Pharmacovigilance is defined by the World Health Organization (2002), as

“Science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other possible drug related problem”

The CHIMES 'Pharmacovigilance' project will determine whether linked healthcare data can be used to identify ‘signals’ that may indicate an adverse drug reaction to medicines used to treat children, particularly for those medicines used unlicensed and/or off label.

The main questions addressed in the Pharmacovigilance project are:

  • Can drug discontinuations, drug switching and dose reductions of medicines specifically prescribed for children be identified in linked healthcare datasets?
  • Can drug discontinuations, switching rates and dose reductions of medicines be used as ‘signals’, in linked healthcare datasets, to indicate an adverse drug reaction to medicines used in the treatment of children?


This is a mixed retrospective and prospective 4 phase study:

Phase 1: Validation

Routinely collected prescribing and dispensing data will be analysed to identify children who have discontinued, switched medication or had a dose reduction within 30 days, 2-3 month, and 4-6 months following initiation of therapy. This will provide novel data to assess the usefulness of both early and late drug discontinuations, dose reductions and switching events as pharmacovigilance signals for drugs specifically used in the treatment of children.

Phase 2: Signal Enhancement

The prescribing doctor and/or the patient (or parent/guardian) involved in a drug discontinuation or switching event will be approached, by letter and a questionnaire, to determine the reasons for the drug discontinuation, switching or dose reduction to assess whether this process increases the likelihood of detecting an ADR signal.

Phase 3: Association and Causality

Having characterised the nature of the adverse events in phase 2, we will use this information to design a retrospective study, using linked routine healthcare data, to establish the risk of specific adverse events occurring and to identify any high risk patient groups and potentially contributing co-medications.

Phase 4: Prospective cohorts

Where uncertainty about the risks/benefits balance of a treatment remains, or in situations where a medicine is new and therefore retrospective analysis is inappropriate, prospective ‘virtual’ prospective cohorts will be established, using linked healthcare data, to investigate health risks proactively.


This project will demonstrate the usefulness of routinely collected NHS data in medicine surveillance. Drug discontinuations, switching and dose reductions will be assessed as acute and chronic pharmacovigilance signals for medicines used to treat children. This project has the potential to provide a novel, proactive approach to pharmacovigilance and risk management in paediatric care within the NHS. This supports the overall aim of CHIMES to ensure more effective treatment and safer use of medicines in children using effective and efficient methods that are a good investment of public money.

If you would like more information please contact Angela Sun (