Monitoring Commercial Ibuprofen Potency Changes Over 1 Year When Stored in a Household Setting

Background: Most over-the-counter medications are labeled for storage in a dry, room temperature environment. Despite this, many households store medications in the bathroom, where temperature and humidity extremes may be experienced. Objective: In this project, we sought to investigate the effect that long-term storage in a household bathroom had on potency of over-the-counter ibuprofen (IBU) products as well as on the emergence of a known toxic degradation product, 4-isobutylacetophenone (4-IBP). Methods: A liquid chromatography-tandem mass spectrometry method was developed for the quantitative determination of IBU and 4-IBP in aqueous samples. Three brands each of IBU tablets (200 mg) and suspensions (100 mg/5 mL) were assayed for IBU concentration at the initiation of the study and once monthly thereafter. The samples were stored in a household bathroom, with continuous temperature and humidity monitoring. Each sample was assayed in triplicate and percent recovery was calculated against freshly prepared standards of IBU using bulk powder. Results: Tablets maintained >90% average strength through 3 months, with statistically significant deviation from initial concentration (2-way analysis of variance, P = .05) detected after 6 to 7 months. Suspensions maintained >90% average strength through 5 months, with statistically significant changes from initial concentration emerging after 7 months. After 12 months, the average strength was 73% and 83% for tablets and suspensions, respectively. 4-IBP was not detected in any of the samples during the duration of the study. Conclusions: These data indicate that, while 4-IBP was not detected following 12-month bathroom storage of commercial IBU products, significant changes in potency should negatively affect efficacy.