Medicines Health Dictionary

Medicines are drugs made stable, palatable and acceptable for administration. In Britain, the Medicines Act 1968 controls the making, advertising and selling of substances used for ‘medicinal purposes’, which means diagnosing, preventing or treating disease, or altering a function of the body. Permission to market a medicine has to be obtained from the government through the MEDICINES CONTROL AGENCY, or from the European Commission through the European Medicines Evaluation Agency. It takes the form of a Marketing Authorisation (formerly called a Product Licence), and the uses to which the medicine can be put are laid out in the Summary of Product Characteristics (which used to be called the Product Data Sheet).

There are three main categories of licensed medicinal product. Drugs in small quantities can, if they are perceived to be safe, be licensed for general sale (GSL – general sales list), and may then be sold in any retail shop. P (pharmacy-only) medicines can be sold from a registered pharmacy by or under the supervision of a pharmacist (see PHARMACISTS); no prescription is needed. P and GSL medicines are together known as OTCs – that is, ‘over-thecounter medicines’. POM (prescription-only medicines) can only be obtained from a registered pharmacy on the prescription of a doctor or dentist. As more information is gathered on the safety of drugs, and more emphasis put on individual responsibility for health, there is a trend towards allowing drugs that were once POM to be more widely available as P medicines. Examples include HYDROCORTISONE 1 per cent cream for skin rashes, CIMETIDINE for indigestion, and ACICLOVIR for cold sores. Care is needed to avoid taking a P medicine that might alter the actions of another medicine taken with it, or that might be unsuitable for other reasons. Patients should read the patient-information lea?et, and seek the pharmacist’s advice if they have any doubt about the information. They should tell their pharmacist or doctor if the medicine results in any unexpected effects.

Potentially dangerous drugs are preparations referred to under the Misuse of Drugs Act 1971 and subsequent regulations approved in 1985. Described as CONTROLLED DRUGS, these include such preparations as COCAINE, MORPHINE, DIAMORPHINE, LSD (see LYSERGIC ACID

DIETHYLAMIDE (LSD)), PETHIDINE HYDROCHLORIDE, AMPHETAMINES, BARBITURATES and most BENZODIAZEPINES.

Naming of drugs A European Community Directive (92/27/EEC) requires the use of the Recommended International Non-proprietary Name (rINN) for medicinal substances. For most of these the British Approved Name (BAN) and rINN were identical; where the two were di?erent, the BAN has been modi?ed in line with the rINN. Doctors and other authorised subscribers are advised to write titles of drugs and preparations in full because uno?cial abbreviations may be misinterpreted. Where a drug or preparation has a non-proprietary (generic) title, this should be used in prescribing unless there is a genuine problem over the bioavailability properties of a proprietary drug and its generic equivalent.

Where proprietary – commercially registered

– names exist, they may in general be used only for products supplied by the trademark owners. Countries outside the European Union have their own regulations for the naming of medicines.

Methods of administration The ways in which drugs are given are increasingly ingenious. Most are still given by mouth; some oral preparations (‘slow release’ or ‘controlled release’ preparations) are designed to release their contents slowly into the gut, to maintain the action of the drug.

Buccal preparations are allowed to dissolve in the mouth, and sublingual ones are dissolved under the tongue. The other end of the gastrointestinal tract can also absorb drugs: suppositories inserted in the rectum can be used for their local actions – for example, as laxatives – or to allow absorption when taking the drug by mouth is di?cult or impossible – for example, during a convulsion, or when vomiting.

Small amounts of drug can be absorbed through the intact skin, and for very potent drugs like OESTROGENS (female sex hormones) or the anti-anginal drug GLYCERYL TRINITRATE, a drug-releasing ‘patch’ can be used. Drugs can be inhaled into the lungs as a ?ne powder to treat or prevent ASTHMA attacks. They can also be dispersed (‘nebulised’) as a ?ne mist which can be administered with compressed air or oxygen. Spraying a drug into the nostril, so that it can be absorbed through the lining of the nose into the bloodstream, can avoid destruction of the drug in the stomach. This route is used for a small number of drugs like antidiuretic hormone (see VASOPRESSIN).

Injection remains an important route of administering drugs both locally (for example, into joints or into the eyeball), and into the bloodstream. For this latter purpose, drugs can be given under the skin – that is, subcutaneously (s.c. – also called hypodermic injection); into muscle – intramuscularly (i.m.); or into a vein – intravenously (i.v.). Oily or crystalline preparations of drugs injected subcutaneously form a ‘depot’ from which they are absorbed only slowly into the blood. The action of drugs such as TESTOSTERONE and INSULIN can be prolonged by using such preparations, which also allow contraceptive ‘implants’ that work for some months (see CONTRACEPTION).