Treating erectile dysfunction by endothelial rehabilitation with phosphodiesterase 5 inhibitors

Grapefruit peel extract mitigates paroxetine-induced erectile dysfunction in rats through stimulation of erectile response, antioxidant status, and inhibition of key enzymes related with impaired penile erection

Despite the antidepressant potency of paroxetine, its side effect of erectile dysfunction is burdensome. Grapefruit peels (GFPs) are underutilized cultivar wastes with wide range of therapeutic potentials which have been attributed to their antioxidant behavior and phenolic contents' abilities to effectively inhibit enzymatic activities and manage endothelial dysfunction in cardiovascular disorders. This study aims to investigate the erectogenic potentials of GFP extract in a rat model of paroxetine-induced ED. Experimental rats were sectioned into five groups: [1: control; 2: paroxetine (10 mg/kg); 3: paroxetine + sildenafil (5 mg/kg); 4: paroxetine + GFP (50 mg/kg); 5: paroxetine + GFP (100 mg/kg)] and treated for 28 days. Sexual behavior of rats was assessed and effect of GFP on ecto-5' nucleotidases, phosphodiesterase-5, and adenosine deaminase (ADA) activities was determined in rats' penile tissues. The levels of malondialdehyde, nitric oxide (NO) as well as superoxide dismutase (SOD) and catalase activities were also determined. HPLC-DAD analysis showed the presence of naringin, rutin, caffeic acid, quercitrin, quercetin, and kaempferol glycoside. Oral administration of paroxetine reduced erectile response as revealed by their low intromission and mounting numbers as well as high intromission and mounting latencies. Paroxetine caused a significant elevation of ADA and phosphodiesterase-5 activities and malondialdehyde levels with drastic reduction in levels of NO, SOD, and catalase activities in rats' penile tissues. However, GFP extract reversed PDE-5, ADA, and antioxidant activities to normal levels, raised the concentration of NO. These results suggest the erectogenic effects and protective potentials of GFP extract against paroxetine-induced erectile dysfunction. PRACTICAL APPLICATION: Grapefruit peels are an environmental menace in many countries and this study showed that the peels can be used in the prevention / management of erectile dysfunction. The therapeutic potentials of the peels are due to the presence of bioactive compounds such as flavonoids and phenolic acids. Therefore, exploring the erectogenic potentials of the peels will translate to conversion of the wastes to therapeutic products.

MANAGEMENT OF ERECTILE DYSFUNCTION IN CARDIOVASCULAR PATIENTS WITH COMORBIDITIES: REVIEW OF THE TRIALS ON CONTINUING THERAPY WITH PHOSPHODIESTERASE-5 MEDICATIONS

The review is focused on the issues of erectile dysfunction (ED) management by long term courses of continuous intake of the phosphodiesteraze-5 type (PDE5) inhibitors. ED is an actual problem of modern healthcare, prevalent and influencing negatively life quality and interpersonal relations. At early stages the management of ED by the PDE5 inhibitor drugs was regarded as symptomatic. However recently there are more and more publications that confirm continuous long term intake of PDE5 inhibitors. This can be explained by the mechanism of this drugs class action that includes the causation of the disorder, particularly, endothelial dysfunction. It is well konwn that in erectile dysfunction there is malfunction of nitric oxide synthesis by endothelium, and long term usage of PDE5 facilitates the increase of biochemical reactions that can be started by nitric oxide. Based on the review data, a proposition made that PDE5 inhibitors are not harmful for cardiovascular system, but may present with positive effects on cardiovascular system in general. The trials towards this direction continue. There is also a suggestion that intake of PDE5 inhibitors helps to restore normal endothelial function that may lead to better condition of cardiovascular system and decrease complications rate.

Erectile Dysfunction Drugs Changed the Protein Expressions and Activities of Drug-Metabolising Enzymes in the Liver of Male Rats

