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 .
Rationale for combination therapy of intraurethral prostaglandin E1 and sildenafil in the salvage of erectile dysfunction patients desiring noninvasive therapy
Corpus cavernosum smooth muscle relaxation and hence penile erection are regulated in part by increases in smooth muscle synthesis of the second messengers cyclic adenosine monophosphate ( cAMP ) and cyclic guanosine monophosphate ( cGMP ) . The object of this study was to determine 30-month follow-up results in motivated patients desiring noninvasive medical therapy using sildenafil citrate ( Viagra ) in combination with intraurethral prostagl and in E1 ( PGE1 ) ( Medicated Urethral System for Erection [ MUSE ] ) .  Twenty-eight patients ( mean±s.d . age , 59±7.3 y ; 17 who had undergone radical prostatectomy and 11 who had a diagnosis of organic erectile dysfunction ) were included in this study . Detailed history taking and physical examinations were performed and vascular risk factors noted . In these patients , treatment with either 100 mg of sildenafil citrate and /or 1000 μg of MUSE had failed . None of these patients desired intracavernosal injection . Duplex Doppler ultrasonography  after redosing was carried out on all patients . Dynamic infusion corpus cavernosography/cavernosometry was obtained in 17 of 28 patients , and combination therapy was initiated using 100 mg of sildenafil citrate orally 60 min before intercourse and 500 μg of MUSE intraurethrally immediately before intercourse . Independently , either 100 mg of sildenafil citrate or 1000 μg of MUSE was not efficacious in inducing an erection sufficient for vaginal penetration in any of the 28 patients . After initiating a combination therapy , at 30 months , all 28 patients were reporting erections sufficient for vaginal penetration , with 3.6 intercourse episodes per month . None of the patients crossed over to intracavernosal therapy or penile prosthesis . During therapy , eight of 28 patients reduced the dose of sildenafil citrate to 50 mg . Combination therapy with MUSE and sildenafil  may be more efficacious in the salvage of patients who desire noninvasive therapy but in whom single-treatment modalities fail . Although both cAMP- and cGMP-mediated vasodilation can lead to penile erection , combining therapies that incorporate both pathways may succeed when single therapies fail
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 .