A randomised, placebo-controlled study to assess the efficacy of twice-daily vardenafil in the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia. Eur Urol. 2008;53:1236-1244. [PMID: 18281145 DOI: 10.1016/j.eururo.2008.01.075]

Chronic low dosing of phosphodiesterase type 5 inhibitor for erectile dysfunction

Oral phosphodiesterase type 5 (PDE5) inhibitors have provided non-invasive, effective, and well-tolerated treatments for patients with erectile dysfunction (ED). However, many patients with ED are unresponsive to 'on-demand' PDE5 inhibitors. In addition, the lack of spontaneity and naturalness of the on-demand regimen could be a reason for decreased compliance with PDE5 inhibitors. Recently, tadalafil and udenafil were approved for low-dose daily administration for the treatment of ED. Since the introduction of the concept of daily administration of PDE5 inhibitors, several reports have supported the potential benefits of this therapy for disease modification, improvement of the treatment response in difficult-to-treat populations, spontaneity, and safety, although further research is needed to better address these hypotheses. In this article, we reviewed the daily administration of PDE5 inhibitors in terms of pharmacokinetics, safety, efficacy, and distinct features.

Les inhibiteurs de la phosphodiestérase de type 5 : une révolution dans le traitement des symptômes du bas appareil urinaire?

Contexte

L’incidence des symptômes du bas appareil urinaire (SBAU) liés à une hypertrophie bénigne de prostate (HBP) augmente avec l’âge puisqu’ils touchent 50 % des patients âgés de plus de 50 ans et 90 % de ceux âgés de plus de 80 ans. La prévalence et la sévérité de la dysfonction érectile (DE) augmentent également avec l’âge. Sa prévalence est évaluée à 31,6 % dans une population générale d’adultes âgés de plus de 40 ans. Les SBAU comme la DE altèrent de façon significative la qualité de vie (QdV) des patients et de leur partenaire. Plusieurs études ont montré que les SBAU constituent un facteur de risque de DE indépendant de l’âge et des autres comorbidités. La sévérité des SBAU est corrélée à celle de la DE. Les hypothèses physiopathologiques pour expliquer le lien entre SBAU et DE sont : une augmentation du tonus sympathique, une altération du système NO/cGMP, une altération du système rho-kinase et une athéromatose pelvienne.

Objectif

Évaluer les résultats et comprendre le mécanisme d’action de l’administration d’un inhibiteur de la phosphodiestérase de type 5 (IPDE 5) sur les SBAU liés à une HBP.

Matériels et méthodes

Une revue de la littérature a été réalisée à partir des articles originaux et des articles de synthèse déjà disponibles, sélectionnés par le moteur de recherche Pubmed de la National Library of Medecine. Les mots clés utilisés pour cette recherche ont été : benign prostatic hyperplasia; cyclic nucleotide phosphodiesterase type 5; LUTS; erectile dysfunction.

Résultats

Cette revue de la littérature montre que l’administration d’un inhibiteur de la phosphodiestérase de type 5 améliore les SBAU de manière significative dans 12 essais cliniques randomisés, avec un bénéfice également sur la DE et l’absence d’effets secondaires indésirables graves rapportés.

Conclusion

Le traitement des SBAU par les IPDEs 5 semble très prometteur, même s’il ne dispose pas d’une AMM dans cette indication en France. Récemment, le tadalafil à la posologie de 5 mg a été approuvé aux États-Unis par la FDA dans les troubles mictionnels liés à l’HBP, avec ou sans DE.

Improving BPH symptoms and sexual dysfunctions with a saw palmetto preparation? Results from a pilot trial

In elderly men, benign prostatic hyperplasia (BPH) is a major risk factor for sexual dysfunctions (SDys). Additionally, the standard treatments for BPH symptoms, alpha blockers and 5-alpha-reductase inhibitors, cause SDys themselves. Preparations from saw palmetto berries are an efficacious and well-tolerated symptomatic treatment for mild to moderate BPH and have traditionally been used to treat SDys. We conducted an open multicentric clinical pilot trial to investigate whether the saw palmetto berry preparation Prostasan® influenced BPH symptoms and SDys. Eighty-two patients participated in the 8-week trial, taking one capsule of 320 mg saw palmetto extract daily. At the end of the treatment, the International Prostate Symptom Score was reduced from 14.4 ± 4.7 to 6.9 ± 5.2 (p < 0.0001); SDys measured with the brief Sexual Function Inventory improved from 22.4 ± 7.2 to 31.4 ± 9.2 (p < 0.0001), and the Urolife BPH QoL-9 sex total improved from 137.3 ± 47.9 to 195.0 ± 56.3 (p < 0.0001). Investigators' and patients' assessments confirmed the good efficacy, and treatment was very well tolerated and accepted by the patients. Correlation analyses confirmed the relationship between improved BPH symptoms and reduced SDys. This was the first trial with saw palmetto to show improvement in BPH symptoms and SDys as well. [Corrections made here after initial online publication.]

