Do vardenafil and tadalafil have advantages over sildenafil in the treatment of erectile dysfunction?

Comparison of the Erectile Dysfunction Drugs Sildenafil and Tadalafil Using Patient Medication Reviews: Topic Modeling Study

BACKGROUND

Topic modeling of patient medication reviews of erectile dysfunction (ED) drugs can help identify patient preferences regarding ED treatment options. The identification of a set of topics important to the patient from social network service drug reviews would inform the design of patient-centered medication counseling.

OBJECTIVE

This study aimed to (1) identify the distinctive topics from patient medication reviews unique to tadalafil versus sildenafil; (2) determine if the primary topics are distributed differently for each drug and for each patient characteristic (age and time on ED drug therapy); and (3) test if the primary topics affect satisfaction with ED drug therapy controlling for patient characteristics.

METHODS

Data were collected from the patient medication reviews of sildenafil and tadalafil posted on WebMD and Ask a Patient. The latent Dirichlet allocation method of natural language processing was used to identify 5 distinctive topics from the patient medication reviews on each drug. Analysis of variance and a 2-sample t test were conducted to compare the topic distribution and assess whether patient satisfaction varies with the primary topics, age, and time on medication for each ED drug. Statistical significance was tested at an alpha of .05.

RESULTS

The patient medication reviews of sildenafil (N=463) had 2 topics on treatment benefit and 1 each on medication safety, marketing claim, and treatment comparison, while the patient medication reviews of tadalafil (N=919) had 2 topics on medication safety and 1 each on the remaining subjects. Sildenafil's reviewers quite frequently (94/463, 20.4%) mentioned erection sustainability as their primary topic, whereas tadalafil's reviewers were more concerned about severe medication safety. Those who mentioned erection sustainability as their primary topic were quite satisfied with their treatment as opposed to those who mentioned severe medication safety as their primary topic (score 3.85 vs 2.44). The discovered topics reflected the marketing claims of blue magic and amber romance for sildenafil and tadalafil, respectively. The topic of blue magic was preferred among younger patients, while the topic of amber romance was preferred among older patients. The topic alternative choices, which appeared for both the ED drugs, reflected patient interest in the comparative effectiveness and price outside the drug labeling information.

CONCLUSIONS

The patient medication reviews of ED drugs reflect patient preferences regarding drug labeling information, marketing claims, and alternative treatment choices. The patient preferences concerning ED treatment attributes inform the design of patient-centered communication for improved ED drug therapy.

Canadian Urological Association guideline: Erectile dysfunction

Erectile dysfunction (ED) impacts the wellness and quality of life of millions of Canadians. An evaluation focused on the identification of reversible and irreversible underlying factors is recommended for patients presenting with ED. Through a shared decision-making model framework, the goal of ED treatment is to improve functional outcomes and enhance sexual satisfaction while minimizing adverse effects associated with treatment. Given that ED is assessed and treated by multiple different types of health practitioners, the purpose of this guideline is to provide the best available evidence to facilitate care delivery through a Canadian lens. After a narrative review of ED assessment and treatment for general readership, five key clinical questions relating to priority areas of ED are assessed using the GRADE and evidence-to-decision-making frameworks.

Therapeutic potential of phosphodiesterase inhibitors in the treatment of osteoporosis: Scopes for therapeutic repurposing and discovery of new oral osteoanabolic drugs

