Ertapenem and meropenem:
| Feature | Ertapenem | Meropenem |
|---|---|---|
| Class | Carbapenem antibiotic | Carbapenem antibiotic |
| Spectrum | Broad, but lacks activity against Pseudomonas aeruginosa, Acinetobacter spp., and Enterococcus spp. | Very broad, including Pseudomonas, Acinetobacter, and some Enterococcus |
| Gram-Positive Coverage | Good activity vs. MSSA, Streptococcus | Good activity vs. MSSA, Streptococcus, Enterococcus faecalis (limited) |
| Gram-Negative Coverage | Covers Enterobacteriaceae, ESBL-producing organisms | Covers Enterobacteriaceae, ESBL, plus Pseudomonas and Acinetobacter |
| Anaerobic Coverage | Excellent (e.g., Bacteroides fragilis) | Excellent |
| Indications | Intra-abdominal infections, skin/soft tissue infections, community-acquired pneumonia, complicated UTIs, prophylaxis for colorectal surgery | Severe hospital-acquired infections, meningitis, febrile neutropenia, intra-abdominal infections, skin/soft tissue infections, complicated UTIs, pneumonia (including HAP/VAP) |
| CNS Penetration | Limited → not used for meningitis | Good penetration → used for meningitis |
| Half-life | ~4 hours (longer) | ~1 hour |
| Dosing (Adults) | 1 g IV once daily | 1 g IV q8h (standard); 2 g IV q8h for meningitis |
| Renal Dose Adjustment | Required if CrCl <30 mL/min | Required if CrCl <50 mL/min |
| Route | IV or IM | IV only |
| Adverse Effects | Similar to meropenem: seizures (rare), GI upset, hypersensitivity | Similar; slightly lower seizure risk than imipenem |
| Clinical Pearls | Convenient once-daily dosing, but avoid in suspected/confirmed Pseudomonas, Acinetobacter, or meningitis | Preferred in critically ill or neutropenic patients due to broader coverage and CNS activity |
Summary for pharmacists:
- Ertapenem = broad-spectrum, once-daily dosing, good for community-acquired and polymicrobial infections, but not for Pseudomonas/Acinetobacter/meningitis.
- Meropenem = broader spectrum, including Pseudomonas and CNS penetration, making it the go-to for hospital-acquired, severe, or resistant infections.