Prophylactic antibiotics are getting another look

Regimen redefines when to prescribe

Prophylactic antibiotics have been in the medical press recently. Give antibiotics to some high-risk heart patients before they undergo dental or surgical procedures, say new recommendations issued by the American Heart Association in Dallas. That prophylactic measure against bacterial endocarditis is hardly news, but when and how to administer antibiotics require a second look. Giving antibiotics appropriately should reduce treatment costs and adverse effects. Antibiotic administration is particularly important for patients likely to develop endocarditis and its complications.

The new recommendations, published in the June 11 issue of the Journal of the American Medical Association, as well as in the July 1 issues of Circulation and Journal of the American Dental Association, define when to consider antibiotics. Major changes in the updated recommendations emphasize that most cases of endocarditis are not attributable to an invasive procedure. Cardiac conditions are stratified into high-, moderate-, and negligible-risk categories based on potential outcome if endocarditis develops.

At-risk are those with a history of the disease, an artificial heart valve, certain congenital heart malformations, hypertrophic cardiomyopathy, or heart valve damage or dysfunction.

The preventive measure is costly, is inconvenient, and causes side effects. The length of the list of conditions where antibiotics are not recommended rivals that of recommended applications.

Antibiotic use on patients with mitral valve prolapse — a large population — has been controversial and is not advocated. Neither is it recommended for patients with isolated atrial septal defects, previous coronary bypass surgery, innocent murmurs, or previous Kawasaki or rheumatic heart disease without valvular dysfunction. In addition, the recommendations do not include local anesthetic injections, suture removal, or dental procedures such as fluoride treatment and orthodontic appliance adjustment. Excluded from the recommendations are vaginal hysterectomy, vaginal or Cesarean delivery, cardiac catheterization, balloon angioplasty, or implanted pacemakers, defibrillators, or stents.

Antibiotics are, however, indicated for patients with valve leakage (mitral regurgitation), detected as a heart murmur or by ultrasound, and thickened valve tissues. The indication extends to tonsillectomy, adenoidectomy, biliary tract surgery, and operations involving the intestinal mucosa.

The new recommendations change the regimen for oral procedures to an initial dose of amoxicillin, 2 grams, with no follow-up dose. Erythromycin is no longer recommended for penicillin-allergic patients; clarithromycin and other alternatives are offered.

Reference

1. Dajani AS, Taubert KA, Wilson W, et al. Prevention of bacterial endocarditis: Recommendations by the American Heart Association. JAMA 1997; 277:1,794-1,801.