Cyclic nucleotide phosphodiesterases (PDEs) are ubiquitously expressed enzymes that hydrolyze phosphodiester bond in the second messenger molecules including cAMP and cGMP. A wide range of drugs blocks one or more PDEs thereby preventing the inactivation of cAMP/cGMP. PDEs are differentially expressed in bone cells including osteoblasts, osteoclasts and chondrocytes. Intracellular increases in cAMP/cGMP levels in osteoblasts result in osteogenic response. Acting via the type 1 PTH receptor, teriparatide and abaloparatide increase intracellular cAMP and induce osteoanabolic effect, and many PDE inhibitors mimic this effect in preclinical studies. Since all osteoanabolic drugs are injectable and that oral drugs are considered to improve the treatment adherence and persistence, osteogenic PDE inhibitors could be a promising alternative to the currently available osteogenic therapies and directly assessed clinically in drug repurposing mode. Similar to teriparatide/abaloparatide, PDE inhibitors while stimulating osteoblast function also promote osteoclast function through stimulation of receptor activator of nuclear factor kappa-B ligand production from osteoblasts. In this review, we critically discussed the effects of PDE inhibitors in bone cells from cellular signalling to a variety of preclinical models that evaluated the bone formation mechanisms. We identified pentoxifylline (a non-selective PDE inhibitor) and rolipram (a PDE4 selective inhibitor) being the most studied inhibitors with osteogenic effect in preclinical models of bone loss at ≤ human equivalent doses, which suggest their potential for post-menopausal osteoporosis treatment through therapeutic repurposing. Subsequently, we treated pentoxifylline and rolipram as prototypical osteogenic PDEs to predict new chemotypes via the computer-aided design strategies for new drugs, based on the structural biology of PDEs.

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.

Design, synthesis and biological evaluation of pyrazolopyrimidinone based potent and selective PDE5 inhibitors for treatment of erectile dysfunction

Our previous discovery of series of pyrazolopyrimidinone based PDE5 inhibitors led to find potent leads but with low aqueous solubility and poor bioavailability, and low selectivity. Now, a new series of same pyrazolopyrimidinone scaffold is designed, synthesized and evaluated for its PDE5 inhibitory potential. In this study, some of the molecules are found more potent and selective PDE5 inhibitors in vitro than sildenafil. The studies revealed that compound 5 is 20 fold selective to PDE5 against PDE6. As PDE6 enzyme is involved in the phototransduction pathway in the retina and creates distortion problem, the selectivity for PDE5 specifically against PDE6 enzyme is preferred for any development candidate and in present study, compound 5 has been found to be devoid of this liability of selectivity issue. Moreover, compound 5 has shown excellent in vivo efficacy in conscious rabbit model, it's almost comparable to sildenafil. The preclinical pharmacology including pharmacokinetic and physicochemical parameter studies were also performed for compound 5, it was found to have good PK properties and other physicochemical parameters. The development of these selective PDE5 inhibitors can further lead to draw strategies for the novel preclinical and/or clinical candidates based on pyrazolopyrimidinone scaffold.

Needs and Expectations of Patients with Erectile Dysfunction: An Update on Pharmacological Innovations in Phosphodiesterase Type 5 Inhibition with Focus on Sildenafil

INTRODUCTION

Phosphodiesterase type 5 inhibitors (PDE5-Is) have an excellent efficacy and tolerability profile and remain the first-line choice for the treatment of erectile dysfunction (ED). However, ED is still an underdiagnosed and undertreated condition, and many men prematurely discontinue therapy with conventional dosage formulations despite successful intercourse.

AIM

To review the unmet needs and expectations of patients with ED and describe the latest pharmaceutical innovations in the field of PDE5-I formulations designed to address these needs, with particular reference to a new orodispersible film (ODF) formulation of the PDE5-I, sildenafil.

METHODS

Online literature search in PubMed and the Cochrane Library.

MAIN OUTCOME MEASURE

To identify English-language publications relevant to the aims of the present review.

RESULTS

Improved recognition and management of ED would enable the early diagnosis of underlying and comorbid conditions that contribute to ED, leading to improved patient health and health-related quality of life. To ensure successful outcomes and patient and partner satisfaction, the complex and personal issues that influence the patient's needs and expectations regarding treatment for ED must be considered along with their personal experiences and preferences. Innovative drug delivery systems, including orally disintegrating formulations, have been developed as alternatives to conventional dosage forms with the aim of improving patient convenience and acceptability and enhancing compliance. These alternative formulations include the sildenafil ODF, which is designed to improve acceptance and compliance over conventional solid dosage forms and extend the treatment options for men with ED by offering a convenient and discrete dosage form of a drug with proven efficacy.

