Onset and duration of action of sildenafil for the treatment of erectile dysfunction

The NO/cGMP/PKG pathway in platelets: The therapeutic potential of PDE5 inhibitors in platelet disorders

Platelets are the "guardians" of the blood circulatory system. At sites of vessel injury, they ensure hemostasis and promote immunity and vessel repair. However, their uncontrolled activation is one of the main drivers of thrombosis. To keep circulating platelets in a quiescent state, the endothelium releases platelet antagonists including nitric oxide (NO) that acts by stimulating the intracellular receptor guanylyl cyclase (GC). The latter produces the second messenger cyclic guanosine-3',5'-monophosphate (cGMP) that inhibits platelet activation by stimulating protein kinase G, which phosphorylates hundreds of intracellular targets. Intracellular cGMP pools are tightly regulated by a fine balance between GC and phosphodiesterases (PDEs) that are responsible for the hydrolysis of cyclic nucleotides. Phosphodiesterase type 5 (PDE5) is a cGMP-specific PDE, broadly expressed in most tissues in humans and rodents. In clinical practice, PDE5 inhibitors (PDE5i) are used as first-line therapy for erectile dysfunction, pulmonary artery hypertension, and lower urinary tract symptoms. However, several studies have shown that PDE5i may ameliorate the outcome of various other conditions, like heart failure and stroke. Interestingly, NO donors and cGMP analogs increase the capacity of anti-platelet drugs targeting the purinergic receptor type Y, subtype 12 (P2Y12) receptor to block platelet aggregation, and preclinical studies have shown that PDE5i inhibits platelet functions. This review summarizes the molecular mechanisms underlying the effect of PDE5i on platelet activation and aggregation focusing on the therapeutic potential of PDE5i in platelet disorders, and the outcomes of a combined therapy with PDE5i and NO donors to inhibit platelet activation.

Hotspots and frontiers in pulmonary arterial hypertension research: a bibliometric and visualization analysis from 2011 to 2020

Pulmonary arterial hypertension (PAH) is a group of devastating and progressive disorders, resulting in relentless increases in pulmonary vascular resistance. The number of studies related to PAH has been increasing in recent years. Our study aims to illustrate trends in PAH research over the past decade using bibliometric analysis. Science Citation Index-Expanded was adopted to search studies concerning PAH between 2011 and 2020. The bibliographic information was converted and analyzed automatically using a bibliometric package in R software and citespace. The annual quantity of publications on PAH showed an overall increase last decade. The United States was the most prolific country with 2,479 publications, and it was also the country that cooperated most with other countries. Hôpital Bicêtre made important research achievements on PAH and was a leader in study cooperation. Marc Humbert led the PAH field by publishing 150 articles in the past decade. During the past decade, there was a close transnational relation among countries or regions, institutions and authors. Further, Circulation was the most cited journal, followed by the Journal of the American College of Cardiology and the American Journal of Respiratory and Critical Care Medicine, with 3,895, 3,406, and 3,170 citations, respectively. The global research status and trend of PAH are deeply understood for the first time using bibliometric and visual methods, and the results of our study bring us a valuable reference for clinical researchers.

This is the first study to illustrate trends in pulmonary arterial hypertension research using bibliometric analysis.

Our study provides extensive and in-depth directions for researchers.

Our study may benefit further researches on the etiology, diagnosis, and treatment of pulmonary arterial hypertension.

A randomized crossover study of compounded liquid sildenafil for treatment of generalized megaesophagus in dogs

OBJECTIVE

To determine whether delivery of compounded liquid sildenafil directly to the stomach of dogs with megaesophagus (ME) would affect esophageal clearance, regurgitation frequency, body weight, or quality of life.

ANIMALS

10 client-owned otherwise healthy dogs with stable ME.

PROCEDURES

A randomized crossover study was performed. Dogs received either sildenafil (1 mg/kg, PO, q 12 h) or a placebo for 14 days, followed by a 7-day washout period, then the opposite treatment for 14 days. Esophageal clearance time was assessed by means of videofluoroscopy prior to treatment and on day 1 of each treatment period. Owners maintained logs of regurgitation episodes and quality of life.

RESULTS

Compounded liquid sildenafil moved into the stomach during 21 of 30 (70%) videofluoroscopy sessions. Sildenafil resulted in a significant reduction in the number of regurgitation episodes (median, 3.5 episodes/wk; range, 0 to 14.5 episodes/wk), compared with baseline (median, 6.5 episodes/wk; range, 1.5 to 19.5 episodes/wk) and the placebo (median, 4 episodes/wk; range, 0 to 28 episodes/wk), and a significant increase in body weight (median, 22.05 kg; range, 6 to 26.3 kg), compared with baseline (median, 21.55 kg; range, 5.1 to 26.2 kg) and the placebo (median, 22.9 kg; range, 5.8 to 25.9 kg). There were no differences in esophageal clearance times or quality-of life-scores between sildenafil and placebo.

CLINICAL RELEVANCE

Although significant differences with placebo administration were identified, clinically relevant improvements were not seen with the use of compounded liquid sildenafil in dogs with ME.

Phosphodiesterase Type 5 Inhibitors Greatly Affect Physicochemical Properties of Model Lipid Membranes

Although phosphodiesterase type 5 inhibitors are widely used and well-studied drugs, the potential benefits of their application in the treatment of various diseases and new drug delivery systems, including liposome forms, are still being discussed. In this regard, the role of the lipid matrix of cell membranes in the pharmacological action of the inhibitors is of special interest. It was shown that sildenafil, vardenafil, and tadalafil caused a significant decrease in the boundary potential of model membranes composed of palmitoyloleoylphosphatidylcholine or its mixture with cholesterol, by 70–80 mV. The reduction in the membrane dipole potential induced by inhibitors led to a 20–25% increase in the conductance of cation-selective pores formed by the antimicrobial peptide gramicidin A. The addition of sildenafil or vardenafil also led to a significant decrease in the temperature of the main phase transition of dipalmytoylphosphatidylcholine, by about 1.5 °C, while tadalafil did not change the melting temperature. Sildenafil, vardenafil, and tadalafil enhanced the pore-forming activity of the antifungal polyene antibiotic nystatin by 11, 13, and 2 times, respectively. This fact might indicate the induction of membrane curvature stress by the inhibitors. The data obtained might be of special interest for the development of lipid-mediated forms of drugs.

Pharmacokinetics and pharmacodynamics of sildenafil in fetal lambs on extracorporeal support

BACKGROUND

Maternal transplacental administration of sildenafil is being considered for a variety of fetal conditions. Clinical translation also requires evaluation of fetal safety in a higher species, such as the fetal lamb. Experiments with the pregnant ewe are curtailed by minimal transplacental transfer as well as limited access to the fetus. The EXTra-uterine Environment for Neonatal Development (EXTEND) model renders the isolated fetal lamb readily accessible and allows for direct fetal administration of sildenafil.

METHODS

Five fetal lambs were placed on extracorporeal support in the EXTEND device and received continuous intravenous (IV) sildenafil (0.3-0.5-0.7 mg/kg/24hr) for a duration of one to seven days. Plasma sildenafil concentrations were sampled at regular intervals to establish the pharmacokinetic profile using population pharmacokinetic modeling. Serial Doppler ultrasound examination, continuous non-invasive hemodynamic monitoring and blood gas analysis were done to evaluate the pharmacodynamic effects and fetal response.

FINDINGS

The target concentration range (47-500 ng/mL) was attained with all doses. Sildenafil induced an immediate and temporary reduction of pulmonary vascular resistance, mean arterial pressure and circuit flow, without change in fetal lactate levels and acid-base status. The duration of the systemic effects increased with the dose.

