Carbapenam
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Carbapenems
Carbapenems are a class of beta-lactam antibiotics with the broadest antibacterial spectrum of any currently available antibiotic group. They are considered "last-resort" or empiric agents for serious, polymicrobial, or drug-resistant infections.
Structure
Carbapenems are synthetic beta-lactam antibiotics structurally related to penicillins. The key structural difference is that the sulfur atom of the thiazolidine ring has been externalized and replaced by a carbon atom, producing a bicyclic core with a beta-lactam ring fused to a five-membered ring.
Drugs in the Class
| Drug | Trade Name | Key Feature |
|---|---|---|
| Imipenem/cilastatin | Primaxin | First carbapenem; requires cilastatin to prevent renal degradation |
| Meropenem | Merrem | Does not require cilastatin; less seizurogenic |
| Ertapenem | Invanz | Once-daily dosing; no Pseudomonas coverage |
| Doripenem | Doribax | Greatest Pseudomonas activity; no longer available in USA |
Mechanism of Action
Like all beta-lactams, carbapenems inhibit bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs), preventing cross-linking of peptidoglycan. They are bactericidal and time-dependent in their killing.
Antibacterial Spectrum
Carbapenems (especially imipenem/meropenem) have the broadest spectrum of any beta-lactam:
- Gram-positive cocci: S. aureus (MSSA), Streptococcus spp., Enterococcus faecalis, Listeria
- Gram-negative rods: E. coli, Klebsiella, Enterobacter, Serratia, Proteus, Acinetobacter, P. aeruginosa, Salmonella, H. influenzae
- Anaerobes: Bacteroides fragilis, Clostridium spp., Peptostreptococcus
Organisms NOT covered (resistant):
- Enterococcus faecium
- MRSA (methicillin-resistant S. aureus)
- Clostridioides difficile
- Stenotrophomonas maltophilia
- Burkholderia cepacia
- Ertapenem specifically: lacks P. aeruginosa, Enterococcus, and Acinetobacter coverage
Pharmacokinetics
| Feature | Details |
|---|---|
| Route | IV (all); ertapenem also IM (mixed with 1% lidocaine due to irritation) |
| Distribution | Penetrate well into body tissues and fluids, including CSF (except ertapenem); meropenem reaches therapeutic CSF levels even without meningeal inflammation |
| Elimination | Renal (glomerular filtration); dose adjustment required in renal insufficiency |
| Half-life | Imipenem ~1 hr; meropenem ~1 hr; ertapenem ~4 hr |
| Imipenem dosing | 0.25-0.5 g IV q6-8h |
| Meropenem dosing | 0.5-1 g IV q8h |
| Ertapenem dosing | 1 g IV/IM once daily |
Imipenem and Cilastatin
Imipenem is inactivated by dehydropeptidase-I in the brush border of the proximal renal tubule. It is therefore always co-administered with cilastatin, a dehydropeptidase inhibitor, to protect the drug from degradation and prolong its activity. Meropenem, doripenem, and ertapenem are not significantly degraded by this enzyme and do not require cilastatin.
Adverse Effects
- GI: Nausea, vomiting, diarrhea (most common)
- Seizures: High doses of imipenem, particularly in patients with renal failure or CNS disease. Meropenem is much less epileptogenic.
- Hypersensitivity: Cross-reactivity with penicillin is possible (shared bicyclic beta-lactam core) - use with caution in true penicillin allergy
- Infusion site reactions
- Eosinophilia and neutropenia (less common than other beta-lactams)
Clinical Indications
Carbapenems are reserved for:
- Polymicrobial infections (mixed aerobic/anaerobic)
- ESBL-producing gram-negative organisms (treatment of choice)
- Enterobacter infections (resist beta-lactamase destruction)
- Resistant P. aeruginosa infections (not ertapenem)
- Empiric therapy for severe, life-threatening infections
- Serious nosocomial infections (hospital-acquired/ventilator-associated pneumonia, complicated UTI, intra-abdominal infections)
Resistance - Carbapenem-Resistant Organisms (CRO)
Carbapenem resistance is a major clinical challenge. Resistant organisms may lack susceptibility to all traditional beta-lactams, fluoroquinolones, and aminoglycosides.