A randomized, placebo-controlled study to assess safety and efficacy of vardenafil 10 mg and tamsulosin 0.4 mg vs. tamsulosin 0.4 mg alone in the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia

INTRODUCTION

Safety and efficacy of tamsulosin and vardenafil are well established: however, there is no report regarding combined therapy with these drugs for lower urinary tract symptoms (LUTSs) secondary to benign prostatic hyperplasia (BPH).

AIM

To compare the safety and efficacy of tamsulosin 0.4 mg/day vs. tamsulosin 0.4 mg/day plus vardenafil 10 mg/day in patients with LUTS/BPH in a randomized trial with 12-week follow-up.

METHODS

We conducted a randomized, double-blind, placebo-controlled study on 60 men with persistent storage LUTS after 2-week run-in with tamsulosin.

MAIN OUTCOME MEASURES

International Prostate Symptom Score (IPSS), IPSS-bother, International Index of Erectile Function, Version 5 (IIEF-5) and Over Active Bladder questionnaire (OAB-q) scores, uroflowmetry data (Qmax, Qave), and postvoiding residual urine were recorded after run-in (baseline), and 2 and 12 weeks after treatment. Differences between vardenafil and placebo at different times were calculated with unpaired samples t-test. Between-group differences in change from baseline to 2 and 12 weeks were evaluated with analysis of variance.

RESULTS

We found a between-group significant difference from baseline to 12 weeks in the following: (i) Qmax (placebo: +0.07, vardenafil: +2.56, P = 0.034); (ii) Qave (placebo: -0.15, vardenafil: +1.02, P = 0.031); (iii) irritative-IPSS subscores (placebo: -1.67, vardenafil: -3.11, P = 0.039); and (iv) IIEF (placebo: +0.06, vardenafil: +2.61, P = 0.030). No patient reported any serious (grade ≥ 2) adverse event (AE). There were no differences in the incidence of common, treatment-related AEs between men undergoing combined therapy or tamsulosin alone.

CONCLUSIONS

The combination of tamsulosin and vardenafil for 12 weeks was well tolerated and more effective to improve both LUTS and erectile function, as compared with tamsulosin alone. Further studies are needed to assess the role of combined therapy of phosphodiesterase type 5 inhibitors and alpha blockers in treating LUTS/BPH.

Benign prostatic hyperplasia: from bench to clinic

Benign prostatic hyperplasia (BPH) is a prevalent disease, especially in old men, and often results in lower urinary tract symptoms (LUTS). This chronic disease has important care implications and financial risks to the health care system. LUTS are caused not only by mechanical prostatic obstruction but also by the dynamic component of obstruction. The exact etiology of BPH and its consequences, benign prostatic enlargement and benign prostatic obstruction, are not identified. Various theories concerning the causes of benign prostate enlargement and LUTS, such as metabolic syndrome, inflammation, growth factors, androgen receptor, epithelial-stromal interaction, and lifestyle, are discussed. Incomplete overlap of prostatic enlargement with symptoms and obstruction encourages focus on symptoms rather than prostate enlargement and the shifting from surgery to medicine as the treatment of BPH. Several alpha antagonists, including alfuzosin, doxazosin, tamsulosin, and terazosin, have shown excellent efficacy without severe adverse effects. In addition, new alpha antagonists, silodosin and naftopidil, and phosphodiesterase 5 inhibitors are emerging as BPH treatments. In surgical treatment, laser surgery such as photoselective vaporization of the prostate and holmium laser prostatectomy have been introduced to reduce complications and are used as alternatives to transurethral resection of the prostate (TURP) and open prostatectomy. The status of TURP as the gold standard treatment of BPH is still evolving. We review several preclinical and clinical studies about the etiology of BPH and treatment options.

