CLINICAL PHARMACOLOGY 2003 (PART 8)

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CLINICAL PHARMACOLOGY 2003 (PART 8)

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In any science there are two basic requirements — classification and nomenclature (names): • Classification: drugs cannot be classified and named according to a single rational system because the requirements of chemists, pharmacologists, and doctors differ. • Nomenclature: nor is it practicable always to present each drug under a single name because the formulations in which they are presented as prescribable medicines may vary widely and commercial considerations are too often paramount. Generic (nonproprietary) names should be used as far as possible when prescribing except where pharmaceutical bioavailability differences have overriding importance. ...

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  1. 6 Classification and naming of drugs SYNOPSIS Drugs may be classified by: In any science there are two basic • Body system, e.g. alimentary, cardiovascular requirements — classification and • Therapeutic use, e.g. receptor blockers, enzyme nomenclature (names): inhibitors, carrier molecules, ion channels • Mode or site of action • Classification: drugs cannot be classified and — molecular interaction, e.g. glucoside, alkaloid, named according to a single rational system steroid. because the requirements of chemists, — cellular site, e.g. loop diuretic, catecholamine pharmacologists, and doctors differ. uptake inhibitor (imipramine) • Nomenclature: nor is it practicable always to • Molecular structure, e.g. glycoside, alkaloid, present each drug under a single name steroid.1 because the formulations in which they are presented as prescribable medicines may vary widely and commercial considerations are too often paramount. Nomenclature (names) Generic (nonproprietary) names should be used as far as possible when prescribing except Any drug may have names in all three of the where pharmaceutical bioavailability differences following classes: have overriding importance. 1. The full chemical name 2. A nonproprietary (official, approved, generic) name used in pharmacopoeias and chosen by official bodies; the World Health Organization (WHO) chooses recommended International Classification Nonproprietary Names (rINN). The harmonisation of names began 50 years ago, and It is evident from the way this book is organised 1 that there is no homogeneous system for classifying The ATC Classification System developed by the Nordic drugs that suits the purpose of every user. Drugs countries and widely used in Europe meets most classification requirements. Drugs are classified according to are commonly categorised according to the con- their Anatomical, Therapeutic and Chemical characteristics venience of who is discussing them: clinicians, into five levels of specificity, the fifth being that for the single pharmacologists or medicinal chemists. chemical substance. 83
  2. 6 CLASSIFICATION AND NAMING OF DRUGS most countries have used rINNs for many years. from confusion with existing names, both The USA is an exception, but even here most nonproprietary and proprietary, and the USA National Names are the same as their rINN desirability of indicating relationships between counterparts. In the UK, the British Approved similar substances.3 Name (BAN) system is being progressively The generic names diazepam, nitrazepam, flur- modified such that the rINN name is adopted; in azepam are all of benzodiazepines. Their pro- many cases this involves only a trivial change. prietary names are Valium, Mogadon and Dalmane In a few cases, there is cause for concern that respectively. Names ending in -olol are adrenoceptor change of name could lead to confusion and blockers; in -pril are ACE-inhibitors; in -floxacin are constitute a public health risk, e.g. adrenaline is quinolone antimicrobials. the BAN, epinephrine is the rINN name. In such Any pharmaceutical company may manufacture instances, both rINN and BAN must currently a drug that has a well-established use and is no appear in the manufacturer's literature. In longer under patent restriction, in accordance with general we use rINNs in this book and aim to official pharmacopoeial quality criteria, and may minimise some unavoidable differences with, apply to the regulatory authority for a licence to where appropriate, alternative names in the text market. The task of authority is to ensure that these and index. generic or multisource pharmaceuticals are inter- 3. A proprietary (brand) name that is the commercial changeable, i.e. they are pharmaceutically and bio- property of a pharmaceutical company or logically equivalent, so that a formulation from one companies. source will be absorbed and give the same blood concentrations and have the same therapeutic efficacy as that from another. (Further formal therapeutic 1. 