Intravesical injections of Onabotulinum toxin A (Botox) is a commonly used treatment modality for Idiopathic detrusor overactivity. There are a number of studies to determine the optimum dose of Botox that is effective and has minimal side-effects or complication rates. A smaller dose of 100 Units of Onabotulinum toxin A (Botox) has become popular recently to treat refractory Idiopathic Detrusor Overactivity (rIDO) in order to reduce the risk of catheter dependence. The safety and efficacy of this regime has been demonstrated using several validated tools. We aim to report outcomes of 100U Botox in rIDO by assessing patients’ global impression of symptom improvement and quality of life (QoL).

We conducted a study from a retrospective surgical database of patients who received intravesical Botox for rIDO. Urodynamic studies were performed in all patients prior to Botox injections. From our procedure database, records were assessed for 107 patients between January 2017 and October 2018. A total of 25 patients with rIDO received 100U of Botox during this period. Data were collected for demographics, injection technique and complications. Patients were contacted and asked to complete questionnaires to include Patients’ global impression scores. Details of pre-operative symptom severity and post-operative symptom improvement and QoL were gathered retrospectively using the Patient Global Impression scales including PGI-S, PGI-I and PGI-QoL. PGI-S is a severity scale which includes responses ‘mild’, ‘moderate’ or ‘severe’. PGI-I evaluates Patient Global impression of improvement of symptoms on a scale of 1 to 7 (‘very much better’ to ‘very much worse’). PGI-QoL is a quality of life assessment scale (scores 0 to 6; Delighted to terrible). In addition, we asked the patients whether they would like further repeat injections when symptoms recur.

Out of the 25 patients who received 100U of Botox, complete dataset was available for 21 patients. The technique used involved intradetrusor trigone sparing injections in all patients.  Mean age was 74 years (range 51 to 91 years). Male: Female ratio was 1: 2 (male: n = 14; female: n = 7). Prior to the procedure, 16 (76%) out of 21 patients reported severe symptoms, whereas the remainder (5 patients) reported ‘moderate’ symptoms on the PGI-S scale. None of the patients reported ‘mild’ symptoms prior to Botox. After the procedure, 4 (19%) reported UTI requiring antibiotics early post-operatively, 2 (10%) had transient urinary retention, whereas only 1 patient had to perform long term ISC. On the PGI-I scale, 17 (81%) patients felt symptom improvement, while 4 (1.9%) patients reported worsening of symptoms. Amongst those who reported symptom improvement, the responses were 'much better' or 'very much better' for 11 (52%) patients. Overall 16 (76%) patients were either 'delighted' (n=4), 'pleased' (n = 4) or 'satisfied' (n = 8) on the PGI-QoL scale. However, a total of 5 patients had a ‘mixed’, ‘unhappy’ or ‘terrible’ response on the quality of life scale. Out of the entire group, 15 (72%) patients wanted to have repeat treatments.

In our study, complication rate amongst patients who received 100U of Botox was acceptable, with a very low catheterisation rate after injections. A high number of patients had ‘severe’ symptoms prior to Botox injections. Three quarters of patients experienced improved symptoms and QoL with 100 Units of Botox. The majority of patients requested repeat treatments due to high satisfaction with the injections.

These outcomes are not dissimilar to those with the traditional dose of 200 Units and are achieved with a much lower risk of catheter dependence. It is conceivable that the response rate may have been higher if the non-responders were contacted early post-operatively and offered a repeat injection earlier. This should form part of an effective Botox service. We recommend further studies to evaluate use of 100U Botox for rIDO and patient satisfaction using PGI scales.