Sildenafil boosts the outcome of NO by inhibiting phosphodiesterase form five (PDE5), that's accountable for degradation of cGMP during the corpus cavernosum. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum.Nosebleeds. Sildenafil could lead to nosebleeds. You may be at larger hazard for this if you take a blood thinner