INTERPRETATION

Immediate temporary pulmonary vascular and systemic hemodynamic changes induced by sildenafil were biochemically well tolerated by fetal lambs on extracorporeal support, with the 0.5 mg/kg/24 h dose balancing rapid attainment of target concentrations with short-lived systemic effects.

RESEARCH IN CONTEXT

None.

SEARCH STRATEGY BEFORE UNDERTAKING THE STUDY

A literature review was conducted searching online databases (Medline, Embase and Cochrane), using search terms: fetal OR prenatal OR antenatal AND sildenafil, without time-limit and excluding human studies. Where relevant, investigators were contacted in order to avoid duplication of work.

EVIDENCE BEFORE THIS STUDY

Prenatal therapy with sildenafil, a phosphodiesterase-5 inhibitor with vasodilatory and anti-remodeling effects on vascular smooth muscle cells, has been considered for a variety of fetal conditions. One multicenter clinical trial investigating the benefit of sildenafil in severe intrauterine growth restriction (the STRIDER-trial) was halted early due to excess mortality in the sildenafil-exposed arm at one treatment site. Such findings demonstrate the importance of extensive preclinical safety assessment in relevant animal models. Transplacentally administered sildenafil leads to decreased pulmonary arterial muscularization, preventing or reducing the occurrence of pulmonary hypertension in rat and rabbit fetuses with diaphragmatic hernia (DH). Validation of these results in a higher and relevant animal model, e.g. fetal lambs, is the next step to advance clinical translation. We recently demonstrated that, in contrast to humans, transplacental transfer of sildenafil in sheep is minimal, precluding the in vivo study of fetal effects at target concentrations using the conventional pregnant ewe model.

ADDED VALUE OF THIS STUDY

We therefore used the extracorporeal support model for fetal lambs, referred to as the EXTra-uterine Environment for Neonatal Development (EXTEND) system, bypassing placental and maternal metabolism, to investigate at what dose the target concentrations are reached, and what the fetal hemodynamic impact and response are. Fetal hemodynamic and metabolic tolerance to sildenafil are a crucial missing element on the road to clinical translation. This is therefore the first study investigating the pharmacokinetics, hemodynamic and biochemical effects of clinical-range concentrations of sildenafil in fetal lambs, free from placental and maternal interference.

IMPLICATIONS OF ALL THE AVAILABLE EVIDENCE

We demonstrated self-limiting pulmonary vasodilation, a decrease of both systemic arterial pressures and circuit flows, induced by clinical range concentrations of sildenafil, without the development of fetal acidosis. This paves the way for further investigation of prenatal sildenafil in fetal lambs on extracorporeal support. A dose of 0.5 mg/kg/24 h offered the best trade-off between rapid achievement of target concentrations and shortest duration of systemic effects. This is also the first study using the EXTEND as a model for pharmacotherapy during pregnancy.

The Solid State Landscape of the Sildenafil Drug

Sildenafil, the active ingredient of the drug developed by Pfizer for the treatment of erectile dysfunction was firstly synthesized in 1989 in the United Kingdom and since then it has become one of the most prescribed drugs for sexual performance in the western world with more than 2.7 million prescriptions in the US in 2021. Since its discovery, this drug compound has attracted the interest of formulators and crystallographers, with a high number of crystal forms of sildenafil being found and characterized, including polymorphs, hydrates, solvates, salts and cocrystals, converting it in one of the most promiscuous multicomponent crystal former drugs in the pharmaceutical sciences arena. In this minireview, the polymorph, pseudopolymorph and multicomponent solid forms landscape of sildenafil is presented through a comprehensive compilation of their 42 solid forms reported in literature.

Effects of chronic type 5 phosphodiesterase inhibition on penile microvascular reactivity in hypertensive patients with erectile dysfunction: a randomized crossover placebo-controlled trial

This randomized crossover and placebo-controlled trial evaluated the effects of daily use of sildenafil citrate (SIL, 1-month 50 mg twice daily) on penile and systemic endothelial microvascular function in hypertensive patients presenting with erectile dysfunction. The effects of SIL on arterial pressure were evaluated using ambulatory blood pressure monitoring (ABPM). Fifty patients diagnosed with primary arterial hypertension and erectile dysfunction (aged 57.4 ± 5.6 years), recruited in a tertiary public hospital, were treated with SIL (50 mg twice daily) or placebo (PLA) for two 30-day periods with a 30-day washout between them. Laser speckle contrast imaging coupled with acetylcholine skin iontophoresis was used to evaluate penile and systemic (forearm) cutaneous microvascular reactivity. SIL treatment increased penile basal microvascular flow (P = 0.002) and maximal endothelial-dependent peak response to skin iontophoresis of acetylcholine (ACh, P = 0.006). The area under the curve of microvascular vasodilation induced by ACh was also significantly increased (P = 0.02). Lastly, SIL treatment did not modify systemic microvascular reactivity. Twenty-four-hour ABPM (P = 0.0002) and daytime (P = 0.002) and nighttime (P = 0.001) mean diastolic blood pressure values were significantly reduced after SIL treatment. The scores of the Simplified International Index of Erectile Function (P < 0.0001) and the number of patients with positive responses to Sexual Encounter Profile question 3 (P < 0.0001) also increased after SIL treatment. Penile endothelium-dependent microvascular reactivity improved after continuous use of sildenafil in hypertensive patients with erectile dysfunction; the treatment also reduced blood pressure, suggesting that, in addition to improving erectile function, daily use of sildenafil could improve blood pressure control.

High efficacy, rapid onset nanobiolosomes of sildenafil as a topical therapy for erectile dysfunction in aged rats

Developing topical sildenafil for local treatment of erectile dysfunction has been of great interest in pharmaceutical research. Sildenafil citrate (SC) exhibited a well-documented success for treatment of several types of erectile dysfunction. However, its oral use is limited by serious adverse effects, poor bioavailability, delayed onset, and drug-drug interactions. This work is the first to design and assess sildenafil-loaded bilosomes for topical local treatment of erectile dysfunction. Different sildenafil-loaded bilosomes were prepared and characterized. Permeability of selected formulations was conducted through full-thickness human skin. Optimized bilosomes integrating sodium tauroglycocholate (STGC) showed spherical shape with good particle size (133 nm), high zeta potential (-53.6 mV) and high entrapment efficiency (87.45%). Ex-vivo permeability study revealed that about 39% of the applied dose permeated within 15 min. Furthermore, in-vivo appraisal of therapeutic efficacy was performed using aged male Sprague-Dawley rats. After single application of 2 mg/kg sildenafil loaded in STGC-bilosomes, behavioral and biochemical evaluation was carried out. Behavioral assessment recorded an increased rats' potency manifested as 2 folds increase in intromission frequency and intromission ratio compared to untreated group. That was accompanied by significant increase in cGMP concentration in corpora cavernosa (P < 0.0001) confirming increased potency. In conclusion, STGC-bilosomes could provide topical treatment of impotence with 20% of the oral dose and fast onset of action (10 min).

Functional Measurement of CYP2C9 and CYP3A4 Allelic Polymorphism on Sildenafil Metabolism

Aim

We aimed to systematically examine the effects of enzymatic activity of 38 human CYP2C9 alleles and 21 human CYP3A4 alleles, including wild-type CYP2C9.1 and CYP3A4.1, which contain the 24 CYP2C9 novel alleles (*36–*60) and 6 CYP3A4 novel alleles (*28–*34) newly found in the Chinese population, on sildenafil metabolism through in vitro experiment.

Methods

The recombinant cytochrome P450 alleles protein of CYP2C9 and CYP3A4 expressed in insect baculovirus expression system were reacted with 10–500 µM sildenafil for 30 minutes at 37°C, and the reaction was terminated by cooling to −80°C immediately. Next, we used ultra-performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) detection system to detect sildenafil and its active metabolite N-desmethyl sildenafil.

