The effectiveness and safety of intracavernosal botulinum toxin injections in the management of erectile dysfunction: a systematic review and meta-analysis of clinical studies.

[BACKGROUND] Patients with erectile dysfunction (ED) are often left with limited nonsurgical options when conventional pharmacotherapies become ineffective. Botulinum neurotoxin serotype A (BoNT-A) intracavernosal injections (ICIs) have been demonstrated in a few clinical studies to be effective and safe in managing ED and may serve as a first- or second-line option.

[AIM] To perform a systematic review and meta-analysis on the effectiveness and safety of BoNT-A ICI in managing ED with a focus on human studies.

[METHODS] A systematic review and meta-analysis of clinical studies was performed in accordance with the PRISMA 2020 statement. Adult men with ED who received BoNT-A were included in the study. The risk of bias assessment of included studies was performed using the JBI assessment checklists.

[OUTCOMES] The effectiveness and safety of BoNT-A ICI. Measures of effectiveness included the increase or change in International Index for Erectile Function (IIEF-EF) score/Sexual Health Inventory for Men (SHIM) score/Erection Hardness Score (EHS) or change in Doppler ultrasound parameters and the percentage of patients achieving the minimal clinically important difference (MCID) score.

[RESULTS] The search retrieved 61 articles, and 2 randomized controlled trials (RCTs) and 4 retrospective studies met the inclusion criteria. Three types of BoNT-A were evaluated: onaBoNT-A, aboBoNT-A, and incoBoNT-A. At least 40% of the patients achieved the MCID (2-7 points increase in the IIEF-EF/SHIM score) depending on the severity of ED) at ≥1 month. When directly comparing all 3 BoNT-A, the overall response rate was 77.5%, with no statistically difference between the 3 types. For aboBoNT-A, 500 U appeared to sustain the effectiveness longer compared to 250 U. OnaBoNT-A improved peak systolic velocity on Doppler ultrasound compared with saline. Meta-analysis of the 2 RCTs demonstrated a mean difference of 4.35 ( = .008) in the SHIM score at 12 weeks in favor of onaBoNT-A over normal saline. No systemic side effects have been reported, and the only infrequent local side effect was transient penile pain. Only one case of priapism was reported.

[STRENGTHS AND LIMITATIONS] This is the first systematic review summarizing data from human studies on ED and BoNT-A ICI. The inclusion criteria and outcomes of the included studies varied, which limited the number of studies included and parameters assessed in the meta-analysis.

[CONCLUSION] BoNT-A may become an acceptable non-surgical option. However, there is a lack of clinical randomized or observational studies on this topic, and more randomized studies with standardized reporting are required to replicate current results and investigate the long-term benefits of BoNT-A as a monotherapy or adjunct therapy in the management of ED.