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Letters to the Editor
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Levothyroxine
Liquid preparations should be a high priority
From Mr A. J. Nunn, FRPharmS
The method of preparing levothyroxine solution suggested by James
Wells (PJ, 11 December, p852) is impractical for extemporaneous dispensing
in the hospital or community pharmacy and has great potential for error
if pure drug is used. The quantity of pure drug required for 100ml of
solution of the strength stated is only 1mg and would require weighing
of a much larger amount, measurement of aliquots from a solution and
further dilution. Furthermore, no evidence of stability has been provided
with the suggested method.
The recent series of letters (PJ,
6 November, p680, and 27 November, p785) about problems with oral liquid
preparations of levothyroxine illustrates another aspect of the ongoing
issues with medicines for children: an authorised indication and dose
are available for levothyroxine but no satisfactory dosage form is marketed
for babies and young children. Tan et al1 reviewing the Australian market
suggest that this is the case for approximately 25 per cent of medicines
intended for children. In France an oral liquid preparation of levothyroxine
(L-Thyroxine Roche; 5µg per drop) is authorised for children. This
preparation can be imported into the UK but why is it not authorised
and marketed here?
The Department of Health and the Medicines and Healthcare products Regulatory
Agency have recently announced a paediatric
strategy to improve the availability
of medicines for children and to standardise the quality of extemporaneous
formulations (PJ, 21 August, p246). This will include invitations to
manufacturers of appropriate preparations authorised in other European
countries to register and market them in the UK. However, this may not
be viable if demand is low and it may be appropriate for importation
to continue, but pharmacists need to know of the availability of these
medicines and both technical and patient information must be translated
into English. Rationalisation of the many different formulae used in
extemporaneous dispensing is to be welcomed if this also leads to evaluation
of their quality, stability and bioavailability. Comparison of preparations
from different commercial and NHS sources has not been undertaken. Such
research should be part of the programme for the Medicines for Children
Research Network, in the process of being established by the DoH, and
the issues should be addressed by the NHS manufacturing review.
The recent correspondence about liquid preparations of levothyroxine
suggests that this drug should be given a high priority for attention
by the DoH, the MHRA and developing research networks.
Tony Nunn
Clinical Director of Pharmacy, Royal Liverpool Children’s NHS
Trust
Reference
1. Tan E, Cranswick NE, Rayner CR, Chapman CB. Dosing information for
paediatric patients: are they really “therapeutic orphans”?
Medical Journal of Australia 2003;179:195–8. |
The
Pharmaceutical Journal