Association Between Inappropriate Use of Over-The-Counter Drugs for Allergic Rhinitis and Side Effects on the Central Nervous system—a Cross-Sectional Survey

Purpose: Antihistamine over-the-counter (OTC) drugs for allergic rhinitis are widely used and cause central nervous system side effects. Most available data on anti-allergic drugs are on controlled usage. It is necessary to investigate the occurrence of side effects in the context of self-medication to avoid inappropriate use. We aimed to clarify the association between the usage of OTC anti-allergic drugs and central nervous system side effects. Patients and Methods: An online, anonymous, cross-sectional study was conducted using a structured questionnaire. People who had used OTC anti-allergic drugs in the year prior to the study were recruited. To assess the association between inappropriate drug use and the occurrence of side effects, a binary logistics regression analysis was performed according to three dosage forms (oral only, nasal only, and oral and nasal combined use). Results: Somnolence was experienced by 59.1% of the participants using the OTC drug for allergic rhinitis. Using logistic regression analysis, “drug use exceeding the upper limit” was seen to be associated with side effects in only oral (Somnolence: OR = 1.41, 95% CI = 1.17–1.70; Dull head: OR=1.41, 95% CI = 1.16–1.70; Loss of concentration: OR = 1.25, 95% CI = 1.04–1.49) and oral and nasal combined use groups (Somnolence: OR = 1.33, 95% CI = 1.04–1.71; Dull head: OR = 1.47, 95% CI = 1.15–1.89; Loss of concentration: OR = 1.51, 95% CI = 1.19– 1.91). Furthermore, “expired drug use” was associated with side effects in the nasal spray-only group (Somnolence: OR = 1.31, 95% CI = 1.07– 1.60; Dull head: OR =1.25, 95% CI = 1.02–1.53; Loss of concentration: OR = 1.24, 95% CI = 1.00–1.54). Conclusion: Inappropriate use was common among users of OTC allergic rhinitis drugs. Differences in side effects depending on the dosage form used were observed.