Before a medicine is marketed, any experience of its safety and efficacy is limited to its use in clinical trials.  Clinical trials usually have strict entry criteria (eg limited comorbidity, age restrictions, non-pregnant etc) and are run for a finite time.  As a result, medicines coming onto the market will have only been tested on a relatively small number of patients for a limited length of time.   Conversely, some ADRs may not be seen until large cohorts of patients have used the drug or the drug has been used for many years.  It is, therefore, not possible to know all the side effects of a drug at the time of marketing.  Pharmacovigilance is the practice of monitoring the safety of medicines and responding to any potential associated hazards throughout the drug’s marketed life and as such is a vital public health function.

Pharmacovigilance involves:

  • Monitoring the use of medicines in everyday practice to identify previously unrecognised ADRs
  • Assessing the risks versus benefits of medicines to determine if any action is necessary to improve their safe use
  • Provide information back to healthcare professionals and patients to optimise safe and effective use

Pharmacovigilance uses information from a wide range of resources including clinical and epidemiological studies, pharmaceutical companies, worldwide regulatory authorities, morbidity and mortality databases as well as the ADR reporting schemes (Yellow Card Scheme in UK).  This information is screened to highlight patterns in ADRs and identify side effects previously unknown with a particular drug or patient group.  The MHRA, working closely with EMA, then has the authority, if necessary, to advise healthcare professionals of risks and help minimise them where possible.  It may:

  • Make changes to warnings of the product information/packaging label
  • Change the specified dose of the medicine
  • Restrict the indications for use of the medicine
  • Change the legal status of the medicine (eg from over-the-counter to prescription only)
  • Remove the medicine from market.



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