These efficacy variables appeared greater at higher doses , although there are no significant differences between 10 and 20 mg dose .
Specific adverse events with vardenafil  included flushing , dyspepsia , headache , and rhinitis .
Vardenafil was not significantly associated with serious cardiovascular events or death .
Vardenafil , in all treatment regimens , shows to possess superior efficacy to placebo in the treatment of patients with erectile dysfunction .
Sildenafil: an orally active type 5 cyclic GMP-specific phosphodiesterase inhibitor for the treatment of penile erectile dysfunction.
Sildenafil ( Viagra , UK-92,480 ) is a novel oral agent under development for the treatment of  penile erectile dysfunction .  Erection is dependent on nitric oxide and its second messenger , cyclic guanosine monophosphate ( cGMP ) . However , the relative importance of phosphodiesterase ( PDE ) isozymes is not clear . We have identified both cGMP- and cyclic adenosine monophosphate-specific phosphodiesterases ( PDEs ) in human corpora cavernosa in vitro . The main PDE activity in this tissue was due to PDE5 , with PDE2 and 3 also identified . Sildenafil is a selective inhibitor of PDE5 with a mean IC50 of 0.0039 microM. In human volunteers , we have shown sildenafil to have suitable pharmacokinetic and pharmacodynamic properties ( rapid absorption , relatively short half-life , no significant effect on heart rate and blood pressure ) for an oral agent to be taken , as required , prior to sexual activity . Moreover , in a clinical study of 12 patients with erectile dysfunction without an established organic cause , we have shown sildenafil to enhance the erectile response ( duration and rigidity of erection ) to visual sexual stimulation , thus highlighting the important role of PDE5 in human penile erection . Sildenafil holds promise as a new effective oral treatment for penile erectile dysfunction
These efficacy variables appeared greater at higher doses , although there are no significant differences between 10 and 20 mg dose .
Specific adverse events with vardenafil  included flushing , dyspepsia , headache , and rhinitis .
Vardenafil was not significantly associated with serious cardiovascular events or death .
Vardenafil , in all treatment regimens , shows to possess superior efficacy to placebo in the treatment of patients with erectile dysfunction .