A systematic review and meta-analysis on the use of phosphodiesterase 5 inhibitors alone or in combination with α-blockers for lower urinary tract symptoms due to benign prostatic hyperplasia

CONTEXT

Several randomized controlled trials (RCTs) on phosphodiesterase type 5 inhibitors (PDE5-Is) have showed significant improvements in both lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) in men affected by one or both conditions, without a significant increase in adverse events. However, the results are inconsistent.

OBJECTIVE

Perform a systematic review and meta-analysis of available prospective and cross-sectional studies on the use of PDE5-Is alone or in combination with α1-adrenergic blockers in patients with LUTS/benign prostatic hyperplasia (BPH).

EVIDENCE ACQUISITION

A systematic search was performed using the Medline, Embase, and Cochrane Library databases through September 2011 including the combination of the following terms: LUTS, BPH, PDE5-Is, sildenafil, tadalafil, vardenafil, udenafil, α-blockers, and α1-adrenergic blocker. The meta-analysis was conducted according to the guidelines for observational studies in epidemiology.

EVIDENCE SYNTHESIS

Of 107 retrieved articles, 12 were included in the present meta-analysis: 7 on PDE5-Is versus placebo, with 3214 men, and 5 on the combination of PDE5-Is with α1-adrenergic blockers versus α1-adrenergic blockers alone, with 216 men. Median follow-up of all RCTs was 12 wk. Combining the results of those trials, the use of PDE5-Is alone was associated with a significant improvement of the International Index of Erectile Function (IIEF) score (+5.5; p<0.0001) and International Prostate Symptom Score (IPSS) (-2.8; p<0.0001) but not the maximum flow rate (Q(max)) (-0.00; p=not significant) at the end of the study as compared with placebo. The association of PDE5-Is and α1-adrenergic blockers improved the IIEF score (+3.6; p<0.0001), IPSS score (-1.8; p = 0.05), and Q(max) (+1.5; p<0.0001) at the end of the study as compared with α-blockers alone.

CONCLUSIONS

The meta-analysis of the available cross-sectional data suggests that PDE5-Is can significantly improve LUTS and erectile function in men with BPH. PDE5-Is seem to be a promising treatment option for patients with LUTS secondary to BPH with or without ED.

An overview of prostate diseases and their characteristics specific to Asian men

In this paper, we reviewed the features of common prostate diseases, such as benign prostatic hyperplasia (BPH), prostate cancer (PCa) and chronic prostatitis (CP) that are specific to Asian men. Compared to the Westerners, Asians exhibit particular characteristics of prostate diseases. Through summarizing the epidemiology, symptomatology, diagnostics and therapeutics of these diseases, we find that Asians have a lower incidence of PCa than whites, but the incidences of BPH and CP are similar. Asian men with CP often suffer from fewer disease sites, but have a higher frequency of pain during urination rather than after sexual climax. Prostate-specific antigen (PSA) is a widely used marker for the diagnosis of PCa in both Asian and Western countries. Although the PSA level may be lower in Asians, the threshold used is based on whites. After reviewing the treatments available for these diseases, we did not find a fundamental difference between Asians and whites. Furthermore, the selection for the most appropriate treatment based on the individual needs of patients remains a challenge to urologists in Asia. After considering the traits of prostate diseases that are specific to Asian men, we hope to pave the way for the development of specific diagnostic and therapeutic strategies targeted specifically to Asian men.

Testosterone regulates smooth muscle contractile pathways in the rat prostate: emphasis on PDE5 signaling

Testosterone (T) plays a permissive role in the development of benign prostatic hyperplasia (BPH), and phosphodiesterase 5 inhibitors (PDE5is) have been found to be effective for BPH and lower urinary tract symptoms (LUTS) in clinical trials. This study investigated the effect of T on smooth muscle (SM) contractile and regulatory signaling pathways, including PDE5 expression and functional activity in prostate in male rats (sham-operated, surgically castrated, and castrated with T supplementation). In vitro organ bath studies, real-time RT-PCR, Western blot analysis, and immunohistochemistry were performed. Castration heavily attenuated contractility, including sensitivity to phenylephrine with SM myosin immunostaining revealing a disrupted SM cell arrangement in the stroma. PDE5 was immunolocalized exclusively in the prostate stroma, and orchiectomy signficantly reduced PDE5 immunopositivity, mRNA, and protein expression, along with nNOS and ROKβ mRNA, whereas it increased eNOS plus α(1a) and α(1b) adrenoreceptor expression in castrated animals. The PDE5i zaprinast significantly increased prostate strip relaxation to the nitric oxide donor sodium nitroprusside (SNP) in control but not castrated rats. But SNP alone was more effective on castrated rats, comparable with sham treated with SNP plus zaprinast. T supplementation prevented or restored all above changes, including SNP and zaprinast in vitro responsiveness. In conclusion, our data show that T positively regulates PDE5 expression and functional activities in prostate, and T ablation not only suppresses prostate size but also reduces prostatic SM contractility, with several potential SM contraction/relaxation pathways implicated. Zaprinast findings strongly suggest a major role for PDE5/cGMP in this signaling cascade. PDE5 inhibition may represent a novel mechanism for treatment of BPH.

