Characteristics of drugs

Medicine in the Greek and Roman civilisations

In the Ancient Greek civilisation (1100–146 BC), the god Asclepius was considered to be the principal god of healing. He combined religion and healing in a temple setting, and his large family represented health or medical ideology. His wife Epione, for example, soothed pain; his daughter Hygeia, the goddess of health, represented the prevention of disease; and Panacea, another daughter, represented treatment. His large temple settings were used to treat both the rich and the poor to cure their illnesses.

Hippocrates (5th century BC) advanced the idea that disease results from natural causes and can be understood only through a study of natural laws and from careful diagnosis. He believed that health was due to a balance of four ‘humours’ ebbing and flowing in the body (blood, phlegm, black bile and yellow bile); hence we have the related terms sanguine, phlegmatic, bilious, choleric and melancholic. He realised that the body has healing powers, and saw the health-care provider’s role as assisting the recuperative process. His ‘doctrine of opposites’, i.e. the concept that opposites cure (cold treats fever, bleeding treats excess humours), was the basis of medicine for many hundreds of years and eventually held up advances in more accurate medical knowledge. Known today as the father of medicine, Hippocrates influenced the principles that control the practice of medicine today, including versions of the Hippocratic Oath that are still read at some medical graduation ceremonies (see Figure 1-1A and CIB 4-6).

Figure 1-1 Famous people from medical history: A Hippocrates; B Galen; C Hildegarde von Bingen; D Avicenna.

Medicine during the Roman Empire (about 100 BC to AD 400) was largely based on Greek traditions of herbal remedies and healing gods. The Romans introduced excellent public health measures, including water supplies and sanitation. Folk remedies included wound dressings of wine, vinegar, eggs, honey, worms and pig dung. Ephedra (ephedrine, a sympathomimetic agent) was used, with good pharmacological rationale, for asthma, cough and haemorrhage. Famous medical men during this era included Dioscorides, a military physician who published a text entitled De Materia Medica (On the Materials of Medicine) on the sources, preparation and uses of hundreds of medically useful natural remedies, including analgesics, antiseptics, emetics and laxatives. Celsus described the four cardinal signs of inflammation, and stressed the importance of moderation, exercise, knowledge of anatomy, and prevention of infection and haemorrhage. Galen of Pergamon (Figure 1-1B) wrote voluminously on medical, scientific, philosophical, ethical and religious issues and considered that bleeding (removal of large volumes of blood) was appropriate treatment for virtually all disorders, as they were all due to an excess of a humour in the body. Galen was famous for his knowledge of drugs, both ‘simples’, i.e. simple herbal or mineral remedies, and complex mixtures that might include exotic herbs, amulets, excrement and antidotes, which came to be known as ‘galenicals’.

The Dark Ages and mediaeval times

The fall of the Roman Empire marked the beginning of the mediaeval period (400–1500 AD). Constantinople (now Istanbul) became the eastern capital of the Byzantine Empire, while the West sank into the Dark Ages as barbarians overran Western Europe. The practice of medicine reverted to folklore and tradition similar to that of the Greeks before Hippocrates. During this time, Christian religious orders built monasteries that became sites for learning, including pharmacy and medicine. They aided the sick and needy with food, rest and herbal medicines from their monastery gardens. Learning was carried out in Latin, and libraries held versions of Greek, Roman and Arabic medical texts. Medicine was a combination of both spiritual methods (prayer, exorcism, trust in relics of the saints) and physical methods (diet, drugs, bleeding and surgery).

One of the most famous women of the Middle Ages, Hildegard of Bingen, was a remarkable writer, composer, prophet, healer and abbess (Figure 1-1C). Her books described the causes of many mental and physical diseases, and medical and toxic properties of herbal, animal and mineral preparations. It is thought that her visions were probably due to the migraines from which she suffered. In some countries, women at this period were allowed to practise medicine and midwifery.

