Sildenafil and erectile dysfunction

Therapeutic Strategies for Erectile Dysfunction With Emphasis on Recent Approaches in Nanomedicine

This review addressed erectile dysfunction, regarding pathophysiology and therapeutic strategies. The line of treatment includes phosphodiesterase type-5 inhibitors and other types of therapy like topical and stem-cell transplant. Scientific literature was assessed to investigate the impact of nanotechnology on erectile dysfunction therapy. Various nanotechnology approaches were applied, like vesicular systems, lipid-based carriers, nanocrystals, dendrimers, liquid crystalline systems and nanoemulsions. Smart nano-systems can alter the landscape of the modern pharmaceutical industry by re- investigation of pharmaceutically suboptimal but biologically active entities for treatment of erectile dysfunction which were previously considered undeveloped.

Usage and perceptions of phosphodiesterase type 5 inhibitors among the male partners of infertile couples

OBJECTIVE

We aimed to investigate the prevalence of erectile dysfunction (ED) and the usage of phosphodiesterase type 5 (PDE5) inhibitors for ED treatment in infertile couples.

METHODS

A total of 260 male partners in couples reporting infertility lasting at least 1 year were included in this study. In addition to an evaluation of infertility, all participants completed the International Index of Erectile Function (IIEF)-5 questionnaire to evaluate their sexual function. The participants were asked about their use of PDE5 inhibitors while trying to conceive during their partner's ovulatory period and about their concerns regarding the risks of PDE5 inhibitor use to any eventual pregnancy and/or the fetus.

RESULTS

Based on the IIEF-5 questionnaire, 41.5% of the participants (108/260) were classified as having mild ED (an IIEF-5 score of 17-21), while 10.4% of the participants (27/260) had greater than mild ED (an IIEF-5 score of 16 or less). The majority (74.2%, 193/260) of male partners of infertile couples had a negative perception of the safety of using a PDE5 inhibitor while trying to conceive. Only 11.1% of men (15/135) with ED in infertile couples had used a PDE5 inhibitor when attempting conception.

CONCLUSION

ED was found to be common in the male partners of infertile couples, but the use of PDE5 inhibitors among these men was found to be very low. The majority of male partners were concerned about the risks of using PDE5 inhibitors when attempting to conceive. Appropriate counseling about this topic and treatment when necessary would likely be beneficial to infertile couples in which the male partner has ED.

Avanafil for erectile dysfunction in elderly and younger adults: differential pharmacology and clinical utility

The treatment modalities of erectile dysfunction range from oral pharmacotherapy to intracavernosal injections, intraurethral pellets, vacuum erectile devices, and the surgical option of penile prosthesis insertion. Oral phosphodiesterase 5 inhibitors still remain the preferred treatment for patients since they are the least invasive, not to mention that they can be prescribed by non-urologists. Due to these factors, there has been development of newer drugs with fewer side effects. This is a review of the second generation phosphodiesterase 5 inhibitor, avanafil, looking into its pharmacology as well as its clinical utility. Avanafil’s faster onset and shorter duration of action has made it preferred as compared to other PDE5 inhibitors for patients with multiple comorbidities.

An update on pharmacological treatment of erectile dysfunction with phosphodiesterase type 5 inhibitors

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5-i) are used for the oral treatment of erectile dysfunction (ED). Since the launch of sildenafil more than 15 years ago, new molecules have become available. At present, in addition to tadalafil and vardenafil, there are three other drugs, udenafil, avanafil and mirodenafil, marketed in some countries which appear to be promising.

AREAS COVERED

The clinical pharmacological differences in dosage and side effects of all PDE5-i are evaluated.

EXPERT OPINION

All PDE5-i are equally effective and safe for the treatment of ED. On-demand use of any PDE5-i is also safe for patients with comorbid conditions. Tadalafil seems to be the preferred drug by patients and physicians, probably due to its peculiar pharmacological profile that makes sexual intercourse more spontaneous for the patients. Preliminary data suggest that the use of vardenafil may also be beneficial in cases of ED associated with premature ejaculation. Daily treatment is another option in men with ED and documented vascular or prostate disease. In geriatric or in difficult-to-treat populations, the evaluation of testosterone plasma levels will help to predict the efficacy of any PDE5-i. Remarkably, when such drugs are withdrawn for any reason, ED most often continues to occur because of the presence of an underlying disease.

Alterations in sperm motility after acute oral administration of sildenafil or tadalafil in young, infertile men

OBJECTIVE

To evaluate the acute effect of sildenafil and tadalafil on seminal parameters in young, infertile patients.

DESIGN

Prospective, randomized, double-blind, crossover clinical investigation on semen parameters after the administration of a single dose of sildenafil (50 mg) or tadalafil (20 mg).

