Antimicrobials · Cephalosporins
The facts most likely to be tested
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Cefepime is a fourth-generation cephalosporin with an expanded spectrum covering both Gram-positive and Gram-negative organisms, including Pseudomonas aeruginosa.
The primary clinical indication for cefepime is empiric therapy for febrile neutropenia and hospital-acquired pneumonia.
Cefepime maintains stability against beta-lactamases produced by many Gram-negative bacteria due to its zwitterionic structure allowing rapid penetration through the outer membrane.
A unique and serious adverse effect of cefepime is neurotoxicity, which manifests as altered mental status, myoclonus, seizures, or non-convulsive status epilepticus.
Patients with renal impairment are at significantly higher risk for cefepime-induced neurotoxicity due to drug accumulation, necessitating dose adjustment.
Cefepime lacks activity against methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus species, and anaerobes.
Cefepime is considered a beta-lactam antibiotic and should be used with caution in patients with a history of anaphylaxis to penicillins.
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A 68-year-old male with a history of stage 4 chronic kidney disease is hospitalized for sepsis secondary to a urinary tract infection. He is started on empiric cefepime. On hospital day 3, the patient becomes increasingly lethargic and develops rhythmic jerking of his upper extremities. His physical exam is notable for myoclonus and confusion. Laboratory studies show a stable creatinine of 3.2 mg/dL and no evidence of metabolic derangement or intracranial hemorrhage.
What is the most likely cause of this patient's clinical deterioration?
Cefepime-induced neurotoxicity
The patient's presentation of myoclonus and altered mental status in the setting of renal insufficiency is a classic board presentation of cefepime neurotoxicity, which is tested as a dose-dependent complication in patients with impaired renal clearance.
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Classification
Fourth-generation cephalosporin with broad-spectrum activity.
Indications
Febrile neutropenia, hospital-acquired pneumonia, and pseudomonal sepsis.
Mechanism of Action
Inhibits bacterial cell wall synthesis by binding to penicillin-binding proteins (PBPs).
Side Effects
Rash, diarrhea, neurotoxicity, seizures.
Contraindications / Monitoring
History of anaphylaxis to cephalosporins. Monitor renal function (CrCl).
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Mechanism of Action
Cefepime binds to penicillin-binding proteins (PBPs), specifically PBP3 and PBP2, disrupting the final stage of peptidoglycan synthesis. This leads to cell lysis and death. Its zwitterionic structure allows rapid penetration through the porin channels of Gram-negative bacteria, enhancing efficacy against Pseudomonas aeruginosa.
Unique Properties
Unlike earlier generations, it maintains stability against many beta-lactamases. It provides the most robust Gram-negative coverage of all cephalosporins, including anti-pseudomonal activity, while retaining excellent Gram-positive coverage similar to first-generation agents.
Indications
It is the gold-standard empiric therapy for febrile neutropenia. It is also indicated for hospital-acquired pneumonia, complicated intra-abdominal infections, and complicated urinary tract infections caused by resistant organisms.
Pharmacokinetics
Excreted primarily via renal filtration. Dosage adjustments are mandatory in patients with renal impairment to prevent accumulation and subsequent neurotoxicity.
Side Effects & Adverse Events
Common effects include nausea, vomiting, and diarrhea. Neurotoxicity, including confusion, encephalopathy, and seizures, occurs primarily in patients with renal failure who receive excessive doses. Clostridioides difficile-associated diarrhea is a significant risk with prolonged use.
Contraindications
Hypersensitivity to cephalosporins or a history of severe IgE-mediated reactions to penicillins. Use with extreme caution in patients with a history of seizure disorders.
Monitoring
Monitor serum creatinine and calculate creatinine clearance to adjust dosing. Observe for signs of neurotoxicity, such as altered mental status or myoclonus, especially in the elderly.
Clinical Pearls
Think of Cefepime when you need to cover Pseudomonas in a patient who cannot tolerate piperacillin-tazobactam. It is the classic board answer for the empiric treatment of febrile neutropenia in oncology patients.