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

Purpose: Inhibiting cyclic guanosine monophosphate metabolism may induce pe nile erection during concomitant nitric oxide production. Vardenafil hydroc hloride is a new, highly selective, potent cyclic guanosine monophosphate p hosphodiesterase 5 inhibitor. We determined the oral effectiveness of varde nafil in a simple and quantitative conscious rabbit model. Materials and Methods: Vardenafil was given orally to conscious rabbits. Er ection was assessed in a time dependent manner by measuring the length of t he uncovered penile mucosa. Erection was evaluated in the absence and prese nce of intravenous sodium nitroprusside, a nitric oxide donor. Results: Vardenafil induced dose dependent penile erection in conscious rab bits after the oral administration of I to 30 mg./kg. The efficacy of varde nafil. was potentiated and effective doses were significantly reduced by th e simultaneous administration of sodium nitroprusside. Conclusions: The effect of vardenafil on penile erection after oral adminis tration was clearly demonstrated in the conscious rabbit model. The time co urse and early onset of activity indicate that it may be useful for treatin g erectile dysfunction. Potentiation of the effect by the nitric oxide dono r sodium nitroprusside implies that it would have enhanced activity during sexual arousal, when nitric oxide is produced endogenously. The clinical de velopment of this product for erectile dysfunction is proceeding.