SETTING

An academic hospital as well as a male infertility center and clinical andrology laboratories.

PATIENT(S)

Eighteen young, infertile men.

INTERVENTION(S)

Oral administration of a single dose of sildenafil (50 mg) or tadalafil (20 mg) in a blind, randomized order. The semen samples were collected 1 or 2 hours after each treatment.

MAIN OUTCOME MEASURE(S)

Changes in sperm parameters after sildenafil and tadalafil administration, compared with the basal conditions.

RESULT(S)

A significant increase in sperm progressive motility (median value, 37.0% vs. 28.5%) was observed after sildenafil administration as compared with baseline; in contrast, a significant decreased value was observed after tadalafil (median value, 21.5% vs. 28.5%).

CONCLUSION(S)

These preliminary results indicate that sperm motility appears to be acutely affected in young, infertile patients by a single dose of sildenafil and tadalafil, with opposite effects: stimulatory by the former and inhibitory by the latter.

The effect of sildenafil citrate and pentoxifylline combined treatment in the management of erectile dysfunction

INTRODUCTION

In the present study, we evaluated the efficacy of sildenafil and pentoxifylline combined therapy in the treatment of vasculogenic erectile dysfunction.

METHODS

Sixty-eight patients with various degrees and types of vasculogenic erectile dysfunction were included in the study. The patients were recommended to take oral sildenafil (minimum two 50-mg tablets/week) 1 h prior to sexual intercourse for 4 weeks. After 4 weeks of washout period, patients were recommended to take combined therapy (minimum two 50-mg tablets/week sildenafil 1 h prior to sexual intercourse and 1.2 g of pentoxifylline/day divided into three doses) for an additional 4-week period. Both treatment regimes were evaluated with the international index of erectile function (IIEF).

RESULTS

Mean IIEF score was higher after sildenafil treatment when compared to pre-treatment score (14.2+/-4.3 and 8.6+/-4.2, respectively, P<0.05). Likewise after the combination treatment, mean IIEF score was higher when compared to pre-treatment score (18.1+/-5.2 and 8.6+/-3.8, respectively, P<0.05). The increase in the IIEF score was 5.62+/-2.08 in the sildenafil only group whereas increase in the IIEF score was 9.51+/-3.77 in the combination therapy group. There was a statistically significant increase in the combination group when compared to the sildenafil only group (P<0.001).

CONCLUSION

Our study suggests that use of sildenafil citrate and pentoxifylline combined therapy could be effective in the management of patients with vasculogenic erectile dysfunction.

The therapeutic dilemma: how to use short-acting PDE5 inhibitor drugs

In the last few years, the clinical context of the diagnosis and treatment of erectile dysfunction (ED) has changed radically. In fact, oral drug treatment with phosphodiesterase type-5 inhibitors (PDE5-i), licensed in the past years, appeared to offer advantages over other medical approaches in terms of ease of administration and cost. PDE5-i are now widely advocated as first-line therapy for ED. PDE5-i represent a class of orally active drugs for ED, which inhibit PDE5 enzyme and in turn enhance smooth muscle relaxation via prolongation of cyclic GMP action within the cavernous smooth muscle. Although the various types of PDE5-i differ with respect to selectivity and pharmacokinetic profiles, efficacy and safety of these agents are mostly comparable in broad populations of men with erectile ED, including those with diabetes, cardiovascular disease or those taking multiple antihypertensive agents. Aim of this article will be to review the different efficacy and safety profiles of oral short-acting compounds and to give indication for treatment of special populations of men with ED.

Are subjects with erectile dysfunction aware of their condition? Results from a retrospective study based on an Italian free-call information service

The aim of the study was to analyse the socio-demographic and epidemiological characteristics of the Italian male population affected by sexual disturbances. Men complaining of erectile dysfunction (ED) who called the Pfizer program "Man and Woman in Health" between April 18th 2001 and May 27th 2002 and asked for information about their medical condition, were interviewed by trained doctors using a computer-assisted questionnaire. 16007 out of 25018 calls were considered for statistical analysis. Mean age of callers was 48.8+/-14.2 yr, reporting ED in 83% of cases. In the majority of men ED was severe (58%) and lasting more than 3 yr (25%). Multivariate analysis revealed that diabetes, depression, prostate surgery, heart disease, neurological disorders, liver and renal diseases were all significant and independent contributors to the degree of erectile impairment adjusted for age (p<0.001). The principal concomitant medications were anti-hypertensive (23%), antidiabetic (9%) and cardiovascular agents (6%). Cigarette smoking was present in 24%. On directed questioning of the caller, anxiety and distress were perceived as the most frequent causes of ED (42%) across all age groups, followed by the presence of concomitant disease/s (26%) especially in aging men. Also, a large number of men (41 %) with severe ED waited for more than 3 yr before looking for medical referral. Interestingly, only 19% had ever tried any specific medication for ED. These data indicate that 5 yr after worldwide approval and release of sildenafil, ED is still largely undiagnosed and under-treated, possibly because it is still perceived as a condition mainly due to distress or advancing age and therefore not deserving medical referral. Effective prevention of ED commences with better awareness of the pathological causes by the population and modification of risk factors by the doctors.

