Prevalence and correlates of exceeding the labeled maximum dose of acetaminophen among adults in a U.S.-based internet survey

ABSTRACT Purpose Acetaminophen is a commonly used analgesic; excessive doses can lead to liver damage. We sought to determine the proportion of acetaminophen users exceeding the recommended maximum daily dose of 4 g and identify correlates of such behavior. Methods U.S. adults were recruited from an internet panel in summer 2010, oversampling past 30‐day acetaminophen users. Among 47 738 starting the study, 5649 completed all phases; individuals with low education were underrepresented. Subjects completed a 7‐day daily diary online, reporting intake of acetaminophen products selected from a comprehensive list; total daily dose was computed from product names. An exit survey elicited: attitudes/knowledge related to product ingredients, label reading, dosing behavior; demographics, medical history, general physical, and mental health status. Unconditional logistic regression identified variables independently associated with use exceeding 4 g. Results Among 3618 acetaminophen users, 163 took >4 g on ≥1 day (4.5%); the median dose was 5.5 g; 26 took >8 g (0.7%). >4‐g users were characterized by chronic pain, poor physical status, and heavy use of medical care. Knowledge of ingredients and recommended OTC doses for all products taken was inversely associated with >4‐g use (multivariable odds ratios [ORs] = 0.5–0.6), as was the attitude to start with the lowest dose (OR = 0.6). The attitude that users could choose their own dose was positively associated (OR = 1.3). Conclusions The results estimate the proportion of acetaminophen users exceeding 4 g in a group of U.S. adults, identify potentially modifiable attitudes and knowledge associated with such use, and characterize subpopulations at higher risk. Copyright © 2012 John Wiley & Sons, Ltd.