Hospitals have been called the greatest medical innovation of the Middle Ages. They were generally hospices attached to monasteries and had multiple purposes, providing religious, nursing and charitable care and also acting as leper houses. Particular saints were attributed the power to heal specific diseases, e.g. St Anthony and ergotism (see CIB 38-4), so a pilgrimage to the appropriate shrine was believed to help cure the condition. Battle wounds always provided a need for surgical and medical care, as victims usually succumbed to infection, haemorrhage or shock. The soporific (sleepinducing) and analgesic effects of the herbs poppy, henbane and mandrake were known and valued; a ‘soporific sponge’ containing a mixture of these herbs was prepared for chewing or inhalation by the patient.

In 1240 AD, the head of the Holy Roman Empire, Frederick II, declared pharmacy to be separate from medicine. Pharmacy was not, however, truly established separately until the 16th century, when Valerius Cordus compiled the first pharmacopoeia (reference text with standard formulae and recipes) as an authoritative standard.

Byzantine and Persian Empires

During this period (324 AD–15th century), in the Byzantine (Eastern Roman) Empire centred around Constantinople (Istanbul) and that of Persia (Iran) occurred the Golden Age of Islamic medicine. The Arabians’ interest in medicine, pharmacy and chemistry was reflected in the hospitals and schools they built, the many new drugs they contributed and their formulation of the first set of drug standards. Folk medicines included camphor, henna, syrup, aloes, amber and musk. The classic Greek medical works were translated into Arabic and an extensive library was collected in Baghdad. The great contribution of Islamic medicine was the establishment of teaching hospitals such as those in Baghdad, Cairo and Damascus; medical education has depended ever since on this style of training for doctors.

The most famous ancient Persian physician is Avicenna (Abu-Ali Ibn Sina Balkhi), who lived in central Asia and Persia around 980–1037 AD (Figure 1-1D). He was a ‘man for all seasons’—physician, philosopher, astronomer, chemist, mathematician, poet, teacher… —and his most famous works, The Book of Healing and The Canon of Medicine, were the standard medical textbooks for hundreds of years, even in French medical schools. Ibn Sina is considered the father of clinical pharmacology, as he introduced systematic experimentation, quantification, randomised clinical trials and efficacy tests into the study of physiology and infectious diseases.

Alkaloids

Alkaloids are organic nitrogen-containing compounds that are alkaline and usually bitter-tasting; the nitrogen atom is usually in a heterocyclic ring of carbon atoms (Figure 1-3A); as many alkaloid drugs are amines, their names often end in the suffix ‘-ine’. They are combined as salts to make them more soluble, e.g. morphine sulfate. It is thought that plants may have evolved the ability to synthesise bitter alkaloids as a defence mechanism against herbivorous animals. Examples of some pharmacologically useful plant alkaloids are listed below, with cross-references to interesting relevant Drug Monographs (DM) and Clinical Interest Boxes (CIBs):

Formerly, the drug company Drug Houses of Australia (earlier known as Felton, Grimwade and Duerdins Pty Ltd) manufactured hyoscine and atropine from Australian Duboisia species; this was important during World War II, when supplies of the antinauseant drug hyoscine from European sources ran out.⁴ In Tasmania, the opium poppy Papaver somniferum is grown and harvested for production of opium alkaloids. Castanospermum australe is a source of the effective antiretroviral alkaloid castanospermine.

Carbohydrates

Carbohydrates are organic compounds of carbon, hydrogen and oxygen. Carbohydrates used in medicine include sugars such as glucose, starches and fibres such as cellulose and inulin (a fructose–furanose polysaccharide used in kidney function tests [Figure 1-3B]), gelling agents such as agar, and gums such as tragacanth and Aloe vera products (CIB 48-2).

Gums and mucilages are plant exudates. When water is added, some of them will swell and form gelatinous masses. When taken orally, they tend to remain unchanged in the gastrointestinal tract, where they act as hydrophilic (waterattracting) colloids, forming watery bulk and exerting a laxative effect. Agar and psyllium seeds are examples of natural laxative gums, whereas methylcellulose and sodium carboxymethylcellulose are synthetic colloids. Gums are also used to soothe irritated skin and mucous membranes, and may be a rich source of starch.

