Currently, botulinum toxin A (BTXA) has been recognized as an effective second-line treatment for refractory idiopathic overactive bladder (OAB) and neurogenic detrusor over activity (NDO). Most published studies have used ona- botulinum toxin (O-BTXA) as the only licensed preparation for refractory idiopathic OAB and only a few studies have investigated the efficacy and outcome of intra-detrusor abo-botulinum toxin (A-BTXA) injection. The primary  objective of the present study was to identify factors related to success, poor response or early failure of intra-detrusor A-BTXA injection in female patients diagnosed with refractory idiopathic OAB.

A total of 35 female patients with refractory idiopathic OAB underwent intra-detrusor A-BTXA injection in our medical center from August 2020 to April 2022. All patients underwent a genital exam, urine analysis, urine culture and urodynamic study (UDS). A total dose of 500 IU of A-BTXA was injected into 20 to 30 points of the urinary bladder. The severity of urinary symptoms and quality of life of the patients were evaluated just before and 6-weeks following the injection using validated ICIQ-OAB and QOL-SF 12 questionnaires, respectively.

The overall success rate of the A-BTXA injection was 51.4%. The (mean ± SD) age of the patients with failed and successful outcome was (52.17 ± 13.82) and (53.41± 18.46). There was no statistically significant correlation between BMI, total parity number, mode of deliveries, menopause status, types of OAB, dosage and the number of previous intra-detrusor injections, with outcome. A history of cystocele repair, hysterectomy, urinary retention, diabetes mellitus, low bladder compliance and high detrusor pressure at Q-max were correlated with poor outcome. An assessment of the urinary symptoms revealed that, the success rate is more likely in patients with nocturia, stress urinary incontinence and high baseline ICIQ-OAB total scores.

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A-BTXA is a safe and effective formulation of botulinum toxin that can be used in the treatment of idiopathic OAB with minimal adverse effects. Identifying factors that predict a poor response can help in counseling patients and avoiding unnecessary procedures. Prior cystocele repair, a history of hysterectomy, a history of urinary retention, diabetes mellitus, low bladder compliance, and high detrusor pressure at Q-max are considered predictors of early failure or a poor response. High baseline ICIQ-OAB total scores, nocturia and stress urinary incontinence are predictors of success. Promising results of our study regarding A-BTXA, make it a good alternative to O-BTXA in cases of treatment failure with O-BTXA or when factors predicting nonresponse to O-BTXA are present.