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Am Fam Physician. 2009;80(9):939-941

Author disclosure: Nothing to disclose.

Clinical Scenario

A 65-year-old woman presents with a history of mitral valve prolapse, and she is planning to undergo an invasive dental procedure. She has been told in the past that she needs antibiotics before such a procedure. However, the effectiveness and potential risks of antibiotic prophylaxis are uncertain for this patient.

Clinical Question

Should physicians give prophylactic antibiotics to protect against bacterial endocarditis in at-risk patients undergoing invasive dental procedures?

Evidence-Based Answer

A single observational study found no evidence that antibiotic prophylaxis reduces the incidence of bacterial endocarditis in high-risk patients about to undergo an invasive dental procedure. It is also uncertain if the potential harms and costs of antibiotics outweigh any benefit.1 Revised American Heart Association (AHA) guidelines do not recommend prophylaxis for patients at moderate risk, such as women with mitral valve prolapse.2

Practice Pointers

Invasive dental procedures have long been implicated as a cause of bacterial endocarditis. Transient bacteremia after dental procedures is well documented.3 Bacteremia resulting in endocarditis on damaged heart valves and protection with prophylactic antibiotics have been demonstrated in animal models, but expert opinion on ideal human prophylaxis has swayed widely over the past few decades.2,4,5

In this Cochrane review, the authors attempted to determine if prophylactic antibiotic administration affects morbidity or mortality in normal- and high-risk patients, and whether possible medication side effects outweigh potential benefits.1 Review of the literature found only one case-control study. Cases were defined as patients with congenital heart disease, coarctation of the aorta, rheumatic and other valvular dysfunction, or mitral valve prolapse who developed bacterial endocarditis within 180 days of a medical or dental procedure that required prophylaxis. The control group consisted of patients who had similar risk factors and procedures that required prophylaxis, but who did not develop endocarditis.

In each group, approximately one sixth of patients who met the criteria received prophylaxis, with no significant difference between groups.1 No studies that reported morbidity or mortality from prophylactic antibiotics for dental procedures were located; however, a few related studies can give some insight. Hypersensitivity to penicillin is thought to affect 1 to 10 percent of patients treated.6 One study in patients with mitral valve prolapse estimated that a patient was five times more likely to die from anaphylaxis from penicillin treatment than from endocarditis.7 Conversely, for 35 years, the Medicines and Healthcare products Regulatory Agency in the United Kingdom had no reported cases of fatal anaphylaxis caused by a one-time 3-g prophylactic amoxicillin dose.8 However, not all events were fully reported.8

In 2007, the AHA reversed previous guidelines in light of the lack of evidence supporting prophylaxis for the prevention of endocarditis, and because of its risk of increasing antibiotic resistance.2 The AHA no longer recommends antibiotics for persons at moderate risk of endocarditis, such as those with mitral valve prolapse. Based on expert opinion, the AHA currently recommends considering prophylaxis only for patients at the highest risk of having a serious adverse outcome from endocarditis (see accompanying table).2,9

Cochrane Abstract

Background: Infective endocarditis is a severe infection arising in the lining of the heart with a high mortality rate. Many dental procedures cause bacteremia, and it was believed that this may lead to bacterial endocarditis in a few persons. Guidelines in many countries have recommended that before invasive dental procedures, antibiotics should be administered to persons at high risk of endocarditis. However, recent guidance by the National Institute for Health and Clinical Excellence in England and Wales has recommended that antibiotics are not required.

Objectives: To determine whether prophylactic antibiotic administration compared with no such administration or placebo before invasive dental procedures in persons at increased risk of bacterial endocarditis influences mortality, serious illness, or endocarditis incidence.

Search Strategy: The search strategy from the previous review was expanded and run on Medline (1950 to June 2008) and adapted for use on the Cochrane Oral Health, Heart, and Infectious Diseases Groups' Trials Registers, as well as the following databases: CENTRAL (The Cochrane Library 2008, Issue 2); EMBASE (1980 to June 2008); and the metaRegister of Controlled Trials (to June 2008).

Selection Criteria: Due to the low incidence of bacterial endocarditis, it was anticipated that few, if any, trials would be located. For this reason, cohort and case-control studies were included where suitably matched control or comparison groups had been studied. The intervention was the administration of an antibiotic compared with no such administration before a dental procedure in persons with an increased risk of bacterial endocarditis. Cohort studies would need to follow those at increased risk and assess outcomes following any invasive dental procedures, grouping by whether prophylaxis was received. Included case-control studies would need to match persons who had developed endocarditis (and who were known to be at increased risk before undergoing an invasive dental procedure preceding the onset of endocarditis) with those at similar risk but who had not developed endocarditis. Outcomes of interest were: mortality or serious adverse event requiring hospital admission; development of endocarditis following any dental procedure in a defined time period; development of endocarditis due to other non-dental causes; any recorded adverse events to the antibiotics; and cost implications of the antibiotic provision for the care of those patients who develop endocarditis.

Data Collection and Analysis: Two review authors independently selected studies for inclusion, then assessed quality and extracted data from the included study.

Main Results: No randomized controlled trials, controlled clinical trials, or cohort studies were included. One case-control study met the inclusion criteria. It collected all the cases of endocarditis in The Netherlands over two years, finding a total of 24 persons who developed endocarditis within 180 days of an invasive dental procedure, definitely requiring prophylaxis according to current guidelines, and who were at increased risk of endocarditis because of a preexisting cardiac problem. This study included participants who died because of the endocarditis (using proxies). Control participants attended local cardiology outpatient clinics for similar cardiac problems, had undergone an invasive dental procedure within the past 180 days, and were matched by age with the other participants. No significant effect of penicillin prophylaxis on the incidence of endocarditis could be seen. No data on other conditions were found.

Authors' Conclusions: There remains no evidence about whether penicillin prophylaxis is effective or ineffective against bacterial endocarditis in persons at risk who are about to undergo an invasive dental procedure. There is a lack of evidence to support previously published guidelines in this area. It is not clear whether the potential harms and costs of antibiotic administration outweigh any beneficial effect. Ethically, physicians need to discuss the potential benefits and harms of antibiotic prophylaxis with their patients before a decision is made about administration.

These summaries have been derived from Cochrane reviews published in the Cochrane Database of SystematicReviews in the Cochrane Library. Their content has, as far as possible, been checked with the authors of the originalreviews, but the summaries should not be regarded as an official product of the Cochrane Collaboration; minorediting changes have been made to the text (

Cardiac transplantation recipients who develop cardiac valvulopathy
Congenital heart defect completely repaired with prosthetic material or device (whether placed by surgery or by catheter intervention) during the first six months after the procedure
Cyanotic CHD not repaired, including palliative shunts and conduits
Repaired CHD with residual defects at the site or adjacent to the site of a prosthetic patch or prosthetic device (which inhibits endothelialization)
Previous infective endocarditis
Prosthetic cardiac valve or prosthetic material used for cardiac valve repair

These are summaries of reviews from the Cochrane Library.

This series is coordinated by Corey D. Fogleman, MD, assistant medical editor.

A collection of Cochrane for Clinicians published in AFP is available at

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