Glycosides

Glycosides are a particular type of carbohydrate, which, on hydrolysis, yields a sugar plus one or more additional active substances. The sugar part is believed to increase the solubility, absorption, permeability and cellular distribution of the glycoside. An important plant glycoside used in medicine is digoxin (Figure 1-3C), found in Digitalis (foxglove) plants and known as a cardiac glycoside because of its stimulant actions on the heart. Glycosides present in other Australian plants, including the oleanders Cerbera and Carissa, are responsible for the poisonous nature of these plants. Cane toads also contain cardioactive glycosides (see ‘Myth busting—cane toads in Australia’, Capon et al, www.raci.org.au/chemaust/docs/pdf/2009/CiA_May09p3.pdf).

Glycosides are also produced during the processes of drug metabolism in the human body, particularly in the liver; in phase II metabolic processes many drug molecules and their metabolites are conjugated with glucuronic acid. Such large compound metabolites are known as glucuronides and are more soluble and hence more excretable than the parent drug molecules; they are also less pharmacologically active, as the large drug–glucuronide combination cannot activate receptors in the same way that the parent drug does (see Table 6-4 and Figure 6-5).

Hydrocarbons

Plants contain many hydrocarbon components, including fats and waxes; oils such as castor, olive and coconut oil; and fatty acids, prostaglandins and balsams. Derivatives such as organic alcohols and esters contribute the fragrances to many plants and perfumes. Castor oil is mainly composed of ricinoleic acid (Figure 1-3D). Hydrocarbons are commonly used by drug companies and hospital pharmacies when preparing formulations of drugs, especially creams and ointments.

Phenols

Many pharmacologically active plant constituents are phenolic, i.e. they contain a benzene ring with a hydroxyl substituent. Examples are the salicylates, including aspirinlike compounds and flavouring agents (e.g. vanillin); isoflavones, including phyto-oestrogens (CIB 38-3); coumarins, including the anticoagulant dicoumarol (Figure 1-3E); cannabinols from marijuana; hypericin (from St John’s wort, used in depression, CIB 18-9 and Figure 1-1E); and poisonous aflatoxins from mouldy peanuts (ethanol from fermented plants and grains is not phenolic but is the prototype alcohol).

Tannins are astringent plant phenolics that have the ability to tan hides (animal skins) by precipitating proteins. Tannins are common plant constituents, especially in bark, and account for some of the brown colour in swamps and rivers and also in cups of tea. In Australian native medicine, kino, the gum exuded from eucalyptus trees, was an important source of tannins, which were used to treat diarrhoea, haemorrhages and throat infections.

Terpenes and steroids

Many plant chemicals, including steroids, are synthesised naturally from terpenes, 10-carbon molecules built up from small 5-carbon building blocks called isoprenes. Plant steroids, with their characteristic 4-ring structures (Figure 33-3), are used as the starting material for the production of many hormones. For example, the production of oestrogenic hormones for use as contraceptives was very difficult and expensive until methods were devised to use the plant sterol diosgenin, from Dioscorea species, in the synthesis of oestrogenic compounds. Other isoprenoid compounds are gossypol, a Chinese male contraceptive agent (Figure 1-3F); the active ingredients of the herbs gentian, valerian, feverfew and ginkgo; carotenoids such as β-carotene (CIB 48-4, DM 48-2); and the poison picrotoxin.

Salicylates, a group of phenolic terpenoid compounds, are important analgesic drugs based on saligenin from willow tree bark; the chemical name for aspirin is acetylsalicylic acid (CIB 15-7, DM 15-2). Pyrethrins, terpene-type compounds with effective insecticidal actions, have been used for centuries: it is reported that Napoleon ordered that the dried flowers of the chrysanthemum plant be used to delouse the French army! Australian research in the pyrethrin industry has discovered semisynthetic derivatives that have longer half-lives than the natural compounds and are therefore more useful in the plant production industries and as insecticides for animals.

Oils

Oils are highly viscous liquids that are high in hydrocarbon content, often flammable and immiscible with water and aqueous solvents. They may be terpene-type compounds, and contain many types of functional groups including ketones, phenols, alcohols, esters and aldehydes. Oils are classified as being of two kinds, volatile or fixed: a fixed oil dropped onto filter paper will leave a greasy stain, whereas a volatile oil will not, as it evaporates. Volatile oils may impart aromas to a plant.