Phosphodiesterase (PDE) inhibitors in the treatment of lower urinary tract dysfunction

Several disorders of the human upper and lower urinary tract, such as urinary stone disease, lower urinary tract symptoms (LUTS) due to benign prostatic hyperplasia (BPH) and detrusor overactivity, can be therapeutically addressed by influencing the function of the smooth musculature of the ureter, prostate or urinary bladder, respectively. In order to ensure a drug effect without significant adverse events, a certain degree of tissue selectivity is mandatory. The treatment of said conditions aims to focus on orally available drugs acting via intracellular signalling pathways. Specifically, the cyclic nucleotide monophosphate cyclic GMP represents an important mediator in the control of the outflow region (bladder, urethra). The use of phosphodiesterase (PDE) inhibitors, such as sildenafil, tadalafil, vardenafil, avanafil or udenafil, known to restrain the degradation of the second messenger cyclic GMP, offers great opportunities in the treatment of lower urinary tract dysfunction. PDE inhibitors are regarded as efficacious, have a rapid onset of action and favourable effect-to-side-effect ratio. The role of PDE5 inhibitors in the treatment of BPH/LUTS and the overactive bladder has already been addressed in randomized, double-blind, placebo-controlled trials, as well as preliminary open-label studies enrolling either several hundreds or only 20 patients. The purpose of this review is to focus on the potential use and clinical significance of PDE inhibitors in the treatment of storage and voiding dysfunctions of the lower urinary tract. The strategy of modulating the activity of PDE isoenzymes might represent a novel approach in patients with lower urinary tract dysfunction (LUTD).

Emerging treatment options for benign prostatic obstruction

Benign prostatic obstruction (BPO) affects an increasing number of men with age. It can cause troublesome lower urinary tract symptoms, can have a negative impact on quality of life, and may be associated with significant morbidity. Currently available medication and surgical treatments are limited by adverse events, invasiveness, and patient compliance. This has driven research into the pathogenesis of benign prostatic hyperplasia and led to the development of novel pharmacological agents and minimally invasive therapeutic interventions. This review highlights emerging treatment options for BPO.

Drugs and future candidates

Antimuscarinic drugs are still first-line treatment for the symptoms of overactive bladder (OAB) and are associated with good initial response rates. Adverse effects and decreasing efficacy over the longer term do, however, limit their overall effectiveness. As such, alternatives to antimuscarinics are needed. The recognition of the functional contribution of the urothelium, the spontaneous myocyte activity during bladder filling, and the diversity of nerve transmitters involved in the symptoms of the OAB has sparked interest in pharmacologic manipulation of both peripheral and central pathophysiology. Some of the treatments currently under investigation are discussed in this review.

Novel drug targets for the pharmacotherapy of benign prostatic hyperplasia (BPH)

Benign prostatic hyperplasia (BPH) is the major cause of lower urinary tract symptoms in men aged 50 or older. Symptoms are not normally life threatening, but often drastically affect the quality of life. The number of men seeking treatment for BPH is expected to grow in the next few years as a result of the ageing male population. Estimates of annual pharmaceutical sales of BPH therapies range from $US 3 to 10 billion, yet this market is dominated by two drug classes. Current drugs are only effective in treating mild to moderate symptoms, yet despite this, no emerging contenders appear to be on the horizon. This is remarkable given the increasing number of patients with severe symptoms who are required to undergo invasive and unpleasant surgery. This review provides a brief background on prostate function and the pathophysiology of BPH, followed by a brief description of BPH epidemiology, the burden it places on society, and the current surgical and pharmaceutical therapies. The recent literature on emerging contenders to current therapies and novel drug targets is then reviewed, focusing on drug targets which are able to relax prostatic smooth muscle in a similar way to the α(1) -adrenoceptor antagonists, as this appears to be the most effective mechanism of action. Other mechanisms which may be of benefit are also discussed. It is concluded that recent basic research has revealed a number of novel drug targets such as muscarinic receptor or P2X-purinoceptor antagonists, which have the potential to produce more effective and safer drug treatments.