CONCLUSION

The sildenafil ODF is an example of an innovative dosage formulation for ED that can be used interchangeably with the conventional film-coated formulation to better address the needs and expectations of men with ED. Jannini EA, Droupy S. Needs and Expectations of Patients with Erectile Dysfunction: An Update on Pharmacological Innovations in Phosphodiesterase Type 5 Inhibition with Focus on Sildenafil. Sex Med 2019;7:1-10.

Bioequivalence study of a new sildenafil 100 mg orodispersible film compared to the conventional film-coated 100 mg tablet administered to healthy male volunteers

A new orodispersible film formulation of the phosphodiesterase type 5 inhibitor, sildenafil, has been developed to examine the advantages of an orally disintegrating film formulation and provide an alternative to the current marketed products for the treatment of erectile dysfunction. The pharmacokinetics of the sildenafil 100 mg orodispersible film (IBSA) was compared to that of the conventional marketed 100 mg film-coated tablet (Viagra®) after single-dose administration to 53 healthy male volunteers (aged 18-51 years) in a randomized, open, two-way crossover bioequivalence study. Each subject received a single oral dose of 100 mg of sildenafil as test or reference formulation administered under fasting conditions at each of the two study periods according to a randomized crossover design. There was a washout interval of ≥7 days between the two administrations of the investigational medicinal products. Blood samples for pharmacokinetic analysis were collected up to 24 h post-dosing. The primary objective was to compare the rate (peak plasma concentration; Cmax) and extent (area under the curve [AUC] from administration to last observed concentration time; AUC0-t) of sildenafil absorption after single-dose administration of test and reference. Secondary endpoints were observed to describe the plasma pharmacokinetic profiles of sildenafil and its metabolite N-desmethyl-sildenafil relative bioavailability and safety profile after single-dose administration. The mean sildenafil and N-desmethyl-sildenafil plasma concentration-time profiles up to 24 h after single-dose administration of sildenafil 100 mg orodispersible film and film-coated tablet were nearly superimposable. The bioequivalence test was fully satisfied for sildenafil and N-desmethyl-sildenafil in terms of rate and extent of bioavailability. Adverse events occurred at similar rates for the two formulations and were of mild-to-moderate severity. The results suggest that the new orodispersible film formulation can be used interchangeably with the conventional film-coated formulation.

In vitro and in vivo investigation of natural compounds from seed extract of Mucuna pruriens lacking l-DOPA for the treatment of erectile dysfunction

OBJECTIVE

To investigate the biological effects of the Mucuna pruriens (M. pruriens) seed extracts that lacked l-DOPA, which was formerly reported as the active ingredient, on erectile dysfunction (ED) both in vitro and in vivo.

METHODS

Seed of M. pruriens plant that cultivated in Mae Taeng District, Chiang Mai Province, Thailand, was collected. Component of its seeds were extracted and isolated into 2 fractions using methanol, polar and nonpolar. Each fraction was investigated for phytochemicals using gas chromatography and mass spectroscopy and was screened for biological activity in vitro using three different cell lines. The most biological active fraction was used to treat both streptozotocin (STZ)-induced diabetes mellitus-erectile dysfunction (DM-ED) male Wistar rats and normal rats (n = 6 per groups) to compare the effect on sexual behavior parameters, including number of intromission, mounting and ejaculation, with that of rats given Sildenafil by individually pairing with their female counterparts. Penile tissues and serums were collected to determine histological structure, related gene expression and biomolecules.

