Analysis of the nervous system and gastrointestinal adverse events associated with solifenacin in older adults using the US FDA adverse event reporting system

BACKGROUND: Antimuscarinics are the backbone of the pharmacological management of overactive bladder. Still, concerns have been raised over the nervous system (NS) adverse drug events (AEs) due to their dissimilarities to muscarinic receptor-subtype affinities. OBJECTIVE: This study aimed to identify the nervous system and gastrointestinal adverse drug events (ADEs) associated with solifenacin use in older adults (≥65 years). METHODS: A case/non-case analysis was performed on the reports submitted to the FDA Adverse Event Reporting System (FAERS) between 01/01/2004 and 30/06/2020. Cases were reports for solifenacin with ≥1 ADEs as preferred terms included in the Medical Dictionary of Regulatory Activities (MedDRA) system organ classes 'nervous system' or 'gastrointestinal' disorders. Non-cases were all other remaining reports for solifenacin. The case/non-cases was compared between solifenacin and other bladder antimuscarinics. Frequentist approaches, including the proportional reporting ratio (PRR) and reporting odds ratio (ROR), were used to measure disproportionality. The empirical Bayesian Geometric Mean (EBGM) score and information component (IC) value were calculated using a Bayesian approach. A signal was defined as the lower limit of 95% confidence intervals of ROR ≥ 2, PRR ≥ 2, IC > 0, EBGM > 1, for ADEs with ≥4 reports. RESULTS: 107 MedDRA preferred terms (PTs) comprising 970 ADE reports were retrieved for nervous system disorders associated with solifenacin. For gastrointestinal disorders, 129 MedDRA PTs comprising 1817 ADE reports were retrieved. Statistically significant results were found for 'altered state of consciousness': ROR = 9.71 (2.13-44.35), PRR = 9.69 (2.12-44.2) and IC = 1.29 (0.93-1.66). CONCLUSIONS: The disproportionality reporting of 'altered state of consciousness', a previously unidentified ADE, was unexpected. Further monitoring of this ADE is needed to ensure patient safety, as this could be linked to poor balance and falls in older adults.