Tadalafil 2.5 or 5 mg administered once daily for 12 weeks in men with both erectile dysfunction and signs and symptoms of benign prostatic hyperplasia: results of a randomized, placebo-controlled, double-blind study

INTRODUCTION

Erectile dysfunction (ED) and lower urinary tract symptoms suggestive of benign prostatic hyperplasia (BPH-LUTS) commonly coexist in aging men. Tadalafil, a phosphodiesterase type 5 inhibitor approved for treating ED, is currently being evaluated for treating BPH-LUTS.

AIMS

This multinational Phase 3 study assessed effects of tadalafil 2.5 or 5 mg once daily on ED and BPH-LUTS in men with both conditions during 12 weeks of double-blinded therapy.

METHODS

Men were ≥ 45 years old, sexually active, and experiencing ED for ≥ 3 months and BPH-LUTS for >6 months. Randomization (baseline) followed a 4-week placebo lead-in; changes from baseline were assessed via analysis of covariance and compared to placebo. A gatekeeping procedure controlled for multiple comparisons of co-primary and key secondary measures at end point (last post-baseline observation).

MAIN OUTCOME MEASURES

The co-primary measures were the International Index of Erectile Function-erectile function (IIEF-EF) domain and International Prostate Symptom Score (IPSS) score; key secondary measures were the Sexual Encounter Profile Question 3 (SEP Q3) and BPH Impact Index (BII). Treatment-emergent adverse events, serious adverse events, orthostatic vital signs, clinical laboratory and uroflowmetry parameters, and postvoid residual volume were assessed.

RESULTS

Tadalafil 2.5 mg (N = 198) and 5 mg (N = 208) significantly improved IIEF-EF domain scores (both P < 0.001) vs. placebo (N = 200) at end point. For IPSS, improvements were significant with tadalafil 5 mg (P < 0.001), but not 2.5 mg, for observations from 2 weeks through end point (least-squares mean ± standard error change from baseline at end point, placebo -3.8 ± 0.5, tadalafil 2.5 mg -4.6 ± 0.4, and 5 mg -6.1 ± 0.4). Tadalafil 5 mg significantly improved SEP Q3 and BII (P < 0.001). Overall, tadalafil was well tolerated with no clinically adverse changes in orthostatic vital signs or uroflowmetry parameters.

CONCLUSIONS

Tadalafil 5 mg significantly improved both ED and BPH-related outcomes through 12 weeks and was well tolerated.

Current benign prostatic hyperplasia treatment: impact on sexual function and management of related sexual adverse events

Benign prostatic hyperplasia (BPH) is a common disease in older men that can lead to lower urinary tract symptoms (LUTS). Male sexual dysfunction is also an age-related condition. Epidemiological studies have confirmed an association between BPH/LUTS and sexual dysfunction in ageing men that is independent of the effects of age, other co-morbidities and lifestyle factors. Proposed pathophysiological mechanisms for BPH/LUTS-associated sexual dysfunction include the nitric oxide/cyclic guanosine monophosphate (NO/cGMP) pathway, rho-kinase and endothelin-1 activity, autonomic nervous system overactivity and the metabolic syndrome, and pelvic organ atherosclerosis. Both BPH/LUTS and sexual dysfunction can have a substantial negative impact on a man's quality of life. However, urologists and primary care physicians appear to under-recognise sexual dysfunction in men with BPH/LUTS. Current guidelines recommend alpha-blockers and 5-alpha reductase inhibitors, either alone or in combination, among appropriate medical treatment options for BPH/LUTS. Randomised, controlled trials demonstrate that these therapies can be associated with sexual adverse effects (AEs) such as loss of libido, erectile dysfunction and ejaculatory disorders. Sexual dysfunction should be fully evaluated in men requiring treatment for BPH/LUTS using validated questionnaires. Management of sexual dysfunction in men treated for BPH/LUTS should involve assessment of co-morbidities and concomitant medications, consideration of lifestyle interventions such as weight loss and increased physical activity to improve risk factors and, if necessary, introduction of pharmacotherapies. In addition, physicians should provide patients with proper counselling on the possible sexual AEs of medical therapies for BPH/LUTS and their impact on sexual satisfaction, while being aware of the possibility that counselling in itself is likely to influence reported rates of sexual dysfunction.