Results

The intrinsic clearance (Vmax/Km) values of most CYP2C9 variants were significantly altered when compared with the wild-type CYP2C9*1, with most of these variants exhibiting either reduced Vmax and/or increased Km values. Four alleles (CYP2C9*11, *14, *31, *49) exhibited no markedly decreased relative clearance (1-fold). The relative clearance of the remaining thirty-three variants exhibited decrease in different levels, ranging from 1.81% to 88.42%. For the CYP3A4 metabolic pathway, when compared with the wild-type CYP3A4*1, the relative clearance values of four variants (CYP3A4*3, *10, *14 and *I335T) showed significantly higher relative clearance (130.7–134.9%), while five variants (CYP3A4*2, *5, *24, *L22V and *F113I) exhibited sharply reduced relative clearance values (1.80–74.25%), and the remaining nine allelic variants showed no statistical difference. In addition, the kinetic parameters of two CYP3A4 variants (CYP3A4*17 and CYP3A4*30) could not be detected, due to the defect of the CYP3A4 gene.

Conclusion

These findings were the first evaluation of all these infrequent CYP2C9 and CYP3A4 alleles for sildenafil metabolism; when treating people who carry these CYP2C9 and CYP3A4 variants, there should be more focus on the relation of dose intensity, side effects and therapeutic efficacy when administering sildenafil. The study will provide fundamental data on effect of CYP2C9 and CYP3A4 allelic variation on sildenafil metabolism for further clinical research.

Stiffness of the Central Corpus Cavernosum on Shear-Wave Elastography Is Inversely Correlated with the Penile Rigidity Score in Patients with Erectile Dysfunction

Purpose

To perform real-time quantitative measurements of penile rigidity for patients with erectile dysfunction (ED) using shear-wave elastography (SWE).

Materials and Methods

A total of 92 patients with clinically diagnosed ED filled out an abridged five-item version of the International Index of Erectile Function (IIEF-5) questionnaire and underwent SWE as well as penile color Doppler ultrasound (CDUS) after intracavernosal injection for penile erection. Elasticity measurements were repeated on two sites of the corpus cavernosum (central and peripheral elasticity of corpus cavernosum [ECC]) and the glans penis during the erection phase. Correlations between penile elasticity and rigidity scores or IIEF-5 were evaluated statistically. Penile elasticity was also compared with the ED types based on CDUS.

Results

The mean age of all patients was 53.5±13.4 years, and the mean IIEF-5 score was 9.78±5.01. The rigidity score and central ECC value demonstrated a significant correlation (r=−0.272; 95% confidence interval: −0.464 to −0.056; p=0.015). The IIEF-5 score was not significantly correlated with penile elasticity. Vascular ED patients showed significantly higher central ECC values than nonvascular ED patients (p<0.001). At a cut-off value of 8.05 kPa, the central ECC had a specificity of 41.5%, a sensitivity of 84.6%, and an area under the ROC curve of 0.720 with a standard error of 0.059 (p=0.019) for predicting vascular ED.

Conclusions

Quantitatively measuring Young's modulus of the corpus cavernosum using SWE could be an objective technique for assessing penile erectile rigidity and the vascular subtype in patients with ED.

Investigation of distinct molecular pathways in migraine induction using calcitonin gene-related peptide and sildenafil

Objective

Migraine displays clinical heterogeneity of attack features and attack triggers. The question is whether this heterogeneity is explained by distinct intracellular signaling pathways leading to attacks with distinct clinical features. One well-known migraine-inducing pathway is mediated by cyclic adenosine monophosphate and another by cyclic guanosine monophosphate. Calcitonin gene-related peptide triggers migraine via the cyclic adenosine monophosphate pathway and sildenafil via the cyclic guanosine monophosphate pathway. To date, no studies have examined whether migraine induction mediated via the cyclic adenosine monophosphate and cyclic guanosine monophosphate pathways yields similar attacks within the same patients.

Methods

Patients were subjected to migraine induction on two separate days using calcitonin gene-related peptide (1.5 µg/min for 20 minutes) and sildenafil (100 mg) in a double-blind, randomized, double-dummy, cross-over design. Data on headache intensity, characteristics and accompanying symptoms were collected until 24 hours after drug administration.

Results

Thirty-four patients were enrolled and 27 completed both study days. Seventeen patients developed migraine after both study drugs (63%; 95% CI: 42–81). Eight patients developed migraine on one day only (seven after sildenafil and one after calcitonin gene-related peptide). Two patients did not develop migraine on either day. Headache laterality, nausea, photophobia and phonophobia were similar between drugs in 77%, 65%, 100%, and 94%, respectively, of the 17 patients who developed attacks on both days.

Conclusion

A majority of patients developed migraine after both calcitonin gene-related peptide and sildenafil. This supports the hypothesis that the cyclic adenosine monophosphate and cyclic guanosine monophosphate intracellular signaling pathways in migraine induction converge in a common cellular determinator, which ultimately triggers the same attacks. Trial registration: ClinicalTrials.gov Identifier: NCT03143465.

Exploration of icariin analog structure space reveals key features driving potent inhibition of human phosphodiesterase-5

The natural product icariin inhibits human phosphodiesterase-5 (PDE5) and represents a unique pharmacophore for treating erectile dysfunction, pulmonary hypertension, and other diseases. In this study, we explore the available icariin-derived chemical scaffolds through medicinal chemistry to develop novel icariin PDE5 inhibitors with improved potency and specificity. We synthesized six novel semi-synthetic icariin analogs as well as three naturally occurring icariin analogs, and characterized the structure-activity relationship in the context of human PDE5 inhibition using in vitro enzyme inhibition and kinetics assays and molecular modeling. Mammalian-cell-based assays and in vitro enzyme inhibition assays against human PDE6C further helped to identify the most potent and selective icariin analogs. Our results reveal the synergistic contribution of functional groups at the C3 and C7 positions of the icariin backbone towards PDE5 inhibition. Whereas a hydrophobic and flexible alkanol group at the C7 position is sufficient to enhance icariin analog potency, combining this group with a hydrophilic sugar group at the C3 position leads to further enhancement of potency and promotes specificity towards PDE5 versus PDE6C. In particular, compounds 3 and 7 exhibit K_i values of 0.036 ± 0.005 μM and 0.036 ± 0.007 μM towards PDE5 respectively, which are approaching those of commercial PDE5 inhibitors, and can effectively reduce GMP levels in cultured human BJ-hTERT cells. This study identifies novel icariin analogs as potent and selective PDE5 inhibitors poised to become lead compounds for further pharmaceutical development.

The first-generation phosphodiesterase 5 inhibitors and their pharmacokinetic issue

Background

Erectile dysfunction (ED) is a relatively frequent disease that negatively impacts the overall quality of life, well‐being, and relationships. Although the use of phosphodiesterase 5 inhibitors (PDE5is) has revolutionized the treatment of ED, a high percentage of ED patients discontinue PDE5i treatment.

Objectives

(i) To analyze the reasons for patient dissatisfaction leading to PDE5i discontinuation; (ii) analyze the pharmacokinetics of new formulations focusing on the time needed to reach an effective plasma concentration of PDE5is (T_onset) following drug intake; and (iii) summarize the physicochemical properties of sildenafil to understand which excipients may increase the absorption rate.

Material and methods

An online PubMed literature search was conducted to identify English language publications from inception to January 2019.

