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Difficulty: MediumPharmacologic Interventions

A 52-year-old woman is evaluated in the hospital for worsening erythema, warmth, and swelling of her right lower extremity. She was admitted 3 days ago for severe cellulitis and was started on empiric intravenous vancomycin and piperacillin-tazobactam. Her past medical history is significant for major depressive disorder and type 2 diabetes mellitus. Her home medications, which were continued on admission, include citalopram, metformin, and insulin glargine.

Today, her temperature is 38.4∘C38.4^\circ\text{C} (101.1∘F101.1^\circ\text{F}), blood pressure is 122/78 mmHg122/78\text{ mmHg}, heart rate is 98/min98/\text{min}, and respiratory rate is 16/min16/\text{min}. The erythema on her right leg has expanded proximally despite 72 hours of antimicrobial therapy. Blood cultures drawn on admission remain negative, but a tissue culture obtained from the leading edge of the cellulitis on admission grows *Enterococcus faecium*. Antimicrobial susceptibility testing reveals resistance to ampicillin and vancomycin. Renal function is within normal limits.

Which of the following is the most appropriate pharmacologic intervention for this patient?

  1. Discontinue vancomycin and start daptomycinAnswer
  2. B
    Discontinue vancomycin and start linezolid
  3. C
    Discontinue vancomycin and start ampicillin-sulbactam
  4. D
    Discontinue vancomycin and start ceftaroline
  5. E
    Increase the dose of intravenous vancomycin

Answer

Discontinue vancomycin and start daptomycin
The correct intervention is to discontinue vancomycin and start daptomycin. This patient has a severe soft tissue infection caused by vancomycin-resistant *Enterococcus faecium* (VRE). Daptomycin, a cyclic lipopeptide, causes rapid depolarization of the bacterial cell membrane and is a first-line, FDA-approved treatment for VRE complicated skin and soft tissue infections. Importantly, it does not interact with the patient's SSRI (citalopram), making it the safest choice.

Step-by-Step Solution

1
Analyze the culture and susceptibility results.
The patient has a soft tissue infection caused by vancomycin-resistant Enterococcus faecium (VRE).
To identify the pathogen and determine which classes of antibiotics will be ineffective.
2
Identify effective antimicrobial options for VRE.
Standard treatments for VRE include daptomycin, linezolid, and tigecycline.
To narrow down the potential therapeutic choices from the options provided.
3
Evaluate the patient's current medication list for potential drug-drug interactions.
The patient is taking citalopram, a selective serotonin reuptake inhibitor (SSRI).
To ensure the chosen antibiotic does not cause dangerous adverse effects when combined with home medications.
4
Select the safest and most effective antibiotic for this specific patient.
Daptomycin is chosen over linezolid.
Linezolid has reversible MAOI activity and can cause serotonin syndrome if given with an SSRI. Daptomycin is safe and effective for VRE soft tissue infections.

Key Concept

Management of VRE infections and avoidance of serotonin syndrome with linezolid.
Estimated Time:1m 30s
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Topics

Pharmacologic Interventions

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