Amoxicillin may be safer than clindamycin as endocarditis prophylaxis

By Lorraine L. Janeczko

Amoxicillin may be safer than clindamycin as endocarditis prophylaxis before dental work, a new study from England suggests.

Dentists have historically given antibiotic prophylaxis (AP) to patients at risk of infective endocarditis. But there is little evidence supporting this controversial approach, researchers write in the Journal of Antimicrobial Chemotherapy, online April 29.

To investigate adverse reactions to amoxicillin and clindamycin when used to prevent endocarditis, Dr. Martin H. Thornhill of the University of Sheffield School of Clinical Dentistry and colleagues reviewed AP prescribing data for England over roughly 10 years from the NHS Business Services Authority.

They also reviewed adverse drug reaction data from the Medicines and Healthcare Products Regulatory Agency's Yellow Card reporting scheme for prescriptions of the standard AP protocol of a single 3 g oral dose of amoxicillin or a single 600 mg oral dose of clindamycin for people allergic to penicillin.

The researchers found that the adverse drug reaction rate reported for amoxicillin AP was 0 fatal reactions per million prescriptions -- actually 0 fatal reactions for nearly 3 million prescriptions -- and 22.62 non-fatal reactions per million prescriptions.

Clindamycin, though, had 13 fatal and 149 non-fatal reactions per million prescriptions, most of which were due to Clostridium difficile infection.

"We were surprised on two counts," Dr. Thornhill told Reuters Health by email.

"Amoxicillin for AP was much safer than we expected (much safer than has been assumed by guideline committees deciding what guidance to give regarding AP)," he said, while "clindamycin proved to be less safe than expected."

The authors suggest incorporating the findings into future discussions of the role of AP to prevent infective endocarditis and into calculations concerning its clinical and cost-effectiveness.

Dr. Thornhill noted that there is still controversy over the use of AP to prevent infective endocarditis, and that while most guideline committees in the world recommend it, those in the UK do not.

"The main concern about giving AP is the risk of provoking an adverse drug reaction," he wrote. "So if AP with amoxicillin is safer than previously thought, it swings the balance of opinion more in favor of giving AP to prevent infective endocarditis. Equally, if AP with clindamycin is less safe than previously thought (it is usually only used for those who could allergic to amoxicillin), it suggests that another alternative needs to be found."

Dr. Thornhill added that uncertainties and concerns still exist about whether AP actually helps prevent infective endocarditis, and his group plans more research to answer this question.

"Proof would require a randomized controlled trial of AP and we would like to do this. However, the size and cost of such a study makes it difficult to obtain the necessary funding," he said.

"It is important that clinicians continue to follow their national guidelines on the use of AP and not change their practice until guideline committees process this information and decide whether or not to change their guidance," Dr. Thornhill advised.

The study has no commercial funding and the authors did not declare any conflicts of interest.

SOURCE: http://bit.ly/1K4micz

J Antimicrob Chemother 2015.

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