PATIENT MISUNDERSTANDING OF DOSING INSTRUCTIONS

OBJECTIVE: To compare outpatients' understanding of medication dosing instructions written in terms of daily frequency with patients' unders tanding of instructions specifying hourly intervals. DESIGN: Prospecti ve cohort study involving patient interviews. SETTING: A university ho spital outpatient pharmacy. PATIENTS: Five hundred patients presenting new and refill prescriptions to the hospital outpatient pharmacy. INT ERVENTION: Patients were interviewed using a standardized questionnair e. MEASUREMENTS AND MAIN RESULTS: Of the 71 patients with prescription s specifying dosing instructions in hourly intervals (e.g., q6h), 55 ( 77%) misinterpreted the recommended frequency of dosage compared with only 4 (0.93%) of the 429 patients with dosing instructions specifying daily frequency (e.g., qid) (relative risk 83; 95% confidence interva l 31-200). This difference remained when patient subgroups were evalua ted by education level, new versus refill prescriptions, and analgesic versus nonanalgesic medications. CONCLUSIONS: This study indicates th at the intended dosing regimen is frequently misunderstood when the ph ysician writes outpatient prescriptions in hourly intervals. To promot e optimal patient compliance, the outpatient prescription label should state the number of times a day a medication is to be taken.