Chapter 15: Medicines optimization: ensuring quality and safety
Skip chapter table of contents and go to main content
Definitions
Medicinal products and medical devices
The definition of a medicine is:
- any substance or combination of substances presented as having properties for treating or preventing disease in human beings; or
- any substance or combination of substances that may be used in or administered to human beings with a view to either (a) restoring, correcting or modifying physiological functions by exerting a pharmacological, immunological or metabolic action, or (b) making a medical diagnosis (Human Medicines Regulations [133]).
The definition of a medical device is any instrument, apparatus, appliance, material or other article, whether used alone or in combination, including the software necessary for its proper application, intended by the manufacturer to be used for human beings for the purpose of:
- diagnosis, prevention, monitoring, treatment or alleviation of disease
- diagnosis, monitoring, treatment, alleviation of or compensation for an injury or handicap
- investigation, replacement or modification of the anatomy or of a physiological process.
Additionally, such devices must not achieve their principal intended action in or on the human body by pharmacological, immunological or metabolic means, but may be assisted in their function by such means.
There are three main types of medical device that incorporate or are used to administer a medicinal product:
- devices that are used to administer medicinal products (e.g. medicine spoons, oral syringes or droppers)
- devices for administering medicinal products where the device and the medicinal product form a single integral product designed to be used exclusively in the given combination and that are not reusable or refillable (e.g. pre‐filled syringes or eye drop containers)
- devices incorporating, as an integral part, a substance that, if used separately, may be considered to be a medicinal product and that is such that the substance is liable to act upon the body with action ancillary to that of the device (e.g. wound dressings with antimicrobial agents) (Council of the European Communities [46]).
Pharmacology
Several terms are relevant to pharmacology:
- Pharmacology can be defined as the study of the effects of drugs on the function of living systems. Its purpose is to understand what drugs do to living organisms and, more practically, how their effects can be applied to the treatment of diseases (Rang et al. [294]).
- Pharmacokinetics looks at the absorption, distribution, metabolism and excretion of drugs within the body (i.e. what the body does to the drugs). When these four factors are considered alongside the dose of the drug given, the concentration of the drug in the body over a period of time can be determined. Pharmacokinetics is most useful when considered with pharmacodynamics, which is the study of the mechanisms of action of drugs and other biochemical and physiological effects (i.e. what the drug does to the body) (Rang et al. [294]).
- The indication for a drug refers to the use of that drug for treating a particular disease. Drugs often have more than one indication, which means that there is more than one disease for which they can be used. Indications may be diagnostic, prophylactic or for therapeutic purposes. The licensed indication(s) for a medicinal product are the indication(s) that have been approved by the medicines regulator, which in the UK is the Medicines and Healthcare products Regulatory Agency (MHRA). This means the product has a current marketing authorization – that is, it can be marketed, advertised and supplied for that/those indications.
- A contraindication to a medicine is a specific situation in which a medicine should not be used, because it may be harmful to the patient. This could be due to the patient's allergy status, co‐morbidities, current disease state or other medicines they are taking.
- A drug interaction occurs when a substance (e.g. another medicine or food) affects the activity of a drug when both are administered together. This action can be synergistic (when the drug's effect is increased) or antagonistic (when the drug's effect is decreased) or a new effect can be produced that neither substance produces on its own. Interactions between drugs are termed ‘drug–drug interactions’ and interactions between drugs and foods are known as ‘drug–food interactions’ (Medicines Complete [195]). It is important not to forget over‐the‐counter, herbal and complementary medicines when considering potential interactions.
- Side‐effects of a medicine are defined by Aronson ([13]) as any effects that are in addition to its intended primary effect that can be harmful, unpleasant or in some cases beneficial to the patient. Harmful or unpleasant side‐effects are more commonly described as ‘adverse drug reactions’ (Aronson [13]).