RESULTS

The phytochemicals of the polar fraction were possibly catechol and its derivatives plus polyphenols, whereas the nonpolar fraction consisted of lipid derivatives. l-DOPA was not detected in either of the extracts. The polar fraction was able to up-regulate the expression of ED-related genes including eNOS and nNOS in vitro which subsequently promotes nitric oxide production and maintains intracellular cyclic guanosine monophosphate levels. When administrated to DM-ED rats, the polar extract significantly improved all sexual behavior parameters in DM-ED rats compared to untreated group (18.3 ± 1.8 to 10.8 ± 2.9 for intromission, 9.8 ± 2.2 to 5.7 ± 1.3 for mounting, and 1.8 ± 0.6 to 0.2 ± 0.4 for ejaculation). That effect might due to the ability of the extract to stimulate the expression of eNOS and nNOS which results in nitric oxide production and subsequently maintains cyclic guanosine monophosphate levels in penile tissue. Moreover, this extract may also prevent penile tissue deterioration due to diabetes.

CONCLUSIONS

The polar extract of M. pruriens seed can be used for ED therapy, especially in patients with metabolic diseases including diabetes. The action of the extract might be due to catechol and its derivatives and polyphenols.

Rapid-Onset Sildenafil Sublingual Drug Delivery Systems: In Vitro Evaluation and In Vivo Pharmacokinetic Studies in Rabbits

The aim of the present study was to prepare sublingual delivery systems for sildenafil and evaluate its relative bioavailability after sublingual administration in rabbits to attain a rapid onset of action with good efficacy at lower doses. For sublingual application, sildenafil and its citrate were formulated in 2 different dosage forms: the first was a sublingual spray consisting of sildenafil in 2 microemulsion systems, oleic acid or propylene glycol (PG), and the second was sublingual tablets prepared with various granulated sublingual sprays adsorbed onto a silicate adsorbant (Florite(®) R), binders (Cyclocel(®) or EMDEX(®)), and disintegrants (Ac-Di-Sol(®) or Kollidon(®) CL). Results showed that sublingual absorption of sildenafil spray prepared with PG was fairly rapid. At a 0.5-mg dose, the mean onset of action was 1.3 ± 0.6 min and lasted for about 1.5 h according to the pharmacokinetic studies. In vivo studies also showed that for sublingual tablets formulated with sildenafil in PG adsorbed onto Florite(®) R at a 1:1 weight ratio then mixed with Cycloel(®) and Ac-Di-Sol(®), the onset action was fast at 1.9 ± 0.4 min and lasted for about 1 h at 0.5 mg. These findings suggest the potential for the sublingual delivery of sildenafil instead of the conventional oral administration.

The efficacy of udenafil in end-stage renal disease patients undergoing hemodialysis

INTRODUCTION

Erectile dysfunction (ED) is frequently observed in end-stage renal disease (ESRD) patients on hemodialysis (HD) compared to non-uremic patients. This situation causes severe psychogenic problems in patients and disrupts the quality of life. Different phosphodiesterase type 5 (PDE-5) inhibitors have been used, and efficacies revealed, for the treatment of ED in HD patients; however, there are no studies related to udenafil use or results for HD patients. This study retrospectively evaluated the efficacy and reliability of udenafil for HD patients.

MATERIALS AND METHODS

The laboratory findings, side effects after treatment, and International Index of Erectile Function (IIEF) scores before and after treatment were compared and evaluated for HD patients who applied to our urology clinic with ED complaints and were treated with udenafil.

RESULTS

The results showed that in the HD patient group with ED, apart from ED, there were severe rates of other sexual dysfunction. In our patient group, there was a statistically significant improvement in all scores for erectile function (p = 0.033), orgasmic function (p < 0.001), sexual desire (p < 0.001), relationship satisfaction (p < 0.001), and general satisfaction (p < 0.001) after treatment. The reported side effects were headache in one patient and dyspepsia in one patient.

CONCLUSION

We concluded that udenafil is an effective and reliable treatment approach for HD patients; however, our results require support from prospective randomized crossover studies with sildenafil.

