What Are the Antibiotic Prophylactic Regimens for Endocarditis?

Surgeons prescribe prophylactic antibiotics before surgery to prevent infection rather than to treat an existing one.

Prophylactic use of antibiotics is the administration of antibiotics before certain surgical procedures to prevent introduction of a bacterial infection to abnormal tissues in the body. For examples, prophylactic antibiotics are used prior to bowel surgery or even significant dental work when the patient has a prosthetic joint or has a deformed or prosthetic heart valve. People who are at a high risk for contracting infective endocarditis because of deformed or prosthetic heart valves take prophylactic antibiotics to minimize the risk of infecting the valve with bacteria introduced into the body during an invasive procedure. 

Infective endocarditis is infection of the inner heart tissue (endocardium) and heart valves. Infective endocarditis is caused by bacteria infecting these tissues after entering the bloodstream.

Infective endocarditis is a serious condition that can destroy the function of the heart and its valves. The condition can cause abscesses in the heart, congestive heart failure and malfunction of the valves.

Infective endocarditis is difficult to treat and potentially fatal, so it is important to prevent its occurrence when possible. 

The link between certain invasive surgical procedures and infective endocarditis was first identified in the 1920s.  In 1955 the American Heart Association (AHA) first recommended the use of prophylactic antibiotics when performing certain invasive surgical procedures to prevent infective endocarditis.

Antibiotic prophylaxis was given for a wide range of invasive procedures, particularly dental procedures, performed on cardiac patients who were considered at risk for infective endocarditis.

Growing bacterial resistance to antibiotics and other factors have prompted changes to the guidelines, however, the drawbacks of widespread prophylactic use include:

• Rising bacterial resistance to antibiotics
• Adverse reactions to antibiotics
• Benefit to extremely few patients

In 2007, the AHA updated its guidelines to reduce the use of prophylactic antibiotics to only those patients with heart disease who had a particularly high risk of adverse outcome from infective endocarditis. Studies conducted since the guideline revisions have shown no appreciable increase in the incidence of infective endocarditis.

Currently, prophylactic antibiotic regimen for endocarditis is only for patients with high-risk cardiac conditions such as:

• Implanted prosthetic cardiac valve
• History of infective endocarditis
• Cardiac valvular disease developed after cardiac transplant  
• Certain kinds of congenital heart disease (CHD) as follows:
  • Unrepaired cyanotic CHD, in which deoxygenated blood bypasses the lungs and enters the system
  • Repaired CHD with prosthetic device implant
  • Repaired CHD with residual defects

Patients with high-risk heart conditions should receive prophylactic antibiotics one hour prior to the following procedures:

• All invasive dental procedures such as
  • Tooth extraction
  • Periodontal surgery
  • Replacement of tooth displaced by trauma
  • Tooth implant placement
• Invasive respiratory tract procedures such as
  • Tonsillectomy
  • Adenoidectomy
• Procedures for treatment of infected skin or musculoskeletal tissue

AHA guidelines dropped the requirement for antibiotic prophylaxis for endocarditis in the following procedures:

• Delivery of pregnant women
• Urogenital and gastrointestinal procedures
• Noninvasive respiratory tract procedures such as bronchoscopy
• Noninvasive dental procedures such as
  • Dental X-rays
  • Placement and adjustment of braces and other orthodontic appliances
  • Treatment of superficial caries
  • Administration of anesthetic injections through noninfected tissue
  • Following shedding of milk teeth
  • After trauma to the lip or mouth

The most common cause for infective endocarditis after invasive dental, oral, respiratory or esophageal procedures is Streptococcus viridans group of bacteria. Other bacteria that can lead to endocarditis are Staphylococcus aureus and Enterococcus group of bacteria. The antibiotics used in prophylaxis specifically target these bacteria.

Following are the antibiotic prophylactic regimens for endocarditis, administered as a single dose 30-60 minutes before the procedure:

Standard general prophylaxis

Oral amoxicillin

• Adults: 2 g
• Children: 50 mg/kg not exceeding 2 g

Unable to take oral medication

Intravenous/intramuscular (IV/IM) ampicillin

• Adults: 2 g
• Children: 50 mg/kg not exceeding 2 g

Allergic to penicillin

Oral clindamycin

• Adults: 600 mg
• Children: 20 mg/kg not exceeding 600 mg

Oral cephalosporin drugs such as cephalexin

• Adults: 2 g
• Children: 50 mg/kg not exceeding 2 g

Oral azithromycin or clarithromycin

• Adults: 500 mg
• Children: 15 mg/kg not exceeding 500 mg

Allergic to penicillin and unable to take oral medication

IV clindamycin

• Adults: 600 mg
• Children: 20 mg/kg not exceeding 600 mg

IV/IM cephalosporin drugs such as cefazolin or ceftriaxone

• Adults: 1 g
• Children: 50 mg/kg not exceeding 1 g