Results

The main reasons for patient dissatisfaction when using PDE5is on demand are the relatively long T_onset after taking vardenafil and sildenafil, including formulations such as film‐coated tablets, fine granules, orally disintegrating tablets (ODTs), and oral thin films (ODFs). The relatively long T_onset, further worsened when accompanied by eating, highlights the following: (i) the need for planning intercourse, determining partner‐related issues; (ii) issues when having sex before the maximum effect of the drug; and (iii) lower drug‐related placebo effects. Some data suggest that sildenafil is a ‘difficult’ molecule, but T_onset can be improved following absorption by buccal mucosa using appropriate excipients.

Conclusions

We conclude that several ODT and ODF formulations can improve the ‘discretion’ issue because they are taken without water, but they have similar pharmacokinetics to corresponding film‐coated tablet formulations. One ODF formulation of sildenafil was characterized by a shorter T_onset and could potentially increase patient satisfaction following treatment. However, more clinical studies are needed to confirm the findings. Surfactants and ascorbic acid appear to be crucial excipients for achieving a high absorption rate, but more studies are needed.

The Serendipitous Story of Sildenafil: An Unexpected Oral Therapy for Erectile Dysfunction

INTRODUCTION

The serendipitous discovery of sildenafil (Viagra [sildenafil citrate]) as a treatment for erectile dysfunction (ED) is one of the most fascinating drug development stories of our time. When sildenafil was approved by the U.S. Food and Drug Administration in 1998, it revolutionized the treatment protocol for men with ED, once considered a psychological issue or an inevitable part of aging.

AIM

To review the discovery of sildenafil and its role in changing the field of sexual medicine in the context of the epidemiology and history of treatment for ED.

METHODS

For this narrative review, a literature search was conducted to identify essential articles and was supplemented by author observations from a historical perspective.

MAIN OUTCOME MEASURE

A broad overview of ED and its past, current, and future treatments.

RESULTS

ED is a prevalent condition for which medical treatment had been limited to genitally localized interventions, including surgery, vacuum pumps, injectable therapies, and intraurethral suppositories. The discovery of sildenafil provided a safe, oral pharmacotherapy for the treatment of ED, sparking greater understanding of the science behind ED and its role in men's overall health.

CONCLUSION

The approval of sildenafil initiated a global conversation about ED that had profound implications for patients, methods of clinical practice, and academic sexual medicine. These changes will catalyze continued advances in ED treatment. Goldstein I, Burnett AL, Rosen RC, et al. The serendipitous story of sildenafil: an unexpected oral therapy for erectile dysfunction. Sex Med Rev 2019;7:115-128.

Comparison of pharmacokinetic characteristics of sildenafil citrate chewable tablets and film-coated tablets in healthy male subjects

UI14SDF100CW is a chewable tablet of sildenafil citrate, which was developed to improve compliance through convenience of administration. The purpose of this study was to compare the pharmacokinetic (PK) properties of sildenafil citrate chewable tablets (UI14SDF100CW) and conventional sildenafil citrate film-coated tablets (Viagra®, Pfizer). A randomized, open-label, single dose, two-treatment, two-period, two-way crossover study was conducted in 60 healthy male volunteers. In each period, the subjects received a single oral dose of UI14SDF100CW or Viagra® (both tablets contain 140.45 mg of sildenafil citrate, which is equivalent to 100 mg of sildenafil). Serial blood samples were collected up to 24 h post-dose for PK analysis. The plasma concentration of sildenafil was determined using a validated HPLC-MS/MS assay. PK parameters of sildenafil were calculated using non-compartmental methods. The plasma concentration-time profiles of sildenafil in both formulations were similar. For UI14SDF100CW, the C_max and AUC_last of sildenafil were 1068.69 ± 458.25 (mean ± standard deviation) mg/L and 3580.59 ± 1680.29 h·mg/L, and the corresponding values for Viagra® were 1146.84 ± 501.70 mg/L and 3406.35 ± 1452.31 h·/L, respectively. The geometric mean ratios (90% confidence intervals) of UI14SDF100CW to Viagra® for C_max and AUClast were 0.933 (0.853–1.021) and 1.034 (0.969–1.108), respectively, which met the bioequivalence criteria of Korean regulatory agency. In conclusion, UI14SDF100CW and Viagra® showed similar PK properties. Therefore, UI14SDF100CW can be an alternative to sildenafil for the treatment of erectile dysfunction, providing better compliance.

The effects of tadalafil and pentoxifylline on apoptosis and nitric oxide synthase in liver ischemia/reperfusion injury

The aim of this study was to investigate the effects of tadalafil (TDF) and pentoxifylline (PTX) on hepatic apoptosis and the expressions of endothelial and inducible nitric oxide synthases (eNOS and iNOS) after liver ischemia/reperfusion (IR). Forty Wistar albino rats were randomly divided into five groups (n=8) as follows: sham group; IR group with ischemia/reperfusion alone; low-dose and high-dose TDF groups received 2.5 mg/kg and 10 mg/kg TDF, respectively; and PTX group received 40 mg/kg PTX. Blood was collected for the analysis of serum alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transferase, uric acid, malondialdehyde (MDA), and total antioxidant capacity (TAC). MDA and TAC also were measured in liver tissue. Histopathological examination was performed to assess the severity of hepatic injury. Apoptosis was evaluated using the apoptosis protease-activating factor 1 (APAF-1) antibody; the expressions of eNOS and iNOS were also assessed by immunohistochemistry in all groups. Serum alanine aminotransferase, aspartate aminotransferase, γ-glutamyl transferase, uric acid, MDA, and TAC, tissue MDA and TAC levels, hepatic injury, and score for extent and for intensity of eNOS, iNOS, and apoptosis protease-activating factor 1 were significantly different in TDF and PTX groups compared to the IR group. High dose-TDF and PTX have the best protective effect on IR-induced liver tissue damage. This study showed that TDF and PTX supplementation may be helpful in preventing free oxygen radical damage, lipid peroxidation, hepatocyte necrosis, and apoptosis in liver IR injury and minimizing liver damage.

Udenafil for the treatment of erectile dysfunction

Erectile dysfunction (ED) is often perceived by both patients and sexual partners as a serious problem that can jeopardize quality of life, psychosocial or emotional well-being, and the partnership in the long term. Since their introduction, oral phosphodiesterase type 5 inhibitors (PDE5Is) have been found to be highly effective and well tolerated, and are available as the first-line therapy for the treatment of ED. Udenafil is one of the selective PDE5Is made available in recent years for the treatment of ED. Udenafil has clinical properties of both relatively rapid onset and long duration of action due to its pharmacokinetic profile, thereby providing an additional treatment option for ED men to better suit individual needs. There is positive evidence that udenafil is effective and well tolerated in the treatment of ED of a broad spectrum of etiologies or severity. Udenafil is as effective in the treatment of diabetes mellitus-associated ED as other PDE5Is. Due to the clinical property of relatively long duration of action, udenafil may be another option in daily dosing treatment for ED, as suggested by its favorable efficacy and safety profile. Most adverse effects reported from clinical trials are mild or moderate in severity, without any serious adverse event, with headache and flushing being the most common. Also, the concomitant use of anti-hypertensive drugs or alpha-1-blockers does not significantly affect the efficacy and safety profile of udenafil. However, additional studies with larger cohorts including prospective, multicenter, comparative studies with patients of different ethnicities are needed to further validate the favorable findings of udenafil in the treatment of ED.

Sildenafil: two decades of benefits or risks?