Tadalafil inhibits the cAMP stimulated glucose output in the rat liver

The purpose of the present work was to verify if tadalafil affects hepatic glucose output, one of the primary targets of cAMP, in the isolated perfused rat liver. No effects on glycogen catabolism and oxygen uptake were found under basal conditions for tadalafil concentrations in the range between 0.25 and 10 μM. However, tadalafil had a clear and time-dependent inhibitory effect on the cAMP- and glucagon-stimulated glucose release. Constant infusion of tadalafil in the range between 0.25 and 10 μM eventually abolished 100% of the stimulatory action of those effectors. The tadalafil concentrations producing half-maximal rates of inhibition of the cAMP and glucagon stimulated glycogenolysis were 0.46±0.04 and 1.07±0.16 μM, respectively. These concentrations are close to the plasma peak concentrations in patients after ingestion of 20 mg tadalafil. The drug also diminished the activity of glycogen phosphorylase a and increased the activities of glucose 6-phosphatase, glucokinase, pyruvate kinase and glucose 6-phosphate dehydrogenase. These actions occurred only in the cellular environment. Tadalafil did not affect binding of cAMP to protein kinase A. Diminution of cAMP-stimulated glucose output is the opposite of what can be expected from a phosphodiesterase inhibition, the most common effect attributed to tadalafil. Diminution of glucose output by tadalafil can be attributed (a) to an interference with glycogen phosphorylase stimulation and (b) to an increased futile cycling of glucose 6-phosphate and glucose with a concomitant increased flow of hexose units into cellular metabolic pathways. The effects described in the present work may prove to represent important side effects of tadalafil.

Vardenafil dihydrochloride

Vardenafil (VAR) is synthetic, highly selective, and potent inhibitor of phosphodiesterase-5 which competitively inhibits cyclic guanosine monophosphate (cGMP) hydrolysis and thus increases cGMP levels. It is clinically approved for treatment of erectile dysfunction in men, including diabetic and postprostatectomy patients. Several methods of VAR synthesis are included in this review. UV spectroscopy of VAR showed a λmax of approximately 270nm, and IR spectroscopy principal peaks were observed at 3420 (NH), 1724 (CO), 1600 (CC, and CN), 1491 (CHCH) cm(-1). Characteristic carbonyl (CO) carbon was observed in nuclear magnetic resonance spectroscopy at 162.44ppm. The molecular mass was observed at m/z=488.9 (molecular weight=488.2) and the fragmentation pattern was studied using ion trap mass spectrometry. In addition, different analytical methods for determination of vardenafil are also described in this profile. Pharmacokinetic properties of VAR have great impact on efficacy. VAR is rapidly absorbed and slowly metabolized, with an absolute bioavailability of 15%. It is extensively metabolized by CYP3A4 into several metabolites, the most pharmacologically active of which is N-desethyl VAR (M1). The elimination half-life of VAR and M1 is about 4-5h. VAR is primarily excreted as metabolites in the feces and to a small extent in urine. VAR is generally well tolerated, with a favorable safety profile and few transient side effects, including headache, flushing, dyspepsia, and rhinitis.

PDE5 inhibitors, sildenafil and vardenafil, reverse multidrug resistance by inhibiting the efflux function of multidrug resistance protein 7 (ATP-binding Cassette C10) transporter

Phosphodiesterase type 5 (PDE5) inhibitors are widely used in the treatment of male erectile dysfunction and pulmonary hypertension. Recently, several groups have evaluated the ability of PDE5 inhibitors for their anticancer activities. Previously, we had shown that sildenafil, vardenafil and tadalafil could reverse P-glycoprotein (ATP-binding cassette B1)-mediated MDR. In the present study, we determined whether these PDE5 inhibitors have the potential to reverse multidrug resistance protein 7 (MRP7; ATP-binding cassette C10)-mediated MDR. We found that sildenafil and vardenafil dose-dependently enhanced the sensitivity of MRP7-transfected HEK293 cells to paclitaxel, docetaxel and vinblastine, while tadalafil had only a minimal effect. Accumulation and efflux experiments demonstrated that sildenafil and vardenafil increased the intracellular accumulation of [(3)H]-paclitaxel by inhibiting the efflux of [(3 H]-paclitaxel in HEK/MRP7 cells. In addition, immunoblot and immunofluorescence analyses indicated that no significant alterations of MRP7 protein expression and localization in plasma membranes were found after treatment with sildenafil, vardenafil or tadalafil. These results demonstrate that sildenafil and vardenafil reverse MRP7-mediated a MDR through inhibition of the drug efflux function of MRP7. Our findings indicate a potentially novel use of PDE5 inhibitors as an adjuvant chemotherapeutic agent in clinical practice.

