Antimicrobials · Cephalosporins
The facts most likely to be tested
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Ceftriaxone is the first-line empiric treatment for Neisseria gonorrhoeae infections.
Ceftriaxone is the drug of choice for bacterial meningitis in combination with vancomycin to cover Streptococcus pneumoniae.
Ceftriaxone is contraindicated in neonates with hyperbilirubinemia due to the risk of biliary sludging and kernicterus.
Ceftriaxone is the preferred agent for the treatment of disseminated Lyme disease involving carditis or neurologic manifestations.
Ceftriaxone is a third-generation cephalosporin that provides excellent coverage against Gram-negative rods and Streptococcus species.
Ceftriaxone is the standard prophylactic antibiotic for meningococcal meningitis exposure in close contacts.
Ceftriaxone is unique among cephalosporins because it is primarily biliary excreted, requiring no renal dose adjustment.
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A 24-year-old male presents to the urgent care clinic with a 2-day history of purulent urethral discharge and dysuria. He reports unprotected sexual intercourse with a new partner one week ago. Physical examination reveals erythema of the urethral meatus and tenderness. A Gram stain of the discharge shows Gram-negative diplococci within neutrophils. The patient has no known drug allergies.
What is the most appropriate pharmacologic treatment for this patient?
Ceftriaxone
The patient presents with classic symptoms of gonorrhea, which is treated with a single dose of intramuscular ceftriaxone as per current CDC guidelines, testing the first-line empiric treatment bet.
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High yield triage
Classification
Third-generation cephalosporin; broad-spectrum beta-lactam antibiotic.
Indications
Gonorrhea, meningitis, community-acquired pneumonia, and pyelonephritis.
Mechanism of Action
Binds penicillin-binding proteins (PBPs) to inhibit bacterial cell wall synthesis.
Side Effects
Biliary sludge, diarrhea, anaphylaxis, and C. difficile colitis.
Contraindications / Monitoring
Neonates with hyperbilirubinemia; monitor LFTs and renal function.
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Mechanism of Action
Ceftriaxone binds to penicillin-binding proteins (PBPs), which are essential enzymes for peptidoglycan cross-linking. This inhibition disrupts the structural integrity of the bacterial cell wall, leading to cell lysis. It exhibits high affinity for Gram-negative organisms while maintaining moderate Gram-positive coverage.
Unique Properties
Unlike most cephalosporins, it has a long half-life allowing for once-daily dosing. It is uniquely eliminated via biliary excretion, making it the preferred choice in patients with renal failure.
Indications
It is the first-line treatment for Neisseria gonorrhoeae (often paired with doxycycline). It is also the drug of choice for bacterial meningitis due to excellent CSF penetration and empiric coverage of Streptococcus pneumoniae.
Pharmacokinetics
Excreted through the biliary tract (40%) and renal route (60%). Because it does not require dose adjustment in renal impairment, it is the safest cephalosporin for patients with CKD.
Side Effects & Adverse Events
Common effects include diarrhea and biliary pseudolithiasis (biliary sludge). C. difficile colitis is a major risk due to broad-spectrum activity. Anaphylaxis is a rare but life-threatening hypersensitivity reaction.
Contraindications
Neonates with hyperbilirubinemia are at risk for kernicterus because ceftriaxone displaces bilirubin from albumin. Concurrent use with calcium-containing IV solutions is contraindicated in neonates due to the risk of precipitate formation in the lungs and kidneys.
Monitoring
Monitor for signs of C. difficile (watery diarrhea). In prolonged therapy, assess LFTs and CBC for potential neutropenia or thrombocytopenia.
Clinical Pearls
Always remember it is the gold standard for gonorrhea. If a board question describes a patient with renal failure needing a cephalosporin, ceftriaxone is the correct answer because it avoids the kidney for primary clearance.