3-( 10, 11 -dihydro-5H-dibenz [b.f]-azepin-5-yl) trials are not demanded for these well-established propyldimethylamine drugs.) A prescription for a generic drug formulation 2. imipramine may be filled for any officially licensed product that 3. Tofranil (UK), Prodepress, Surplix, Deprinol.etc the dispensing pharmacy has chosen to purchase (on (various countries) economic criteria, see 'generic substitution' below).4 The proprietary name is a trade mark applied to In this book proprietary names are distinguished by particular formulation(s) of a particular substance an initial capital letter. by a particular manufacturer. Manufacture is con- fined to the owner of the trade mark or to others The full chemical name describes the compound licensed by the owner. It is designed to maximise for chemists. It is obviously unsuitable for prescribing. the difference between the names of similar drugs marketed by rivals for obvious commercial reasons. A nonproprietary (generic,2 approved) name is To add confusion, some companies give their pro- given by an official (pharmacopoeia) agency, e.g. prietary products the same names as their generic WHO. products in an attempt to capture the prescription Three principles remain supreme and market, both proprietary and generic, and some unchallenged in importance: the need for market lower-priced generics of their own pro- distinction in sound and spelling, especially when prietaries. When a prescription is written for a the name is handwritten; the need for freedom proprietary product, pharmacists under UK law must dispense that product only. But by agreement 2 The generic name is now widely accepted as being 3 synonymous with the nonproprietary name. Strictly 'generic' R B Trigg 1998 Chemical Nomenclature. Kluwer Academic, (L. genus, race, a class of objects) should refer to a group or Dorerechat, pp 208-234. 4 class of drug, e.g. benzodiazepines, but by common usage EU Medicines Evaluation Agency and USA Food and Drug the word is now taken to mean the nonproprietary name of Agency guidelines are available that give pharmacokinetic individual members of a group, e,g, diazepam. limits that must be met. 84
  3. NOM ENCLATURE 6 with the prescribing doctor, they may substitute an the ingredients, so proprietary names are used in approved generic product (generic substitution). many cases, there being no alternative. What is not permitted is the substitution of a International travellers with chronic illnesses different molecular structure deemed to be pharma- will be grateful for recommended International cologically and therapeutically equivalent (therapeutic Nonproprietary Names (above) as proprietary names substitution). often differ from country to country. The reasons are linguistic as well as commercial (see below). NONPROPRIETARY NAMES The principal reasons for advocating the habitual PROPRIETARY NAMES use of nonproprietary (generic) names in prescribing are: The principal noncommercial reason for advocating the use of propritary names in prescribing is Clarity: because it gives information of the class of consistency of the product, so that problems of drug e.g. nortriptyline and amitriptyline are plainly quality, especially of bioavailability, are reduced. related, but their proprietary names Allegron and There is substance in this argument, though it is Lentizol are not. It is not unknown for prescribers, often exaggerated. when one drug has failed, unwittingly to add or It is reasonable to use proprietary names when substitute another drug of the same group (or even dosage, and therefore pharmaceutical bioavailability, the same drug) thinking that different proprietary are critical so that small variations in the amount of names must mean different classes of drugs. Such drug available for absorption can have big effects occurrences underline the wisdom of prescribing on the patient, e.g. drugs with low therapeutic ratio, generically, so group similarities are immediately digoxin, hormone replacement therapy, adreno- apparent, but point up the requirement of brand cortical steroids (oral), antiepileptics, cardiac anti- names to be as distinct from each other as possible. arrhythmics, warfarin. Also, with the introduction Relationships cannot and should not be shown by of complex formulations, e.g. sustained-release, it is brand names. important clearly to identify these, and use of proprietary names has a role. Economy: drugs sold under nonproprietary names The pharmaceutical industry regards freedom to are usually, but not always, cheaper than those sold market proprietary names and to advertise or, as it under proprietary names. calls the latter, to 'effectively [bring] to the notice of the medical profession', as two of the essentials of Convenience: pharmacists may supply whatever the 'process of discovery in a vigorous competitive version they stock5 whereas if a proprietary name is environment'.7 used they are obliged to supply that preparation The present situation is that industry spends an alone. They may have to buy in the preparation enormous amount of money promoting its many named even though they have an equivalent in names for the same