Use of Sildenafil Citrate for the Treatment of Erectile Dysfunction in Stallions: First Case Reports

Pharmacological aids can be useful alternatives to enhance penile erection and/or improve ejaculatory function, thereby prolonging the reproductive life of stallions with ejaculatory disorders. This study aimed to evaluate the effects of sildenafil citrate in the treatment of erectile dysfunction and on semen quality in two aged stallions, a Quarter Horse (18 years) and a Mangalarga Marchador (25 years), presented to the Veterinary Hospital of FMVZ-UNESP, Botucatu, SP, Brazil. The treatment consisted of oral administration of sildenafil citrate at 0.2 mg/kg. Thirty minutes after administration, the Quarter Horse stallion achieved full erection and ejaculated in all collection attempts (100%; 3/3), with semen parameters within normal ranges for the species. The Mangalarga Marchador showed a partial response to treatment, with successful ejaculation in only one of three attempts (33.3%) and exhibited oligozoospermia, possibly associated with previously identified age-related testicular degeneration concurrent with the erectile dysfunction. To the best of the authors' knowledge, this is the first report on the use of sildenafil citrate for managing erectile dysfunction in stallions, demonstrating its therapeutic potential. However, the results suggest individual variability in response to treatment, indicating the need for additional controlled studies to establish more precise dose-response protocols.