Oils are frequently used as flavouring agents, in perfumery, in chemical industries and for therapeutic actions as antiseptics, carminatives (soothing to the stomach) and antispasm agents. Eucalyptus, peppermint and clove oils are examples of volatile oils used in medicine. Castor oil is an example of a fixed oil used in medicine, while olive oil is a fixed oil used in cooking. Camphor, menthol (Figure 1-3F) and thymol are related aromatic agents used in respiratory medicine. The Australian species myrtaceae and melaleucas contain many fragrant and useful oils, including eucalyptus and tea-tree oils (CIB 28-12).

Chemical names

The chemical name is a precise description of the drug’s chemical composition and molecular structure. It is particularly meaningful to medicinal chemists—who should be able to draw the chemical structure if given the chemical name—but may be virtually unintelligible to others. As chemical names are too complicated to remember easily, or fit on a prescription pad or pharmacy bottle label, drugs likely to reach the market and be used medically are allocated or given a name that is simpler, more euphonious and easier to spell.

Approved (generic) names

The approved name is usually suggested by the manufacturer and approved by the local drug regulating authority; it becomes the official drug name, e.g. the Australian Approved Name (AAN) or European Approved Name (EAN). It is a shorter name, usually derived from the chemical name, and is the name listed in official compendia such as the Australian Medicines Handbook or the British Pharmacopoeia. The approved name needs to be distinct in sound and spelling so that it is not easily confused with other drugs (but see CIB 1-5), and preferably related to the names of pharmacologically similar drugs (see Table 1-3).⁵

Table 1-3 Families of drugs

ACE = angiotensin-converting enzyme (converts angiotensin I to angiotensin II, which acts to decrease the diameter of arteries and arterioles [vasoconstriction] and hence to raise blood pressure); HMG-CoA = 3-hydroxy-3-methylglutaryl coenzyme A (a coenzyme involved in the early stages of cholesterol synthesis).

Strictly speaking, the term generic name refers to a group name, e.g. the penicillins, the salicylates, the β-blockers; however, it has come to be used interchangeably with the approved name. For example, we speak of ‘generic prescribing’, meaning prescribing using the approved name of a drug (amoxycillin) rather than one proprietary

or brand name (e.g. Amoxil). In this text we will always use generic (approved) names for drugs but may sometimes add a trade name⁶ if it is well known enough (e.g. Valium, Prozac or Viagra) to help students identify a particular drug. Note that approved names use lower-case letters, whereas a trade name always begins with an upper-case letter.

Proprietary (trade or brand) names

When a drug company markets a particular drug product, it selects and copyrights a proprietary or trade name for its drug (CIB 1-4). This copyright restricts the use of the name to that individual drug company and refers only to that formulation of the drug. To encourage doctors to prescribe particular versions of the drug and to promote sales of trade name drugs, extensive advertising is usually necessary; this expense is eventually borne by the consumer.

International Nonproprietary Names (INN) and European Approved Names

Since the United Kingdom’s entry into the European Community (EC) in 1973, and the recent adoption of European Approved Names (EAN) for drugs, the British medical and pharmaceutical establishments have had to accept the use of INN in the EC as the EAN for drugs. Examples of INN are norepinephrine (formerly noradrenaline), sulfonamides (sulphonamides), furosemide (frusemide), diethylstilbestrol (stilboestrol) and ciclosporin (cyclosporin) (see Longmore et al [2008]). These changes have not yet been adopted in Australia or New Zealand. We suspect and hope that the old terminology will continue in Australia and New Zealand; for example, although the INN for the sympathomimetic neurotransmitter is ‘norepinephrine’ in the EC, USA and Canada, the type of neurotransmission is still called ‘noradrenergic’ and the receptors ‘adrenoceptors’.