article, and the community, as stock. Mixtures of drugs are sometimes given non- represented in the UK by the Department of Health, proprietary names, having the prefix co- to indicate spends a small sum trying to persuade doctors to more than one active ingredient, e.g. co-amoxiclav use nonproprietary names. Ordinary doctors who for Augmentin, but many are not because they exist prescribe for their ordinary patients are the targets for commercial advantage rather than for therapeutic of both sides. need.6 No prescriber can be expected to write out This state of affairs is confusing for prescribers. Generic names are intentionally longer than trade 5 names to minimise the risk of confusion, but the use This can result in supply of a formulation of appearance of accepted prefixes and stems for generic names different from that previously used. Patients naturally find this disturbing. 6 7 This is a practice largely confined to the UK. It is unknown Annual Report, 1963-1964. Association of the British in Europe, and not widely practised in the USA. Pharmaceutical Industry. 85
  4. 6 CLASSIFICATION AND NAMING OF DRUGS works well and the average name length is four remarkably narrow, and once the decision is taken syllables, which is manageable. to "think generic" surely the effort required is The search for proprietary names is a 'major small'.10 And, we would add, worthwhile. problem' for pharmaceutical companies, increasing, as they are, their output of new preparations. A Confusing names. The need for both clear thought company may average 30 new preparations (not and clear handwriting is shown by medicines of new chemical entities) a year, another warning of totally different class that have similar names. the urgent necessity for the doctor to cultivate a Serious events have occurred due to confusion of sceptical habit of mind. names and dispensing the wrong drug, e.g. Lasix The names that 'look and sound medically (frusemide) for Losec (omeprazole) (death); AXT seductive' are being picked out. 'Words that survive (intending zidovudine) was misinterpreted in the scrutiny will go into a stock-pile and await inexorable pharmacy and azathiorine was dispensed [do proliferation of new drugs'.8'9 not use abbreviations for drug names]; Daonil One firm (in the USA) commissioned a computer (glibenclamide) for De-nol (bismuth chelate) and for to produce a dictionary of 42 000 nonsense words of Danol (danazol). It will be noted that nonproprietary an appropriate scientific look and sound. An official names are less likely to be confused with other said, classes of drugs. Thinking up names has been driving us cuckoo around here ... proper chemical names are hopeless for trade purposes, of course. ... Doctors GUIDETO FURTHER READING are the market we shoot for. A good trade name carries a lot of weight with doctors ... they're more Aronson J K 2000 'Where name and image meet' — apt to write a prescription for a drug whose name the argument for 'adrenaline'. British Medical is short, and easy to spell and pronounce, but has Journal 320: 506-509 an impressive medical ring. ... We believe there are Controversies in therapeutics 1988 The cases for and enough brand new words in this dictionary to keep against prescribing genetic drugs. British Medical us going for years. ... We don't yet know what Journal 297: (Collier J Generic prescribing benefits proportion of names is unpronounceable ... how patients) 1596 (Cruickshank J M Don't take many are obscene, either in English or in other innovative research-based pharmaceutical languages, and how many are objectionable on companies for granted) 1597 grounds of good taste: 'Godamycin' would be a Furberg C D, Herrington D M, Psaty B M 1999 Are mild example.9 drugs within a class interchangeable? Lancet 354: 1201-1204 (and correspondence Lancet 2000 355: For the practising doctor (in the UK) the British 316-317 National Formulary provides a regularly updated George C F 1996 Naming of drugs: pass the and comprehensive list of drugs in their non- epinephrine please. British Medical Journal 312: proprietary (generic) and proprietary names. 'The 1315 (and correspondence British Medical Journal range of drugs prescribed by any individual is 1996 313: 688-689) Jack D B, Soppitt A J 1991 Give a drug a bad name. 8 Pharmaceutical companies increasingly operate worldwide British Medical Journal 303:1606 and are liable to find themselves embarrassed by Taussig H B 1963 The evils of camouflage as unanticipated verbal associations. For example, names illustrated by thalidomide. New England Journal marketed (in some countries) such as Bumaflex, Kriplex, of Medicine 180: 92, Editorial, p. 108 Nokhel and Snootie conjure up in the minds of native English-speakers associations that may inhibit both doctors and patients from using them (see Jack and Soppitt in Guide to Further Reading). 9 New Yorker, 14 July 1956. 10 Editorial 1977 British Medical Journal 4: 980 and subsequent correspondence. 86
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