A conscious-rabbit model to study vardenafil hydrochloride and other agents that influence penile erection

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.

Relationship between Response to PDE5 Inhibitors and Penile Duplex Doppler Ultrasound in Erectile Dysfunction

The relationship between the results of penile duplex Doppler ultrasound (PDDU) and response to vardenafil was investigated in patients diagnosed with erectile dysfunction (ED). Data from 148 patients with ED were analyzed retrospectively. Patients who did not respond to therapy were classified in to Group I (n = 32), those who responded partially were classified into Group II (n = 40), and complete responders were classified into Group III (n = 76). Age, comorbidities, and vascular and penile pathologies were compared among the three groups. While diabetes mellitus (DM) and dyslipidemia positivity adversely affected the response to treatment, the presence of hypertension (HT), Peyronie’s disease and priapism increased the therapeutic response to the treatment (p < 0.05). Arterial insufficiency was present in 20 (30.3%), 25 (37.9%) and 21 (31.8%) of the patients in Group I, Group II and Group III, respectively (p = 0.001). Venous insufficiency was observed in three (14.3%) patients in Group I and in eight (85.7%) patients in Group III (p = 0.001). Arterial/venous insufficiency was seen in 9 (30%), 14 (46.7%) and 7 (23.3%) of the patients in Group I, Group II and Group III, respectively (p = 0.001). The response rate to treatment was highest in normal patients according to PDDU, followed by patients with venous insufficiency. In addition, it was found that DM decreased the response to treatment, whereas the response increased in cases with HT, priapism and Peyronie’s disease.

Animal models of erectile dysfunction

Animal models have contributed to a great extent to understanding and advancement in the field of sexual medicine. Many current medical and surgical therapies in sexual medicine have been tried based on these animal models. Extensive literature search revealed that the compiled information is limited. In this review, we describe various experimental models of erectile dysfunction (ED) encompassing their procedures, variables of assessment, advantages and disadvantages. The search strategy consisted of review of PubMed based articles. We included original research work and certain review articles available in PubMed database. The search terms used were “ED and experimental models,” “ED and nervous stimulation,” “ED and cavernous nerve stimulation,” “ED and central stimulation,” “ED and diabetes mellitus,” “ED and ageing,” “ED and hypercholesteremia,” “ED and Peyronie's disease,” “radiation induced ED,” “telemetric recording,” “ED and mating test” and “ED and non-contact erection test.”

A Review of the Pathophysiology and Novel Treatments for Erectile Dysfunction

Erectile dysfunction (ED) affects up to 50% of men between the ages of 40 and 70. Treatment with PDE-5 inhibitors is effective in the majority of men with ED. However, PDE-5 inhibitors are not effective when levels of nitric oxide (NO), the principle mediator of erection, are low. The pharmacologic actions of three new potential treatments for ED are discussed in this paper: (1) sGC stimulators/activators, (2) Rho-kinase inhibitors, and (3) sodium nitrite.

Erectile dysfunction and lower urinary tract

During the last decades it turned out that the NO/cGMP signaling cascade is one of the most prominent regulators of a variety of physiological and pathophysiological processes in a broad range of mammalian tissues. Thus cGMP is a key second messenger and targeting this pathway by increasing intracellular cGMP levels is a very successful approach in pharmacology as shown for nitrates, PDE5 inhibitors and more recently for stimulators of the guanylate cyclase. Besides the beneficial effects of cGMP elevation in cardiac, vascular, pulmonary, renal or liver disorders the launch of PDE5 inhibitors for the treatment of erectile dysfunction 10 years ago, has directed a lot of attention to the NO/cGMP signaling in the lower urinary tract. Triggered by the use of PDE5 inhibitors in ED it turned out that cGMP is a common regulatory mechanism for lower urinary tract function also beyond ED. In recent years intense research and development efforts were undertaken to elucidate the role of the NO/cGMP and to fully exploit the therapeutic implications of cGMP elevation in urological disorders in ED and beyond. Therefore we have summarized the effects of cGMP elevation for treatment of erectile dysfunction in males and in females. We have also reviewed the recent pre-clinical and clinical lines of evidence for treatment options of benign prostatic hyperplasia and lower urinary tract symptoms in male patients and overactive bladder and urinary incontinence in female patients. In addition we also touch more speculative concepts using cGMP elevating drugs for the treatment of premature ejaculation, peyornies disease and stone disease.