Erectile dysfunction (ED) is a major health problem and is mainly associated with the persistent inability of men to maintain sufficient erection for satisfactory sexual performance. Millions of men are using sildenafil, vardenafil, and/or tadalafil for ED treatment. Cytochrome P450s (CYPs) play a central role in the metabolism of a wide range of xenobiotics as well as endogenous compounds. Susceptibility of individuals to the adverse effects of different drugs is mainly dependent on the expression of CYPs proteins. Therefore, changes in activities of phase I drug-metabolising enzymes [arylhydrocarbon hydroxylase (AHH), dimethylnitrosamine N-demethylase (DMN-dI), 7-ethoxycoumarin-O-deethylase (ECOD), and ethoxyresorufin-O-deethylase ((EROD)] and the protein expression of different CYPs isozymes (CYP1A2, CYP2E1, CYP2B1/2, CYP3A4, CYP2C23, and CYP2C6) were determined after treatment of male rats with either low or high doses of sildenafil (Viagra), tadalafil (Cialis), and/or vardenafil (Levitra) for 3 weeks. The present study showed that low doses of tadalafil and vardenafil increased DMN-dI activity by 32 and 23%, respectively. On the other hand, high doses of tadalafil, vardenafil, and sildenafil decreased such activity by 50, 56, and 52%, respectively. In addition, low doses of tadalafil and vardenafil induced the protein expression of CYP2E1. On the other hand, high doses of either tadalafil or sildenafil were more potent inhibitors to CYP2E1 expression than vardenafil. Moreover, low doses of both vardenafil and sildenafil markedly increased AHH activity by 162 and 247%, respectively, whereas high doses of tadalafil, vardenafil, and sildenafil inhibited such activity by 36, 49, and 57% and inhibited the EROD activity by 39, 49, and 33%, respectively. Low and high doses of tadalafil, vardenafil, and sildenafil inhibited the activity of NADPH-cytochrome c reductase as well as its protein expression. In addition, such drugs inhibited the expression of CYP B1/2 along with its corresponding enzyme marker ECOD activity. It is concluded that changes in the expression and activity of phase I drug-metabolising enzymes could change the normal metabolic pathways and might enhance the deleterious effects of exogenous as well as endogenous compounds.

The efficacy of combination treatment with injectable testosterone undecanoate and daily tadalafil for erectile dysfunction with testosterone deficiency syndrome

INTRODUCTION

Both testosterone therapy and chronic treatment with phosphodiesterase type 5 inhibitors (PDE5Is) have positive effects on the histology of penile corpora and erectile function. However, few clinical studies have evaluated the efficacy of combination therapy with both testosterone replacement and chronic PDE5Is.

AIM

This study was designed to evaluate the efficacy and safety of combination treatment with long-acting injectable testosterone undecanoate (TU) and a once-daily tadalafil 5 mg for erectile dysfunction with testosterone deficiency syndrome.

METHODS

Sixty patients were consecutively enrolled and followed for 36 weeks. Thirty patients were randomly assigned to group I and received 1,000 mg of parenteral TU on day 1, followed by additional injections at weeks 6 and 18 with on-demand tadalafil 10-20 mg during the 30 weeks of treatment. The remaining 30 patients received the same dose and schedule of TU as group I, and were prescribed once-daily tadalafil 5 mg during 30 weeks.

MAIN OUTCOME MEASURES

Serological tests were performed, and the International Index of Erectile Function (IIEF), Aging Males' Symptoms (AMS) questionnaires, and Global Assessment Question (GAQ) were administered to the patients.

RESULTS

Total IIEF and AMS scores were significantly improved during the 30 weeks of treatment in both groups. When IIEF scores were compared between the two groups, group II showed better symptom scores than group I at weeks 6 and 30. A similar pattern was observed when comparing AMS scores between the groups. At week 36, changes in IIEF and AMS scores that indicated worsened symptoms compared with week 30 were observed in both groups; group II showed better symptom scores than group I. On the GAQ, the ratio of patients reporting improvement in erectile function was significantly higher in group II than group I.

CONCLUSIONS

The combination of long-acting injectable TU and once-daily tadalafil 5 mg produced a significant improvement in erectile function. Moreover, the improvement in erectile function was well maintained, even after the cessation of treatment.

Efficacy and safety of long-term tadalafil 5 mg once daily combined with sildenafil 50 mg as needed at the early stage of treatment for patients with erectile dysfunction

This study aimed to evaluate the efficacy and safety of long-term and low-dose tadalafil combined with sildenafil as needed at the early stage of treatment for erectile dysfunction (ED). We enrolled 180 patients with ED 1 : 1 to tadalafil 5 mg once daily or once-a-day tadalafil 5 mg combined with sildenafil 50 mg as needed. The efficacy measures included the 5-item version of the International Index of Erectile Function (IIEF-5) and the Sexual Encounter Profile (SEP). The safety was assessed by observing drug tolerability and adverse events. Total IIEF-5 scores of patients with severe ED in combined medication group were significantly higher than in tadalafil alone group. Question 2 scores of IIEF-5 of patients with moderate and severe ED in combined medication group were significantly higher than in tadalafil alone group. The significant improvement in question 3 scores of IIEF-5 existed only in patients with severe ED receiving combined medication. The percentage of 'yes' responses to SEP4, SEP5 and partner's SEP3 were improved significantly in combined medication group. There was no difference between two groups in the incidence of adverse events. Our results suggest that combined medication can better improve erectile function, especially for patients with severe ED.

