E-drug: Tablet-splitting with FDCs, esp. antiretrovirals (cont'd)
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This is really a pharmacist's or a pharmaceutical scientist's
question. Do you have a paediatric pharmacist among your
advisers? Calling Great Ormond Street's Pharmacy Dept might be
worthwhile, since paediatric pharmacists have a good information
network and are often faced with the problem of turning adult
medicines into children's doses.
My guess is that specific studies on active substance distribution in
combination ARV tablets have not been done, and the objections to
tablet splitting are based on general experience and old studies of
other medicines.
One objection to tablet splitting is that it is often uneven, especially
if the tablet is not scored to help it to split evenly. This leads to
uneven levels of drug in each portion of tablet - but if the tablet has
been pretty evenly split, does a slight variation in dose matter? It
might with some very potent drugs (doses in micrograms), but
often doesn't with larger dose tablets. Do very small dose variations
matter with ARVs? Hospital pharmacists have ways of avoiding the
problem by weighing whole tablets, grinding them to a fine powder
and then weighing off the portion required for a paediatric dose.
However, this depends on having precise weighing equipment and
wouldn't be possible in low technology settings. It can also be
wasteful if unwanted portions cannot be properly stored for use as
later doses.
A second objection is that the distribution of drug substance within
the tablet might be uneven, but this is not very likely if the
production process conforms to good manufacturing practice. Drug
substances are mixed with inactive ingredients in bulk before the
tableting process begins, so they must be very thoroughly mixed in
order to achieve the correct dose in each tablet; if they weren't
properly mixed, batches would fail quality control tests and
production costs would rise, so it is in the formulator's interests to
get the mixing right first time.
Carolyn Green
Freelance consultant pharmacist
19E Sussex Heights
St Margaret's Place
Brighton BN1 2FR
UK
tel: +44 (0)1273 738998 (home/office)
+44 (0)771 309 5240 (cellphone)
e-mail: greencm@dial.pipex.com
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