Objective: We studied the rationale for using standard and increased dosages of solifenacin and trospium against overactive bladder (OAB) symptoms of different severity among elderly patients. Methods: A total of 327 patients took part in the study: 199 women and 128 men older than 65 years (median age 69.1). The state of the lower urinary tracts was estimated by cystometry, ICIQ-SF and bladder diaries. Frequency of urgency urinary incontinence (UUI) was taken as a criterion of OAB symptom severity. Result: Administration of double-dosed trospium and solifenacin leads to decrease of frequency of UUI both in the group with severe symptoms (B1: 6.1 (0.5) →2.4 (0.9), p ⩽ 0.05), and in the group with moderate symptoms of OAB (A1: 2.8 (0.8) →0.5 (0.4), p ⩽ 0.001). Under a combination of trospium and solifenacin in doses recommended by manufacturers, UUI decreased authentically in the group with moderate symptoms (A2: 2.9 (0.5) →0.9 (0.5), p ⩽ 0.05) and unauthentically in the group with severe symptoms of detrusor dysfunction (B2: 7.0 (1.2) → 4.3 (1.5), p ⩾ 0.05). During the experiment six patients (1.8%) elected not to participate because of intolerable adverse events. Forty-seven more individuals (14.4%) felt adverse effects, among which the most frequent were: xerostomia (15 patients or 4.6%), faintness (nine patients or 3.8%), dryness of integuments (six patients or 1.8%). Conclusion: A standard-dose combination of solifenacin and trospium in older patients with moderate symptoms of OAB enables a good therapeutic effect in a short time without increasing risk of side effects. High therapeutic doses of antimuscarinic drugs are reasonable for older men and women with severe symptoms of OAB. Increasing the dose of simultaneous use of solifenacin and trospium yields a good therapeutic effect to correct UUI; however, it raises the hazard of appearance of adverse effects. The number of side effects in the group of elderly individuals who were taking the combination of increased and standard dosages of solifenacin and trospium does not significantly differ.