A drug, also medicine and medication, is a chemical substance or complex of chemical substances with an intended pharmacological, immunological or metabolic effect on the (animal or human) body. The science of medicines is called pharmacy. The science of the effects of drugs in the human body (human) pharmacology. Prescribing drugs is also known as pharmacotherapy or drug therapy. Many medicines have a vegetable, animal or other biological origin such as the alkaloids, certain insulins or penicillins respectively, but most are made synthetically today. For practical reasons, raw materials of vegetable or animal origin are often used as starting materials for the synthesis of medicines.
According to the definition in the Dutch Medicines Act, a medicine does not always have to cure, and it also includes, for example, diagnostic agents and agents that are used preventively (prophylactically). For example, the following products fall under the definition of medicinal product:
medicines with a therapeutic (healing) effect - for example an antibiotic,
agents with a prophylactic (preventive) effect - for example an antimalarial drug.
drugs that serve to make a diagnosis - for example, eye drops that are used by the ophthalmologist during consultation hours,
agents that serve to restore, improve or modify physiological functions in humans - for example, a drug used in diabetes, high cholesterol or high blood pressure. In practice, compared to the total amount of available drugs, there are , only a very limited number have a curative effect and the vast majority of drugs have no curative effect, but are used to influence physiological functions.
Medicines can be classified in many ways: for example, common methods are
by therapeutic purpose, for example preventive means;
by therapeutic effect, for example antihypertensive agents;
to organ systems of the human body;
by chemical structure, for example benzodiazepines;
by mode of action, e.g. substitution;
by mode of action or mechanism of action, for example alkylating agents;
by origin, for example digitalis glycosides;
to rules on provision, for example Opium Act drugs;
by route of administration, for example suppositories;
by release form, for example capsules or tablets;
by duration of action, for example long-acting sleeping pills;
according to the way they are removed from the body, for example substances with renal clearance. A classification that is widely used internationally is the ATC/DDD classification. ATC stands for Anatomical Therapeutic Chemical. This classification is given by the World Health Organization in Norway. An ATC code for a medicine consists of 7 letters/numbers, divided into 5 levels.
For example, the drug Metformin (a drug for diabetes) is classified as follows:
A - Gastrointestinal Tract and Metabolism (Level 1: Main Anatomical Group)
A10 - drugs used in diabetes (level 2: therapeutic subgroup)
A10B - oral hypoglycaemic drugs (level 3: pharmacological subgroup)
A10BA - biguanides (level 4: chemical subgroup)
A10BA02 - metformin (level 5: chemical name)
Classification by therapeutic target
Causal therapy: fighting the cause of a disease.
Symptomatic therapy: combating the consequences of a disease.
Palliative therapy: relieving pain (healing is not a goal, often in terminal patients)
Preventive therapy: preventing a disease.
Diagnostic administration: the administration of a substance with the aim of finding out which condition the patient is suffering from or which is the cause of the condition.