Title: Effect of N-Acetylcysteine on Prothrombin Time and Coagulation Factors
题目：N-乙酰半胱氨酸对凝血酶原时间和凝血因子的影响
Author 作者: Bryan Hayes

In the treatment of acetaminophen poisoning with N-acetylcysteine (NAC), the PT/INR can be slightly elevated even in the absence of hepatotoxicity. Considering Prothombin Time (PT) is one of the criteria used to assess severity of liver damage in this setting, it is important to know how much the PT/INR can be affected by NAC and if it has an actual effect on coagulation factor levels.
用N-乙酰半胱氨酸（NAC）治疗对乙酰氨基酚中毒时，即使在没有肝毒性，PT/ INR​​也可以略有升高。由于凝血酶原时间（PT）是用来评估在此情况下肝损害严重程度的标准之一，因此要知道NAC可使PT/ INR增高多少和它对凝血因子水平的影响是重要的。
N-acetylcysteine has been shown to slightly increase the PT by up to 3.5 seconds in healthy volunteers.
在健康志愿者中，N-乙酰半胱氨酸可以稍微增加PT（高至3.5秒）
A more recent study by the same authors demonstrated a reduction in vitamin K-dependent clotting factor activity (II, VI, IX, and X) after NAC administration in healthy volunteers.
由同样作者最近的研究表明，健康志愿者在用NAC后维生素K依赖性凝血因子的活性（II，VI，IX，X）有减少
Clinical Practice Pearls 临床实践要点
The elevation in PT/INR after NAC administration is real, not simply laboratory interference.
However, the PT/INR elevation and decrease in coagulation factors is modest and not likely clinical significant.
Many poison center guidelines allow for an INR up to 2 to be considered 'normal' to account for this phenomenon in this setting.
用NAC后PT/ INR​​升高是事实，不是简单的由实验室误差造成
然而，PT/ INR​​增高和凝血因子减少是轻微的，很可能没有什么临床意义
在这种情形下，许多毒物中心的指南将INR为2视为“正常”
References 参考文献：
1. Pizon AF, et al. The in vitro effect of n-acetylcysteine on prothrombin time in plasma samples from healthy subjects. Acad Emerg Med 2011;18:351-4. [PMID 21496136]
2. Jang DH, et al. In vitro study of n-acetylcysteine on coagulation factors in plasma samples from healthy subjects. J Med Tox 2013;9:49-53. [PMID 22733602]