title: The in vitro effect of N-acetylcysteine on prothrombin time in plasma samples from healthy subjects.
abstract: OBJECTIVE
  In the treatment of acetaminophen toxicity, clinicians believe that N-acetylcysteine (NAC) artificially elevates prothrombin time (PT), potentially obscuring signs of liver damage. However, the effect of NAC on human blood coagulation remains unverified. The purpose of this study was to evaluate the effect of NAC on PT prolongation in human plasma.
  
  
  METHODS
  The authors obtained blood samples from 33 volunteer subjects. The blood plasma samples were divided into four 1-mL aliquots. The first aliquot was used as a control. To three additional aliquots, varying amounts of NAC were added, maintaining constant volume with a maximum dilution of 0.5%. The four concentrations of NAC (control, 250, 500, or 1,000 mg/L) were incubated at 37°C for 1 hour, and PT was measured. PT values were compared using fixed effects regression.
  
  
  RESULTS
  Mean (± standard deviation [SD]) PT values for the control, 100, 500, and 1,000 mg/L NAC values were 13.9 (±1.01), 14.2 (±1.08), 15.5 (±1.21), and 17.4 (±1.72) seconds, respectively. At the 1,000 mg/L concentration, two PTs exceeded 22 seconds, and half exceeded 17 seconds. PT increased with NAC concentrations (fixed effects regression p < 0.001) in a dose-dependent manner.
  
  
  CONCLUSIONS
  In this in vitro human model, NAC had a dose-dependent effect on PT.
authors.affiliation: Department of Emergency Medicine, Division of Medical Toxicology, University of Pittsburgh School of Medicine, PA, USA.
authors.forename: Anthony F
authors.initials: AF
authors.lastname: Pizon
authors.forename: David H
authors.initials: DH
authors.lastname: Jang
authors.forename: Henry E
authors.initials: HE
authors.lastname: Wang
mesh_terms: D000082:Acetaminophen / Q000506:poisoning; D000111:Acetylcysteine / Q000009:adverse effects / Q000494:pharmacology*; D000328:Adult; D001777:Blood Coagulation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D011517:Prothrombin Time
chemical_list: D000082:Acetaminophen; D000111:Acetylcysteine