Efficacy and safety of flexible-dose vardenafil in men with type 1 diabetes and erectile dysfunction

INTRODUCTION

Erectile dysfunction (ED) affects up to 70% of men with diabetes, occurring with a higher prevalence in those with type 1 diabetes than with type 2 diabetes. Studies investigating treatment of ED in men with diabetes have largely been conducted in a total male population with diabetes. Limited data are available on the efficacy and safety of the potent oral phosphodiesterase-5 inhibitor vardenafil in men with ED and type 1 diabetes.

AIMS

To evaluate the safety and efficacy of flexible-dose vardenafil therapy in a prospective randomized study in phosphodiesterase 5 inhibitor-naïve subjects with type 1 diabetes and ED.

METHODS

In this multicenter, double-blind, placebo-controlled clinical trial, phosphodiesterase-5 inhibitor-naïve patients were randomized to receive placebo (N = 149) or flexible-dose (5-20 mg) (N = 153) vardenafil.

MAIN OUTCOME MEASURE

Sexual Encounter Profile diary questions 2 and 3, concerning success rates of vaginal insertion and maintenance of erection to allow successful intercourse, respectively.

RESULTS

Vardenafil significantly improved mean success rates for Sexual Encounter Profile 2 and 3 compared with baseline and placebo at 4, 8, and 12 weeks (P < 0.0001, intention to treat and last observation carried forward). These rates were unaffected by stratification into distinct subsets according to the level of HbA(1c) (HbA(1c) < 7%, good glycemic control; HbA(1c) >7- < or = 8%, moderate glycemic control; and HbA(1c) > 8%, poor glycemic control). Vardenafil treatment also significantly improved the Erectile Function domain score (P < 0.0001) of the International Index of Erectile Function compared with placebo, in addition to scores for the other individual domains of the International Index of Erectile Function. The most commonly reported treatment-emergent adverse events were headache (3.1%) and flushing (2.5%), which were mild to moderate and transient in nature.

CONCLUSION

These data suggest that vardenafil significantly improves erectile function in men with type 1 diabetes and is well tolerated, regardless of the level of glycemic control.

Up-titration of vardenafil dose from 10 mg to 20 mg improved erectile function in men with spinal cord injury

AIM

Vardenafil is a highly selective phosphodiesterase type-5 inhibitor for the treatment of erectile dysfunction (ED). Efficacy of vardenafil has been demonstrated in various ED populations, but that in Japanese patients with spinal cord injury (SCI) has not been assessed.

METHODS

This was an open-label, multicenter, flexible dose, 12-week study in patients with ED due to SCI. Following a 4-week observation period, patients received vardenafil 10 mg for 4 weeks, and based on efficacy, tolerability and patient preference, doses for the remaining 8 weeks were decided by investigators. The primary efficacy parameter was erectile function domain score of the International Index of Erectile Function.

RESULTS

Ten patients took 10 mg all through the study, while 22 patients took 20 mg after completing 4 weeks' treatment with 10 mg. The erectile function domain score increased from 12.2 at baseline to 25.0 at Last Observation Carried Forward (LOCF) in the former group and from 10.3 to 22.5 in the latter group, respectively. Importantly, there was a 5.0 point increase in erectile function domain score after up-titration in the latter group. Drug-related adverse events were observed in 22% of patients including hot flushes (9%) and headache (6%), but these were transient and mild in intensity. Serious adverse events and adverse events leading to discontinuation of the study drug were not reported.

CONCLUSIONS

Vardenafil 10 and 20 mg was well tolerated and improved erectile function in patients with SCI. Of interest, erectile function was further improved by 20 mg in patients who were not sufficiently treated with 10 mg.

