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University of Pennsylvania Medical Center Guidelines for Antibiotic Use
| Clinical Setting | Empiric Treatment | Likely Pathogens | Definitive Treatment | Dosage Regimen | Duration |
| Native valve | vancomycin + gentamicin1 | S. aureus | nafcillin2 + gentamicin |
2gm IV q 4 hour peak conc. of 3-4 mcg/ml (consult pharmacokinetics) |
4-6 weeks 3 days only |
viridans streptococci if MIC < 0.13 |
12-18mu/d IV in 6 divided doses | 4 weeks | |||
penicillin G + gentamicin |
12-18mu/d IV in 6 divided doses peak conc. of 3-4 mcg/ml (consult pharmacokinetics) |
2 weeks 2 weeks | |||
viridans streptococci if MIC 0.1 to 0.54 |
penicillin G + gentamicin |
18mu/d IV in 6 divided doses peak conc. of 3-4 mcg/ml (consult pharmacokinetics) |
4 weeks 2-4 weeks | ||
viridans streptococci if MIC > 0.5 |
penicillin G + gentamicin |
18-30mu/d IV in 6 divided doses peak conc. of 3-4 mcg/ml (consult pharmacokinetics) |
4-6 weeks 4-6 weeks | ||
| S. pneumoniae | penicillin G5 | 20mu/d IV in 6 divided doses | 4-6 weeks | ||
| Enterococcus spp.6 | ampicillin + gentamicin |
2gm IV q 4 hr peak conc. of 3-4 mcg/ml (consult pharmacokinetics) |
4-6 weeks 4-6 weeks | ||
| Prosthetic Valve7 | vancomycin + gentamicin | S. aureus | as above2 ± rifampin9 | 300 mg q 8 hr or 600mg q 12 hr, both PO (IV is available) | 6 weeks8 |
| coagulase negative staphylococcus | vancomycin + | see this link | 6 weeks | ||
| gentamicin + | peak conc. 3-4 mcg/ml (consult pharmacokinetics) | 2 weeks | |||
| rifampin9 | 300 mg q 8 hr PO (IV is available) | 6 weeks | |||
1For SBE or chronic endocarditis, can await cultures if patient clinically stable
2If beta-lactam allergy or MRSA-use vancomycin
3Alternative: ceftriaxone 2gm IV/IM q 24hr x 4-6 weeks
4Or, if organism is nutritionally deficient
5Up to 25% of isolates penicillin resistant; obtain MICs
6Review susceptibilities-30% of isolates multidrug resistant; penicillin G 18-30mu/day can be substituted for ampicillin if microorganism susceptible
7Surgery usually required
8May require subsequent oral therapy
9Rifampin should not be added to the regimen until the organism is shown to be susceptible to gentamicin, as otherwise rifampin resistance is likely to develop. If the isolate is gentamicin-resistant then the possibility of adding a gentamicin substitute should be discussed with an expert, before starting rifampin. Rifampin administration increases warfarin clearance and patients receiving warfarin may require an increased warfarin dosage, based on prothrombin time.
updated 7/30/2007 by Paul Edelstein