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Letters to the Editor
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Antibiotic resistance
Reclassification of trimethoprim
From Dr C. Edwards, MRPharmS
I read in Pharmacy Magazine (July 2005) that a spokesperson for the Royal
Pharmaceutical Society had expressed support for the proposal to reclassify
trimethoprim as a P medicine. Although I have been a long time protagonist
of changes from POM to P medicines, I fear that this proposal may be a
step too far.
The consultation document acknowledges that increased use of trimethoprim
may contribute to increased resistance. This agrees with the generally
accepted wisdom about antibiotic usage and although based largely on circumstantial
evidence, it is a message which the medical profession has received from
the Government.1
Our local microbiology laboratory has reported a rising resistance of urinary
coliforms to trimethoprim from samples from primary care over recent years
matching its increased usage and, currently, this resistance is reported
to be 30 per cent. Such a significant degree of resistance makes one question
the efficacy of this agent as a first-line, empirical treatment and wonder
whether its increased availability will render it useless. It may be argued
that many urine samples which are sent to laboratories are collected from
patients who have failed first-line treatment and therefore represent an
atypical sample. However there are parallels with amoxicillin here, which
has now lost its place as the first-line empirical choice for the treatment
of urinary tract infections (UTIs).
The consultation document argues that over-the-counter (OTC) availability
will not increase overall use of trimethoprim, but will instead substitute
prescriptions.
This is speculative and I doubt that it will be the case. The consultation
paper also suggests that the use of less appropriate antibiotics will decrease
as a result of reclassification (presumably by reducing GP prescribing)
but at current levels of resistance, I cannot think of many agents which
would be described as “less appropriate”.
The fact that 50 per cent of urine samples have negative cultures also
raises the question of the appropriateness of antibiotic therapy, despite
some small studies indicating that trimethoprim may afford symptomatic
relief in such cases.
GPs will not receive this proposal well. The OTC availability of antibiotics
flies in the face of government directives to reduce usage of these agents.
The Medicines and Healthcare products Regulatory Agency consultation document
quotes a report published by a working party of the British Society for
Antimicrobial Chemotherapy, which states that previously diagnosed, uncomplicated
lower UTIs may be suitable for self-medication with antibacterials.2 However,
what in fact was reported was that such antibacterials should be agents
indicated only for UTI. Trimethoprim is not such a drug. It is licensed
for use in respiratory infection and in fact has also been used to treat
methicillin-resistant Staphylococcus aureus. There is no reference to it
being appropriate for OTC use for UTIs in the working party report.
The consultation paper argues that resistance is less likely to occur if
trimethoprim is avoided in patients who have had antibiotics in the previous
six months. Although this may be true, it still does not rule out the association
of population usage with development of resistance. In any case this measure
would seem to be fairly pointless in a population where resistance levels
are already 30 per cent.
I would urge all pharmacists to seek the opinion of their GP colleagues
about the wisdom of this proposal and to respond to the MHRA’s consultation
document. If the proposal were to be approved, the working relationship
between GPs and pharmacists could be seriously dented because the perception
could be that one group is pulling in a different direction to the other.
We have come close to that situation with simvastatin and I hope that pharmacy
will not trip itself up through its overzealousness.
Clive Edwards
Newcastle upon Tyne
References
1. Standing Medical Advisory Committee Sub-Group on Antimicrobial Resistance.
The Path of Least Resistance. London: Department of Health; 1998.
2. Reeves DS, Finch RG, Bax RP, Davey PG, Po AL, Lingam G et al. Self-medication
of antibacterials without prescription (also called ‘over the counter’ use)
A report of a Working Party of the British Society for Antimicrobial Chemotherapy.
Journal of Antimicrobial Chemotherapy 1999; 44: 163-177. |
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