Vardenafil 20-mg demonstrated superior efficacy to 10-mg in Japanese men with diabetes mellitus suffering from erectile dysfunction

AIM

Vardenafil is a highly selective and potent phosphodiesterase type-5 inhibitor for the treatment of erectile dysfunction (ED). The efficacy of vardenafil has been demonstrated in a broad range of ED populations, but has not yet been assessed in Japanese patients with diabetes mellitus (DM), although DM is frequently associated with difficult-to-treat ED. This is the first study to investigate whether high-dose vardenafil (20 mg) can demonstrate superior efficacy to the usual dose (10 mg) in this subpopulation in Japan.

METHODS

The study was a randomized, placebo-controlled, double-blind, multi-centre, parallel group comparison 12-week study. Following 4 weeks observation period, 778 patients aged 26-64 years old with ED and DM (HbA1c >12% at screening was excluded) both of more than 3 years duration were randomly allocated to one of the three groups, vardenafil 10 mg, 20 mg, or placebo (randomization ratio 3:3:1). Erectile function (EF) domain score of the International Index of Erectile Function was estimated as the primary efficacy parameter.

RESULTS

Vardenafil 10 and 20 mg both significantly improved the EF domain score from 13.6 and 13.9 at baseline to 21.8 and 22.9 at last observation carried forward (LOCF), respectively, compared to placebo (13.7 at baseline to 16.3 at LOCF; p<0.0001). In addition, vardenafil 20 mg demonstrated superior efficacy to 10 mg (p<0.05), and the difference was more evident in severe ED patients (baseline EF domain score <11). The safety profile was comparable between these two doses (drug-related adverse events: 6.6, 22.0 and 24.2% in placebo, vardenafil 10 mg, and 20 mg arms, respectively). The most common adverse events were hot flush, headache and nasal congestion, which were mild in intensity and transient, and are known to be common to PDE5 inhibitors.

CONCLUSION

In Japanese men with DM and ED, vardenafil 10 mg and 20 mg were effective in improving erectile function with comparable safety profiles. Vardenafil 20 mg demonstrated superior efficacy compared with 10 mg, suggesting incremental clinical benefit in using the higher dose in this difficult-to-treat population.

EAU Guidelines on erectile dysfunction: an update

The introduction of new oral therapies has completely changed the diagnostic and therapeutic approach to erectile dysfunction. A panel of experts in this field has developed guidelines for the clinical evaluation and treatment based on the review of available scientific information.

Comparison of different heterocyclic scaffolds as substrate analog PDE5 inhibitors

Several different heterocyclic systems were compared as PDE5 inhibitor scaffolds. In addition to the known 3H-imidazo[5,1-f][1,2,4]triazin-4-ones and pyrazolopyrimidinones, isomeric imidazo[1,5-a][1,3,5]triazin-4(3H)-ones were also shown to be potent and selective PDE inhibitor scaffolds with in vivo activity. SAR trends were elucidated for sulfonamide derivatives with generality across different scaffolds.

In vivo and in vitro response of corpus cavernosum to phosphodiesterase-5 inhibition in the hypercholesterolaemic rabbit

OBJECTIVE

To investigate the effects of hypercholesterolaemia (HC) on rabbit corpus cavernosa in vivo and in vitro, and evaluate the efficacy of vardenafil and sildenafil in normal and HC rabbits, as the phosphodiesterase-5 (PDE-5) inhibitors vardenafil and sildenafil are widely used for treating erectile dysfunction (ED) and most organic causes of ED are associated with vascular risk factors like HC.

MATERIALS AND METHODS

Male New Zealand White rabbits were randomly divided into two groups; 11 HC rabbits were fed a 2% cholesterol diet, and 12 age-matched control rabbits received a regular diet. After 12-14 weeks, erectile responses to intravenous sodium nitroprusside (SNP) and PDE-5 inhibitors were evaluated for 2 h in conscious rabbits. Penile length was measured and the area under the curve calculated. Relaxant responses of corpus cavernosal strips to electrical-field stimulation (EFS) were measured before and after exposure to PDE-5 inhibitors and the nitric oxide synthase inhibitor N'-nitro-L-arginine methyl ester.