Classification systems

Drug classification can be approached from many perspectives. Using the example of amoxycillin again, this could be classified by:

Not surprisingly, students are often confused by drug classification, particularly as sometimes the same drug may be classified into various groups depending on the clinical use, e.g. aspirin-like drugs may be classified as analgesics, antipyretics, anti-inflammatory agents or antithrombotics. Probably the most useful methods involve classification by clinical indication, by body system or by mechanism of action. This book uses these approaches where appropriate; examples include the titles of Chapter 24, ‘Lipid-lowering drugs’, and Chapter 45, ‘Antifungal and antiviral drugs’. An example of drugs classified by body system can be found in Unit IV, ‘Drugs affecting the central nervous system’, whereas in Chapter 18, ‘Psychotropic agents’, antidepressants are grouped together under ‘Tricyclic antidepressants’ (a chemical class), ‘Monoamine oxidase inhibitors’ or ‘Selective serotonin reuptake inhibitors’ (mechanisms of action). Such drug classifications can help the health-care professional understand and learn about the individual agents available for drug therapy.

Prototype drugs

Pharmacology is easier to understand and learn when key, or prototype, drugs are studied. A prototype drug is usually the most important drug in a particular drug class, to which other drugs in the class can be compared. In this text, many prototype drugs are described in detail in a consistent format called a Drug Monograph (DM); thus, diazepam can be viewed as the prototype benzodiazepine antianxiety agent (DM 16-1). When a new similar drug becomes available, the practitioner can associate it with its drug group and prototype, and make inferences about many of its basic qualities before focusing on specific properties (usually pharmacokinetic) to differentiate it from the prototype and other drugs in the same group.

Prescription-only or OTC drugs

A drug may be classified as a prescription-only drug, which means that it requires a legal prescription to obtain it, or it may be a non-prescription or over-the-counter (OTC) drug, which means that it may be purchased without a prescription, possibly in a pharmacy, supermarket or general store. Some prescription drugs may be purchased OTC, usually in lower drug dosages that are considered to be relatively safe for sale, for conditions that may not warrant a person visiting a doctor or for which important drugs need to be readily available. An example is the nonsteroidal anti-inflammatory drug naproxen, which is available as an OTC drug (S2, Pharmacy-Only) in a 220-mg to 275-mg strength (packs of of × 12, 24 or 30 tablets) for treatment of headache/toothache or dysmenorrhoea, but requires a prescription (S4) for the 250-( × 50 or × 100), 500-or 550-mg ( × 50) or for the 750- or 1000-mg ( × 28) tablets for arthritis and bone pain.⁷ Drug schedules are considered in more detail in Chapters 2 and 4 and Appendix 5, and OTC medicines in Chapter 3.

WHO Essential Medicines List

It is recognised that with the enormous range of drugs available, few countries or health services can subsidise or provide the whole range of drugs, and no retail or hospital pharmacies could stock them all. To assist in decision making with respect to which drugs are the most important, the World Health Organization (WHO) through its Expert Committee on the Selection and Use of Essential Medicines has derived a Model List of about 280 core drugs in some 27 main categories (see Appendix 6), which are considered essential to provide ‘minimum medicine needs for a basic health-care system, listing the most efficacious, safe and cost-effective medicines for priority conditions’. This is useful for all countries attempting to curtail rapidly increasing expenditure on drugs, and is particularly useful for developing countries, allowing them to concentrate on providing the most important drugs. A statement by WHO defined essential drugs as ‘those that satisfy the healthcare needs of the majority of the population… they should therefore be available at all times in adequate amounts and in the appropriate dosage forms, and at a price that individuals and community can afford’.

The selection of drugs is determined by a committee of scientists and clinicians and is updated at regular intervals. These drugs first require market approval on the basis of efficacy, safety and quality as well as value for money. Listing ‘essential’ drugs inevitably raises concerns, particularly from the manufacturers of drugs not on the list, which may be seen as ‘non-essential’. A table adapted from the WHO Model List of drugs is included as Appendix 6, showing categories of essential drugs and, where possible, an example of therapeutic groups.

There is a separate Model List of medicines for children, and a ‘complementary list’ of approximately 67 medicines for which specialised doctors or facilities are required.

Australian top 10 drugs

The Australian Commonwealth Department of Health regularly audits the usage of prescription drugs in Australia and publishes lists of the top 10 drugs, scored by numbers of daily doses, by prescription counts and by cost to the government (i.e. to taxpayers). The lists for drug use in the year 2008/09 are summarised in Table 1-4; note that only subsidised drugs are audited here, not those bought OTC or provided under private prescriptions.