Effect of acute in vivo sildenafil citrate and in vitro 8-bromo-cGMP treatments on semen parameters and sperm function

OBJECTIVE

To determine the effect of acute in vivo sildenafil citrate (VIAGRA) and in vitro 8-Bromo-cGMP treatments on semen parameters and sperm function.

DESIGN

Prospective double-blind, placebo-controlled, crossover, two-period clinical investigation.

SETTING

Healthy volunteers in an academic research environment.

PATIENT(S)

Twenty male volunteers with normal erectile function and normal electrocardiogram were recruited.

INTERVENTION(S)

In vivo: 50 mg of sildenafil citrate (VIAGRA) or placebo was administered p.o., and semen samples were collected 1 hour after administration of the test drug. In vitro: 8-Bromo-cGMP (20 microM; 60 minutes) was added to semen samples.

MAIN OUTCOME MEASURE(S)

Macroscopic and microscopic seminal parameters were measured and motility studies performed. Various acrosome reaction studies and sperm-zona pellucida binding studies were also done.

RESULT(S)

Either sildenafil citrate (VIAGRA) or 8-Bromo-cGMP treatments had no effect on both macroscopic and microscopic seminal parameters as well as the acrosome reaction. Sperm-zona pellucida binding results were however increased to 148.75% and 134%, respectively, by these treatments. Various kinematical parameters increased after treatment with the most significant increase detected in the population of rapid cells.

CONCLUSION(S)

VIAGRA can be used successfully to enhance sperm motility and binding to the oocyte especially during fertility treatments.

Acute electroretinographic changes during sildenafil (Viagra) treatment for erectile dysfunction

The authors describe their findings on 12 subjects who were treated with 50 mg of sildenafil (Viagra) and underwent ERG measurements prior to and 1 hour after ingestion. The Naka-Rushton equation was used to describe the b-wave luminance-response function of the scotopic ERG. Statistically significant differences were noted in the Vmax and K values. Sildenafil ingestion resulted in an increase in Vmax (higher rod response to light stimuli) and a decrease in K (higher sensitivity).

Androgens improve cavernous vasodilation and response to sildenafil in patients with erectile dysfunction

OBJECTIVES

We have recently shown that, in men with erectile dysfunction (ED), free testosterone (FT) directly correlates with penile arterial inflow. This led us to further investigate the effect(s) of androgen administration on cavernous arteries in patients failing sildenafil treatment.

DESIGN

Prospective randomized placebo-controlled pilot study.

PATIENTS

Twenty patients with arteriogenic ED as evaluated by dynamic colour duplex ultrasound (D-CDU) studies, normal sexual desire but testosterone (T) and FT in the lower quartile of normal range (low-normal), not responding to sildenafil treatment (100 mg) on six consecutive attempts.

MEASUREMENTS

All patients had D-CDU, hormonal [LH, prostate-specific antigen (PSA), total and free testosterone, sex hormone-binding protein (SHBG), oestradiol], biochemical [haematocrit, low-density lipoprotein (LDL) and HDL cholesterol, triglycerides], and sexual evaluations [International Index of Erectile Function (IIEF)] before and after 1 month of therapy with transdermal testosterone (5 mg/day, n = 10) or placebo along with sildenafil treatment on demand. Measurement of flow parameters by D-CDU on cavernous arteries was the primary endpoint of the study. Improvement of erectile function was assessed using the IIEF questionnaire and the Global Assessment Question (GAQ).

RESULTS

One month treatment with transdermal testosterone led to a significant increase in T and FT levels (23.7 +/- 3.3 SD vs. 12.8 +/- 2.1 nmol/l and 473 +/- 40.2 vs. 260 +/- 18.1 pmol/l, P < 0.01, respectively). In addition testosterone administration induced a significant increase in arterial inflow to cavernous arteries measured by D-CDU (32 +/- 3.6 vs. 25.2 +/- 4 cm/s, P < 0.05), with no adverse effects. Also, a significant improvement in erectile function domain score at IIEF was found in the androgen but not in the placebo-treated patients (21.8 +/- 2.1 vs. 14.4 +/- 1.4, P < 0.05) which was associated with significant changes in the GAQ score (80%vs. 10%, P < 0.01).

