UMEM Educational Pearls

Takeaways

Recent study evaluated whether an acetaminophen (APAP) level obtained less than 4-hour post acute ingestion can predict which patient would not require n-acetylcysteine (NAC).  APAP cutoff level of 100 ug/mL was used for analysis. This was a secondary analysis of the Canadian Acetaminophen Overdose Study database (retrospective study). 

 

Bottom line:

  1. If initial APAP level of 100 ug/mL was applied as a cutoff point, it missed 27 patients (N= 1821) who had toxic APAP level at > 4-hour post ingestion that require NAC.  
  2. Only a very low (< 15 ug/mL) or undetectable initial APAP reliably identify (sensitivity 100%) patients who do not require NAC.
  3. Absorption of APAP can be delayed by coingestion of opioids or antimuscarinics.

 

 

In-Depth

 

Table 2. Diagnostic accuracy of acetaminophen concentration obtained 2 to 4 hours post-ingestion to identify subsequent potentially toxic concentration measured 4 to 20 hours pos-ingestion.

 

Subsequent 4-hour equivalent [APAP]

[APAP] obtained 2 to 4 hours post-ingestion

>150 ug/mL

< 150 ug/mL

<10

0

89

10-20

2

79

20-50

6

209

50-100

19

249

100-150

46

253

150-200

161

195

200-300

276

46

300-450

148

5

>450

38

0

 

References

Yarema MC, et al. Can a serum acetaminophen concentration obtained less than 4 hours post-ingestion determine which patients do not rquire treatment with acetylcysteine? Clin Toxicol 2016; online early: doi: 10.1080/15563650.2016.1247959