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In 2000 and 2001, the Institute of Medicine published two reports that have defined the hazards of modern medicine.1,2 These reports estimated that medical errors in the United States kill 44,000-98,000 patients each year and harm countless others. A medication error is a failure in the treatment process that leads to, or has the potential to lead to, harm to the patient. This definition reminds us of the distinction between the drug itself (the active component) and the whole product, which also contains supposedly inactive excipients. Although the definition covers a wide range of compounds, it does not include medications when they are used to probe systems for non-diagnostic purposes, such as the use of phenylephrine to study baroreceptor reflexes in a physiological or pharmacological experiment.
With these definitions in mind, a medication error can be defined as ‘a failure in the treatment process that leads to, or has the potential to lead to, harm to the patient’.8,9 The ‘treatment process’ involves all medications, as defined above. The term ‘failure’ in the definition implies that certain standards should be set, against which failure can be judged. An adverse event is ‘any abnormal sign, symptom or laboratory test, or any syndromic combination of such abnormalities, any untoward or unplanned occurrence (e.g. An ADR is ‘an appreciably harmful or unpleasant reaction, resulting from an intervention related to the use of a medicinal product’4. 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). However, it is important to detect medication errors, whether important or not, since doing so may reveal a failure in the treatment process that could on another occasion lead to harm. 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.
Knowledge-based errors (through lack of knowledge)—for example, giving penicillin, without having established whether the patient is allergic.
Mistakes (knowledge- and rule-based errors), slips (action-based errors) and lapses (memory-based errors) have been called ‘active failures’.18 However, there are several properties of systems (so-called ‘latent factors’) that make prescribers susceptible to error. Errors in prescribing can be divided into irrational prescribing, inappropriate prescribing, ineffective prescribing, underprescribing and overprescribing, and errors in writing the prescription. The reports offered recommendations that were consistent with other high-hazard industries, identifying systems rather than individuals as the cause for repeated human error. It will be reviewed by the American Society of Anesthesiologists and published at their discretion.
Medication (the process) is the act of giving a medication (the object) to a patient for any of these purposes.
Contextual classification deals with the specific time, place, medicines and people involved. In an Australian study, communication problems with senior staff and difficulty in accessing appropriate drug-dosing information contributed to knowledge-based prescription errors.19 These types of errors should be avoidable by being well informed about the drug being prescribed and the patient to whom it is being given.
Examples of other types of medication errors under the same headings are given in reference 8. They also identified simulation as a powerful tool for producing positive change within the flawed health care system.
They can be classified, using a psychological classification of errors, as knowledge-, rule-, action- and memory-based errors.
They should institute or observe measures to ensure that failure to meet the standards does not occur or is unlikely.
Modal classification examines the ways in which errors occur (for example, by omission, repetition or substitution). Failing to prescribe an anticoagulant for a patient in whom it is indicated (underprescribing) or prescribing one when it is not indicated (overprescribing) are different types of error from errors that are made when writing a prescription.
Although medication errors can occasionally be serious, they are not commonly so and are often trivial.
Of those, only ?0.1% were thought to be clinically important, giving an annual incidence of such errors of about 50 000. Psychological classification is to be preferred, as it explains events rather than merely describing them. Proper rules and education help to avoid these types of error, as do computerized prescribing systems.Action-based errors (called slips)—for example, picking up a bottle containing diazepam from the pharmacy shelf when intending to take one containing diltiazem.
However, it is important to detect them, since system failures that result in minor errors can later lead to serious errors. In the Australian study mentioned above most errors were due to slips in attention that occurred during routine prescribing, dispensing or drug administration. Reporting of errors should be encouraged by creating a blame-free, non-punitive environment.
These can be minimized by creating conditions in which they are unlikely (for example, by avoiding distractions, by cross-checking, by labelling medicines clearly and by using identifiers, such as bar-codes);22 so-called ‘Tall Man’ lettering (mixing upper- and lower-case letters in the same word) has been proposed as a way to avoid misreading of labels,23 but this method has not been tested in real conditions. Errors in prescribing include irrational, inappropriate, and ineffective prescribing, underprescribing and overprescribing (collectively called prescribing faults) and errors in writing the prescription (including illegibility).
A subset of action-based errors is the technical error—for example, putting the wrong amount of potassium chloride into an infusion bottle. 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.
This type of error can be prevented by the use of checklists, fail-safe systems and computerized reminders.Memory-based errors (called lapses)—for example, giving penicillin, knowing the patient to be allergic, but forgetting. In balanced prescribing the mechanism of action of the drug should be married to the pathophysiology of the disease.
These are hard to avoid; they can be intercepted by computerized prescribing systems and by cross-checking.
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