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to say and impossible to remember, and they are usually left to research chemists. Many drugs can also be known by the name of the chemical class they belong to, such as opioids or benzodiazepines. But it is the generic, or official, name of the drug that health practitioners should always recognise a drug by. This name should be sufficiently different from any other drug name to minimise the risk of any drug being mistaken for another. With a few exceptions, generic names are usually the same regardless of where in the world you are, and they often derive in some way from the name of the chemical class of the drug, which is often convenient as it makes it easy to identify the class a drug belongs to by its generic name. The generic names of drugs belonging to the statin class of drugs, for example, end in ‐statin, with agents such as atorvastatin, rosuvastatin, fluvastatin and simvastatin. Generic names of drugs belonging to the beta‐blocker class end in ‐olol and include propranolol, atenolol, pindolol and nebivolol.

      Many drug formulations will also have a trade name given to the particular drug formulation by the company that produced it. These names may relate to the generic name or they may relate more closely to their therapeutic use, but because of the multiple formulations available and multiple companies producing them, the trade names of drugs will vary widely depending on where the drug is sold and what it is sold for. Needless to say, these names are not a reliable way to identify the drugs but unfortunately, they are often the most prominent and eye‐catching name on the packaging, which will mean that patients will usually refer to drugs by the trade name, unless they are receiving a generic version of the drug. To try and reduce confusion, the Australian government, for example, passed a law, effective February 1, 2021, that requires prescribers to write the generic name of the medication first on any prescription, either without a trade name or with the trade name in brackets after it. Combined with requirements for drug manufacturers to make the generic name of the active drug in the medication more prominent on the packaging than the trade name, the aim is to increase awareness of the active ingredients in medications and to reduce confusion.

With the huge range of drugs currently licensed for use, there are often multiple individual drugs available for any particular indication, so it is important that we also classify our drugs to make talking about them easier. We can classify drugs based on their chemical structures, mechanism of action or broader area of therapeutic use. The functional classifications (those relating to what the drugs do or what they are used for) are the most widely used, as they reflect the clinical uses of the drugs, but we often refer to certain groups of drugs by their chemical classification, as usually all agents belonging to a certain chemical class also have a predictable effect on function. Table 1.1 gives some examples of the ways in which drugs are named and categorised.

      Look‐alikes and sound‐alikes

      Mistaking one medication for another because the two names (either generic or trade names) sound alike or the packages look alike is a common cause of medication error. Errors due to look‐alike sound‐alike (LASA) medications have become so widespread that the World Health Organization launched a worldwide effort to reduce medication errors that come about in this way (WHO, 2007), and many governments have made changes to their medication labelling and naming The addition of ‘tall man’ writing in the name of a drug has been introduced in the UK, Canada, Australia and the US to make the differences between drug names clearer. This technique involves capitalising the parts of the name that are most likely to be misread, for example:

      AmiloRIDE, AmlodiPINE, BuPROPion, BupreNORphine.

      The mix of capitalised lettering in the name disrupts rapid reading and forces a more careful observation of the name.

The main element in reducing medication errors, however, continues to be careful cross‐checking of LASA medications prior to administration, and ensuring that look‐alike medications are not stored in close proximity to each other. Because the packaging and appearance of medications can change, the generic name of the medication should always be checked, and the identity of a medication should never be assumed from its appearance without checking the label. For example, a 500 mL or 1000 mL bag of clear fluid could be Hartmann solution, sodium chloride or glucose 10%.

Table 1.1 Categorisation of drugs based on clinical usage, general action or specific mechanism of action.

Generic name	Trade names	Chemical class	Therapeutic use	General action	Specific mechanism of action
Diazepam	Valium® Valpam® Antenex®	Benzodiazepines	Anxiolytics	Central nervous system depressants	GABA agonists
Atorvastatin	Lipitor® Torvastat®	Statins	Cholesterol synthesis inhibition	Lipid‐lowering agents	HMG Co‐A reductase inhibitors
Candesartan	Candesan® Adesan® Atacand®	‐	Antihypertensives	Blood pressure‐lowering agents	Angiotensin receptor antagonists
Salmeterol	Serevent®	‐	Acute asthma control	Bronchodilators	Long‐acting beta‐2 agonists
Diclofenac	Voltaren® Voltarol® Difenac® Clonac®		Analgesic, anti‐inflammatory	Non‐steroidal anti‐inflammatories	Cyclo‐oxygenase inhibitors

      GABA, gamma‐aminobutyric acid; HMG‐CoA, 3‐hydroxy‐3‐methylglutaryl coenzyme A.

How drugs bring about their actions

      With only one or two exceptions (such as drugs which absorb other substances, e.g. charcoal or resins), drugs act by binding chemically to specific binding sites. It is this fact which explains the various observed characteristics of a drug, for example, the relationship between the shape of a drug molecule and its actions; the relationship between how readily it binds to its site of action and the concentration of drug needed at the site of action to bring about a therapeutic effect; the relationship between the number of different binding sites the drug can bind to and the number of different effects it produces; the strength with which it binds to the site and length of time for which it exerts its effects, and so on.

      The site at which a drug binds to have its effects is known as the receptor for that drug, and it may be a receptor normally used by endogenous signalling molecules, such as hormones or neurotransmitters, or a binding site on an enzyme, ion channel or transport molecule. A substance binding at any of these sites would be able to alter physiological function when the structure to which the drug is binding is itself responsible for producing various physiological changes.

How are we able to manipulate physiological function using drugs?

Physiological

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