Cefazolin and rifampin: A coagulopathy-inducing combination

Area of Science:

• Pharmacology
• Infectious Diseases
• Drug Safety

Background:

• Prosthetic joint infections often require combination antibiotic therapy.
• Rifampin is crucial for treating staphylococcal infections with retained implants.
• Cefazolin is a standard beta-lactam antibiotic for susceptible staphylococcal infections.

Observation:

• An 86-year-old patient with comorbidities developed significant bleeding and elevated INR post-hip arthroplasty.
• The patient received a regimen including rifampin and cefazolin for a prosthetic joint infection.
• Bleeding occurred after cefazolin was substituted for ceftriaxone, with both drugs administered concurrently with rifampin.

Findings:

• The Naranjo scale identified rifampin and cefazolin as the probable cause of the patient's elevated international normalized ratio (INR).
• The adverse event was classified as 'definitely avoidable' by the Liverpool drug reaction assessment tool.
• This case highlights a rare but potentially severe interaction leading to hypoprothrombinemia.

Implications:

• Clinicians should be vigilant for hypoprothrombinemia when prescribing concurrent rifampin and cefazolin.
• Monitoring prothrombin time and INR is essential in patients receiving these antibiotics, especially those with risk factors.
• Awareness of this drug interaction can guide preventative strategies and improve patient safety in managing prosthetic joint infections.