The effects of phosphodiesterase type 5 inhibitors on penile rigidity variables during a period with no sexual stimulation: a laboratory setting double-blind study

OBJECTIVE

To investigate the effects of phosphodiesterase type 5 (PDE5) inhibitors on erectile variables during a period with no sexual stimulation in a laboratory setting double-blind study.

PATIENTS AND METHODS

In all, 80 men without erectile dysfunction (ED) but with lifelong premature ejaculation (PE) were included in the study. The men were divided equally in to four groups and received either placebo, vardenafil (10 mg), sildenafil (50 mg) or tadalafil (20 mg) in a double-blind study design. The men attended the laboratory following 3 days of sexual abstinence and placebo or one of the PDE5 inhibitors was ingested after ≥ 2 h of fasting and non-smoking. The men were then immediately placed in a silent room and real-time penile rigidity and tumescence monitoring with Rigiscan Plus (Rigiscan Plus® System, Osbon Medical Systems, Augusta, GA, USA) began. The men read some magazines or newspapers that contained no sexually stimulating material for 1.5 h. There was no interaction between the men and observer during the test period. Times to first measured and total durations of base and tip rigidities, and also total and per minute rigidity were evaluated.

RESULTS

The recorded base and/or tip rigidity ratios were 40% (eight of 20), 71% (12/17), 47% (nine of 19) and 70% (14/20) in men who took placebo, sildenafil, tadalafil and vardenafil, respectively (P = 0.126). The ratio of men who could obtain ≥ 60% base and/or tip rigidities were 10% (two of 20), 41% (seven of 17), 26% (five of 19) and 55% (11/20) in placebo, sildenafil, tadalafil and vardenafil groups, respectively (P < 0.05). The median time to first measured base rigidity was 58.0, 21.5, 54.5 and 57 min with placebo, sildenafil, tadalafil and vardenafil, respectively (P = 0032). The median total duration of recorded base rigidity was 4.0, 27.5, 10.0 and 11.5 min in men who took placebo, sildenafil, tadalafil and vardenafil, respectively (P = 0.013). The median total base rigidity (area under the curve) was 72.8, 699.0, 360.5 and 553.0 with placebo, sildenafil, tadalafil and vardenafil, respectively (P = 0.016).

CONCLUSIONS

Significant penile rigidities were obtained with PDE5 inhibitors during the short test period, with no sexual stimulation, in laboratory conditions. This finding might support the use of PDE5 inhibitors in men who need penile rehabilitation.

Open-label, Intermittent Dose, Prospective Study Evaluating the Effects of Tadalafil on Lower Urinary Tract Symptoms and Erectile Function in Patients with Benign Prostatic Hyperplasia: Continuation and Durability of Effects

PURPOSE

Benign prostatic hyperplasia is often accompanied by age-related comorbidity, such as erectile dysfunction (ED). Recent data suggest an association between ED and lower urinary tract symptoms (LUTS), and increasing evidence indicates that the clinical use of phosphodiesterase type 5 (PDE5) inhibitors provides relief from LUTS. The aim of the present study was to investigate the effects of tadalafil (20 mg once every 3 days for 12 weeks, p.o.) in men with moderate-to-severe ED and LUTS and to investigate the duration of the effects of tadalafil beyond treatment cessation.

MATERIALS AND METHODS

Men with an International Index of Erectile Function-5 (IIEF-5) score of less than 11 (representing "moderate-to-severe" ED status) and with an International Prostate Symptom Score (IPSS) of more than 8 (representing "moderate-to-severe" LUTS status) were enrolled. IPSS (total score, storage subscore, and voiding subscore) and IIEF-5 scores before treatment (baseline), during treatment (weeks 4 and 12 after treatment commencement), and after treatment (weeks 16 and 20after treatment commencement) were compared.