RESULTS

HC rabbits had a lower erectile response to SNP than controls; in both control and HC rabbits there was a greater erectile response after simultaneous exposure to SNP and vardenafil, or SNP and sildenafil. However, the responses of the HC rabbits were still significantly less than those of the controls. Corpora from control rabbits responded to EFS with greater relaxations at all frequencies, except 1 Hz. Corpora from both HC and control rabbits had greater responses to EFS after exposure to vardenafil and sildenafil; N'-nitro-L-arginine methyl ester diminished the response to EFS.

CONCLUSIONS

There was a significantly lower in vivo and in vitro erectile response in HC rabbits than in controls; erectile function measured in conscious rabbits can be used to assess quantitatively the efficacy of different agents, e.g. sildenafil and vardenafil, in pathological animals. In addition, both agents improve in vitro responses of erectile tissue from HC rabbits to EFS.

Vardenafil (Levitra) for erectile dysfunction: a systematic review and meta-analysis of clinical trial reports

Trials of the efficacy and safety of vardenafil in the treatment of male erectile dysfunction (ED) were meta-analysed. All available databases were searched (January 1, 2001-November 30, 2003). Trials were eligible if they included men with ED, compared vardenafil with placebo, were randomized, were at least of 12 weeks duration, and assessed clinically relevant outcomes. Two reviewers independently evaluated study quality and extracted data in a standardized fashion. Nine trials (6809 men) met the inclusion criteria. In results pooled from seven fixed-dose trials, vardenafil increases the Erectile Function domain of the International Index of Erectile Function questionnaire by 6.18 units (weighted mean difference (WMD)). Vardenafil also increases the percentage of erections firm enough to allow vaginal penetration (WMD: 26) and the percentage of sexual attempts that were successful per participant (WMD: 29.8). The percentage of men agreeing with the statement that 'the treatment they have been taking over the past 4 weeks improved their erections', is also in favour of vardenafil (relative risk (RR): 3). These efficacy variables appeared greater at higher doses, although there are no significant differences between 10 and 20 mg dose. The same results were extracted for the two flexible 'as needed' dosing trials. Discontinuations are greater at the vardenafil groups compared to placebo (RR: 2.25). Specific adverse events with vardenafil included flushing, dyspepsia, headache, and rhinitis. Vardenafil was not significantly associated with serious cardiovascular events or death. Vardenafil, in all treatment regimens, shows to possess superior efficacy to placebo in the treatment of patients with erectile dysfunction. More data is needed on patients' subgroups.

DA-8159 has erectile potentials much longer than the plasma half-life in a conscious rabbit model

DA-8159 is a pyrazolopyrimidinone derivative which is a potent and selective phosphodiesterase type 5 inhibitor. The efficacy of oral DA-8159 has been demonstrated in conscious and spinalized rabbits by its enhancement of nitric oxide-induced erections. The aim of this study was to investigate the time dependency of this efficacy on its plasma concentration in rabbits. DA-8159 was given orally to normal rabbits at a dose of 10 or 30 mg/kg in order to determine its pharmacokinetic parameters. After then, to investigate the relationship between penile erectile activity and plasma half-life, a dose of 10 mg/kg DA-8159 was administered and the erectile response was examined in a time-course manner by measuring the length of the uncovered penile mucosa after the intravenous administration of sodium nitroprusside, which was administered 1, 3, 6, 8, 24 hours after administering DA-8159. DA-8159 was absorbed rapidly with a Tmax of 0.6 hours in 30 mg/kg and 1.0 hour in the 10 mg/kg group, and T1/2 of 1.23 hours in 30 mg/kg and 1.17 hours in 10 mg/kg, respectively. DA-8159 was not detected in the blood plasma 3 hours (10 mg/kg) or 6 hours (30 mg/kg) after administration. In an erection test, DA-8159 alone (10 mg/kg) induced a penile erection for approximately 2 hours but there was no significant erection thereafter. Although the DA-8159-induced penile erection disappeared, an intravenous injection of sodium nitroprusside significantly induced a penile erection for 6 hours, when the plasma drug concentration was below the detection limit and a no longer visible erection was noted. These results demonstrate that DA-8159 is absorbed and rapidly cleared in rabbits. In addition, it can enhance a sodium nitroprusside-induced penile erection even after 6 hours, which is approximately five times longer than the plasma half-life in the rabbits. These results suggest that DA-8159 may have an erectile potential for much longer than its measured half-life.

