Pharmacovigilance

Introduction

Pharmacovigilance is defined as "science and activities relating to the detection, assessment, understanding and prevention of adverse effects or any other medicine-related problem".

When marketing approval for a medication occurs, safety data from the clinical trial and nonclinical studies are abridged in the labelling; however, adverse drug events may not have been fully detected by this time.

  • The clinical trial process involves studying these products in a relatively small number of selected individuals for a short period of time.
  • Certain side effects may only emerge once these products have been used by a heterogenous population, including people with other concurrent diseases, and over a long period of time.

Consequently, data from post marketing studies and the spontaneous reports are reviewed periodically, and a formal evaluation occurs when new information suggests important safety issues.



Spontaneous Reporting

Spontaneous reporting systems collect data about suspected ADRs in a central database.

  • It is relatively cheap to administer, can follow a product throughout its life and can cover all products on the market.
  • Such schemes are, however, passive surveillance systems, which rely on
    • Voluntary reporting from patients, pharmacists and other healthcare providers.
    • The ability of reporters to recognise possible ADRs and to distinguish these from symptoms related to the underlying disease.
  • Moreover, it is unable to quantify any particular risk associated with an individual drug.
    • The number of reports is known, but estimates of the incidence of reactions cannot be made, because the population exposed to the drug cannot be ascertained accurately.
    • Only a minority of reactions are reported.



Active Surveillance Programs

Pharmacoepidemiologists pool large claims and electronic health database to determine the presence and magnitude of drug-event associations and detect signals that could represent important new problems with marketed drugs.

  • Robust and systematic method employed include case-controlled studies, cohort studies and case-registry studies.



Summary

Despite the increasing importance placed on pharmacovigilance and improvements worldwide in the systems for detecting ADRs, the time between an ADR first being reported and the date of withdrawal has not changed in 60 years, taking approximately 6 years.



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