RESULTS

IPSS and IIEF-5 scores were significantly different between baseline and week 12 after treatment commencement. Furthermore, these scores were significantly different between baseline and week 20 after treatment commencement. However, except for IIEF-5 scores, no significant differences were observed between week 12 and week 20.

CONCLUSIONS

Treatment with 20 mg tadalafil (once every 3 days) had beneficial effects on LUTS and ED beyond treatment cessation in patients with moderate-to-severe ED and LUTS.

Increased cyclic guanosine monophosphate production and endothelial nitric oxide synthase level in mononuclear cells from sildenafil citrate-treated patients with erectile dysfunction

Mononuclear cells express enzymes involved in the NO/cyclic guanosine monophosphate (cGMP) generating system, as well as PDE5. The objective of the study was to determine the effect of sildenafil citrate administration on the level of proteins involved in the NO/cGMP generating system in mononuclear cells from patients with ED. Twenty-one patients with ED (International Index of Erectile Function-Erectile Function Domain (IIEF-EFD) 17.9+/-0.8) were enrolled and 100 mg sildenafil citrate on-demand was administered during 12 weeks. All patients showed cardiovascular risk factors. After sildenafil citrate administration, IIEF-EFD score was improved (26+/-1.2 P<0.05). In the mononuclear cells, the protein level of endothelial NO synthase (eNOS) was higher after sildenafil citrate treatment. It was accompanied by reduction in the circulating plasma levels of both high-sensitive C-reactive protein and soluble intercellular adhesive molecule-1. The protein level of soluble guanylate cyclase and PDE5 did not change in the mononuclear cells after sildenafil citrate treatment. However, in the mononuclear cells exogenous NO induced a higher cGMP production after 12-weeks sildenafil citrate administration. In conclusion, in mononuclear cells from patients with ED sildenafil citrate administration increased the level of eNOS protein and increased cGMP production in response to NO. Moreover, sildenafil citrate administration reduced the plasma circulating levels of two biomarkers associated with inflammation.

Novel approaches to improving endothelium-dependent nitric oxide-mediated vasodilatation

Endothelial dysfunction, which is defined by decreased endothelium-dependent vasodilatation, is associated with an increased number of cardiovascular events. Nitric oxide (NO) bioavailability is reduced by altered endothelial signal transduction or increased formation of radical oxygen species reacting with NO. Endothelial dysfunction is therapeutically reversible and physical exercise, calcium channel blockers, angiotensin converting enzyme inhibitors, and angiotensin receptor antagonists improve flow-evoked endothelium-dependent vasodilation in patients with hypertension and diabetes. We have investigated three different approaches, with the aim of correcting endothelial dysfunction in cardiovascular disease. Thus, (1) we evaluated the effect of a cell permeable superoxide dismutase mimetic, tempol, on endothelial dysfunction in small arteries exposed to high pressure, (2) investigated the endothelial signal transduction pathways involved in vasorelaxation and NO release induced by an olive oil component, oleanolic acid, and (3) investigated the role of calcium-activated K channels in the release of NO induced by receptor activation. Tempol increases endothelium-dependent vasodilatation in arteries from hypertensive animals most likely through the lowering of radical oxygen species, but other mechanisms also appear to contribute to the effect. While oleanolic acid leads to the release of NO by calcium-independent phosphorylation of endothelial NO synthase, endothelial calcium-activated K channels and an influx of calcium play an important role in G-protein coupled receptor-evoked release of NO. Thus, all three approaches increase bioavailability of NO in the vascular wall, but it remains to be addressed whether these actions have any direct benefit at a clinical level.

Oral phosphodiesterase-5 inhibitors and sperm functions

This review aims to elucidate the possible effects of phosphodiesterase-5 (PDE5) inhibitors on sperm functions. PDEs hydrolyze cyclic nucleotides, and together with adenylyl and guanylyl cyclase, which catalyze the formation of cAMP and cGMP, regulate the levels of these second messengers in cells. cGMP-specific PDE5 is one of the PDEs that have been intensively studied because of its fundamental pharmacological relevance, as oral PDE5 inhibitors are used successfully in treating erectile dysfunction. In addition, they have shown diverse beneficial actions in different disease categories. Specific relevance of the cGMP system in reproductive functions has been recently proposed. Its use was shown to be devoid of effects on semen volume, concentration, sperm membrane integrity or sperm penetration assay. Most available studies demonstrated a significant increase in sperm motility and viability both in vivo and in vitro, which seems to be enhanced at low doses and reduced at high concentrations. Also, these molecules showed a role in capacitation and a debated one concerning acrosome reaction. However, due to the relative short period since the launching of oral PDE5 inhibitors, more investigations should be carried out in wider scales to assess their effect(s) on variant sperm function that could be beneficial as potential therapeutic approaches.

