Experimental data support the concept of cavernosal damage and suggest a protective role for daily dosage of a PDE5-I ; however , similar data have not yet been replicated in humans .
Penile rehabilitation programs are common in clinical practice , but there is no definitive evidence to support their use or the best treatment strategy .
PDE5-Is are efficacious and safe in young patients with normal preoperative erectile function who have undergone bilateral nerve-sparing radical prostatectomy .
On-dem and use of a PDE5-I may be at least as efficacious as daily use .
PDE5-I use in penile rehabilitation programs is not supported by rigorous level 1 evidence -based medicine .
PDE5-Is are an efficacious and safe treatment for post-RP ED in properly selected patients .
The experimental results on the protective role of daily dosages of PDE5-Is , while robust , have not been replicated in humans .
CONTEXT  Erectile dysfunction ( ED ) after radical prostatectomy ( RP ) has a significant negative impact on a patient 's health-related quality of life .
Phosphodiesterase type 5 inhibitors ( PDE5-Is ) have recently been utilized not only as a treatment of ED in this population but also as a preventive strategy in penile rehabilitation programs .
OBJECTIVE To eluci date the pathophysiologic mechanisms of post-RP ED , to assess the need for rehabilitation following surgery , and to analyze the basic scientific evidence and clinical applications of PDE5-Is for the prevention and treatment of ED .
EVIDENCE SYNTHESIS Post-RP ED has many factors .
Cavernosal nerve injury induces pro-apoptotic factors ( ie , loss of smooth muscle ) and pro-fibrotic factors ( ie , an increase in collagen ) within the corpora cavernosa .
Penile weight and cell subtype specific changes in a post-radical prostatectomy model of erectile dysfunction.
PURPOSE We evaluated neurogenic erectile dysfunction , focusing on the post-radical prostatectomy model . We investigated changes in DNA , protein and apoptotic cells of the rat penis after  denervation . Gross morphometry was measured to eluci date the impact of chemical changes . MATERIAL S AND METHODS Postpubertal male Sprague-Dawley rats were r and omized to bilateral or unilateral cavernous nerve transection , or sham operation .  Wet weight , DNA content and protein content were measured . Tissue sections were stained for apoptosis by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling and the apoptotic index was calculated . Dual staining was performed for endothelial and smooth muscle cells to identify apoptotic cells . RESULTS Penile wet weight was significantly decreased at all time points after bilateral neurotomy ( p < 0.0005 ) . Unilateral neurotomy allowed much greater preservation of penile weight . DNA content was significantly decreased in bilaterally denervated penes and unchanged in unilaterally operated penes . Protein content was not significantly altered in the bilateral or unilateral cohorts . Bilateral neurotomy induced significant apoptosis , while unilateral surgery caused significantly less apoptosis . Each population had apoptotic clustering just beneath the tunica albuginea , which was mostly smooth muscle cells . CONCLUSIONS These data suggest the importance of neural integrity to maintain penile homeostasis . The loss in penile weight was consistent with the anecdotal experience of many clinicians . Decreased DNA content may have been due to significant levels of apoptosis in smooth muscle cells . Preserved protein content may suggest an increase in extracellular protein , as postulated in corporeal fibrosis . The subtunical population of apoptotic smooth muscle cells revealed a mechanism for veno-occlusive dysfunction observed after radical prostatectomy . These effects were significantly moderated in the unilateral model , reinforcing the critical nature of neural integrity
Experimental data support the concept of cavernosal damage and suggest a protective role for daily dosage of a PDE5-I ; however , similar data have not yet been replicated in humans .
Penile rehabilitation programs are common in clinical practice , but there is no definitive evidence to support their use or the best treatment strategy .
PDE5-Is are efficacious and safe in young patients with normal preoperative erectile function who have undergone bilateral nerve-sparing radical prostatectomy .
On-dem and use of a PDE5-I may be at least as efficacious as daily use .
PDE5-I use in penile rehabilitation programs is not supported by rigorous level 1 evidence -based medicine .
PDE5-Is are an efficacious and safe treatment for post-RP ED in properly selected patients .
The experimental results on the protective role of daily dosages of PDE5-Is , while robust , have not been replicated in humans .
CONTEXT  Erectile dysfunction ( ED ) after radical prostatectomy ( RP ) has a significant negative impact on a patient 's health-related quality of life .
Phosphodiesterase type 5 inhibitors ( PDE5-Is ) have recently been utilized not only as a treatment of ED in this population but also as a preventive strategy in penile rehabilitation programs .
OBJECTIVE To eluci date the pathophysiologic mechanisms of post-RP ED , to assess the need for rehabilitation following surgery , and to analyze the basic scientific evidence and clinical applications of PDE5-Is for the prevention and treatment of ED .
EVIDENCE SYNTHESIS Post-RP ED has many factors .
Cavernosal nerve injury induces pro-apoptotic factors ( ie , loss of smooth muscle ) and pro-fibrotic factors ( ie , an increase in collagen ) within the corpora cavernosa .