7. Glossary of terms


Any use of an illegal drug or use of a medicine for a non-therapeutic purpose (eg to alter state of consciousness or to seek a ‘high’)


Addiction is compulsive substance-seeking behaviour, sometimes also termed ‘substance abuse’; it can involve impaired control over drug use, craving, compulsive use, and continued use despite harm from the substance. Addiction, which can involve genetic, psychosocial and environmental factors, is quite distinct from physical and psychological dependence.


A chemical substance that binds to a receptor and mimics the effect of the physiological (endogenous) substance binding to the receptor


A substance that binds to a receptor but produces no effect and inhibits an agonist from binding to the receptor.

Anticholinergic effects

SeeAntimuscarinic effects—most anticholinergic effects involve the muscarinic receptor for acetylcholine

Antimuscarinic effects

Reduction or blocking of the effects of parasympathetic nerves; antimuscarinic effects include dry mouth, difficulty swallowing, blurred vision, confusion, palpitations, constipation, and urine retention


Class of medicines which have a sedating effect, most often used for anxiety and insomnia, but also used for muscle relaxation, managing convulsions, and as premedication for surgery and certain procedures. The class includes: chlordiazepoxide, diazepam, flurazepam, lorazepam, midazolam, nitrazepam, oxazepam, and tempazepam


Narrowing of the airways (bronchioles), reducing the flow of air into the lungs; asthma is characterised by bronchoconstriction


Dependence is a state that develops as a result of repeated use of a certain chemical substance (eg alcohol, benzodiazepine, opioid, or even medicines for reducing blood pressure). It represents the resetting of homeostasis because of the persisting presence of the chemical substance


Deliberate and unauthorised transfer of a controlled substance from legitimate supply chain or intended recipient


Feeling of dissatisfaction, anxiety and restlessness


Exaggerated sensitivity to a normally painful stimulus

Iatrogenic effect

An adverse effect which results from medical treatment


Partial or complete non-mechanical blockage of the small intestine, or large intestine, or both


The UK Medicines and Healthcare products Regulatory Agency is the government body responsible for regulating medicines and medical devices and equipment used in healthcare, and for investigating harmful incidents arising from the use of medicines or medical devices


Constriction of the pupil of the eye, often as a side-effect of certain drugs


Abnormal dilation of the pupil of the eye, often as a side-effect of certain drugs or because of disease


Brief, involuntary twitching of the muscles which may produce a spasmodic or jerking movement.


A substance that induces insensibility or stupor; the term is often used for opioids which have a potential for including dependence and addiction


A narcotic substance derived from the opium poppy


A substance that acts on the opioid receptor with similar effects to those of morphine. An opioid can be a substance that occurs naturally in the body (eg endorphins and enkephalins), or it can be derived from the opium poppy (ie an opiate), or it can be synthetic (eg methadone and pethidine)


The occurrence of two or more different forms of genetically determined entities (eg enzymes and receptors), due to variation in the genetic material between individuals

Prokinetic drug

A drug that increases gastrointestinal motility by promoting intestinal peristalsis


A chemical agent (or synapse) that produces its effects via the serotonin transmitter system.


Serotonin (also called 5-hydroxytryptamine) is a neurotransmitter in the brain. It also has activity on platelets, gastrointestinal system and on blood vessels

Serotonin syndrome

A potentially life-threatening medical emergency, characterised by excessive serotonin stimulation. This is usually the result of an overdose of a single serotonergic substance or the mixture and additive effect of several serotonergic substances. A variety of symptoms are produced (typically autonomic effects such as tachycardia and diarrhoea, somatic effects such as hyperreflexia and cognitive effects such as agitation). The effects may range from the mild to the extreme and potentially fatal.


Tolerance follows repetitive exposure to a drug, leading to a reduction of the pharmacological effect of that drug

Transdermal patch

An adhesive pad, containing a medicine, which, when affixed to the skin, releases the medicine at a controlled rate into the skin and thence into the bloodstream


Excessive urea and other waste products in the blood