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Pharmacoepidemiology and pharmacovigilence


Learning objectives: You will learn about the availability and use of prescribing and pharmacy sales data, and the importance of analysing and keeping abreast of trends from this and associated data to inform prescribing behaviour and patient care.

This section outlines the data available for prescriptions administered in the NHS, and the importance of reviewing the data and taking into account all the settings and healthcare professionals involved in administering prescriptions.

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Resource text

Pharmacoepidemiology, including use of prescribing and pharmacy sales data

Prescribing of medicines is one of the main interventions in the delivery of health care. Medicine usage accounts for a substantial proportion of the Health Service's budget each year. Pharmacoepidemiology is the study of the distribution and determinants of pharmaceutical drug use in populations and the analysis of the outcomes of drug therapies.

Pharmacoepidemiologic data come from both clinical trials and epidemiological studies, with emphasis on methods for the detection and evaluation of drug-related adverse effects, assessment of risk versus benefit ratios in drug therapy, patterns of drug utilisation, and the cost-effectiveness of specific drugs. The General Practice Research Database is also another source of information. The electronic data was available from 1987 and contains anonymised information on patients' medical history. It is possible within this database to link diagnoses to prescribing data which enable studies of regional and national trends. It consists of data from around 490 practices in the United Kingdom and covers about 5.5% of the national population.

In addition, a system called (electronic Prescribing Analysis and Cost data) is used in primary care and captures data on all medicines dispensed by community pharmacists and dispensing practices, according to which practice issued the prescription. The Prescription Pricing Authority (PPA) collects and collates all primary care prescribed medication data. Prescribing data are uploaded to a national database managed by the PPA and updated on a monthly basis (five weeks after the dispensing month).


With the increasing expenditure each year on medicines, and the rise in antibiotic resistant infections, there is increasing emphasis on seeking ways to improve the quality and cost-effectiveness of prescribing. These include publications, education programmes, and audits of drug therapy. The Medicine Utilisation Review (MUR) is becoming an increasingly important part of pharmacoepidemiology. Pharmacovigilance involves the identification and evaluation of drug safety issues and risk-benefit of drug use. The Medicines and Healthcare Products Regulatory Agency (MHRA) is the government agency that is responsible for regulating healthcare technologies such as drugs, and monitoring the safety of the products, including conducting inspections and issuing drug alerts as required.

Trends in prescribing by general practice can be analysed according to:

  • reporting period (i.e. month, quarter, year)
  • prescribing organisation (e.g. practice, PCT)
  • BNF classification (including presentation level)
  • controlled drugs tag.

The data available includes:

  • budgets and expenditure forecasts
  • costs and volumes of prescribing
  • prescribing totals by prescribers at all BNF levels
  • prescribing from the Nurse and Extended Nurse Formularies
  • working environment for nurses and supplementary prescribers (i.e. community or practice)
  • patient list sizes
  • low Income Scheme Index scores for practices
  • average Daily Quantities and Defined Daily Doses
  • prescribing On Behalf Of PCT/Practice
  • dispensing contractor name and address
  • standardised rates using Astro PUs (Age, Sex and Temporary Resident Originated Prescribing Units)

This service is available to:

  • Primary Care Trusts (PCTs)
  • Strategic Health Authorities (SHAs)
  • agencies acting on behalf of groups of other organisations
  • national users including:
    • Department of Health (DH)
    • National Institute for Health and Clinical Excellence (NICE)
    • Healthcare Commission
    • National Prescribing Centre (NPC)
    • Health and Social Care Information Centre Prescribing Support Unit (PSU).
    • Public Health Observatories (PHOs)

Information is available at a variety of levels:

  • prescriber, practice, & PCT level for PCT users
  • PCT and SHA level for SHA and National users

Limitations of prescribing data

There are three particular limitations with the ePACT data:

1. ePACT data do not include prescriptions dispensed in hospitals or mental health units, or private prescriptions.

2. ePACT data do not link to demographic or to diagnosis information on patients. Therefore, they cannot be used to provide prescribing information on age and sex or for prescribing of specific conditions where the same drug is licensed for more than one indication.

3. ePACT data cannot indicate whether a prescription for patient 1 for one month is equivalent to two fortnightly prescriptions for patient 2, but the latter will have two entries on the system.

Local formularies

Local formularies and accompanying guidelines have been developed at primary care trust level to support evidence based, cost effective prescribing.

Non-medical prescribing (NMP)

Prescribing rights have been extended to nurses, midwives and specialist community public health nurses, pharmacists, physiotherapists, chiropodists/podiatrists and optometrists. Further expansion of formularies and professions is anticipated. It is important that these activities are acknowledged and harnessed to deliver safe, effective patient care. However, further developments are required to ensure effective capture, analysis and dissemination of the information associated with NMP.


Donaldson LJ, Donaldson RJ Essential Public Health 2nd edition Petroc Press 2003

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