**1. Introduction**

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic bladder inflammatory disease characterized by bladder pain and frequency urgency. Current treatments using pain killer or anti-inflammatory medications cannot completely eradicate symptoms and increase bladder capacity [1]. Several intravesical or oral medications, such as pentosanpolysulphate, amitryptynine, and cyclosporin have been tried, but their therapeutic efficacy

**Citation:** Jhang, J.-F.; Yu, W.-R.; Kuo, H.-C. Comparison of the Clinical Efficacy and Adverse Events between Intravesical Injections of Platelet-Rich Plasma and Botulinum Toxin A for the Treatment of Interstitial Cystitis Refractory to Conventional Treatment. *Toxins* **2023**, *15*, 121. https://doi.org/10.3390/ toxins15020121

Received: 26 December 2022 Revised: 19 January 2023 Accepted: 31 January 2023 Published: 2 February 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

has been proven ineffective [2–6]. The lack of a reliable effective therapy for IC/BPS may be related to its poorly understood pathophysiology. One of the most common findings in bladder mucosal biopsies from patients with IC/BPS is denudation or thinning of the bladder epithelium, suggesting an altered regulation of urothelial homeostasis [7,8]. Other bladder abnormalities include an increased nerve fiber density, inflammatory cell infiltrations, and noxious sensory receptor immunoreactivity [9]. Although investigations on this topic have been enthusiastically performed, the etiology of IC/BPS remains unknown. Treatment based on a single pathophysiology might not be sufficient to solve the underlying pathology of IC/BPS.

Intravesical botulinum toxin A (BoNT-A) and platelet-rich plasma (PRP) injections are novel treatments for IC/BPS refractory to conventional therapies. BoNT-A can reduce the release of acetylcholine and inflammation-related neuropeptides from nerve terminals [10]. The BoNT-A injection can eliminate noxious stimulation and reduce bladder suburothelial inflammation, thus improving urothelial regeneration and IC/BPS symptoms. PRP can also produce new inflammation and override unresolved inflammation in IC/BPS bladders [11]. Through repeated injections, the bladder inflammation is eliminated and regeneration of the defective urothelium is improved, resulting in a healed bladder urothelium with adequate barrier function and a reduction in bladder pain [12]. Although there is solid evidence that BoNT-A improves the IC/BPS condition, a decrease in detrusor contractility following treatment may contribute to a poor response to the BoNT-A injection [13]. On the other hand, the PRP injection does not have such adverse events. However, the effect of PRP on inflammation might be less remarkable than that of BoNT-A; frequent monthly PRP injections are necessary to achieve a therapeutic efficacy similar to that of BoNT-A on IC/BPS [14].

Patients with chronic IC/BPS usually cannot be successfully treated with conventional medical or intravesical treatments. Although previous clinical trials provided evidence that intravesical BoNT-A or PRP injections were effective [11–13], the true clinical efficacy and patients' satisfaction have not been reported in real life practice. To date, there has been no head-to-head comparison between these two treatment modalities. Therefore, we compared these two novel therapies to establish which treatment provides superior treatment efficacy and safety.
