A medication (a medicinal product) is ‘a product that contains a compound with proven biological effects, plus excipients or excipients only; it may also contain contaminants; the active compound is usually a drug or prodrug, but may be a cellular element’.A codicil to this definition stipulates that a medicinal product is one that is intended to be taken by or administered to a person or animal for one or more of the following reasons: as a placebo; to prevent a disease; to make a diagnosis; to test for the possibility of an adverse effect; to modify a physiological, biochemical or anatomical function or abnormality; to replace a missing factor; to ameliorate a symptom; to treat a disease; to induce anaesthesia.
A medication error is a failure in the treatment process that leads to, or has the potential to lead to, harm to the patient.
Medication errors can occur in deciding which medicine and dosage regimen to use (prescribing faults—irrational, inappropriate, and ineffective prescribing, underprescribing, overprescribing); writing the prescription (prescription errors); manufacturing the formulation (wrong strength, contaminants or adulterants, wrong or misleading packaging); dispensing the formulation (wrong drug, wrong formulation, wrong label); administering or taking the medicine (wrong dose, wrong route, wrong frequency, wrong duration); monitoring therapy (failing to alter therapy when required, erroneous alteration).
An error is ‘something incorrectly done through ignorance or inadvertence; a mistake, e.g.
in calculation, judgement, speech, writing, action, etc.’The term ‘failure’ in the definition implies that certain standards should be set, against which failure can be judged.
From 1983 to 1993 the numbers of deaths from medication errors and adverse reactions to medicines used in US hospitals increased from 2876 to 7391 These increases are not surprising—in recent years hospitals have seen increased throughput of patients, new drugs have emerged that are increasingly difficult to use safely and effectively, medical care has become more complex and specialized, and the population has aged, factors that tend to increase the risk of medication errors.
The best way to understand how medication errors happen and how to avoid them is to consider their classification, which can be contextual, modal, or psychological.Errors in prescribing include irrational, inappropriate, and ineffective prescribing, underprescribing and overprescribing (collectively called prescribing faults) and errors in writing the prescription (including illegibility).Avoiding medication errors is important in balanced prescribing, which is the use of a medicine that is appropriate to the patient's condition and, within the limits created by the uncertainty that attends therapeutic decisions, in a dosage regimen that optimizes the balance of benefit to harm.In a survey of 40 000 medication errors in 173 hospital trusts in England and Wales in the 12 months to July 2006, collected by the National Patient Safety Agency, ∼15% caused slight harm and 5% moderate or severe harm.Since ∼3 billion prescriptions are dispensed each year in the USA, ∼50 million would contain errors.All those who deal with medicines should establish or be familiar with such standards.They should institute or observe measures to ensure that failure to meet the standards does not occur or is unlikely.A Venn diagram showing the relation among adverse events, ADRs and medication errors; the sizes of the boxes do not reflect the relative frequencies of the events illustrated (Reproduced from reference 8, with permission from Wolters Kluwer Health/Adis ©; Adis Data Information BV (2006); all rights reserved).); of those that are detected a minority actually result in ADRs, or at least serious ones.For example, in a UK hospital study of 36 200 medication orders, a prescribing error was identified in 1.5% and most (54%) were associated with the choice of dose; errors were potentially serious in 0.4%.An ADR is ‘an appreciably harmful or unpleasant reaction, resulting from an intervention related to the use of a medicinal product’.Some medication errors result in ADRs but many do not; occasionally a medication error can result in an adverse event that is not an ADR (for example, when a cannula penetrates a blood vessel and a haematoma results).