definitions and example sentences — medicines, dosage, and drug safety for B1–C1 ESL learners.
Pharmacology vocabulary is vital for anyone studying medicine, training as a pharmacist, or simply trying to understand the leaflet inside a packet of tablets. These words appear on prescriptions, on the labels of medicines bought from a chemist, and in conversations with doctors and pharmacists. For B1 to C1 learners, knowing this vocabulary helps you take medicines safely and discuss treatment with confidence.
This page covers 20 key pharmacology words and phrases that you will meet in real situations — reading the recommended dosage on a label, collecting a repeat prescription, or asking the pharmacist about a possible side effect. Each term comes with a clear definition and a natural British example sentence so you can see exactly how it is used in context.
If you would like to broaden your medical English, take a look at our related Health vocabulary, Medical Procedures vocabulary, and Immunology vocabulary pages. Together, these lists give you the confidence to handle pharmacy visits, doctor's appointments, and medicine labels in English.
Word List
| Word / Phrase | Meaning | Example Sentence |
|---|---|---|
| medication | a medicine or drug used to treat, prevent, or relieve a medical condition | The doctor reviewed all the medication she was taking before adding a new tablet. |
| prescription | a written instruction from a doctor allowing a patient to collect a particular medicine from a pharmacy | He took his prescription to the chemist and collected his tablets within an hour. |
| dosage | the amount and frequency of a medicine that a patient should take | Always follow the dosage printed on the label and never take more than instructed. |
| dose | a single measured quantity of a medicine taken at one time | She missed her morning dose and took it as soon as she remembered. |
| side effect | an unwanted effect caused by a medicine in addition to its intended benefit | A common side effect of this antibiotic is mild nausea during the first few days. |
| contraindication | a reason why a particular medicine or treatment should not be used in a given patient | Pregnancy is listed as a contraindication for this drug on the patient leaflet. |
| adverse reaction | a harmful and unintended response to a medicine taken at a normal dose | The patient developed a rash, which the pharmacist recorded as an adverse reaction. |
| active ingredient | the substance in a medicine that produces its therapeutic effect | The active ingredient in this painkiller is paracetamol. |
| generic drug | a medicine sold under its chemical name rather than a brand name, usually cheaper but equally effective | The pharmacist offered a generic drug that works exactly like the branded version. |
| over-the-counter | describing medicines that can be bought without a prescription | You can buy these hay-fever tablets over-the-counter at any pharmacy. |
| interaction | the way two or more medicines affect each other when taken together, sometimes harmfully | The pharmacist warned him about a dangerous interaction between the two drugs. |
| efficacy | the ability of a medicine to produce the intended result under ideal conditions | Clinical trials measured the efficacy of the new vaccine over six months. |
| placebo | a substance with no active medicine, used in trials to compare against a real treatment | Half of the volunteers were given a placebo instead of the test drug. |
| tolerance | a reduced response to a medicine after repeated use, so a larger dose is needed for the same effect | Patients can build up a tolerance to strong painkillers over many months. |
| indication | a medical condition for which a particular medicine is officially recommended | The main indication for this drug is high blood pressure. |
| antibiotic | a medicine that kills bacteria or stops them growing, used to treat infections | The GP prescribed a course of antibiotic tablets for the chest infection. |
| analgesic | a medicine that relieves pain; a painkiller | She took a mild analgesic to ease the headache before the meeting. |
| pharmacist | a trained professional who prepares and dispenses medicines and advises patients on their use | The pharmacist explained how often to take the tablets and what to avoid. |
| half-life | the time it takes for the amount of a drug in the body to fall to half its original level | This medicine has a short half-life, so it must be taken three times a day. |
| absorption | the process by which a medicine passes from the gut or skin into the bloodstream | Taking the tablet with food can slow its absorption into the body. |
Practice These Words
Flash Cards
Review pharmacology vocabulary with spaced repetition
Wordsearch
Find pharmacology words hidden in the grid
Quiz
Test your pharmacology vocabulary knowledge
Practice What You've Learned
LexFizz has 30 free interactive exercises — no sign-up needed.
Browse All Exercises →Related Vocabulary Topics
Frequently Asked Questions
What is the difference between a dose and a dosage?
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.
What is a side effect, and how is it different from an adverse reaction?
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.
What does contraindication mean?
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.
What is the difference between a prescription and an over-the-counter medicine?
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.
What is a generic drug?
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.
What is a drug interaction?
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.
What is the difference between an antibiotic and an analgesic?
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.
What does the half-life of a drug tell us?
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.
Why are placebos used in drug trials?
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.
What is the best way to learn pharmacology vocabulary?
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.