Resistance Mechanisms:
- Carbapenemases (serine carbapenemases - KPC, OXA; metallo-beta-lactamases - MBL/NDM/VIM)
- Outer membrane porin loss
- Efflux pump upregulation
Newer Agents for CROs:
| Combination | Active Against |
|---|---|
| Meropenem-vaborbactam (Vabomere) | KPC-producing Enterobacterales |
| Imipenem-cilastatin-relebactam (Recarbrio) | KPC-producing Enterobacterales, hospital/VAP |
| Ceftazidime-avibactam | KPC, AmpC, OXA-48 (not MBL) |
| Cefiderocol | All classes including MBL |
- None of the carbapenem/beta-lactamase inhibitor combinations cover metallo-beta-lactamases (MBL/NDM), except cefiderocol.
- Colistin (5 mg/kg once, then 1.67 mg/kg q8h) remains an option for pan-resistant CRO infections.
Beta-Lactamase Inhibitor Activity Summary
| Inhibitor | Class A (KPC) | Class B (MBL) | Class C (AmpC) | Class D (OXA) |
|---|---|---|---|---|
| Vaborbactam | + | - | - | - |
| Relebactam | + | - | + | +/- |
| Avibactam | + | - | + | +/- |
Sources:
- Lippincott Illustrated Reviews: Pharmacology, Ch. 29
- Katzung's Basic and Clinical Pharmacology, 16th Ed., Ch. 43
- Jawetz, Melnick & Adelberg's Medical Microbiology, 28th Ed.
- Goldman-Cecil Medicine, 2-Vol Set, Ch. 281
NSAIDs drugs lipincott create a a good dedign pic
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Here's your Lippincott-based NSAIDs infographic! It covers all the key pharmacology:
- Mechanism - COX-1/COX-2 inhibition pathway, with aspirin's unique irreversible acetylation
- Drug classification - non-selective vs. COX-2 selective (celecoxib) with all major agents
- 3 therapeutic actions - anti-inflammatory, analgesic, antipyretic
- Adverse effects - GI ulceration, renal effects, CV risk, Reye syndrome, bronchospasm
- Aspirin's special role - low-dose antiplatelet (TXA2 inhibition) vs. high-dose anti-inflammatory
- Key contraindications - PUD, renal insufficiency, 3rd trimester pregnancy, children with viral illness
Create a PPTX presentation on NSAID drug interactions and monitoring
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Your presentation is ready!
NSAIDs Drug Interactions Monitoring
Presentation · PPTX
9 slides, dark navy/teal/amber design theme. Here's what's inside:
| Slide | Content |
|---|---|
| 1 - Title | Cover slide with topic overview |
| 2 - Mechanism & COX Selectivity | COX pathway diagram + selectivity table for all major NSAIDs (aspirin through celecoxib) |
| 3 - Drug Interactions Part 1 | Warfarin, Aspirin+NSAIDs, Antihypertensives, Lithium - with mechanism, effect, severity badge & management |
| 4 - Drug Interactions Part 2 | Methotrexate, SSRIs/SNRIs, Corticosteroids, CYP2C9 inhibitors, Cyclosporine, Probenecid |
| 5 - Adverse Effects Profile | GI, Renal, Cardiovascular effects in color-coded columns |
| 6 - Special Populations | Pregnancy, Pediatrics, Elderly, Renal/Hepatic impairment, CVD - 6 cards with specific guidance |
| 7 - Monitoring Parameters | Full monitoring table (renal, GI, CBC, LFTs, INR, lithium levels) + GI protection strategy + patient counselling |
| 8 - Quick Reference Table | All 10 interactions in one severity-coded table (MAJOR/MODERATE) |
| 9 - Key Takeaways | 6 clinical pearls summarizing the whole presentation |
All content sourced from Lippincott Illustrated Reviews: Pharmacology, 8th Edition.
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