Relation of Health Literacy to Exceeding the Labeled Maximum Daily Dose of Acetaminophen.

Introduction: Acetaminophen is a commonly used analgesic/antipyretic; overdoses can lead to liver damage. Little is known about the relationship of health literacy to exceeding the recommended maximum daily dose (4 g).

Methods: Subjects were recruited at 23 U.S. malls in 2011. Health literacy was measured by Rapid Estimate of Adult Literacy in Medicine (REALM), classified as very low (VLL, score <45); low (LL, 45-60); or adequate (AL, >60). Participants completed a 7-day acetaminophen use diary by daily telephone interview; an exit interview covered demographics, physical/mental health, medical history, medication label reading, and medication-taking knowledge/attitudes. Acetaminophen products were identified from a comprehensive list; subjects were not required to know their medications contained acetaminophen. Seven hundred fifty-six subjects aged ≥18 years had taken acetaminophen in the past 30 days and completed 7 diary days with ≥1 day of acetaminophen use, plus the exit survey. Analysis was conducted in 2012-2014.

Results: VLL were more likely than AL individuals to exceed 4 g on ≥1 day (OR [95% CI]=3.8 [1.5, 9.6]; 4.0 [1.3, 12] after controlling for five REALM score-related factors). On usage days, VLL individuals were also more likely to exceed 4 g (3.3 [1.1, 10], by generalized estimating equations; 2.4 [0.9, 6.6], direct effect after accounting for mediation by other deviations from label recommendations).

Conclusions: VLL individuals exceed the recommended maximum acetaminophen dose more often than AL individuals. Other identified characteristics related to health literacy do not explain this, but it is partly mediated by increased frequency of other label deviations.