The number of prescriptions for antibiotic prophylaxis before invasive dental procedures has dropped sharply in England since 2008, while the incidence of infective endocarditis has risen significantly in the same time period, researchers found.
A study led by Dr. Martin Thornhill of the University of Sheffield (England) School of Clinical Dentistry, and published online Nov. 18 in the Lancet (doi: 10.1016/S0140-6736(14)62007-9) showed that after the National Institute for Health and Care Excellence issued guidelines against antibiotic prophylaxis, even for patients at high risk of endocarditis, prescriptions fell precipitously from a mean 10,900 per month in 2004-2008 in England to a mean 2,236 a month between April 2008 and April 2013, with only 1,235 issued in the last month of the study period. The NICE guidance, which went further than other published recommendations that have aimed to limit, but not eliminate, the use of antibiotic prophylaxis as a form of endocarditis prevention, cited the absence of a robust evidence base supporting its effectiveness, and also the risk of adverse drug reactions.
Dr. Thornhill and his colleagues reviewed both national prescription records and hospital discharge records for patients with a primary diagnosis of infective endocarditis. Prescriptions of antibiotic prophylaxis for the prevention of infective endocarditis fell significantly after introduction of the NICE guidance.
The incidence of infective endocarditis, in contrast, rose by 0.11 cases per 10 million people per month following the 2008 guidance (95% confidence interval, 0.05-0.16; P < .0001). By March 2013, the researchers found that there were 34.9 more cases per month than would have been expected had the previous trend continued (95% CI, 7.9-61.9). Moreover, the increase was significant for patients determined to be at low or moderate risk as well as for those deemed high risk. The researchers did not find a statistically significant increase in endocarditis-related mortality corresponding to the drop in prescriptions.
Dr. Thornhill and his colleagues cautioned that their results did not establish a causal association between the drop in prescriptions and the rise in cases, and that further investigations were now warranted.
The study was funded by Heart Research UK, Simplyhealth, and the U.S. National Institutes of Health. Two of its authors were involved in guidelines on infective endocarditis issued by the American Heart Association in 2007. One author helped produce European Society of Cardiology endocarditis guidelines in 2009, and also acted as a consultant to NICE during the drafting of the 2008 guidelines on antibiotic prophylaxis in endocarditis.