Onabotulinum toxin injection in neurogenic detrusor overactivity: intradetrusor versus suburothelial

Abstract

We read with interest the article 'Intradetrusor versus suburothelial onabotulinum toxin A injections for neurogenic detrusor overactivity: a pilot study' published in Spinal Cord by Krhut et al. 1 The authors need to be commended for undertaking one of the first randomized controlled studies to compare intradetrusor versus suburothelial injections of onabotulinum toxin A. We have a few comments regarding this study. The authors describe using International Units (IU) of onabotulinum toxin. We understand that onabotulinum toxin is not dispensed in IU; rather it is marketed as Allergan Units (U) (http:// www. medicines.org.uk/ EMC /medicine/112/SPC/BOTOX þ 100 þ Units/). A review article in European Urology also uses U when discussing dosage. 2 We feel that U rather than IU should be used for the purpose of standardization. The authors also describe the injection technique very well using ultrasound measurement of bladder wall thickness. While there is evidence to suggest extravesical spread in association with botulinum toxin injections, we feel that in practice it is very difficult be certain clinically that all injections have been undertaken into the detrusor or suburothelially. Consequently, it is difficult to base the results on this variation. Indeed, due to this uncertainty, this aspect was not commented upon in the recent review by Mangera et al. 2