Oral phosphodiesterase type 5 inhibitors: nonerectogenic beneficial uses

INTRODUCTION

Phosphodiesterase type 5 (PDE5) hydrolyses cyclic guanylate monophosphate (cGMP) specifically to 5' GMP. PDE5 inhibitors were a breakthrough medication that addressed a previously unfulfilled medical need. They promoted vascular relaxation in the corpora cavernosa and penile erection during sexual stimulation. Sildenafil, vardenafil, and tadalafil were approved then introduced as effective treatments for male erectile dysfunction. This impact has stimulated academic, clinical, and industrial research.

AIM

To highlight the nonerectogenic beneficial uses of oral PDE5 inhibitors.

METHOD

A systematic review of published studies in this affair based on a Pubmed and medical subject heading databases search of all concerned articles.

MAIN OUTCOME MEASURES

Demonstrated beneficial as well as applicable uses of oral PDE5 inhibitors.

RESULTS

As chemical molecules, these drugs were shown to exert potential nonerectogenic beneficial effects. They showed efficacy as a useful adjunct in the management of pulmonary hypertension. Additional uses were extended to different utilities: essential hypertension, benign prostatic hyperplasia, gastrointestinal disorders, endothelial dysfunction, female sexual dysfunction, genital blood flow, exercise capacity, Raynaud's phenomenon, sperm motility, etc.

CONCLUSION

Exploring PDE5 inhibitors for their possible medical applications in diverse specialties seems to be beneficial in making use of these molecules for the welfare of humanity.

[Is rehabilitation of erectile function following pelvic surgery reasonable? Review of the literature: from sports to PDE5 inhibitors]

Increasingly, urologists are seeing patients with erectile dysfunction after pelvic operations. In most cases, radical prostatectomy is the cause. Even when a nerve-sparing procedure is performed, approximately 50% of the patients suffer from erectile dysfunction. This report discusses the causes and theoretical therapies, including lifestyle changes, strategies for neuroregeneration and the associated prevention of apoptosis of the smooth muscle of the corpus cavernosum and improvement of the corpora cavernosa by increased oxygenation. According to the international literature, many of these agents and lifestyle modifications display promise for treating impotence. Early treatment for patients recovering from pelvic operations seems to be reasonable. It is assumed that the natural recovery of erections may take as long as 18 to 24 months postsurgery or even longer; however, treatment modalities may reduce the time to erectile recovery.

Daily Administration of Phosphodiesterase Type 5 Inhibitors for Urological and Nonurological Indications

OBJECTIVES

Although the discovery of phosphodiesterases (PDEs) was made soon after the identification of cyclic adenosine monophosphate nearly half a century ago, their true importance in medicine has taken many decades to be realised. The recognition of the important role PDE enzymes play and the impact of altering intracellular cyclic nucleotide levels became significant for most urologists and clinicians in the early 1990s with the discovery of sildenafil, a PDE5 inhibitor (PDE5-I). Once approved around the world, on-demand use of PDE5-Is became the gold standard. Recently, the potential beneficial effects of PDE5-Is on the pulmonary, vascular, and other systems has led to examination of alternative dosing regimens. In this review, we have synthesised the available published peer-reviewed literature to provide a critical contemporary view of evolving indications for PDE5-Is and how alternative dosing regimens may impact on sexual and other functions.

METHODS

MEDLINE search of all peer-reviewed English literature for the period 1990-2007.

RESULTS

The plethora of articles detailing potential uses of PDE5-I in multiple fields of medicine was uncovered. Use of alternative dosing regimens shows great promise across a number of clinical indications, including post-radical retropubic prostatectomy, pulmonary hypertension, endothelial dysfunction, and salvage of on-demand PDE5-I nonresponders.

CONCLUSIONS

Use of PDE5-I on a daily basis may evolve into a major form of drug administration both for men with erectile dysfunction and for those with a myriad of other conditions shown to benefit from this approach.

