The oral efficacy of vardenafil hydrochloride for inducing penile erection in a conscious rabbit model

Purpose: Inhibiting cyclic guanosine monophosphate metabolism may induce penile erection during concomitant nitric oxide production. Vardenafil hydrochloride is a new, highly selective, potent cyclic guanosine monophosphate phosphodiesterase 5 inhibitor. We determined the oral effectiveness of vardenafil in a simple and quantitative conscious rabbit model. Materials and Methods: Vardenafil was given orally to conscious rabbits. Erection was assessed in a time dependent manner by measuring the length of the uncovered penile mucosa. Erection was evaluated in the absence and presence of intravenous sodium nitroprusside, a nitric oxide donor. Results: Vardenafil induced dose dependent penile erection in conscious rabbits after the oral administration of I to 30 mg./kg. The efficacy of vardenafil. was potentiated and effective doses were significantly reduced by the simultaneous administration of sodium nitroprusside. Conclusions: The effect of vardenafil on penile erection after oral administration was clearly demonstrated in the conscious rabbit model. The time course and early onset of activity indicate that it may be useful for treating erectile dysfunction. Potentiation of the effect by the nitric oxide donor sodium nitroprusside implies that it would have enhanced activity during sexual arousal, when nitric oxide is produced endogenously. The clinical development of this product for erectile dysfunction is proceeding.