Veterinary medicines in-use shelf life
What is an in-use
shelf-life?
An in-use shelf-life is the time period following the
first broaching of a container (for example via a needle entering a bung or
the unscrewing of a cap) after which any remaining product in the container
should be destroyed. Veterinary medicines, human medicines, and increasingly
other types of products such as cosmetics and shampoos specify an in-use
shelf-life on their labels.
Why is it necessary to
have an in-use shelf-life?
An in-use shelf-life is needed to provide assurance of
the appropriate quality of the product throughout its use, thereby helping
to ensure the safety and efficacy of the product. A product used outside its
in-use shelf-life may have insufficient levels of the active substance and
this may lead to inefficacy (or in some cases contribute to the development
of resistance), or it may contain harmful levels of degradation products, or
it may be contaminated with micro-organisms which would further challenge an
animal whose health may already be compromised.
Why don’t all medicines
have an in-use shelf-life?
Only products which are susceptible to degradation or
contamination after first broaching of the pack carry an in-use shelf-life.
For example, micro-organisms will not usually survive in non-aqueous
environments. Therefore, for a non-aqueous pour-on product which has been
shown not to be prone to degradation when exposed to the atmosphere an
in-use shelf-life will not be specified.
Why do so many
medicines have a 28 day in-use shelf-life?
The in-use shelf-life specified depends on the product,
in particular its physical, chemical and microbiological characteristics.
The in-use shelf-life is not always 28 days. It may be less than this, for
example if the active substance is prone to degradation following exposure
to the atmosphere, or it may be longer than this, for example for a product
which is very stable and which will not support the growth of
micro-organisms (which can be the case for certain oily/non-aqueous
injections).
However, many of the multi-dose parenteral (injectable)
products do specify a 28 day maximum in-use shelf-life. The main reason for
this is that the EU guidelines for veterinary and human medicines** on the
“maximum shelf-life for sterile veterinary products after first opening or
following reconstitution” both indicate that, from a microbiological point
of view, for aqueous preserved sterile products and non-aqueous sterile
products the in-use shelf-life should not normally exceed 28 days. There are
examples of oily injections in the UK where the in-use shelf-life exceeds 28
days. In these instances the company has conducted additional microbial
challenge studies beyond those set out in the European Pharmacopoeia.
Is it possible to
extend an in-use shelf-life?
Marketing Authorisation Holders (the companies who
produce the product) can apply to the regulatory body who approve veterinary
medicines, The Veterinary Medicines Directorate, in some circumstances to
vary their authorisation to permit a longer in-use shelf-life. However,
there will be significant additional costs involved in generating the data
and significant costs involved in making the changes.
Can smaller pack sizes
be produced by companies?
Another option to try to avoid wastage of medicines would
be for Marketing Authorisation Holders to produce smaller pack sizes, but
again this will involve varying the authorisation and is likely to involve
the need for the generation of further data, with the inevitable additional
costs that this involves. In the past medicines where manufacturers had both
large and small pack sizes on the market, a frequent problem that was
encountered was that the smaller packs were not purchased and used by vets
who were attempting to make savings based on economies of scale. As a
result, the smaller pack sizes were discontinued.
**(EMEA/CVMP/198/99 and CPMP/QWP/159/96 respectively)
Note- this NOAH briefing document is based on the contents of a VMD
document addressing the same issue. The full VMD document can be accessed
via the following link-
http://www.vmd.gov.uk/VetSQP/In_use_shelf_life.pdf
September 2010
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