Safety and efficacy of vardenafil in patients with erectile dysfunction: Result of a bridging study in Japan

AIM

Vardenafil is a selective and highly potent phosphodiesterase type 5 (PDE5) inhibitor for the treatment of erectile dysfunction (ED), with improved selectivity for PDE5 and demonstrated efficacy for improving sexual function in men with ED. The current study investigated the safety and efficacy of this new PDE5 inhibitor in Japanese men with ED.

METHODS

This was a prospective, double blind, randomized clinical trial designed to evaluate the efficacy and safety of vardenafil. Following a 4-week treatment-free observation period, 283 eligible patients were randomized to 12 weeks treatment with vardenafil 5 mg, 10 mg, 20 mg, or placebo. Primary efficacy responses were assessed using the scores of Q3 and Q4 of the international index of erectile function (IIEF).

RESULTS

All three vardenafil doses showed significantly better improvement than the placebo group in Q3 and Q4 scores of the IIEF questionnaire, either at 12 weeks or at the 'last observation carried forward' (LOCF, P < 0.0001). Q3 scores were improved to 4.06 with vardenafil 5 mg, 4.53 with vardenafil 10 mg, and 4.64 with vardenafil 20 mg, versus 3.17 with placebo. Comparable scores for Q4 were 3.47, 4.15 and 4.31 versus 2.31 for placebo. Up to 86% of patients achieved improved erections as assessed by the global assessment question (GAQ). Reported adverse event rates were 35.3%, 45.3% and 54.5% with vardenafil 5 mg, 10 mg and 20 mg, respectively, versus 21.1% in the placebo group. No serious adverse drug reactions were reported. The most common treatment-emergent adverse events were transient headache, flushing and rhinitis, which were mostly mild.

CONCLUSION

Vardenafil is an effective and well-tolerated treatment for ED and provides improvement in key indices of erectile function among Japanese men with ED. The results of our trial show that up to nearly 90% of patients achieve improved erections with the administration of vardenafil.

Efficacy of Vardenafil in Men with Erectile Dysfunction: A Flexible-Dose Community Practice Study

OBJECTIVE

To determine the efficacy and tolerability of flexible dosing with vardenafil in a broad population of men with erectile dysfunction (ED).

METHODS

10-week, open-label, flexible-dose study starting with vardenafil 10 mg, titrating to 5 mg or 20 mg at weeks 2 and 6 based on efficacy and tolerability, set in 78 community practice centers in Germany and France. Participants comprised 398 men aged > or =18 years with ED. Main outcome measures were self-reported improvement in erections according to a Global Assessment Question (GAQ), diary questions from the Sexual Encounter Profile (SEP2 and SEP3), and the erectile function domain score from the International Index of Erectile Function (IIEF) questionnaire.

RESULTS

In a last observation carried forward (LOCF) analysis, a total of 92% (336/366) of men with ED reported an improvement of erections according to the GAQ. Per-patient success rates for penetration (SEP2) and maintenance (SEP3) of erection for intercourse were 89% (348/390) and 78% (303/390), respectively. Mean erectile function domain scores increased from 13.9 at baseline to 25.9 at LOCF. Vardenafil was generally well tolerated; headache (6%, 25/398) and flushing (6%, 24/398) were the most frequent adverse events.

CONCLUSIONS

In this community practice setting, vardenafil was shown to be a highly effective and generally well-tolerated treatment for men with ED when dosing was titrated by the physician to individual patient requirements.

