You are viewing an older, archived article. There may be more up to date articles on this subject, try a new search


Background, Goal and Objectives Polypharmacy PDF
Polypharmacy - weighing up the benefits and harms
Elderly people are at increased risk of drug related problems
Drugs associated with increased risk of adverse drug reactions in elderly people
Common drug interactions in elderly people
Recognising adverse drug reactions
Risk factors for drug related problems in elderly people
A really good recipe for DRP
Drug related harm; terms and definitions
Hospital admissions for adverse drug reactions
Commonly reported adverse drug reactions
References, Bibliography

Drug related harm; terms and definitions

Drug related problem (DRP) now sometimes referred to as Medicines related problem

An event or circumstance involving a patient’s drug treatment (or lack of drug treatment) that actually or potentially interferes with the achievement of an optimal outcome. Adapted from Hepler and Strand, 1990.
DRPs include:
  • Untreated indications
  • Drug use without a clear indication
  • Sub-therapeutic dosage
  • Excessive dosage
  • Adverse drug reaction
  • Drug interaction
  • Drug withdrawal reaction
  • Medication error
  • Non-adherence to drug treatment
  • Therapeutic failure
(Adapted from Hanlon et al, 2004)
DRPs cause significant morbidity and mortality in the general population. Some authors have estimated that the economic cost of DRP rank around fourth behind, cardiovascular disease, cancer and diabetes in the developed world (Johnson and Bootman, 1995).
A recent systematic review reported that a median 7.1% (range 5.7–16.2) of hospital admissions result from drug related problems, of which 59% were considered preventable (Winterstein et al, 2002).

Adverse drug event (ADE)

An injury resulting from the use of a drug

An adverse drug event is a broader term which includes adverse drug reactions plus harm from the use of the drug including prescribing, administration, overdoses, dose reductions and discontinuations of therapy (medication errors).

1. Severe bronchospasm following use of metoprolol in an asthmatic patient with a history of beta-blocker induced bronchospasm. This is a medication error as the history was not recognised. The metoprolol unmasked and aggravated the bronchospasm rather than causing it directly. 3. Severe bradycardia resulting from the administration of three times the intended dose of metoprolol (47.5 mg TID instead of daily). Another medication error which could be due to an incorrect prescription or incorrect reading or interpretation of the prescription.
2. Metoprolol stopped suddenly resulting in tachycardia and hypertension. This is also a medication error resulting from abrupt discontinuation of the metoprolol and associated rebound effects. The dose should have been gradually reduced. NB the term adverse drug event does not include situations when a drug is not used when the patient could potentially benefit from it. For example, failure to use a beta-blocker in a patient with stable well controlled COPD and heart failure or post myocardial infarction. This is an “untreated indication”.

Adverse drug reaction (ADR)

A response to a drug which is noxious and unintended and which occurs at doses normally used in man for prophylaxis, diagnosis or therapy of a disease or for the modification of physiological function.

In other words, harm directly caused by the drug at normal doses. For example, depression caused by a beta-blocker.

Adverse drug reactions fall in to one of two main categories:
Type A reactions are predictable, dose-related reactions where the intensity of the effect increases with dose or reduced clearance of the drug from the body, i.e. increased blood concentrations. For example, the anticholinergic effects (constipation, blurred vision) of amitriptyline will tend to worsen if the dose is increased from 25 mg to 50 mg daily. In addition the patient will tend to become more drowsy and sedated. For some adverse drug reactions there appears to be a threshold drug dose or concentration at which a type B reaction becomes more likely. For example, it is difficult to predict who will get confusion due to cimetidine or ranitidine, but the elderly seem to be more susceptible especially if the dose is not reduced according to the decline in renal function. Similarly, the risk of the rare allopurinol hypersensitivity syndrome is increased if the dose is not adjusted in renal impairment.
Type B reactions are not related to dose and are largely unpredictable (idiosyncratic). These represent many potentially serious adverse reactions such as blood dyscrasias and hepatotoxicity.

Page  1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 Page 9