Practical Aspects of Botulinum Toxin-A Treatment in Patients With Overactive Bladder Syndrome

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Int Neurourol J. 2015;19(4):213-219

Publication date (electronic) : 2015 December 28

doi : https://doi.org/10.5213/inj.2015.19.4.213

Chun-Hou Liao¹, Hann-Chorng Kuo^,2

¹Department of Urology, Cardinal Tien Hospital and Fu-Jen Catholic University, New Taipei, Taiwan

²Department of Urology, Buddhist Tzu Chi General Hospital and Tzu Chi University, Hualien, Taiwan

Corresponding author: Hann-Chorng Kuo http://orcid.org/0000-0001-7165-4771  Department of Urology, Buddhist Tzu Chi General Hospital, 707, Section 3, Chung-Yang Road, Hualien, Taiwan  E-mail: hck@tzuchi.com.tw / Tel: +886-3-8561825 / Fax: +886-3-8560794

Received 2015 September 19; Accepted 2015 November 2.

Abstract

INTRODUCTION

Conservative measures and oral medications such as muscarinic receptor antagonists or β3-adrenoceptor agonists are the first-line treatments for overactive bladder syndrome (OAB) [1,2]. However, insufficient efficacy and/or intolerable adverse effects (AEs) are associated problems in some patients despite effective symptom relief [3,4]. Intravesical onabotulinumtoxinA (BoNT-A) injection is an effective treatment for patients with OAB or idiopathic detrusor overactivity (IDO) that is refractory to antimuscarinics [5-10]. The indications and contraindications of intravesical BoNT-A for OAB are summarized in Table 1. An injectable dose of 100 U has been recommended to achieve an optimal balance between benefit and safety in patients with OAB, while a dose of 50 U did not show results different from those of placebo in double-blind, dose-ranging trials [7,8]. In addition, postvoid residual (PVR) urine volumes >200mL were more commonly noted in patients treated with BoNT-A doses >150U [11]. A clinical research program that comprised 2 large phase III, randomized, placebo-controlled studies showed that treatment with 100-U BoNT-A was generally well tolerated, and most treatment-related AEs were localized to the urinary tract [9,10]. However, widespread use of this treatment is limited by increased PVR urine volume and urinary tract infections (UTIs), problems that have yet to be resolved [12-14].

Table 1.

Indications and contraindications of intravesical BoNT-A for OAB

INJECTION TECHNIQUES

The injection methods, including location and depth, number of sites, and volume at each site, varied among previous studies. Currently, the most commonly recommended dose of BoNT-A for OAB is 100 U (total volume of 10 mL), and should be administered as evenly distributed intradetrusor injections (5 U) across 20 sites approximately 1 cm apart (0.5 mL per injection site; Fig. 1A) using a flexible or rigid cystoscope [15]. The trigone of the bladder is usually spared of the injection. The instillation of local anesthetics into the bladder and/or general sedation during the treatment can also be used.

Fig. 1.

(A) Intravesical onabotulinumtoxinA was administered as evenly distributed injections across 20 sites, (B) intradetrusor injection, (C) suburothelial injection.

Regarding injection location, Kuo [16] reported that bladder base/trigone injections are as safe and effective as bladder body injections with or without trigone involvement in a single-blind, randomized, paralleled, active controlled trial. Another randomized controlled trial also investigated the efficacy and safety of intravesical BoNT-A injections with trigone inclusion [17]. The results of these trials support that intravesical BoNT-A injections at different sites are effective and safe regardless of trigone sparing or inclusion. The diffusion pattern of BoNT-A in guinea pig bladders was investigated by examining the expression of the cleaved form of 25-kDa synaptosome-associated protein (cSNAP-25) with different injection volumes and administration protocols [18]. A single BoNT-A injection could spread the neurotoxin activity to the opposite side of the bladder. Injection volume, rather than injection number, may be another important determinant of the diffusion and action of BoNT-A in the bladder. Liao et al. [19] prospectively compared the therapeutic effects and safety of different numbers of BoNT-A injections for patients with OAB. Different injection numbers produced similar therapeutic outcomes and AEs. These researchers suggested that 1-mL BoNT-A injections (10U) at 10 sites were adequate for achieving an optimal therapeutic effect in patients with OAB.

As observed in previous studies, injection depth also varied and depended to some extent on the length of the needle-tip [15]. Although intradetrusor injection remains the standard treatment technique approved by the Food and Drug Administration (Fig. 1B) [14,15], suburothelial injection is another choice that reportedly prevents extravasation of BoNT-A (Fig. 1C) [20]. Another study conducted by Krhut et al. [21] also compared the effects of suburothelial and intradetrusor injections of BoNT-A for neurogenic IDO. Although the results in both groups were comparable, the researchers favored the suburothelial injection technique because it allowed more precise toxin localization.

CLINICAL EFFICACY

Both the phase III trials (n=1,105) included patients with ≥3 urge urinary incontinence (UUI) episodes over 3 days, >8 micturition episodes per day, ≤100 mL of PVR urine volume, and those whose symptoms were not adequately managed with anticholinergics [9,10]. Statistically significant and clinically relevant reductions in all OAB symptoms were found after intravesical BoNT-A treatment. A 3- to 4-fold greater reduction from baseline in the mean daily frequency of UI episodes was reported at week 12 with BoNT-A vs. placebo (–2.65 vs. –0.87, P<0.001) that corresponded to mean percentage reductions from the baseline of 47.9% with BoNT-A vs. 12.5% with placebo. A higher proportion of BoNT-A–treated patients reported a positive response (greatly improved or improved) vs. placebo-treated patients (60.8% vs. 29.2%, P<0.001) [10]. Chapple et al. [9] observed similar positive findings of BoNT-A treatment significantly decreasing the number of UI episodes per day, and the reduction from baseline was greater than that with placebo (–2.95 for BoNT-A vs. –1.03 for placebo, P<0.001). Treatment with BoNT-A also significantly improved daily micturition episodes, urgency episodes, and nocturia (Table 2). Improvement in patient’s quality of life (QoL) was also reportedly associated with clinically meaningful improvements in OAB symptoms after BoNT-A treatment [9,10]. In addition, improvements in OAB symptoms were observed in patients with UI regardless of the number of anticholinergic therapies used or the reason for inadequate OAB management [22]. In another retrospective study, BoNT-A injections were shown to be more effective in patients with anticholinergic intolerability than in those with poor medication efficacy (86% vs. 60%, P=0.02) [23].

