Reporting Adverse Drug Reactions: A guide for healthcare professionals
May 2006
Why are pharmacovigilance and reporting ADRs important?
The limitations of clinical trials mean that when a drug is first marketed, much may be known about its efficacy while relatively little may be known about its safety (see box 1) (see reference 14). For example, at least 30,000 people need to use a medication in order to identify, with 95 per cent power, an adverse reaction with an incidence of one in 10,000.8 A relative lack of widespread clinical trials for medicines to treat children means that many drugs are initially only licensed for use in adults, which can leave ‘no alternative to the prescriber than to use “off-label” and unauthorised products’ (see reference 15) in this population. Thus, the need for post-marketing surveillance can be seen as a means to identify drug safety problems not picked up by pre-marketing tests and promulgate any necessary advice and/or regulatory action to prescribers and users.
Pharmacovigilance through, for example, spontaneous ADR reporting or large scale databases, is used to generate hypotheses and signals about potential hazards of marketed drugs that require further investigation. Spontaneous reporting of suspected ADRs is particularly useful in identifying rare or delayed reactions; as such a system enables medicines to be monitored throughout their lifetime. See appendix B for some of the more recent drug safety problems to be identified by the Yellow Card spontaneous ADR reporting scheme.
Limitations of most clinical trials in highlighting a drug’s safety
- Homogeneous sample populations
Most trials assess relatively healthy patients with only one disease and mostly exclude specific groups such as pregnant women, children, and elderly people. - Sample size
Small sample size (up to 1,000 patients) reduces the chance of finding rare adverse effects. - Limited duration
Trials of short duration preclude the discovery of long-term consequences such as cancer. - Inability to predict the real world
Drug interactions can be substantial in a population as patients may take drugs concomitantly, a situation that can almost never be predicted from clinical trials.
In addition to contributing to the safety profiles of existing drugs, pharmacovigilance activities help to improve the knowledge set and contribute to the breadth of epidemiological data. Pharmacovigilance is, therefore, vital for the advancement of future research, medical understanding, drug development and epidemiological studies. Large-scale databases containing longitudinal patient or prescription data reflect routine usage of medications in the general population and provide denominator data which can be used to identify trends (see reference 16).
Any improvements in drug safety or understanding will ultimately lead to improvements in patient care and thus the benefits of effective pharmacovigilance should be appreciated and pursued by all healthcare professionals. Effective spontaneous reporting of suspected ADRs also relies on good communication between healthcare professionals and patients, which in turn should assist good relationships and can improve patient care.
As the Yellow Card Scheme relies on the goodwill of reporters, healthcare professionals should consider it their professional duty to report ADRs. The importance of pharmacovigilance and reporting ADRs is reflected in the General Medical Council’s (GMC) core guidance Good medical practice, which states that in providing care, doctors have a duty to ‘report adverse drug reactions as required under the relevant reporting scheme, and cooperate with requests for information from organisations monitoring the public health’ (see reference 17).