Sildenafil is a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE-5). A patent was registered for this drug in 1990, which expired in 2010. Since expiration, the drug has been marketed under various trade names or as generic drugs. Numerous clinical trials have been conducted addressing the effectiveness of the drug for erectile dysfunction (ED) and its safety regarding the presence or absence of specific comorbidities. After over 20 years in the market, we need to ask: has the scientific community reached a general consensus as to the overall efficacy and safety of the drug? Can we firmly state that the benefits of the drug outweigh its risks? This review suggests that sildenafil is an effective and easily manageable treatment for erectile dysfunction, both in the absence and in the presence of comorbidities. After two decades of the emergence of sildenafil as a drug of choice for the treatment of ED (and the numerous studies and clinical trials undertaken during this time span), it is now possible to state that the benefits of the drug do outweigh the risks, and represent an significant improvement in the quality of life in men with ED.

Korean Society for Sexual Medicine and Andrology (KSSMA) Guideline on Erectile Dysfunction

In February 2011, the Korean Society for Sexual Medicine and Andrology (KSSMA) realized the necessity of developing a guideline on erectile dysfunction (ED) appropriate for the local context, and established a committee for the development of a guideline on ED. As many international guidelines based on objective evidence are available, the committee decided to adapt these guidelines for local needs instead of developing a new guideline. Considering the extensive research activities on ED in Korea, data with a high level of evidence among those reported by Korean researchers have been collected and included in the guideline development process. The latest KSSMA guideline on ED has been developed for urologists. The KSSMA hopes that this guideline will help urologists in clinical practice.

A phase II, single-blind, randomized, crossover evaluation of the safety and efficacy of avanafil using visual sexual stimulation in patients with mild to moderate erectile dysfunction

OBJECTIVE

To evaluate the safety, efficacy and time course of three doses of avanafil (50 mg, 100 mg and 200 mg) compared with sildenafil 50 mg or placebo, given in conjunction with visual sexual stimulation (VSS) videos in men with mild to moderate erectile dysfunction (ED).

PATIENTS AND METHODS

Male patients, 35-70 years of age, with mild to moderate ED of ≥6 months duration, were included in the study. During the course of the study, each patient received placebo, active control (sildenafil 50 mg), and one dose of avanafil (50 mg, 100 mg or 200 mg), all administered in random order at least 72 h apart. RigiScan® (Dacomed Corp., Minneapolis, MN, USA) monitoring was used in conjunction with 20-min VSS videos (20, 60, and 100 min after dosing) to determine the duration of and time to ≥60% penile rigidity, maximum rigidity, tumescent activity units (TAUs), rigidity activity units (RAUs), and responses to the five-point Erection Assessment Scale. Safety assessments included adverse events (AEs), vital sign changes in response to dosing, laboratory results (complete blood counts, chemistry panel, prostate-specific antigen, serum testosterone, prothrombin time and urine analysis) and physical examination findings.

RESULTS

Eighty-three patients were randomized and received at least one dose of study medication; 82 patients completed the study. Peak response to avanafil occurred in the early interval (20-40 min after dosing), while peak response to sildenafil occurred either in the middle (60-80 min) or late (100-120 min) intervals after dosing. Results were qualitatively similar for all other efficacy endpoints. During the 20-40-min interval, the majority of values for TAUs and RAUs with the avanafil 50-mg, 100-mg and 200-mg treatments were significantly superior to placebo (P < 0.05). Avanafil treatment was generally well tolerated; facial flushing (7-15%) was the most commonly observed AE, and no visual disturbances were reported.

CONCLUSION

A favourable safety profile and improvement in sexual function, coupled with rapid onset of action and durability of effect, make avanafil an attractive option for males with ED, especially in the setting of on-demand treatment.

ADMET considerations for phosphodiesterase-5 inhibitors

INTRODUCTION

ADMET (absorption, distribution, metabolism, excretion, and toxicity) profiling is an important aspect of all drug developments. The pharmaceutical industry must always consider ADMET properties in order to optimize drug candidates and to introduce new formulations against existing marketed drugs. Consequently, candidate drug development may be halted early in the discovery phase or during the more costly drug development process because of their poor ADMET properties.

AREAS COVERED

The main focus of this article is ADMET profiling, pharmacokinetic (PK) drug interactions, mechanisms and possible adverse drug reactions (ADRs) for approved phosphodiesterase-5 inhibitors (PDE5Is). The authors also look at the efficacy and non-erectogenic benefits of current PDE5Is, which are widely used by patients with erectile dysfunction (ED). The authors also discuss other unapproved PDE5Is such as aildenafil and udenafil, which are currently in use in clinical trials.

EXPERT OPINION

The authors believe that the enhancing effect of PDE5Is on the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) pathway means that PDE5Is could be used to treat various conditions. An important issue in their development is 'cross-talk' between PDE5 and other PDEs and thus their specificity for other PDEs. But while it might be difficult to achieve the ideal ADMET profile, it should not necessarily prevent further development of a lead PDE5I. The risk assessment of PDE5Is, with respect to their ADMET properties, is therefore very important for predicting drug-drug interactions, possible side effects, ADRs and its future clinical applications.

Evaluation of penile erection rigidity in healthy men using virtual touch tissue quantification

Background

The aim of the study was to describe the shear wave velocity (SWV) values of the penis by virtual touch tissue quantification (VTTQ) and to examine the clinical usefulness of this procedure in evaluation of the rigidity changes in penile erection.

Patients and methods.

VTTQ was performed in 37 healthy volunteers. In the course of erection, SWV values of glans penis, corpus penis and radix penis were quantified and grades of erection were documented. The SWV values at different grades of erection were compared.

Results

The axial and radial SWV values of glans penis, corpus penis and radix penis all significantly decreased from Grade 0 to Grade 4 of erection. At Grade 4, they were less than one-third of that at Grade 0 (axial direction: 0.79 ± 0.13 vs. 2.79 ± 0.32 for glans penis, P<0.001; 0.77 ± 0.19 vs. 2.84 ± 0.30 for corpus penis, P<0.001 and 0.76 ± 0.15 vs. 2.81 ± 0.34 for radix penis, P<0.001; radial direction: 0.82 ± 0.15 vs. 2.83 ± 0.31 for glans penis, P<0.001; 0.79 ± 0.18 vs. 2.81 ± 0.27 for corpus penis, P<0.001 and 0.81 ± 0.16 vs. 2.82 ± 0.33 for radix penis, P<0.001).

Conclusions

VTTQ can provide numerical measurements of penile rigidity and can effectively and sensitively indicate the axial and radial rigidity changes in penile erection, which provide a new approach to assessing the erectile function.

Development of sildenafil-loaded orally disintegrating tablet with new lactate salt

To develop a sildenafil lactate-loaded orally disintegrating tablet with a faster drug effect onset and immediate action of erection, the orally disintegrating tablets were prepared with various amounts of menthol and colloidal silica using the direct compression technique followed by vacuum drying. Their tablet properties such as friability, hardness, wetting time and disintegration time were investigated. The oral bioavailability of sildenafil in the orally disintegrating tablet was then compared with the sildenafil citrate-loaded commercial tablet (Viagra(®)) in rabbits. Sildenafil lactate was a new salt form with more improved solubility and alleviated bitterness compared with commercial salt, sildenafil citrate. As the amount of menthol in the orally disintegrating tablet increased, the friability increased and hardness decreased, resulting in a shorter wetting time and disintegration time. Colloidal silica did the opposite. The sildenafil lactate-loaded orally disintegrating tablet prepared with 45 mg/tab of menthol and 1.5 mg/tab of colloidal silica gave a hardness of 3-4 KP, friability less than 0.5% and disintegration time less than 30 s, suggesting that it was a practical and commercial product with good tablet property and excellent efficacy. Furthermore, it gave higher AUC and C(max), and shorter T(max) values than did the commercial tablet, indicating that it improved the oral bioavailability of sildenafil in rabbits compared with the commercial tablet. Thus, the sildenafil lactate-loaded orally disintegrating tablet might induce a fast onset of action and immediate erection compared with the sildenafil citrate-loaded commercial tablet.