Table 2.

Clinical efficacy of intravesical BoNT-A for OAB in phase III trials

Cui et al. [24] documented a systematic review and meta-analysis regarding the efficacy and safety of BoNT-A for treating idiopathic OAB. Compared to the outcomes with placebo, the mean number of daily UI episodes decreased (–2.77 vs. –1.01, P<0.00001); mean number of daily micturition episodes decreased (–1.61 vs. –0.87, P< 0.00001); maximum cystometric capacity (MCC) increased (91.39 vs. 32.32, P<0.00001); volume of voided urine increased (44.29 vs. 7.36, P<0.00001), while 29.20% (BoNT-A) vs. 7.95% (placebo) of patients became incontinence-free (odds ratio [OR], 4.89; P<0.00001) after BoNT-A treatment [24]. Another updated systematic review reported that BoNT-A treatment leads to significant improvement in bladder daily parameters such as daily frequency (–29%), daily urgency (–38%), and daily incontinence (–59%) (all P<0.02). The urodynamic parameters of MCC and maximum detrusor pressure improved by 58% (P=0.04) and –29% (P=0.002), respectively [25].

A total of 839 patients were evaluated in a long-term, open-label extension study (clinical trial identifier: NCT00915525) to evaluate long-term efficacy of BoNT-A treatment [26]. A reinjection was performed upon patient’s request after 2 UI episodes in a 3-day void diary. Patients experienced consistent response with re-treatments for all efficacy endpoints from treatment cycle 3. In the subset of 345 patients who reached week 12 of treatment cycle 3, the mean reductions in daily frequency of UI were –3.07, –3.49, and –3.49 episodes at week 12 after the first, second, and third BoNT-A treatments, respectively. The corresponding proportions of patients with a positive treatment response were 63.6%, 76.9%, and 77.3%, respectively [27].

Dowson et al. [28] collected prospective data regarding repeated injections of 200 U of BoNT-A from a single center. A total of 207 injections were administered to 100 patients. All patients took 1 injection, 53 took 2, 20 took 3, 13 took 4, 10 took 5, 5 took 6, 3 took 7, 1 took 8, 1 took 9, and 1 took 10 injections. A statistically significant reduction in frequency, urgency, and UUI was observed after the first BoNT-A injection compared to baseline. This improvement was maintained after repeated injections and did not vary statistically between injection-periods. Thirty-seven patients stopped treatment after the first 2 injections; thereafter, dropouts were rare. The most common reasons for discontinuing treatment were poor efficacy (13%) and clean intermittent catheterization (CIC)-related issues (11%). The incidence of CIC after the first injection was 35%. Bacteriuria was detected in 21% of patients. The mean interinjection interval was 322 days [28]. Mohee et al. [29] also observed that two-thirds of the patients discontinued treatment because of treatment-associated tolerability issues.

SAFETY AND TOLERABILITY

Treatment with BoNT-A was generally well tolerated, and most AEs were localized to the urinary tract. Uncomplicated UTI was the most frequently reported AE in both phase III studies: 15.5% with BoNT-A vs. 5.9% with placebo [10] and 24.1% with BoNT-A vs. 9.6% with placebo [9]. In both the studies, a change from baseline in PVR urine volume ≥200 mL was found in 8.7% and 8.8% of patients in the BoNT-A group, 6.1% and 6.9% of patients initiated CIC [9,10]. In a systematic review and meta-analysis, BoNT-A was often associated with complications resulting from PVR (P<0.00001), UTI (P<0.00001), and CIC (P<0.00001) [24]. The risk of UTI significantly increased to 21% in the BoNT-A group and was 7% in the placebo group (P<0.001); the risk of intermittent self CIC increased from 0% to 12% (P<0.001) [24].

In an interim analysis of a long-term extension study in which 253 patients had reached week 12 of treatment cycle 3, the proportion of patients reporting urinary retention was stable after every BoNT-A treatment cycle, with 4.0%, 3.4%, and 3.2% reporting it after cycles 1, 2, and 3, respectively. The proportion of patients requiring CIC due to increased PVR urine volume also remained stable, with 4.6%, 4.1%, and 4.7% requiring it after cycles 1, 2, and 3, respectively [27]. Kuo et al. [12] investigated the risk factors for increased AEs after BoNT-A injection in patients with IDO. Male sex, baseline PVR urine volume ≥100 mL, comorbidity, and BoNT-A dose >100 U are risk factors for increased incidence of AEs. In another retrospective analysis, Osborn et al. [13] observed that an increased preoperative PVR urine volume was a risk factor for urinary retention.

BONT-A TREATMENT IN SPECIFIC PATIENT GROUPS

CONCLUSIONS

Intravesical BoNT-A is an effective treatment for OAB or IDO in elderly patients. The current recommended dose is 100 U administered as evenly distributed intradetrusor injections (5 U) across 20 sites using a flexible or rigid cystoscope. Treatment was generally well tolerated, and most treatment-related AEs were localized to the urinary tract.

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