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Journal of The Korean Society of Emergency Medicine 2003;14(1): 56-60. |
| The Clinical Use of the Plasma Acetaminophen Halflife in NAC-treated Acetaminophen Overdose |
| Seung Ho Lee, Mi Jin Lee, Woon Jeung Lee, Won Jae Lee, Se Kyung Kim |
| Department of Emergency Medicine, College of Medicine, The Catholic University of Korea, Seoul, Korea. emmam@catholic.ac.kr |
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| ABSTRACT |
PURPOSE:
A plasma acetaminophen halflife of more than 4 hours has been correlated with hepatotoxicity in acetaminophen overdosing not treated with an antidote.
However, the acetaminophen halflife has not been studied in patients receiving the antidote N-acetylcysteine (NAC).
METHODS:
Ninety-eight (98) patients with acetaminophen overdoses, all of whom were treated with N-acetylcysteine were studied. A minimum of 2 plasma acetaminophen valu e s > 2.0 microgram/ml were available for calculating the acetaminophen halflife, assuming first-order kinetics.
RESULTS:
Overall, the median acetaminophen halflife was 6.2 hours (range, 1.15~103.9 hours). Sixty-two (62) patients with no hepatotoxicity (AST < 100 U/L), 13 patients with little hepatotoxicity (100 U/L < AST < 1,000 U/L), 17 patients with severe hepatotoxicity (AST > 1,000 U/L) without acute hepatic failure, and 6 patients with hepatotoxicity (AST > 1,000 U/L) with hepatic failure had acetaminophen halflives of 3.7 hours (range, 1.15~23.2 hours), 5.9 hours (range, 1.96~26.2 hours), 6.3 hours (range, 2.19~15.38 hours), and 32.8 hours (range, 5.48~103.9 hours), respectively (p<0.05). A receiver operating characteristic curve analysis showed that an acetaminophen halflife of 5.19 hours provided better discrimination (sensitivity=69.6%, specificity=84.0%, accuracy=80.6%).
CONCLUSION:
The acetaminophen halflife correlates well with the degree of liver damage in patients treated with N-acetylcysteine. Longer halflives reflect a greater toxic effect on the liver. |
| Key words:
Acetaminophen, Elimination halflife, N-acetylcysteine |
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