Chloramphenicol use remains 40% higher ‘due to OTC status’

There has been a sustained surge in the use of the antibiotic chloramphenicol since it was made available over the counter (OTC) for eye infections in 2005, reveals a new study that reopens the debate over risks of increasing access to antibiotics.

The Welsh study showed a steady year-on-year increase in overall supply in chloramphenicol the three years after it started being sold in pharmacies.

Although use subsequently levelled off slightly, it remained 40% up on previous levels over the next two years. The study also showed no signficant reduction in NHS drug costs or GP workload after the introduction of the OTC antibiotic.

The researchers suggested that widespread ‘misdiagnosis’ by pharmacists could be behind the rise.

Pulse previously reported concerns among GPs and public health experts after a 48% increase in overall use of chloramphenicol was found two years after it was made available OTC.

Ministers subsequently moved to ban further OTC antibiotics, after plans were announced by the MHRA to reclassify trimethoprim and nitrofurantoin for treatment of urinary tract infections as pharmacy-only medicines.

Stopping the inappropriate use of antibiotics has become even more of a priority over the past year, with doctors called on by the chief medical officer to help combat the ‘catastrophic threat’ of antimicrobial resistance, by reducing their prescribing and introducing diagnostics to target antibiotic use.

The latest findings question how appropriately chloramphenicol drops and ointment are being used for eye complaints, and experts have again warned of the risks of fuelling demand for antibiotics.

The Cardiff University researchers analysed NHS Wales data on primary care prescribing between June 2004 and December 2010, and OTC sales data from June 2005 to December 2010.

Both prescribed and sold supplies of chloramphenicol eye drops rose after OTC sales began in 2005, with overall packs used at around 90,000 in 2004 to 2005 and rising to a peak of 140,000 in 2007 to 2008, before settling at just over 130,000 in 2008 to 2009 and 2009 to 2010.

Although the amount of eye drops supplied on prescription dipped in the first year after they were available OTC, they subsequently returned to similar levels as before the antibiotic went OTC.

An increase in sales of chloramphenicol eye ointment after it became available from pharmacists in 2007 followed a similar pattern, as did overall sales of both types of preparation for the full five-year period.

The researchers concluded: ‘Over the five-year period following OTC availability sales of ophthalmic chloramphenicol grew substantially before appearing to stabilise. Their apparent lack of impact on prescription use meant that there was no saving to the NHS drug budget nor a reduction in GP workloads.’

Noting that conventional signs and symptoms that pharmacists rely on to distinguish bacterial from viral conjunctivitis are not very informative, they added: ‘It is not improbable that some of the increase in OTC ophthalmic chloramphenicol sales has arisen because of misdiagnosis and therefore reflects inappropriate use.’

Dr Nicholas Brown, president of the British Society for Antimicrobial Chemotherapy, said although chloramphenicol was generally ‘well marshalled’ by pharmacists, its OTC availability would still increase the risk of increasing resistance to the antibiotic.

He said: ‘The BSAC does not support widening access to antibiotics by making them available over the counter, and extreme caution is needed when doing so. 

‘This paper demonstrates increasing availability of antimicrobial agents increases usage, which will in turn increase pressure on selection for resistance. It is this topic that is of paramount concern to us and we have and continue to work to ensure antimicrobial agents remain prescription only medicines to preserve their efficacy in fighting infectious diseases now and in the future.’

Dr Anthony Brzezicki, a GP in South Croydon and chair of Croydon CCG, said in some cases OTC chloramphenicol does seem to be used inappropriately. He said: ‘I do not see most cases who attend pharmacy for chloramphenicol. I do, however, see people who have been advised to take drops with too much time between them – for example, once daily – so they do not work, or who have sensitised their eyes by taking them for too long, sometimes for two weeks or more.

‘So I think there is scope for improving the advice given to people who buy OTC drops.’

Dr Martin Duerden, a part-time GP in Conwy, Wales and RCGP expert clinical adviser on prescribing, said: ‘This research paper on OTC chloramphenicol eye drops suggests that provision OTC has been in addition to GP prescribing in Wales and has therefore not reduced consultations for conjunctivitis.  It is likely that this is the same across the UK. 

‘A possible explanation is that families who used to self-treat or use other OTC eye drops now buy chloramphenicol. Those who went to their GP continue to do so, expect chloramphenicol, and still get it on prescription.’

He added: ‘The reality is that chloramphenicol eye drops are only needed for severe conjunctivitis and there is clear evidence that with a “watch and see” strategy many people do not need treatment and get better anyway. We need to change both clinical practice and patient understanding to enable reduced use.

‘I have concerns that there is both overuse and inappropriate use of this treatment and we really must reserve chloramphenicol so that it remains a viable drug for the future. I think we should stop providing it OTC.’

Int J Pharm Pract 2013; available online 17 April