penicillin for secondary prevention of rheumatic fever or for other purposes are likely to have viridans group streptococci in their oral cavity that are relatively resistant to penicillin or amoxicillin. In such cases, the provider should select either clindamycin, azithromycin, or clarithromycin for IE prophy- laxis for a dental procedure, but only for patients shown in Table 3. Because of possible cross-resistance of viridans group streptococci with cephalosporins, this class of antibi- otics should be avoided. If possible, it would be preferable to delay a dental procedure until at least 10 days after comple- tion of the antibiotic therapy. This may allow time for the usual oral flora to be reestablished. Patients receiving parenteral antibiotic therapy for IE may require dental procedures during antimicrobial therapy, particu- larly if subsequent cardiac valve replacement surgery is antici- pated. In these cases, the parenteral antibiotic therapy for IE should be continued and the timing of the dosage adjusted to be administered 30 to 60 minutes before the dental procedure. This parenteral antimicrobial therapy is administered in such high doses that the high concentration would overcome any possible low-level resistance developed among mouth flora (unlike the concentration that would occur after oral administration). Patients Who Receive Anticoagulants Intramuscular injections for IE prophylaxis should be avoided in patients who are receiving anticoagulant therapy (Class I, LOE A). In these circumstances, orally administered regi- mens should be given whenever possible. Intravenously administered antibiotics should be used for patients who are unable to tolerate or absorb oral medications. Patients Who Undergo Cardiac Surgery A careful preoperative dental evaluation is recommended so that required dental treatment may be completed whenever possible before cardiac valve surgery or replacement or repair of CHD. Such measures may decrease the incidence of late prosthetic valve endocarditis caused by viridans group streptococci. 