Cutaneous microcirculatory function predicts the responsiveness to tadalafil in patients with erectile dysfunction and coronary artery disease

Despite the proven clinical efficacy of phosphodiesterase inhibitors in the treatment of erectile dysfunction (ED), some patients do not respond to the medication. By means of nailfold capillary microscopy in patients with concomitant coronary artery disease (CAD) and ED, it was evaluated whether the extent of microvascular dysregulation predicts the responsiveness to tadalafil (TAD) in terms of erectile function. The ED of each patient was assessed by the International Index of Erectile Function (IIEF). Patients presenting both, documented CAD and ED, showed a significantly reduced capillary red blood cell velocity (v(RBC)) at rest and after 3 min of ischemia compared with age-matched controls. At 2 h after intake of 20 mg of TAD, a significant increase of v(RBC) at rest as well as during postischemic hyperemia was found. Patients who reported no improvement of their ED after the use of TAD demonstrated no changes in the duration of postischemic (DpH) hyperemia, or even a reduction of the DpH. The majority of the patients, who reported at least one successful sexual intercourse due to TAD, had a prolongation of DpH. We conclude that assessment of microvascular regulation by nailfold capillary microscopy can predict the probability of a treatment failure with phosphodiesterase inhibitors in patients with ED. Moreover, as endothelial dysfunction is the common underlying pathophysiological process of ED and cardiovascular diseases, the test may help to identify patients at risk for the development of atherosclerosis and following cardiovascular events.

Evaluation of an alternative dosing regimen with tadalafil, three times per week, for men with erectile dysfunction: SURE study in Italy

AIM

To examine the preference for two dosing regimens of 20 mg of tadalafil, on demand or three times per week, in men affected with erectile dysfunction (ED) in Italy.

METHODS

Scheduled Use versus on demand Regimen Evaluation (SURE) is a multicenter, crossover and open-label study, involving 94 urology centers in Italy. Patients aged 18 years or older affected with ED for at least 3 months were enrolled and randomized to 20 mg of tadalafil treatment on demand or three times per week for 5-6 weeks. After a 1-week washout, patients were crossed over to the alternate regimen for 5-6 weeks. A treatment preference question was used to determine the preferred treatment regimen. International Index of Erectile Function (IIEF) and Sexual Encounter Profile (SEP) questionnaire were used as efficacy measures.

RESULTS

A total of 1 058 men (mean age 54.8 years), were randomized to treatment. Overall, 59.1% of patients preferred the on-demand regimen and 41.9% preferred the three times per week dosing. Both regimens were efficacious and well tolerated. Although a statistically higher improvement of the IIEF erectile function (IIEF-EF) domain score and the SEP questionnaire was reported for the three times per week compared to the on-demand treatment regimen, this difference was numerically minimal and lacking in clinical significance.

CONCLUSION

Tadalafil is effective and well tolerated whether used on demand or three times per week. Patients should be given the option to choose the best treatment regimen according to personal needs and preferences.

[Lifestyle, erectile dysfunction, hormones and metabolic syndrome. Opportunities for gender-specific prevention for men]

German men tend to be less health conscious and show less of an interest in preventative behaviours. However, urological symptoms can provide the grounds for a doctor's visit and conversation. Modifiable lifestyle factors such as obesity, lack of exercise and smoking play a role in the development, progression or remission not only of erectile dysfunction (ED), but also in cardiovascular disease and the metabolic syndrome. Moreover, age-related testosterone deficiency can negatively impact the overall health as well as the sexual function of men. Recommendations to alter behaviours in the context of ED management and, if necessary, testosterone replacement, provide the urologist with the opportunity for broad gender-specific prevention for his male patients.

An Alternative dosing Regimen with Tadalafil 3 Times/Week in the Treatment of Erectile Dysfunction: Italian Data from the SURE Study

Aim.

To evaluate the preference for 2 dosing regimens of tadalafil 20 mg, on demand or 3 times/week, in Italian men affected by erectile dysfunction (ED).

Materials and Methods.

SURE is a multicenter, crossover, open-label study, involving 94 urology centers in Italy. Patients aged 18 or more, affected by ED for at least 3 months were enrolled into the study and randomized to a tadalafil 20 mg treatment on demand or 3 times/week for 5–6 weeks. After a 1-week washout period, patients were crossed over to the alternate regimen for 5–6 weeks. A treatment preference question (TPQ) was used to determine the preferred treatment regimen. IIEF and SEP questionnaires were used as efficacy measures.

Results.