Table 1-4 Australia’s top 10 drugs, 2008/09^*

DDD = defined daily dose.

^* Note that the audit does not score drugs prescribed by private prescription or under PBS co-payment, or bought OTC. It is difficult to compare usage and costs between years, as the accounting periods are not for exactly the same number of weeks each time data are published.

Source: Australian Prescriber 2009; 32(6): 159, sourced from Drug Utilisation Sub-Committee database, September 2009.

Understandably, the government is concerned about the widespread use of the ‘statin’ drugs, used to lower blood cholesterol levels. As can be seen, in the list of drugs by cost, statins occupy three of the top five places. When these drugs were listed on the PBS there was a massive blow-out in their use, partly by people wishing to reduce their cardiovascular risk without the inconvenience of raising their exercise levels or decreasing their food intake! The top three statins together accounted for almost A$1 billion expenditure in the 2008/09 health budget. There are strict guidelines that must be met before these drugs can be prescribed on the PBS, including documentation of blood lipid levels and risk category (cardiovascular, diabetes, family history, age), and lipidlowering dietary therapy attempted before and during statin treatment. There is concern, however, that patients who are denied a prescription by one doctor may simply ‘shop around’ until they find a doctor who will decide that they meet the ‘high-risk’ criteria.

Comparing the lists of top 10 drugs by DDD/1000 population/day over the last few years, some interesting trends emerge:

New Zealand’s Pharmaceutical Management Agency (PHARMAC) also publishes lists of the most prescribed medications, as a ‘top 20’. Their top 10 in 2007 were as follows: paracetamol, aspirin, simvastatin, omeprazole, amoxycillin, amoxycillin + clavulanate, metoprolol, salbutamol, diclofenac, cilazapril.

The main differences appear to be the slightly different statins and ACE inhibitors used in New Zealand (cilazapril is not available in Australia), the inclusion of amoxycillin and diclofenac and absence of an angiotensin-receptor antagonist (like irbesartan) from the New Zealand list.

What patients want to know

There is a huge—often overwhelming—amount of information available on most drugs; when it comes down to the basics, what patients most want to know is:

These are the questions that health professionals must be ready to answer.

Official sources, pharmacopoeias and formularies

Official sources of drug information are published by governments and government bodies such as departments of health and hospitals, and by pharmaceutical societies and medical colleges, and contain legally accepted standards for drugs. Pharmacopoeias are reference texts containing a compendium or collected body of drug information relevant to a particular country. The pharmacopoeia usually contains information on all of the authorised drugs available within the country, including their descriptions, formulae, strengths, standards of purity and dosage forms.

Formularies are similar but may also include information on drug actions, adverse effects, general medical information, guidelines for pharmacists dispensing medicines, and the ‘recipes’ for formulation or production of different medicines, such as tablets, injections, ointments and eye-drops. A national formulary may also be used by the government to limit the drugs available or subsidised, in order to encourage rational, cost-efficient prescribing and enhance the quality use of medicine (QUM; see Chapter 2). Examples of official drug information sources are:

In New Zealand, there is no national formulary, but the BNF and APF are legal standards and are used for teaching. The Pharmaceutical Schedule from PHARMAC lists subsidised medicines and is updated every few months (see www.pharmac.govt.nz). The Medsafe website (www.medsafe.govt.nz/) is a great source of independent information for both health professionals and consumers (and students), with prescriber update articles, medicine data sheets, reporting of adverse reactions, ‘patient info leaflets’ and media releases, plus information about related topics including classification and regulation of medicines, medical devices, drug abuse, patient support groups, clinical trials and complementary medicines.

Semi-official sources

Semi-official sources of drug information may be published by government bodies or other groups, such as medical and pharmacology societies or independent publishers, and may include drug bulletins, reference books and updates, but no drug advertisements. While not official standards, they attempt to provide up-to-date, independent and unbiased information on drugs. Depending on the publication, information such as lists of food additives, patient support organisations, poisons information centres and prescribing guidelines may be included. Examples include the Australian Prescriber (a free bi-monthly independent review journal) which includes Medicines Safety Updates, the Therapeutic Guidelines series, the Paediatric Pharmacopoeia (Pharmacy Department, Melbourne Royal Children’s Hospital), National Prescribing Service newsletters, reference books such as the Australian Prescription Products Guide (known as the PP Guide), the Merck Index, Drug Interactions: Facts, and Drug Interactions: Analysis and Management, and journals such as Current Therapeutics and Drugs.

