Within a week after initiation of effective antimicrobial therapy, almost 75 per cent of patients with IE, including those with PVE, are afebrile and 90 per cent have defervesced by the end of the second week of treatment. Persistence or recurrence of fever more than 7 to 10 days after initiation of antibiotic therapy identified patients with increased morality rate and with complications of infection or therapy.  Patients must be carefully monitored during therapy and for several months thereafter. Failure of antimicrobial therapy, myocardial or metastatic abscess, emboli, hypersensitivity to antimicrobial agents, and other complications of therapy (catheter-related infection, thrombophlebitis) or intercurrent illness may be manifested by persistent or recurrent fever. Drug reactions have accounted for fever in 17 to 28 per cent of these patients.  In 33 to 45 per cent of patients, persistent fever was associated with significant intracardiac complications, many of which require surgical intervention.

Renal function should be monitored in patients receiving vancomycin or aminoglycosides, and the complete blood counts should be checked at least weekly in patients receiving high dose beta-lactam antibiotics or vancomycin.