Effect of sildenafil citrate on intraocular pressure and blood pressure in human volunteers

Anecdotal reports have suggested that the vasodilator, sildenafil citrate, which evokes its effect via a select inhibition of PDE5, has the potential to increase intraocular pressure (IOP) in some individuals. An ocular hypertensive effect by sildenafil was also recently described in a sheep animal model. In contrast, clinical studies have not found a direct association between sildenafil ingestion (commonly consumed as Viagra) and changes in IOP. However, some such studies also reported no effects of sildenafil on systemic blood pressure (BP) at the time of the IOP determination. Given this surprising result, our purpose was to repeat a study in human volunteers in the city of Corrientes, Argentina to corroborate the effects of sildenafil on human IOP and systemic BP. For the present study, 9 healthy volunteers (male and female, 18-74 years old) were selected as subjects after ophthalmic and cardiovascular evaluation indicated that they exhibited normal parameters for their age. In a masked, placebo-controlled study, the subjects ingested 100 mg sildenafil citrate (provided as Vorst from Laboratorios Bernabo, Argentina) in one session, and a placebo on a second separate occasion. IOP was measured with a Goldman applanation tonometer by an ophthalmologist, and BP by a second physician, neither of whom witnessed the tablet ingestion by the volunteers, nor provided with information on the nature of the test compounds. A third individual administered the tablets. The average baseline IOP of this group of 9 was 13.1 ± 0.6 mm Hg. Subsequent to sildenafil ingestion, IOP increased by 26% to 16.5 ± 0.8 mm Hg 60 min later (P < 0.005, as paired data), and returned to control values within 2 h. Both systolic and diastolic BP were significantly reduced by sildenafil ingestion. At the point of maximal systemic hypotension (90 min), the systolic and diastolic pressures declined by 15% and 13%, respectively. No significant changes in IOP or BP were recorded after ingestion of the placebo. Our results suggest that sildenafil can elicit a transient IOP increase that may be of importance to patients chronically treated with PDE5 inhibitors for various vascular diseases (e.g., pulmonary hypertension). We discuss possible mechanisms by which PDE5 inhibition might lead to a rise in IOP.

Understanding the effects of sildenafil treatment on erection maintenance and erection hardness

INTRODUCTION

Erectile dysfunction (ED) is defined as the inability to attain and/or maintain penile erection sufficient for satisfactory sexual performance. Although intuitively related, the link between erection hardness and erection maintenance has not been formally established and quantified.

AIM

To understand the components of erection maintenance through statistical modeling.

METHODS

Data from a double-blind placebo-controlled trial of fixed-dose sildenafil (100 or 50 mg, 8 weeks) with open-label extension of flexible-dose sildenafil (100 and 50 mg, 4 weeks) were analyzed. Erection maintenance was assessed with item 4 (how often erection was maintained) or item 5 (difficulty in maintaining erection) of the International Index of Erectile Function (IIEF). Erection hardness was assessed with the Erection Hardness Score.

MAIN OUTCOME MEASURES

Longitudinal modeling estimated mean treatment differences averaged over the double-blind phase for sildenafil 100 mg vs. placebo and 50 mg vs. placebo. Statistical mediation analysis was applied to partition the effect of sildenafil (pooled into one treatment group) on erection maintenance directly and indirectly through erection hardness.

RESULTS

Longitudinal mean differences for sildenafil 100 and 50 mg vs. placebo were high (P < 0.0001 for each), with large standardized effect sizes (>0.8). Mediation modeling showed that sildenafil treatment affected maintenance directly as well as indirectly via erection hardness, when measured by IIEF item 4 (direct effect, 44.6%; indirect effect, 55.4%) or IIEF item 5 (direct effect, 56.9%; indirect effect, 43.1%).

CONCLUSIONS

Sildenafil treatment significantly improved erection maintenance, a physiologic requirement for satisfactory sexual performance. According to our model, only approximately half of the effect of sildenafil on erection maintenance was estimated to be driven through direct effects. Rather, the effect of sildenafil on erection maintenance seems to be substantially driven by erection hardness. Therefore, achievement of optimal initial erection hardness appears to be an important treatment goal for enhancing erection maintenance and achieving successful ED treatment.

Feasibility of dynamic 3-D color Doppler ultrasound for imaging penile vascular change in renal transplant patients with erectile dysfunction responding to sildenafil

Renal transplant recipients (RTRs) have a high incidence of erectile dysfunction (ED). Differentiation of penile vasculogenic impotence from other causes is important for treatment. Conventional 2-D color Doppler assessment after intracavernosal stimulant injection often fails to produce reliable results because of limited views by the cross-sectional imaging and the painful procedure. In comparison to the findings in three healthy volunteers, we determined cavernosal vascular hemodynamics in eight RTRs with ED before and after oral sildenafil by using live 3-D ultrasound and dynamic 3-D color Doppler. Results showed that, before sildenafil, penile arterial flow signals could only be reliably detected in one patient. After sildenafil, all had reliably detectable flow with grades II to III erection. Our data suggest that 3-D volumetric changes of the penis and its vasculature during erection can be studied by this technique and that this method could be useful for the evaluation of new drugs and therapeutic biofeedback.

Rehabilitation of erectile function following radical prostatectomy

The concept of muscle rehabilitation after nerve injury is not a novel idea and is practiced in many branches of medicine, including urology. Bladder rehabilitation after spinal cord injury is universally practiced. The erectile dysfunction (ED) experienced after radical prostatectomy (RP) is increasingly recognized as being primarily neurogenic followed by secondary penile smooth muscle (SM) changes. There is unfortunately no standard approach to penile rehabilitation after RP because controlled prospective human studies are not available. This article reviews the epidemiology, experimental pathophysiological models, rationale for penile rehabilitation, and currently published rehabilitation strategies.

Phosphodiesterase type 5 inhibitor therapy: identifying and exploring what attributes matter more to clinicians and patients in the management of erectile dysfunction

BACKGROUND

Erectile dysfunction (ED) is increasingly being recognized as a sentinel marker of future subsequent cardiovascular disease (CVD). Predicted increases in the prevalence of ED are due to a combination of an aging population and the increasing presence of comorbid conditions (hypertension, dyslipidemia, and diabetes). The dichotomy of the situation is that ED is often associated with these comorbidities, potentially leading to greater CVD risk, and conversely, these comorbidities have also been shown to increase the risk of developing ED. The successful treatment of ED with phosphodiesterase type 5 (PDE5) inhibitor therapy, therefore, is of paramount importance because it not only plays a critical role in restoring erectile function, but also provides clinicians with the opportunity to mitigate existing cardiovascular comorbidities or prevent the occurrence of CVD in this patient population.

METHODS

This review is based on an electronic literature search of databases, including MEDLINE/PubMed, with information selected for its relevance to PDE5 inhibitor therapy comprising efficacy (e.g., first-dose success) in men with ED with or without comorbidities, onset and duration of action at specific time points, and patient preference.

RESULTS

The introduction of PDE5 inhibitors represented a major advance in the treatment of ED. In spite of the availability of these agents, a large percentage of men are still not being treated, in many cases because of their reluctance to seek medical help. Moreover, many men who start treatment with PDE5 inhibitors discontinue treatment. Reasons for discontinuation are many and complex, including lack of initial or first-time success. Although of major concern to both patients and clinicians, there remains limited published clinical data on this specific parameter in the pertinent patient population and from prospective, randomized clinical studies.

