And unlike single-use products, vials licensed
for multiple use contain preservatives, which
reduce the risk of any contamination replicating,
should it occur.
describes measures, which, if followed, support
the continued integrity of the vials prepared
throughout the period of use. It also covers steps
which should be taken to ensure that the
administration is done correctly. This is
important. Although the products the guidance
relates to are all for diagnostic use and therefore
are not in themselves harmful from a therapeutic
point of view, if administered incorrectly they can
lead to misdiagnosis, delays in diagnosis and
unnecessary radiation exposure.
What are the risk factors associated with
individual injectable medicines, their
preparation and administration?
There are a number of risks that must be
considered.
Radiation risk to operators
First of all, I would like to make it clear that if
handled correctly, the radiation risks to patients
and staff are extremely low. It is important to
remember that there are risks in everything we
do, and the extremely low risk of harm to
patients as a result of their radiation exposure
is very carefully assessed and offset against the
overall benefit of their having the test in
question.
Operator radiation doses are measured and
assessed routinely in the Radiopharmacy – both
the dose received to the entire body, as well as
that received to the fingers. Most operators
making up technetium-99m radiopharmaceuticals
will have a low whole body dose. To put this in
perspective, a typical dose may be in the region
of 4mSv a year, compared with the average dose
received in the UK of 2.7mSv, and a resident
of Cornwall of just under 8mSv. 3
However, nothing is totally devoid of risk,
and the higher the radiation exposure to the
radiopharmacy operator or patient, the higher
the risk. Therefore keeping the exposure levels
low for both groups is vital. The Safe Drawing Up
document, therefore, incorporates radiation
safety recommendations as well as advice for
minimising risk of repeated radiation exposure,
for example.
What are the current issues of using
multidose vials?
Ideally parenteral products should be for single
use. 2 This is the ideal, because they can be
discarded after the dose has been drawn up and
there is much less risk of contamination of the
vial. Some radiopharmaceuticals are presented as
single-use vials. These tend to be newer products,
where the patient numbers are low or where the
amount of ligand is particularly important – say,
for example, in the case of radiolabelled
antibodies such as LeukoScan (a
radiopharmaceutical used for imaging infection).
Why then, are so many diagnostic
radiopharmaceuticals presented as multidose
vials? The answer, although to some extent
historical, lies in their radioactive nature.
A certain amount of overage is required if
making up a vial of product for a single patient.
Each time a vial is made, the generator elution
vial has to be handled. This accounts for
a significant proportion of the operator’s
radiation exposure. The more vials made, the
more times the elution vial has to be handled.
If more overage has to be allowed overall, the
total amount of radioactivity used from the vial
will also be higher.
Both these factors result in a Health and Safety
risk to the operator making the products, which
is reduced as follows through the use of
multidose vials:
• Less total activity is handled as a result because
there is less wastage
• The generator elution vial is handled less.
Risk of microbial contamination of the product
If manipulations are carried out at ward or
clinic level and injections are not administered
immediately, there is an increased risk of
microbial contamination that can lead to
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