Introduction

1. Has OTC availability of chloramphenicol eye drops increased use and bacterial resistance? Anne Hinchliffe† Roger Walker†‡ †National Public Health Service for Wales, Cardiff and ‡Medicines and Health Research Group, Welsh School of Pharmacy, Cardiff, Wales Introduction Results In June 2005 chloramphenicol 0.5% eye drops were reclassified from a prescription only medicine to pharmacy medicine status and became available over-the-counter (OTC). The mean rates of prescribed ophthalmic chloramphenicol (drops and ointment) in Wales and England during 2006 (42.7 and 37.3 items per 1000 population respectively) were lower than the mean rates prior to OTC availability (44.8, 95% C-I 43.5 - 46.1 and 42.7, 95% C-I 37.5 - 48.0). The reductions in prescribed chloramphenicol eye drops and ointment in 2006 were more than compensated by the OTC sale of eye drops in both England and Wales. Overall combined (OTC and prescribed) supply increased in Wales during 2005 and again in 2006. Similar increases were observed in England (Table 1) This study investigated the impact of the increased access to chloramphenicol eye drops on: (i) overall combined supply (OTC and prescribed) of ophthalmic chloramphenicol preparations; and (ii) the emergence of antimicrobial resistance. Table 1Prescribed and OTC supply of chloramphenicol (items per 1000 population) in Wales and England Method The study had an ecological design and involved a retrospective analysis (January 2001 to December 2006) of primary care prescription data and pharmacy sell-in data. Prescribing data for chloramphenicol eye drops and ointment were obtained from the Prescription Pricing Authority in England (2003-06) and Health Solutions Wales (2001-06). The combined prescribing rate (items per 1000 population per year) for both chloramphenicol eye drops and ointment in 2006 was compared with the mean rate prior to reclassification. Data on the number of packs of Optrex Infected Eyes (chloramphenicol 0.5% eye drops) supplied by wholesalers to community pharmacists (except Boots) were obtained from IMS Health. Data for the two OTC chloramphenicol-containing eye drops (Brochlor; Boots Pharmacy Antibiotic eye drops) also available at the time of the study were not available. Data on antimicrobial resistance in Wales were obtained from primary care eye swabs sent to National Public Health Service microbiology laboratories that were part of the Welsh Antimicrobial Resistance Programme Surveillance Unit. No resistance data were available for England. The percent of eye swabs containing Gram positive organisms resistant to chloramphenicol was calculated for each year from 2004 to 2007. Statistical analyses were undertaken using SPSS version 12.0.1. There was an increase from 2004 to 2006 in the percent of chloramphenicol resistant eye swabs (p= 0.01, 95% C-I 0.00 - 0.02) but by 2007 resistance levels appeared to be returning to 2004 levels (p>0.05) (Table 2). Table 2Percent of chloramphenicol resistant samples in Wales, 2004-2007 Conclusions Reclassification of chloramphenicol eye drops resulted in an increase in overall supply of ophthalmic chloramphenicol. This was observed using data for the brand leader but excluded data for other OTC products and the sale of own brand and branded OTC preparations from a large pharmacy chain. The increase in supply did not result in a sustained increase in antimicrobial resistance in the eye swabs tested. Antimicrobial resistance can increase over time and monitoring needs to be ongoing. Acknowledgement: We are grateful to IMS Health for the supply of OTC sell-in data and to Dr M. Heginbothom (NPHS) for antimicrobial resistance data.