CONCLUSION

Data from studies suggests that the available PDE5 inhibitor therapies are effective in treating men with ED, including those who have increased CVD risk and those who have clinically identified cardiovascular comorbidities such as hypertension, dyslipidemia, and/or diabetes. According to data from studies, the attributes of PDE5 inhibitor therapy that matter more to clinicians and patients and that hold influence over treatment compliance include effectiveness in patients with cardiovascular comorbidities, first dose effectiveness or early success, rapid onset of action, reliability, and tolerability.

Correlations between increased erection hardness and improvements in emotional well-being and satisfaction outcomes in men treated with sildenafil citrate for erectile dysfunction

To explore relationships between erection hardness and other outcomes in men with erectile dysfunction (ED). Pooled analyses were conducted on 27 randomized, double-blind, placebo-controlled trials and six open-label trials from the worldwide sildenafil database. Outcomes included erection hardness graded subjectively, hardness and sexual satisfaction questions from the International Index of Erectile Function, general and sexually-specific emotional well-being from the self-esteem and relationship questionnaire, and the erectile dysfunction inventory of treatment satisfaction. Hardness outcomes improved (with a possible dose-response relationship for the achievement of fully hard and rigid erections) and correlated positively with the other outcomes. Sildenafil 100 mg produced optimal erection hardness (fully hard and rigid erections) in a substantial proportion of men with ED. Because optimal erection hardness correlated positively with some emotional well-being and satisfaction outcomes, sildenafil 100 mg may be the most appropriate dosage for treatment of ED for most men.

ORIGINAL RESEARCH—ED PHARMACOTHERAPY: Do Food and Dose Timing Affect the Efficacy of Sildenafil? A Randomized Placebo‐Controlled Study

INTRODUCTION

Sildenafil citrate has been used worldwide by men with erectile dysfunction. The prescribing information for sildenafil suggests ingestion 1 hour before sexual activity and also notes reduced maximum plasma concentration and delayed time to maximum concentration following ingestion with a high-fat meal. The clinical impact of coingestion of food and these factors has never been evaluated.

AIM

To determine, using a naturalistic study design, whether sildenafil taken 1 hour before or during a meal compared with usual ingestion 30-60 minutes before sexual activity affects efficacy or patient satisfaction.

METHODS

After a 1-2-week washout, 48 men (29-79 years old), currently satisfied with sildenafil, followed each of four regimens: (A) sildenafil 1 hour before a meal and placebo 30-60 minutes before planned coitus vs. (B) placebo 1 hour before a meal and sildenafil 30-60 minutes before coitus; and (C) sildenafil during a meal and placebo 30-60 minutes before coitus vs. (D) placebo during a meal and sildenafil 30-60 minutes before coitus. Subjects were not instructed to change their regular dietary habits during the course of the study.

MAIN OUTCOME MEASURES

Change from baseline in the International Index of Erectile Function (IIEF) Erectile Function (EF) domain score, responses to Sexual Encounter Profile (SEP) questions 2 (erection sufficient for penetration) and 3 (erection sufficient to complete intercourse), and measures of patient preference and satisfaction.

RESULTS

Mean changes in IIEF-EF domain scores were 11.4 for regimens A and B and 11.2 for C and D. Positive SEP2 responses were recorded for 93.9% and 91.8% of intercourse attempts in A and B and 91.4% and 92.6% in C and D. Corresponding results for SEP3 were 84.7% and 85.9%, and 83.4% and 87.5%, respectively. There were no significant differences between pairs of treatments on satisfaction. The time between sildenafil ingestion and intercourse attempt (0-0.5 to >10 hours) had no significant effect on responses to SEP2, but decreased responses to SEP3 from a maximum of 92.8% at 1.5-2 hours to 81.6% at more than 10 hours (P = 0.003).

CONCLUSIONS

No significant loss of efficacy occurs when sildenafil is taken shortly before or with a meal. The duration of action for sildenafil may exceed 10 hours.

ORIGINAL RESEARCH—OUTCOMES ASSESSMENT: Quality of Erection Questionnaire Correlates: Change in Erection Quality With Erectile Function, Hardness, and Psychosocial Measures in Men Treated With Sildenafil for Erectile Dysfunction

INTRODUCTION

The validated Quality of Erection Questionnaire (QEQ) is a six-question, patient-reported outcome measure for comprehensively evaluating satisfaction with the quality of erections in terms of hardness, onset, and duration, which can be used to develop and monitor individualized treatment goals.

AIMS

To further validate the QEQ by determining responsiveness/sensitivity to change in erectile function, erection hardness grade, and psychosocial outcomes in men treated with sildenafil for erectile dysfunction (ED).

METHODS

This open-label, noncomparative, multicenter trial of sildenafil (50 or 100 mg as needed for 10 weeks) enrolled men with ED who were in a stable, sexual relationship for at least 6 months. Previous phosphodiesterase type 5 inhibitor use must have been no more than 6 doses ever and no doses more recently than the previous 4 weeks.

MAIN OUTCOME MEASURES

The baseline to week 10 change in the QEQ total score and its correlations with the end-of-treatment Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS) score and with changes in: (i) International Index of Erectile Function (IIEF) domain scores; (ii) Self-Esteem And Relationship (SEAR) questionnaire component scores; and (iii) the frequency of erections graded hard enough for penetration (grade 3) or completely hard (grade 4) on the event log Erectile Hardness Grading Scale.

RESULTS

The mean +/- standard deviation transformed QEQ total score tripled from 22.0 +/- 21.1 to 69.9 +/- 35.9 (P < 0.0001), and correlated positively with the end-of-treatment EDITS index score (r = 0.71) and with changes in IIEF domain scores (r = 0.29-0.86), SEAR component scores (r = 0.37-0.78), and the percentage of occasions that grade 3 or 4 erections were achieved (r = 0.66).

CONCLUSIONS

The brief, easy-to-administer QEQ is responsive to the benefits of sildenafil treatment of men for ED and has convergent validity with measures of clinical and psychosocial outcomes.

Erectile function and assessments of erection hardness correlate positively with measures of emotional well-being, sexual satisfaction, and treatment satisfaction in men with erectile dysfunction treated with sildenafil citrate (Viagra)

We aimed to determine whether erectile function (EF) and assessments of erection hardness correlate positively with measures of psychosocial outcomes (ie, emotional well-being, sexual satisfaction, and satisfaction with erectile dysfunction [ED] treatment) in men treated with sildenafil citrate (Viagra; Pfizer Inc, New York, NY). Data were collected from 33 worldwide phase 2, 3, and 4 sildenafil clinical trials, which included almost 10,000 men with ED. Most of these trials were randomized, double-blind, and placebo-controlled (n = 27) and were undertaken to assess doses of 50 mg adjustable to 25 mg or 100 mg, depending on efficacy and tolerability (n = 32). Doses were taken approximately 1 hour before anticipated sexual activity but not more often than once daily. EF was assessed with use of the EF domain of the International Index of Erectile Function (IIEF) and with assessments of erection hardness (Erection Hardness Grading Scale [EHGS] and IIEF Q2 [the frequency of erections hard enough for penetration]). Change (baseline to end point) in emotional well-being in men treated for ED was assessed with the Self-Esteem and Relationship (SEAR) questionnaire, which consisted of the Confidence domain (ie, the Self-Esteem subscale and Overall Relationship subscale) and the Sexual Relationship domain. End point treatment satisfaction (overall, speed of onset, and duration of action) was assessed with the Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS). The IIEF was used to assess change and end point sexual satisfaction by means of the Intercourse Satisfaction domain, Q7 (frequency of satisfactory sexual intercourse), and the Overall Satisfaction domain (ie, Q13, satisfaction with sex life, and Q14, satisfaction with sexual relationship). In men treated with sildenafil for ED, scores for measures of EF (IIEF EF domain, IIEF Q2) and the percentage of erections graded completely hard and fully rigid (EHGS grade 4) correlated positively with scores for measures of psychosocial outcomes (SEAR emotional well-being, IIEF sexual satisfaction, and EDITS ED treatment satisfaction), indicating that when EF improved and erection hardness increased, these measures of psychosocial function also improved.