Vardenafil: a review of its use in erectile dysfunction

Vardenafil (Levitra) is a potent and highly selective oral phosphodiesterase type 5 (PDE5) inhibitor. Vardenafil improved erectile function in men with mild to severe erectile dysfunction (ED) of varying aetiology in two randomised, double-blind, multicentre, fixed-dose studies of 12 or 26 weeks' duration. Men receiving vardenafil 10 or 20 mg had significantly greater improvements in International Index of Erectile Function (IIEF) questionnaire erectile function domain scores than placebo recipients. Moreover, improvements in penetration and maintenance of erection (assessed using IIEF or Sexual Encounter Profile [SEP] questions) were significantly greater with vardenafil 5-20 mg than with placebo. Improvements in IIEF intercourse satisfaction and orgasmic function domain scores were significantly greater with vardenafil 10 or 20 mg than with placebo and the proportion of patients with a positive response to a Global Assessment Question (GAQ) concerning improvement in erections after 12 or 26 weeks' therapy was significantly higher with vardenafil 5-20 mg than with placebo. Vardenafil improved erectile function in men with ED associated with diabetes mellitus or ED following unilateral or bilateral nerve-sparing radical retropubic prostatectomy in two randomised, double-blind, multicentre, fixed-dose, 3-month studies. In both studies, improvements from baseline in the erectile function domain score of the IIEF and in positive responses to SEP questions were significantly greater with vardenafil 10 or 20 mg than with placebo. In addition, a significantly higher proportion of vardenafil 10 or 20 mg recipients than placebo recipients had positive GAQ responses. Vardenafil was generally well tolerated in men with ED; treatment-emergent adverse events were of mild to moderate intensity and transient in nature. The most commonly reported adverse events (typical of those seen with PDE5 inhibitors) in vardenafil 5-20 mg recipients included headache, flushing, rhinitis, dyspepsia and sinusitis. There were no reports of abnormal colour vision in men with ED taking vardenafil at clinically recommended doses (5-20 mg).

CONCLUSION

Vardenafil is a potent and highly selective oral PDE5 inhibitor. It is effective and generally well tolerated in men with mild to severe ED of varying aetiology, as well as in men with ED associated with diabetes mellitus or ED after radical prostatectomy. Vardenafil should be considered a first-line treatment option in men with ED who are suitable candidates for oral PDE5 inhibitor therapy.

Vardenafil Treatment for Erectile Dysfunction

OBJECTIVE:

To review the pharmacology, pharmacokinetics, clinical trial data, and adverse effects of vardenafil in the treatment of erectile dysfunction (ED).

DATA SOURCES:

Literature searches were performed using the MEDLINE database (referenced citations through December 2002), and the references of all identified articles were scanned for additional publications of interest. Unpublished information provided by the manufacturer and proceedings of professional meetings were also evaluated.

STUDY SELECTION AND DATA EXTRACTION:

All available studies were utilized to obtain information regarding pharmacology. Only human studies were used to gather pharmacokinetic, drug interaction, efficacy, and safety data.

DATA SYNTHESIS:

Vardenafil is a potent and selective inhibitor of the phosphodiesterase 5 (PDE5) enzyme that has been shown to improve erectile function in several populations of men with ED. Vardenafil has a rapid onset of action, is hepatically metabolized, and has a half-life of 4–6 hours. Clinical trials in otherwise healthy men with ED, men with ED and diabetes, and men with ED and a history of prostatectomy have demonstrated vardenafil's efficacy. Adverse effects appear to be relatively mild in intensity and dose dependent, with 22–61% of subjects reporting adverse effects.

CONCLUSIONS:

Vardenafil is a safe and effective oral agent for the treatment of ED. Its greater potency and PDE5 selectivity compared with sildenafil appear to confer a lower risk of vision-related adverse effects, but other clinical consequences of these differences are currently unclear.