Development of udenafil-loaded microemulsions for intranasal delivery: in vitro and in vivo evaluations

To achieve rapid onset of action and improved bioavailability of udenafil, a microemulsion system was developed for its intranasal delivery. Phase behavior, particle size, transmission electron microscope (TEM) images, and the drug solubilization capacity of the microemulsion were investigated. A single isotropic region was found in pseudo-ternary phase diagrams developed at various ratios with CapMul MCM L8 as an oil, Labrasol as a surfactant, and Transcutol or its mixture with ethanol (1:0.25, v/v) as a cosurfactant. Optimized microemulsion formulations with a mean diameter of 120-154 nm achieved enhanced solubility of udenafil (>10mg/ml) compared with its aqueous solubility (0.02 mg/ml). An in vitro permeation study was performed in human nasal epithelial (HNE) cell monolayers cultured by the air-liquid interface (ALI) method, and the permeated amounts of udenafil increased up to 3.41-fold versus that of pure udenafil. According to the results of an in vivo pharmacokinetic study in rats, intranasal administration of udenafil-loaded microemulsion had a shorter T(max) value (1 min) compared with oral administration and improved bioavailability (85.71%) compared with oral and intranasal (solution) administration. The microemulsion system developed for intranasal administration may be a promising delivery system of udenafil, with a rapid onset of action and improved bioavailability.

Tadalafil rehabilitation therapy preserves penile size after bilateral nerve sparing radical retropubic prostatectomy

OBJECTIVE

To evaluate the change in penile size r bilateral nerve sparing retropubic radical prostatectomy (BNSRRP) and possible effect of Tadalafil.

MATERIALS AND METHODS

A total of 65 patients underwent BNSRRP and they were evaluated prospectively for a whole year of follow-up. The patients were randomized to control without rehabilitation (Group 1) or Tadalafil rehabilitation group (Group 2). The patients were evaluated at months 3, 6 and 12 postoperatively for erectile function, penile measurements (flaccid penile length, penile length at maximum erection, penile circumference at flaccid status, and penile circumference at maximum erection), penile abnormalities and general health status. Statistical analysis was performed by Chi-Square test and significance was defined as p value < 0.05.

RESULTS

In Group 1 there was significant decrease in penile measurements at month 3 compared to preoperative measurements. There was decrease in all parameters at month 6 compared to month 3 but only the decrease in penile length at maximum erection was significant. There were no significant differences between postoperative months 6 and 12 for all measurements. In Group 2 there was a tendency to decrease in all measurements at month 3 compared to baseline. There was no significant difference for penile measurements between postoperative 3rd and 6th months and between 6th month and the first year.

CONCLUSION

Although further large sampled trials are needed to describe the possible positive effect of tadalafil or other PDE5-I 's on penile size after BNSRRP, tadalafil rehabilitation is effective in preserving penile size especially in the early postoperative period after BNSRRP.

Effects of sildenafil and vardenafil on erectile dysfunction and health-related quality of life in haemodialysis patients: a prospective randomized crossover study

BACKGROUND

Erectile dysfunction (ED) is prevalent in end-stage renal disease (ESRD) and has been associated with impaired health-related quality of life (HRQoL). HRQoL, in turn, is related to morbidity and mortality in ESRD patients. Previous studies have shown improved HRQoL with ED treatment using sildenafil and vardenafil. However, no study has examined the effects of sildenafil or vardenafil on HRQoL in impotent ESRD patients. Furthermore, vardenafil has never been tested and its safety profile has not been determined in ESRD patients. The aim of this randomized crossover study was to compare the effects of sildenafil and vardenafil on measures of HRQoL and on ED scores as well as to determine the safety profile of vardenafil in ESRD patients.

