Serum alanine aminotransferase elevation during 10 days of acetaminophen use in nondrinkers

To describe the changes in serum alanine aminotransferase (ALT) levels in nondrinkers receiving acetaminophen for 10 days.

Prospective, open-label study.

Outpatient clinical research center.

Twenty-four healthy volunteers who reported an average alcohol consumption of less than one drink/day for the 30 days preceding study enrollment.

Patients were administered acetaminophen 4 g/day for 10 days (study days 1-10).

Serum ALT level, total bilirubin level, and international normalized ratio (INR) were measured on study days 0, 4, 7, 9, 11, and 14. Median ALT level increased from 24 U/L on day 0 to 39 U/L on day 7, and remained elevated through day 11 (39 U/L); these increases were statistically significant (p=0.0002). Median ALT level began to trend down by day 14 (35 U/L). Fourteen subjects (58%) had ALT levels above the upper limit of normal; the largest elevation was 3.8 times the upper limit of normal (day 7). No increases in INR or total bilirubin level were noted during the study, and no subject developed symptoms of liver injury (e.g., abdominal pain, jaundice).

Daily use of acetaminophen at the maximum dose of 4 g/day for 10 days caused asymptomatic ALT level elevations in subjects who do not consume alcohol. The clinical implication of these elevations remains unclear. Future studies should evaluate ALT changes and their clinical effects when acetaminophen is given for long periods of time.