Vardenafil: A new approach to the treatment of erectile dysfunction

Vardenafil is a phosphodiesterase type-5 (PDE-5) inhibitor developed as an oral therapy for erectile dysfunction (ED). Multiple phase 3 clinical trials have been completed and vardenafil is expected to launch worldwide in 2003. Two pivotal, randomized, double-blind, multicenter studies have evaluated the use of vardenafil in men with ED. Vardenafil improved the rate of achieving and maintaining an erection during sexual intercourse. Improvement also was noted in other aspects of sexual function, including confidence, orgasmic function, and overall satisfaction. Vardenafil produces clinically and statistically significant improvements in erectile function regardless of age, baseline severity, and etiology and is efficacious for the treatment of ED in diabetic and postprostatectomy patients. Vardenafil has a rapid onset of action and completion of successful sexual intercourse is possible for some patients 16 minutes after its administration. Twenty milligrams of vardenafil has sustained long-term efficacy by providing up to 92% of patients with improved erections during more than 2 years of treatment. Vardenafil is well tolerated, with an adverse event profile typical of the class of PDE-5 inhibitors. The most common adverse events were headache, flushing, rhinitis, and dyspepsia, which were mild or moderate and generally decreased with continued treatment. Vardenafil may be associated with transient reductions in blood pressure and commensurate increases in heart rate, with the overall incidence of cardiovascular-related adverse events similar to that of placebo.

Nitric oxide-releasing drugs

Pharmacological compounds that release nitric oxide (NO) have been useful tools for evaluating the broad role of NO in physiology and therapeutics. NO deficiency has been implicated in the genesis and evolution of several disease states. Both medical needs and commercial opportunities have fostered attempts to modulate NO in the human body for therapeutic gain. Strategies for NO modulation encompass antiinflammatory, sexual dysfunction, and cardiovascular indications. Apart from newly developed drugs, several commonly used cardiovascular drugs exert their beneficial action, at least in part, by modulating the NO pathway. This review discusses the fundamental pharmacological properties and mechanisms of action of NO-releasing drugs. Some of these compounds may enter in the clinical arena providing important therapeutic benefits in human diseases.

DA-8159, a new PDE5 Iihibitor, induces penile erection in conscious and acute spinal cord injured rabbits

OBJECTIVES

DA-8159 is a pyrazolopyrimidinone derivative showing potent and selective phosphodiesterase 5 (PDE5) inhibition. In the previous study, DA-8159 induced a dose-dependent increase in the intracavernous pressure (ICP) in anaesthetized dogs. The aim of this study was to investigate the effects of DA-8159 on penile erection in conscious and acute spinal cord injured (ASCI) rabbits.

METHODS

DA-8159 was given orally (0.3 to 10mg/kg) to normal rabbits and ASCI rabbits with a surgical transection of the spinal cord at the L2-L4 lumbar vertebra or ischemic-reperfusion. The erection was evaluated in a time-course manner by measuring the length of the uncovered penile mucosa in the absence or presence of intravenous sodium nitroprusside (SNP), a nitric oxide (NO) donor.

RESULTS

DA-8159 induced a dose-dependent penile erection in both the conscious and ASCI rabbits. The efficacy of DA-8159 was potentiated and the effective doses were significantly decreased by an intravenous injection of SNP. Potentiation of the effect by a nitric oxide donor implies that DA-8159 can enhance the erectile activity during sexual arousal.

CONCLUSION

These results demonstrate that DA-8159 may be a useful treatment option for erectile dysfunction in patients with or without a spinal cord injury, but further evaluation of the effects of DA-8159 on humans must be performed.

Vardenafil, a new phosphodiesterase type 5 inhibitor, in the treatment of erectile dysfunction in men with diabetes: a multicenter double-blind placebo-controlled fixed-dose study

OBJECTIVE

This study evaluated the efficacy and safety of vardenafil treatment for erectile dysfunction (ED) in men with diabetes.

