Aminotransferase Trends During Prolonged Acetaminophen Dosing

The objective of this study is to monitor liver function tests (blood levels of an indicator of liver function) of healthy people taking the maximum labeled daily dose of acetaminophen compared to people taking placebo for 16 to 40 days. Those people that continue to have normal liver tests after 16 days will have completed their part of the study. People that develop abnormal liver function tests will continue taking acetaminophen or placebo, and have their liver tests monitored closely for up to an additional 24 days. This is to (1) make sure these tests return to normal and (2) determine when these tests return to normal while still taking acetaminophen or placebo. If at any time the liver tests indicate anything more than a minor increase, you would be immediately told to stop taking the study drug.

Secondary objective is to determine the proportion of subjects that have detectable acetaminophen-protein adducts after daily dosing.

Acetaminophen use is common and many consumers take 4g/day for longer than 4 days. The use of 4g/day of acetaminophen for more than 4 days causes an asymptomatic ALT elevation in some people. This elevation most likely resolves while continuing treatment, but it is possible that some individuals may go on to develop clinical liver injury. By carefully following healthy subjects who are taking the maximal daily dose of acetaminophen, we can safely determine if the ALT elevation resolves or progresses to clinical liver injury. If a subject develops clinical liver injury we can intervene before irreversible injury occurs.

• Drug Toxicity
• Healthy

• Drug: acetaminophen
  500 mg caplets; 2 capsules (1 g)/dose; 4 doses (4 g)/day, 4 hours apart for 16 to 40 days.
  Other Name: tylenol
• Drug: placebo
  placebo caplets, 2 caplets per dose, 4 doses per day, 4 hours apart for 16 to 40 days
  Other Name: placebo

• Experimental: 1
  acetaminophen
  Intervention: Drug: acetaminophen
• Placebo Comparator: 2
  placebo
  Intervention: Drug: placebo

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Inclusion Criteria:

• age 18 or older

Exclusion Criteria:

1. History of acetaminophen ingestion on any of the four days preceding study enrollment
2. Measurable serum acetaminophen level at time of enrollment
3. Viral markers of Hepatitis B or C, or viral markers of Hepatitis A with an ALT level greater than ULN during screening laboratory testing
4. Serum ALT or AST level greater than ULN at Screening or Day 0
5. Total bilirubin level greater than ULN at Screening or Day 0
6. INR level greater than ULN at Screening
7. Alkaline phosphatase level greater than ULN at Screening
8. Platelet count less than 125 10^9/L at Screening
9. Known cholelithiasis
10. Positive pregnancy test at Screening (female participants only)
11. History of consuming more than an average of 3 alcohol containing drinks daily over the preceding 2 weeks
12. History of consuming 3 or more alcohol containing drinks on any given day during the 2 weeks prior to study enrollment
13. New prescription medication started within the previous 30 days
14. Currently taking isoniazid
15. Currently taking warfarin
16. Currently adheres to a fasting type diet as determined by self report
17. Currently has anorexia nervosa as determined by self report
18. Participant is clinically intoxicated, psychiatrically impaired or unable to give informed consent for any reason
19. Known hypersensitivity or allergy to acetaminophen