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module menu icon Introduction

According to Epilepsy Action, epilepsy affects over 600,000 people in the UK. NICE advises approximately two thirds of patients with active epilepsy effectively control their seizures with anti-epileptic medication.1

It is important for patients with chronic medical conditions to receive a continuous and uninterrupted supply of their medicine. This 'continuity of supply' means that a patient receives uninterrupted access to their medication in order to effectively manage their medical condition(s). However, does 'continuity of supply' refer to the generic drug itself, or the brand name, or a specific manufacturer's product? Does it matter if the patient receives different formulations of a drug? What impact, if any, could product switching have on the patient and the management of their condition?

Variations in availability and in price affect the generic product supplied by wholesalers to pharmacies. Switching between different generics, or between a brand and a generic, is therefore commonplace. In general, we are confident when switching between products because we know that in order for a generic product to have a licence approved, it must be shown to be 'bioequivalent' to the 'originator' or reference product (usually the original brand). In other words, a generic formulation must produce the same biological response as the original branded drug and all generics are compared to that originator.

However, we know there can be slight differences between formulations of the same drug. Different excipients, different coatings, even differences in tablet compression can all affect the pharmacokinetics of a formulation. We also know that slight differences in rate or extent of absorption of a drug will affect its plasma concentrations, or its bioavailability. For most drugs these slight differences in bioavailability are not clinically significant. But in some cases, for instance drugs with a narrow therapeutic range, small changes in plasma concentration could significantly affect the clinical response. In these cases, switching between different formulations could have significant consequences for the patient.

OBJECTIVES

By the end of this module you will be able to:

  • Explain the concepts of continuity of supply and product switching.
  • Identify factors that affect the clinical significance of product switching.
  • Describe the impact on patients of loss of control of epilepsy treatment.
  • Describe the Commission on Human Medicine's review into switching of anti-epileptic drugs.
  • Discuss the CHM categorisation of antiepileptic drugs and its rationale.
  • Identify which category an anti-epileptic drug falls into.
  • Discuss the increased risks associated with phenytoin.
  • Advise healthcare professionals and patients on the issues and actions to take in relation to anti-epileptic drugs and the continuity of supply.
 
 
 
 

 

 

 

 
 
 
 
1 NICE CG 137 https://www.nice.org.uk/guidance/cg137/chapter/Introduction