Onabotulinum toxin A in children with refractory idiopathic overactive bladder: medium-term outcomes

Botulinum toxin-A (BtA) has been used for refractory idiopathic overactive bladder (IOAB) in children. Data on the optimum dose success rates, duration of effect, complications and medium-term outcomes are limited. This study aims to analyse the authors' experience to provide medium-term results of BtA in symptomatic refractory patients.

Patients with refractory IOAB who were treated with BtA (Botox®) were retrospectively analysed. All patients had urodynamic study before treating with BtA. Group A had low-dose BtA (LDBtA) at 5 units/kg (maximum 150 units), and Group B had high-dose BtA (HDBtA) at 10 units/kg (maximum 300 Units). Post-BtA clinical response, functional bladder capacity (FBC) and postvoid residual (PVR) were assessed in addition to the duration of response.

Thirty-nine patients, 11 male and 28 female, were analysed. Forty-six percentage had symptom improvement (73% of males and 36% of females [P = 0.072, ns]). The difference in response rates between LDBtA and HDBtA was not statistically significant (P = 0.684). Increase in total bladder capacity (TBC) was greater in those given HDBtA (P ≤ 0.001), but the increase in FBC was not different between the groups, due to greater PVRs in the HDBtA group. Nine patients (23%) developed UTI; however, six of these patients suffered with UTI pre-BtA as well. Only three were asymptomatic after a single treatment with BtA. The remainder required further BtA or oral anticholinergic therapy. At a median follow-up of 35.4 months (interquartile range [IQR] 25.2-46.6), 12 (31%) were asymptomatic and off all therapy, 18 (46%) were still symptomatic despite therapy and 9 (23%) had their symptoms controlled on continuing treatment.

Botulinum toxin-A improves symptoms in 46% of children after the first injection in refractory IOAB. Although HDBtA resulted in greater increase in bladder capacity, it conferred no advantage in terms of success rate or duration of response. Five units/kg may be an optimum dose to use as a first treatment with the understanding that some patients will require a higher dose. And, there will be a cohort of patients who need a dose lower than 5 units/kg. A higher dose is more likely to lead to PVR leading to urine stasis and UTIs. The success of BtA only lasts until its effect wears off, and the majority of this cohort (36/39) required continuing treatment with repeat BtA or anticholinergic agents. However, it remains a useful option in patients who are intolerant or unresponsive to anticholinergic medication with symptomatic resolution in 30% at medium-term follow-up.