Pharmacoepidemiology, including use of prescribing and pharmacy sales data; pharmacovigilance


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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[1].

Pharmacoepidemiology is the science concerned with the benefit and risk of drugs used 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, the cost-effectiveness of specific drugs.

Within the NHS the system (electronic Prescribing Analysis and Cost data), used in primary care, captures data on all medicines dispensed by community pharmacists and dispensing practices, according to which practice issued the prescription.  

Within the NHS the Prescription Pricing Authority (PPA) collect and collate all primary care prescribed medication data.  Prescribing Data are uploaded to a national database managed by the PPA and updated on a monthly basis (5 weeks after the dispensing month). 


Trends in prescribing by general practice can be analysed according to[2]:

  • Reporting period (i.e. month, quarter, year)
  • Prescribing organisation (e.g. practice)
  • BNF classification (chapter to 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 Practice
  • Dispensing contractor name and address
  • Standardised rates using Astro PUs (Age, Sex and Temporary Resident Originated Prescribing Units).

This service is available via NHS Net to:

  • CCGs
  • Strategic Health Authorities (SHAs)[equivalents –requires updating]
  • Agencies acting on behalf of groups of other organisations
  • National Users including:
    o   Department of Health (DH)
    o   National Institute for Health and Clinical Excellence (NICE)
    o   Healthcare Commission
    o   National Prescribing Centre (NPC)
    o   Health and Social Care Information Centre Prescribing Support Unit (PSU)
    o   Public Health Observatories (PHOs).

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. 

Limitations of prescribing data

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

PACT 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]

PACT data cannot indicate whether a prescription for patient 1 for 1 month is equivalent to 2 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 CCG 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 nurse, 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 and effective patient care[4].  However, further developments are required to ensure effective capture, analysis and dissemination of the information associated with NMP.


[1] Donaldson LJ, Donaldson RJ Essential Public Health 2nd edition Petroc Press 2003
[2] [accessed 30/11/2007]
[3] [accessed 30/11/2007]
[4] [accessed 30/11/2007]



             © M Goodyear & N Malhotra 2007, D Lawrence 2018