Introduction: Intravesical Botulinum Toxin Type A (BoNT-A) is a commonly performed Urological procedure to treat neuropathic and non-neuropathic patients with detrusor overactivity. Botulinum toxin is also commonly used by other medical specialities to treat other pathologies such as migraine, spasticity and for cosmetic reasons. It was noted that, these patients are receiving Botulinum Toxin injections in multiple body sites, which may risk large cumulated doses. This risks toxicity or an immunological response that reduces efficacy of subsequent treatments.
Aims: This study aims to investigate what percent of patients receiving intravesical BoNT-A, were also receiving extravesical-site Botulinum Toxin over a set time period, and to identify what is the total safe cumulative maximum dose that can be administered to a patient.

Methods: 105 patients underwent intravesical BoNT-A between October 2018 – October 2019 (according to a prospectively filled intravesical BoNT-A database). Patients were asked and their records examined to ascertain whether they received other-site injections, including the dose of Botulinum Toxin and frequency.

Results: 25 patients were uncontactable. Of the remaining 80 patients, 30 were neuropaths (37.5%) and 50 were non-neuropaths (62.5%). 7 out of 80 patients received extravesical-site
Botulinum Toxin injections (9%). Of these, 2 out of 7 patients’ doses were not found, and one patient’s formulation of Botulinum Toxin received was not found. Please see attached table. 
Of these 7 patients receiving other-site Botulinum Toxin injections, 6 were neuropaths. 

The Allergan© Summary of Product Characteristics for Botox® 100 units states that the “maximum cumulative dose should not exceed 400 Units in a 12-week interval“.

A significant proportion of this urology patient cohort receives extravesical-site injections, for a range of indications, doses and frequencies. Some of them have no record of other-site doses, or product type received. The majority of these patients are neuropaths. This highlights the issue of potential safety risks to these patients. As cumulative doses are not clearly documented, there is a risk of overdosing these patients.

Moreover, at higher Botulinum Toxin doses, there is a higher risk of adverse effects, and antibody formation which may impair the effect of future Botulinum Toxin injections. In order to minimise the risk of overdosing or needless cancellations, one solution may be to create a universal, pan-hospital “Botulinum Toxin Passport” for these patients. This passport would be used similarly to warfarin anticoagulation booklets: each encounter where the patient receives an injection of Botulinum Toxin would be recorded on it. It would enable more consistent documentation of patients’ various Botulinum Toxin encounters and each clinician would be able to ascertain whether it is safe to proceed with further Botulinum Toxin injections.

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Nuanthaisong U, Abraham N, Goldman HB. Incidence of adverse events after high doses of onabotulinumtoxinA for multiple indications. Urology 2014 Nov;84(5):1044-1048.
Bristol B. Whiles M, Joshua Caldwell B, Priya Padmanabhan, MD, MPH, FACSa. Check your units: Exceeding the maximum recommended dose of Botulinum toxin A in urologic patients.