Actual use of and adherence to ibuprofen 400 mg tablet dosing instructions in a simulated OTC environment
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OBJECTIVE: Evaluate adherence of US consumers to proposed label directions for a new 400 mg ibuprofen formulation.

METHODS: In this single-arm, open-label, multicenter, 30-day study simulating an over-the-counter (OTC)-like environment, US analgesic consumers reviewed proposed product packaging for a new 400 mg ibuprofen formulation and made a purchase decision. Purchasers used the product as needed and recorded use over 30 days. Outcomes included the percentage of participants who exhibited correct or acceptable product use for the primary endpoint (not exceeding 1,200 mg/day > 2 times during the study) or secondary endpoint (not exceeding 400 mg/dose > 2 times during the study) and adherence to the labeled dosing interval of 6 - 8 hours. Primary endpoint success was met if the lower bound of the 95% confidence interval (CI) was ≥ 85%.

RESULTS: Of 685 purchasers providing use data, correct or acceptable use behavior occurred in 95.2% (95% CI: 93.6%, 96.8%) regarding total daily dose and in 84.4% (95% CI: 81.7%, 87.1%) regarding the number of tablets taken per dosing occasion. Most participants (87.3%) never used > 1,200 mg/day or took > 1 tablet/dose (78.1%). Nearly 43% of subjects re-dosed within 6 hours of the previous dose; of these, ~ 82% re-dosed between the 4- and 6-hour time intervals. Adverse events were consistent with prior ibuprofen 200 mg experience.

CONCLUSION: This study provides evidence that a majority of US consumers would be able to use OTC ibuprofen 400 mg tablets in a manner consistent with product labeling. Misuse rates were low and unlikely to generate an excess risk of clinically important adverse events.
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