1058 men, mean age 54.8 years, were randomized to treatment. Overall, 59.1% of patients preferred the on-demand regimen and 41.9% preferred the 3 times/week dosing regimen. Both regimens were efficacious and well tolerated.

Conclusions.

Tadalafil is effective and well tolerated whether used both on demand and three times/week. Patients should be given the possibility to choose the best treatment regimen according to personal needs and preferences. (Urologia 2007; 74: 30–6)

[Metabolic syndrome and erectile dysfunction. Epidemiologic associations and pathogenetic links]

There is abundant evidence for the association between erectile dysfunction (ED) and the traditional atherosclerotic risk factors, such as dyslipidemia, hypertension, glucose intolerance, and obesity, that make up the metabolic syndrome. Recent findings have demonstrated a linear relationship between the number of these risk factors and the prevalence of ED. There is also growing evidence that endothelial dysfunction characterized by decreased bioavailability of nitrogen monoxide (NO) and a proinflammatory, prothrombotic, and proliferative phenotype is the common pathogenetic pathway linking ED to peripheral vascular diseases. Since ED often occurs several years before any clinical manifestation of systemic cardiovascular disease, ED should be seen as a warning of early atherosclerotic disease and an opportunity for doctor and patient to initiate preventive measures.

Management of sildenafil treatment failures

PURPOSE OF REVIEW

Although oral type 5 phosphodiesterase inhibitors are considered as first-line therapy for the majority of causes of erectile dysfunction, because of their high efficacy, ease of use, and acceptable safety profile, there are some who fail to respond, mainly because of end-organ failure. This communication reviews the management of sildenafil failures in light of recent advances.

RECENT FINDINGS

Sildenafil failures can be attributed to either lack of efficacy or side effects; issues may involve the physician, patient, and his partner. Physicians may contribute to sildenafil failure and discontinuation because of inadequate instructions, lack of adequate follow-up, suboptimal dosing, lack of adequate trial, and insufficient clarification about safety issues. Studies have demonstrated that progression of endothelial dysfunction and diminished cavernosal smooth-muscle content are recognized organic factors which cause end-organ dysfunction and ultimately treatment failure.

SUMMARY

Proper counseling, medication optimization, and modifying associated risk factors can provide success in men who had initially failed sildenafil therapy for erectile dysfunction. Other treatment modalities that may be considered when sildenafil failure occurs include vacuum devices, intraurethral, and intracavernosal administration of vasoactive drugs alone or combined with sildenafil. Penile prosthesis implantation is considered as a last resort, if all first-line and second-line therapies fail.

Evaluation of tetrahydrobiopterin (BH4) as a potential therapeutic agent to treat erectile dysfunction

AIM

Nitric oxide (NO)-mediated smooth muscle relaxation causes penile erections. The endothelial NO synthase (eNOS) coenzyme tetrahydrobiopterin (BH4) converts eNOS-mediated catalytic activity from oxygen radical to NO production, improving endothelial function and vascular smooth muscle relaxation.

METHODS

Using quantitative immunohistochemistry, 8-isoprostane and nitrotyrosine concentrations were compared in cavernosal tissue from 17 potent and 7 impotent men, and the effect of single oral doses of BH4 on penile rigidity and tumescence was investigated. The pharmacodynamic effect of single oral doses of BH4 on penile rigidity and tumescence was investigated in a randomized, placebo-controlled, double-blind cross-over fashion in 18 patients with erectile dysfunction (ED) while receiving visual sexual stimulation.

RESULTS

8-Isoprostane content in endothelium and smooth muscle was significantly higher in impotent patient samples; the level of nitrotyrosine was unchanged in ED patients. Relative to placebo, a single dose of 200 mg BH4 led to a mean increase in duration of > 60% penile rigidity (33.5 min [95% confidence interval (CI): 13.1-49.3] at base and 29.4 min [95% CI: 8.9-42.2] at tip). A 500-mg dose increased the relative duration of > 60% penile rigidity by 36.1 min (95% CI: 16.3-51.8) at the base and 33.7 min (95% CI: 11.4-43.9) at the tip. Treatments were well tolerated.

CONCLUSION

BH4 treatment is suggested to switch eNOS catalytic activity from super-oxide to NO formation, leading to a reduced formation of free radical reaction product 8-isoprostane without alteration of nitrotyrosine. The observed results make BH4 a suitable candidate as an ED treatment through reconstitution of altered catalytic activity of the eNOS.