Some reference texts, e.g. the MIMS Annual, Mosby’s GenRx and the United States Pharmacopeial Convention’s Drug Information for the Health Care Professional (USP DI), provide actual photographs of drug formulations to assist in identifying an unknown tablet or capsule. In addition, manufacturers often place numbers with letters on their solid-dose formulations to aid in identification.

The Cochrane Collaboration is an international organisation that prepares systematic reviews of the effects of health-care interventions, such as clinical trials of drugs or other therapeutic techniques, with the aim of helping all people make well-informed decisions about health care. It aims to avoid duplication of studies, minimise bias and provide relevant, up-to-date easily accessible information. There are Cochrane databases of reviews, clinical trials, methodologies and economic evaluations, among others.

Consumer medicine information

Handing out consumer medicine information (CMI) pamphlets to patients is encouraged as an important way to improve people’s involvement with and understanding of the drugs they are prescribed. In Australia, all products have had CMI handouts since the end of 2002. They are particularly important when a drug is first provided, the dose or formulation changed or the information revised (see Aslani [2007]).

Drug or poisons information centres and pharmacists

Drug information centres, usually located in the pharmacy departments of major teaching hospitals, are set up to disseminate information about drugs, adverse reactions, drug interactions, treatment of drug overdoses and other related information, to maximise safety, efficacy and economy in drug use (see Appendix 6 and Australian Medicines Handbook, Appendix E). They are excellent sources of information for both the public and health professionals and for answering difficult pharmacological questions. In addition, pharmacists in hospitals and retail chemist shops are usually available and willing to provide drug information.

A new arm of the Community Quality Use of Medicines program was launched in Australia in January 2004, with pocket-sized ‘Medimate’ booklets distributed to doctors and pharmacists for patients. Each booklet contained general information about medicines, other therapies, CMI leaflets, use of OTC medicines, side effects and information sources, and questions that consumers should ask about their medicines, and provided a tear-off slip that could be filled in to summarise the person’s drug therapy. The Medimate website, run by the National Prescribing Service (http://www.nps.org.au/consumers/tools__and__tips/medimate), has similar information, as well as links to publications, videos and interviews, with information available in several languages.

Other drug information sources

An up-to-date pharmacology textbook is a valuable source of drug information for inclusion in the health-care professional’s library. Various ‘drug guides’ also exist, acting as quick reference sources of summarised information on drugs. Most of these have grown rather too large to fit in the pocket of a doctor’s, nurse’s or pharmacist’s uniform, but are useful on the desk or ward station. Examples are Havard’s Nursing Guide to Drugs and the MIMS bi-monthly drug reference guide.

Drug companies applying for registration of their products must supply to health authorities an enormous amount of information on all aspects of the drug, to prove safety, efficacy and cost-effectiveness. A summary of this information is available in publications such as the MIMS Annual, the PP Guide and in CMI sheets, advertisements and promotions. As this material is supplied by drug companies, it is inherently likely to be less objective than information in independent sources such as the Australian Medicines Handbook or Australian Prescriber. (Ethical aspects of drug advertising are discussed in Chapter 4.) It is important to consider the source of such information and beware of bias or selectivity of information.

Metric system

Dosage calculations

A thorough understanding of arithmetic (fractions, ratios and proportions) is necessary for correct calculations and safe drug administration. When in doubt, it is advisable to double-check all calculations with another health-care professional, especially with a pharmacist who will be highly trained in dose and concentration calculations. The examples of dose calculations at the end of this chapter are the types of problems that may be encountered. Each problem is solved in a step-wise manner and, where appropriate, helpful hints are included. (Note: for a review of arithmetic methods required in dose calculations, and more detailed explanations of methods used, see Gatford and Phillips [2006]).

Some helpful hints