Acetaminophen levels 4 and 7 hours after 2000 and 3000 mg single doses in healthy adults.

Purpose: Therapeutic acetaminophen levels are not achieved at currently recommended doses. The purpose of this study is to determine acetaminophen levels in healthy adults after taking a single dose well in excess of the recommended dose.

Methods: 24 healthy adults received single 2 or 3 gram acetaminophen doses. Serum acetaminophen levels were drawn at 4 and 7 hours after the dose.

Results: The 2 gram doses (6 subjects) ranged from 23 to 40 mg/kg of body weight. The 3 gram single doses (18 subjects) ranged from 38 to 69 mg/kg of body weight. Mean 4-hour acetaminophen levels for 2 and 3 gram doses were 8.8 (SD 3.6, range 3-13) and 21.8 (SD 6.5, range 6-32) mcg/ml, respectively. Mean 7-hour acetaminophen levels for 2 and 3 gram doses were 1.5 (SD 1.4, range 0-3) and 7.7 (SD 4.6, range 0-17) mcg/ml, respectively.

Conclusions: Dosing by weight (i.e., mg/kg) appears to provide a more predictable dose-response relationship. Optimal adult dosing appears to be somewhere in the 20 to 30 mg/kg range based on the premise that the 4 hour level is a trough level that should be in the low therapeutic range.