Effects in animals
1) Effect on lower urinary tract tissue (prostate, urethra, and trigone of the urinary bladder)
Silodosin exhibited a potent antagonistic action against noradrenalin induced contractions in isolated rabbit prostate, urethra, and trigone of the urinary bladder.
2) Effect on urethral pressure
In anesthetized male rats, phenylephrine-induced increases in urethral pressure in the region of the prostate were selectively inhibited by silodosin. The inhibitory dose was lower than hypotensive dose.
In anesthetized male dogs, increased urethral pressure in the region of the prostate due to electrical stimulation of the hypogastric nerve was also selectively inhibited by silodosin. The inhibitory dose was lower than the hypotensive dose.
3) Effect in prostatic hypertrophy model
In a male rat prostatic hypertrophy model prepared by administration of sex hormone, bladder irritation symptoms associated with urinary retention were inhibited.
4) In a 104-week administration study in mice, it has been reported that the frequency of seminal vesicle dilatation was increased at doses of 20 mg/kg/day or more.
5) In a study on fertility and early embryogenesis until implantation in rats, it has been reported that deciduation of sperm cells in seminiferous tubules was observed at doses of 200 mg/kg/day or more and atrophy/degeneration of seminiferous tubules as well as decreased sperm survival and sperm count were observed at a dose of 600 mg/kg/day.