METHODS

In 32 haemodialysis patients with impotence, ED and HRQoL were evaluated by the International Index of Erectile Function (IIEF-5) and the 36-item Short-Form Health (SF-36) surveys, respectively. Patients were randomized into sildenafil and vardenafil groups. After a 4-week treatment and 2-week washout periods, crossover was performed and an additional 4-week treatment was administered. IIEF-5 and SF-36 surveys were given before and after each treatment period. Adverse effects were evaluated by interview. Friedman tests and Bonferroni-adjusted Wilcoxon signed-rank tests were used to compare groups and for post hoc analysis, respectively.

RESULTS

IIEF-5 and SF-36 scores were significantly improved by both sildenafil and vardenafil compared to pretreatment values. There were no differences between sildenafil and vardenafil with respect to the studied parameters. Adverse effect profiles were also similar. No patient dropped out because of side effects.

CONCLUSIONS

Sildenafil and vardenafil caused similar improvements in ED and HRQoL in haemodialysis patients. Vardenafil was well tolerated in our patient population.

Toward a new 'EPOCH': optimising treatment outcomes with phosphodiesterase type 5 inhibitors for erectile dysfunction

Despite the marked adverse impacts of erectile dysfunction (ED) on quality of life and well-being, many patients (and/or their partners) do not seek medical attention for this problem, do not receive treatment or discontinue such treatment even when it has effectively restored erectile responses to sexual stimulation. Phosphodiesterase type 5 (PDE5) inhibitors are considered first-line therapies for men with ED. To help physicians maximise the likelihood of treatment success with these agents, we conducted an English-language PubMed search of articles involving approved PDE5 inhibitors dating from 1 January 1998 (the year in which sildenafil citrate was introduced), through 31 August 2008. In addition to sildenafil, tadalafil and vardenafil, search terms included 'adhere*', 'couple*', 'effect*', 'effic*', 'partner*', 'satisf*', 'succe*' and 'treatment outcome.' Based on our analysis, physician activities to promote favourable treatment outcomes may be captured under the mnemonic 'EPOCH': (i) Evaluating and educating patients and partners to ensure realistic expectations of therapy; (ii) Prescribing a treatment individualised to the couple's lifestyle needs and other preferences; (iii) Optimising treatment outcomes by scheduling follow-up visits with the patient to 'fine-tune' dosages and revisit key educational messages; (iv) Controlling comorbidities via lifestyle counselling, medications and/or referrals and (v) Helping patients and their partners to meet their health and psychosocial needs, potentially referring them to a specialist for other forms of therapy if they are not satisfied with PDE5 inhibitors.

The ENDOTRIAL study: a spontaneous, open-label, randomized, multicenter, crossover study on the efficacy of sildenafil, tadalafil, and vardenafil in the treatment of erectile dysfunction

INTRODUCTION

The three effective, commercially available drugs for the treatment of erectile dysfunction-sildenafil, vardenafil, and tadalafil-inhibit the same substrate, the erectolytic enzyme phosphodiesterase type 5 (PDE5). Although there are pharmacological differences between these three compounds, few comparative studies have been conducted to date.

AIM

The aim of this study was to determine the efficacy of sildenafil, tadalafil, and vardenafil in a randomly assigned 8-week fixed regimen.

METHODS

This was a spontaneous, open-label, randomized, multicenter, crossover study where the patients were randomized to receive sildenafil 50 mg, sildenafil 100 mg, tadalafil 20 mg, or vardenafil 20 mg.

MAIN OUTCOME MEASURES

The primary outcome included the posttreatment analysis of erectile function domains of the abridged International Index of Erectile Function (IIEF5+1). The secondary objectives included the analysis of peak-systolic velocities (PSVs), end-diastolic velocities (EDVs), and resistive index (RI), and the estimate of the percentage of men with normal penile hemodynamic parameters after each treatment.