CONCLUSIONS

In patients with arteriogenic ED and low-normal androgen levels, short-term testosterone administration increases T and FT levels and improves the erectile response to sildenafil likely by increasing arterial inflow to the penis during sexual stimulation.

Subjective visual halos after sildenafil (Viagra) administration: Electroretinographic evaluation

PURPOSE

The ophthalmologic and electroretinographic (ERG) findings in one subject with subjective visual disturbances after sildenafil administration are described.

DESIGN

Interventional case report.

METHODS

A complete ophthalmologic examination was performed, including best-corrected visual acuity and ERG, repeated 1 and 2 hours after administration of 100 mg of sildenafil.

MAIN OUTCOME MEASURES

Rod responses were obtained over a range of retinal illuminances from those producing a minimum detectable response to those producing rod saturation. Intensity amplitude function was determined.

RESULTS

At 2 hours after 100 mg of oral sildenafil, we observed significant variations from baseline in parameters of best-fit Naka-Rushton function; V(max) was notably higher, and K was 0.14 log units lower than baseline.

CONCLUSIONS

Sildenafil administration resulted in a higher rod response to light stimuli and in a higher rod sensitivity. These findings are consistent with the weak PDE-6 inhibition induced by sildenafil.

Androgens and penile erection: evidence for a direct relationship between free testosterone and cavernous vasodilation in men with erectile dysfunction

OBJECTIVE

Androgens are essential in the maintenance of nitric oxide-mediated erectile activity in the rat. The objective of the present study was to investigate the role of androgens in regulating trabecular smooth muscle relaxation in the corpus cavernosum in response to vasoactive challenge in men with erectile dysfunction (ED).

DESIGN

Retrospective, double-blind correlation analyses.

PATIENTS

Fifty-two impotent patients without confounding risk factors for ED were obtained from a total of 250 undergoing diagnostic evaluation.

MEASUREMENTS

All patients had dynamic colour duplex ultrasound (D-CDU) and hormonal evaluation for LH, total and free testosterone, SHBG and oestradiol.

RESULTS

Based upon D-CDU results patients were diagnosed as having arteriogenic (AR, n = 18; mean age 51) or corporeal venocclusive (CVO, n = 13; mean age 49) ED; in other patients (n = 21, mean age 43) a diagnosis of psychogenic (P)-ED was made by comprehensive psychogenic testing and confirmed by normal D-CDU results. AR and CVO patients had altered compliance of cavernous arteries recorded by D-CDU [20-25% lower resistive index (RI) than patients with psychogenic ED], and lower free testosterone (FT) levels than psychogenic patients [42.3 +/-3.5 SE and 49.3+/-5.2 vs. 75.2+/-7.6 pmol/l, respectively; P<0.01]. More important, in all patients there was a strong direct correlation between resistive index values and FT levels (r = 0.47, P = 0.002); the relationship was maintained also when adjusted for age, SHBG and oestradiol (r = 0.37, P = 0.02).

CONCLUSIONS

These results indicate that in men with erectile dysfunction low free testosterone may correlate independently of age with the impaired relaxation of cavernous endothelial and corporeal smooth muscle cells to a vasoactive challenge. These findings give clinical support to the experimental knowledge of the importance of androgens in regulating smooth muscle function in the penis.

Effects of sildenafil (Viagra) administration on seminal parameters and post-ejaculatory refractory time in normal males

Sildenafil is a specific inhibitor of phosphodiesterase (PDE) type 5 and represents a powerful therapy for male erectile dysfunction (ED) of different aetiology. Recently, sildenafil has been shown to restore erections in temporary ED related to the need of semen collection for assisted reproductive techniques. In this study, we investigated whether sildenafil administration modifies seminal parameters and/or erectile function in normal healthy volunteers. In a double-blind, randomized, placebo-controlled, cross-over two period investigation we enrolled 20 healthy male volunteers (mean +/- SE age 32 +/- 0.5 years). Subjects were not using any medication for the 3 month period prior to the study and were engaged in a stable relationship with proven fertility. The effects of sildenafil (100 mg) on seminal parameters and erectile function after audiovisual sexual stimulation were evaluated by semen analysis and by colour-Duplex ultrasound (the Resistive Index) respectively. In all subjects, sildenafil caused no changes in seminal and erection parameters when compared to placebo. Interestingly, sildenafil administration led to a marked reduction of the post-ejaculatory refractory time (10.8 +/- 0.9 min versus 2.6 +/- 0.7 min for placebo and sildenafil respectively; P < 0.0001). These results indicate that in normal subjects acute sildenafil treatment does not modify semen characteristics and has a positive influence over the resumption of erections following ejaculation in the presence of a continuous erotic stimulus.