Predictors of misunderstanding pediatric liquid medication instructions

Our objective was to determine the level of adult understanding of dosage instructions for a liquid medication commonly prescribed for children.

Structured interviews were conducted with 373 adults waiting for an appointment at family medicine clinics serving low-income populations in Shreveport, La; Chicago; and Jackson, Mich, from July 2003-August 2004. Subjects were asked to read a prescription label for amoxicillin and explain how they would take the medication. Correct interpretation was determined by a panel of blinded physician reviewers who coded subjects' verbatim responses. Qualitative methods were used to determine the nature of incorrect responses.

Twenty-eight percent of subjects misunderstood medication instructions. The prevalence of misinterpreting instructions among subjects with adequate, marginal, and low literacy was 18%, 34%, and 43%, respectively. Common causes for misunderstanding included problems with dosage measurement (28%; ie, tablespoon instead of teaspoon) and frequency of use (33%; ie, every 3 hours instead of every 6-8 hours). In an adjusted analysis that excluded literacy, African Americans were more likely to misunderstand instructions than Caucasians (adjusted odds ratio [AOR] 1.63, 95% confidence interval [CI]=1.02-2.61). When literacy was included in the model, the effect of race on misunderstanding was reduced and nonsignificant. Inadequate and marginal literacy remained independent predictors of misunderstanding (inadequate--AOR 2.90, 95% CI= 1.41-6.00; marginal--AOR 2.20, 95% CI=1.19-3.97).

Misinterpretation of pediatric liquid medication instructions is common. Limited literacy is a significant risk factor for misunderstanding and could contribute to racial disparities. Instructions should be written in a concise manner and standardized to ensure comprehension.