RESEARCH DESIGN AND METHODS

In this prospective multicenter double-blind placebo-controlled fixed-dose parallel-group phase III trial, 452 patients with diabetes (type 1 or type 2) and ED were randomized to take 10 or 20 mg vardenafil or placebo as needed for 12 weeks. Efficacy responses were assessed by International Index of Erectile Function domain scores, rates of vaginal penetration and successful intercourse, and a global assessment question (GAQ) about erection improvement during the previous 4 weeks.

RESULTS

After 12 weeks of treatment, a dose-dependent (P = 0.02) improvement in erections was noted for the GAQ, with 57 and 72% of men taking 10 mg or 20 mg vardenafil, respectively, reporting improved erections, in contrast to 13% after taking placebo (P < 0.0001). For the erectile function domain, dose-dependent (P = 0.03) final scores for the 10- and 20-mg dose were 17.1 and 19.0 compared with 12.6 for placebo (P < 0.0001). Both vardenafil doses significantly enhanced the rates of successful penetration (P < 0.0001) and successful intercourse (P < 0.0001) compared with placebo. Vardenafil treatment was effective in increasing intercourse success rates at all levels of baseline ED severity, at each level of plasma HbA(1c), and for type 1 and 2 diabetes. Treatment-emergent adverse events were primarily mild to moderate headache (<or=13%), flushing (<or=10%), and rhinitis (<or=10%).

CONCLUSIONS

Vardenafil statistically improved erectile function and was generally well tolerated in these diabetic patients with ED.

BAY 41-2272: a stimulator of soluble guanylyl cyclase induces nitric oxide-dependent penile erection in vivo

OBJECTIVES

To determine the effectiveness of BAY 41-2272 on penile erections in an in vivo rabbit model. The nitric oxide (NO)-dependent increase of intracellular cyclic guanosine monophosphate (cGMP) by cGMP-phosphodiesterase (PDE5) inhibition has been shown to be an effective mechanism in the treatment of erectile dysfunction. Direct, NO-independent stimulation of soluble guanylyl cyclase should also lead to elevated cGMP levels in tissues and could be an attractive alternative therapeutic option for the treatment of erectile dysfunction. BAY 41-2272 is a novel non-NO-based direct stimulator of soluble guanylyl cyclase that activates purified enzyme in a synergistic fashion with NO.

METHODS

BAY 41-2272 was administered to conscious rabbits intravenously (IV) and orally (PO). Erection was assessed in a time-dependent manner by measuring the length of the uncovered penile mucosa. Erections were evaluated in the absence and presence of NO (with intravenous sodium nitroprusside [SNP] as the NO donor).

RESULTS

BAY 41-2272 only induced weak penile erections in conscious rabbits after IV (1 mg/kg) and PO (10 mg/kg) administration in the absence of an NO donor. However, the efficacy of BAY 41-2272 was potentiated by the simultaneous administration of SNP. Through simultaneous SNP administration, the effective doses of BAY 41-2272 were reduced significantly (minimal effective dose 0.1 mg/kg IV and 1 mg/kg PO).

CONCLUSIONS

The results of this study clearly demonstrated the effect of BAY 41-2272 on penile erection in the conscious rabbit model after PO and IV administration. The time-course and onset of erection was concurrent with the stimulation by exogenous NO (SNP), suggesting that this new pharmacologic mechanism of soluble guanylyl cyclase stimulation could be used in the treatment of erectile dysfunction. Because the effect is increased by SNP, it can be expected that BAY 41-2272 would have enhanced activity during sexual arousal, when NO is produced endogenously.

Vardenafil

Vardenafil hydrochloride is a potent and highly selective inhibitor of phosphodiesterase Type 5 that increases blood flow to the penis during sexual stimulation and helps restore the ability to achieve and sustain an erection in men with erectile dysfunction. Vardenafil was developed specifically to be an effective and safe oral medication for the treatment of erectile dysfunction, with potential advances over existing therapies. This review summarises key findings during the rapid and aggressive development of this compound, from in vitro assays to Phase III trials with both broad and special populations. Emphasis is placed on the presentation of data that demonstrates the clinical effectiveness and safety of this agent which is anticipated to be available in 2003.