RESULTS

In all groups of patients taking sildenafil 50 mg, sildenafil 100 mg, tadalafil 20 mg, and vardenafil 20 mg at a frequency reflecting the common treatment regimens in real life, there was a statistically significant baseline-to-end point improvement in subjective perception of erectile function measured by IIEF5+1. When the four groups were compared, the treatments were not different in modifying IIEF5+1 and penile flow parameters. However, the within-group analysis showed that PSV improved in the sildenafil 50 mg group and that PSV together with RI significantly ameliorated in patients receiving 100 mg of sildenafil. Regression analysis confirmed an independent effect of sildenafil on hemodynamic efficacy parameters.

CONCLUSIONS

An overall equivalence was demonstrated in the subjective perception of treatment benefits for all the PDE5i tested. However, sildenafil, in a dose-dependent manner, was the unique PDE5i able to ameliorate some of the penile flow parameters within the 8-week treatment period. These findings should be interpreted conservatively because of the observational nature of the study.

Intranasal microemulsion of sildenafil citrate: in vitro evaluation and in vivo pharmacokinetic study in rabbits

The purpose of the present study was to prepare intranasal delivery system of sildenafil citrate and estimate its relative bioavailability after nasal administration in rabbits to attain rapid onset of action with good efficacy at lower doses. Sildenafil citrate saturated solubility was determined in different solvents, cosolvents, and microemulsion systems. For nasal application, sildenafil citrate was formulated in two different systems: the first was a cosolvent system (S3) of benzyl alcohol/ethanol/water/Transcutol/taurodeoxy cholate/Tween 20 (0.5:16.8:47.7:15.9:1:18.1% w/w). The second was a microemulsion system (ME6) containing Oleic acid: Labrasol/Transcutol/water (8.33:33.3:16.66:41.66% w/w). The prepared systems were characterized in relation to their clarity, particle size, viscosity, pH, and nasal ciliotoxicity. In vivo pharmacokinetic performance of the selected system ME6 (with no nasal ciliotoxicity) was evaluated in a group of six rabbits in a randomized crossover study and compared to the marketed oral tablets. The targeted solubility (>20 mg/ml) of sildenafil citrate was achieved with cosolvent systems S1, S3, and S5 and with microemulsion systems ME3-ME6. The saturated solubility of sildenafil citrate in cosolvent system S3 and microemulsion system ME6 were 22.98 +/- 1.26 and 23.79 +/- 1.16 mg/ml, respectively. Microemulsion formulation ME6 showed shorter t (max) (0.75 h) and higher AUC((0-infinity)) (1,412.42 ng h/ml) compared to the oral tablets which showed t (max) equals 1.25 h and AUC((0-infinity)) of 1,251.14 ng h/ml after administration to rabbits at dose level of 5 mg/kg. The relative bioavailability was 112.89%. In conclusion, the nasal absorption of sildenafil citrate microemulsion was found to be fast, indicating the potential of nasal delivery instead of the conventional oral administration of such drug.

Conformational variations of both phosphodiesterase-5 and inhibitors provide the structural basis for the physiological effects of vardenafil and sildenafil

Vardenafil has higher affinity to phosphodiesterase-5 (PDE5) than sildenafil and lower administered dosage for the treatment of erectile dysfunction. However, the molecular basis for these differences is puzzling because two drugs have similar chemical structures. Reported here is a crystal structure of the fully active and nonmutated PDE5A1 catalytic domain in complex with vardenafil. The structure shows that the conformation of the H-loop in the PDE5A1-vardenafil complex is different from those of any known structures of the unliganded PDE5 and its complexes with the inhibitors. In addition, the molecular configuration of vardenafil differs from that of sildenafil when bound to PDE5. It is noteworthy that the binding of vardenafil causes loss of the divalent metal ions that have been observed in all the previously published PDE structures. The conformational variation of both PDE5 and the inhibitors provides structural insight into the different potencies of the drugs.