Research instruments for the diagnosis and treatment of patients with erectile dysfunction

As the incidence and prevalence of erectile dysfunction (ED) increase, healthcare providers will require robust, accurate, and efficient tools for appropriately diagnosing and treating patients with ED. Moreover, clinicians will need effective follow-up tools that assess treatment efficacy and satisfaction, to help patients meet their expectations for successful treatment of ED. We provide a summary of some of the most commonly used instruments for the diagnosis and assessment of ED treatment efficacy that will be referred to in this supplement.

Erection hardness: A unifying factor for defining response in the treatment of erectile dysfunction

The extensive sildenafil citrate erectile dysfunction (ED) database of double-blind, placebo-controlled clinical trials was examined to determine the relation between erection hardness graded on the Erectile Hardness Grading Scale (EHGS) and (1) erectile function (EF), as assessed by the EF domain of the International Index of Erectile Function (IIEF); (2) frequency of erections hard enough for penetration, as assessed by IIEF Q2; and (3) the percentage of successful sexual intercourse attempts according to patient event logs. Pooled data from 6549 men with ED provided strong proof and improved characterization of the response to sildenafil. Almost half of men with ED and a baseline IIEF EF domain score classified as "severe ED" (< or = 10) shifted to a score classified as "no ED" (> or = 26). Sildenafil recipients showed greater mean improvement from baseline to end point in IIEF Q2 scores versus placebo, regardless of baseline ED severity, and a higher mean percentage of successful sexual intercourse attempts occurred during the last 4 weeks of treatment versus placebo (5.4-fold vs 2.0-fold increase from baseline). At end point, 95% of men who scored "no ED" on the IIEF EF domain and 92% of men who reported "almost always/always" achieving an erection hard enough for penetration (IIEF Q2) had graded their erections hard (rigid) enough for penetration (grade 3) or completely hard and fully rigid (grade 4) during the last 4 weeks of treatment, suggesting that the IIEF EF domain and IIEF Q2 may be good surrogate end points for erection hardness. Furthermore, during the last 4 weeks of treatment, the percentage of grade 3 and/or 4 erections correlated positively with the percentage of successful sexual intercourse attempts. Hence, hard erections may be considered a unifying factor that defines response to ED treatment. Completely hard and fully rigid erections (grade 4) should be recognized as the optimal goal of an ED therapy. Evidence presented here demonstrates that sildenafil significantly improved EF as assessed by the IIEF EF domain and assessments of erection hardness in patients with ED; a dose-response relation was observed in the proportions of men with ED who graded their erections hard (rigid) enough for sexual penetration or completely hard and fully rigid.

Evaluation of the Sexual Assessment Monitor, a diagnostic device used to electronically quantify ejaculatory latency time: findings from three studies

OBJECTIVE

To validate the Sexual Assessment Monitor (SAM), a novel apparatus designed to collect electronic data on ejaculatory latency time (ELT) for diagnosing premature ejaculation (PE), and for accurately measuring treatment outcomes in clinical trials.

PATIENTS, SUBJECTS AND METHODS

Men with PE, and healthy volunteers aged 18-75 years, were enrolled in three open-label studies, conducted in the UK. The SAM, which consists of a control box with two front attachments, a vibrator and sensor, was attached to the penis. The vibrator, which provides stimulation, was positioned at the frenulum using a soft cuff; the vibrator intensity was set at 80 units for most subjects. The sensor is an indium-gallium elasticated loop, which was positioned around the base of the penis to detect ejaculatory pulses. These pulses were transmitted to a data recorder in the control box. The data, which are displayed graphically as traces, were automatically classified by a computer-generated algorithm to quantify ELT.

RESULTS

In all, 53 healthy volunteers and 58 men with PE provided 213 and 195 evaluable records, respectively. Most were complete records (99% and 96%). The pooled data showed that the ELT was much higher for healthy volunteers than for men with PE (geometric means: 687 vs 169 s, respectively), with a healthy volunteer to PE patient ratio of 2.87 (P < 0.001). Only 6.3% of subjects reported mild adverse events, which were unrelated to the SAM.

CONCLUSIONS

These open-label studies show that the SAM can consistently and safely measure times to erection (from the start of vibration) and ejaculation, and ELT in healthy volunteers and men with PE. These findings show that the SAM has the potential to become the 'gold standard' in the diagnosis of PE and in clinical trials design.

Sildenafil: from angina to erectile dysfunction to pulmonary hypertension and beyond

In less than 20 years, the first selective type 5 phosphodiesterase inhibitor, sildenafil, has evolved from a potential anti-angina drug to an on-demand oral treatment for erectile dysfunction (Viagra), and more recently to a new orally active treatment for pulmonary hypertension (Revatio). Here we describe the key milestones in the development of sildenafil for these diverse medical conditions, discuss the advances in science and clinical medicine that have accompanied this journey and consider possible future indications for this versatile drug.

Phosphodiesterase type 5 inhibitors' extended duration of response as a variable in the treatment of erectile dysfunction

The phosphodiesterase type 5 (PDE5) inhibitors, sildenafil, tadalafil and vardenafil, are a class of medications that are safe and effective in treating erectile dysfunction (ED). Yet, resuming sexual activity following a period of abstinence in response to ED may be anxiety-provoking for the man, his partner and their relationship, causing the sexual encounter to become a stressful event. The differences between PDE5 inhibitors in terms of duration of action can be successfully utilized by healthcare professionals to mitigate some of the psychosocial barriers that interfere with treating ED. PDE5 inhibitors with a longer duration of responsiveness provide some men with ED and their partners, a treatment option that may offer greater flexibility and potentially less anxiety surrounding the resumption of sexual activity. Shorter-acting PDE5s may be preferred by men/couples with predictable sexual scripts, excellent communication strategies and concerns regarding the duration of side effects.

Increased phosphodiesterase-5 expression is involved in the decreased vasodilator response to nitric oxide in cirrhotic rat livers

BACKGROUND/AIMS

Cirrhotic livers have a deficient vasodilator response to nitric oxide (NO). The vasodilator effect of NO is normally limited by the degradation of its second messenger cyclic guanosine 3', 5' monophosphate by phosphodiesterases. We investigated (1) the phosphodiesterase-5 (PDE-5) expression in normal and cirrhotic rat livers, (2) the location of the deficient response to NO in cirrhotic livers, and (3) the effect of the PDE-5 inhibitor Sildenafil citrate on this deficient response.

METHODS

Normal and ascitic cirrhotic rats were subjected to liver perfusion with continuous measurement of both perfusion and sinusoidal (wedge hepatic) pressures. After incubation with N-monomethyl-l-arginine and pre-constriction with Methoxamine, concentration-response curves to the spontaneous NO donor S-nitroso-N-acetylpenicillamine were obtained in the absence or presence of Sildenafil (10(-8)M).

RESULTS

PDE-5 expression (Western blot) in cirrhotic livers was higher than in normal livers (P=0.042). Compared to normal livers, cirrhotic livers showed a decreased response to S-nitroso-N-acetylpenicillamine in the pre-sinusoidal area (P=0.003) but not in the sinusoidal/post-sinusoidal area (P=0.433). In the presence of Sildenafil, normal and cirrhotic livers showed similar pre-sinusoidal (P=0.419) and sinusoidal/post-sinusoidal (P=0.875) responses to S-nitroso-N-acetylpenicillamine.

CONCLUSIONS

Increased PDE-5 expression is involved in the decreased vascular response to NO in cirrhotic livers.