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Intracavernosal botulinum toxin type A in refractory erectile dysfunction: umbrella review with GRADE certainty
Vanessa Talavera Cobo1, Carlos Andrés Yánez Ruiz1, Mario Daniel Tapia Tapia1
1Department of Urology, Clinica Universidad de Navarra, Av. Pío XII 36, 31008 Pamplona, Spain.
Background:
Erectile dysfunction (ED) is a prevalent and burdensome condition. Intracavernosal botulinum toxin type A (BoNT-A) has been investigated as an alternative for refractory patients to standard therapies; however, the methodological quality and degree of primary study overlap across published systematic reviews remain uncharacterized.
Objectives:
To synthesize evidence on the efficacy and safety of intracavernosal BoNT-A for ED, and to evaluate methodological quality, risk of bias, primary study overlap, and certainty of evidence.
Methods:
This umbrella review was conducted according to a predefined protocol and reported in accordance with Preferred Reporting Items for Overviews of Reviews 2022 statement. PubMed (MEDLINE), Web of Science, Scopus, Cochrane Library, Epistemonikos, and LILACS were searched from inception to January 2026. Google Scholar was additionally searched. Eligible studies were systematic reviews evaluating intracavernosal BoNT-A for ED. Methodological quality was assessed with AMSTAR-2, review-level risk of bias with Risk of Bias in Systematic Reviews (ROBIS), primary study overlap with the corrected covered area (CCA), and certainty of evidence with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) framework.
Results:
Four systematic reviews were included, encompassing 10 unique ED-specific primary studies (n = 865). The CCA was 53.3%, indicating very high overlap. Three reviews were rated critically low and one as low confidence by AMSTAR-2. All four reviews were judged to be at high overall risk of bias using ROBIS. Improvements in erectile function were consistently reported across reviews; however, substantial heterogeneity precluded robust quantitative synthesis. GRADE certainty of evidence was low for erectile function improvement and short-term safety, and very low for response rate and long-term safety.
Conclusion:
Although some systematic reviews included in this umbrella review reported improvements in erectile function following intracavernosal BoNT-A, the overall certainty of evidence is low to very low across all pre-specified outcomes. Substantial heterogeneity, very high primary study overlap, and methodological shortcomings in available reviews substantially limit the ability to draw firm conclusions regarding its clinical use. Rigorous randomized trials with standardized protocols are required before this intervention can be considered for clinical adoption.