Efficacy and safety of tadalafil once daily in the treatment of men with lower urinary tract symptoms suggestive of benign prostatic hyperplasia: results of an international randomized, double-blind, placebo-controlled trial

BACKGROUND

Tadalafil is being investigated for the treatment of lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH-LUTS).

OBJECTIVE

To assess efficacy, including onset, and safety of tadalafil on BPH-LUTS and the subject's and clinician's perception of changes in urinary symptoms.

DESIGN, SETTING, AND PARTICIPANTS

This randomized, double-blind, placebo-controlled, 12-week trial enrolled men ≥45 yr of age with BPH-LUTS for >6 mo, International Prostate Symptom Score (IPSS) ≥13, and maximum urine flow rate (Q(max)) ≥4 to ≤15 ml/s.

INTERVENTION

Tadalafil 5mg (n=161) or placebo (n=164), once daily.

MEASUREMENTS

Analysis of covariance (ANCOVA) modeling evaluated change from baseline in continuous efficacy variables. Categoric efficacy variables were analyzed with the Cochran-Mantel-Haenszel test, and between-group differences in treatment-emergent adverse events (TEAEs) were assessed using the Fisher exact test. RESULTS AND LIMITATION: Tadalafil significantly improved IPSS results, from baseline to endpoint, compared to placebo (-5.6 vs -3.6; p=0.004). Reduction in IPSS results was apparent after 1 wk and significant after 4 wk (tadalafil -5.3 vs placebo -3.5; p=0.003). The BPH Impact Index (BII) was not assessed at week 1; however, BII improvement was apparent at 4 wk (tadalafil -1.8 vs placebo -1.2; p=0.029) and continued at 12 wk (tadalafil -1.8 vs placebo -1.3; p=0.057). Tadalafil significantly improved the International Index of Erectile Function-Erectile Function score in sexually active men with erectile dysfunction (ED; 6.7 vs 2.0; p<0.001) at 12 wk (not assessed at week 1). Few subjects reported one TEAE or more (p=0.44). For tadalafil, the most common TEAEs were headache (3.7%) and back pain (3.1%). Tadalafil did not significantly improve Q(max) or reduce postvoid residual volume.

CONCLUSIONS

Tadalafil 5mg once daily for 12 wk resulted in a clinically meaningful reduction in total IPSS results as early as 1 wk and achieved statistical significance at 4 wk in men with BPH-LUTS. The adverse event profile was consistent with that previously reported in men with ED.

TRIAL REGISTRATION

This clinical trial is registered on the clinicaltrials.gov website (http://www.clinicaltrials.gov). The registration number is NCT00827242.

Phosphodiesterase type 5 inhibitors in the management of non-neurogenic male lower urinary tract symptoms: critical analysis of current evidence

CONTEXT

A large body of epidemiologic data suggests a causal relationship between lower urinary tract symptoms (LUTS) and erectile dysfunction (ED). Recently reported studies on phosphodiesterase type 5 inhibitors (PDE5-Is) and LUTS have further contributed to the understanding of mechanisms involved in this relationship and of potential treatment options.

OBJECTIVE

A nonsystematic descriptive review was performed to summarize the literature concerning the role of PDE5-Is in men with LUTS, particularly looking at data derived from clinical trials in relation to the different PDE5-Is or their association with α-blockers.

EVIDENCE ACQUISITION

A comprehensive electronic search was conducted in October 2010 using the Medline database to identify all publications relating to ED and BPH and treatment with sildenafil, vardenafil, tadalafil, udenafil, UK-369003, and combination therapy with alfuzosin and tamsulosin.

EVIDENCE SYNTHESIS

In studies in which either ED or LUTS was the entry criterion, sildenafil appears to improve both erectile function and LUTS in subjects with ED. Placebo-controlled trials of tadalafil and vardenafil showed improvement of LUTS secondary to benign prostatic hyperplasia (BPH), but none of the studies showed a significant effect on urodynamic measures. Exploratory studies with UK-369003 showed improvements in LUTS and ED. Sildenafil or tadalafil associated with alfuzosin or tamsulosin showed greater benefits for the combination therapy for both LUTS and ED. The coadministration of udenafil and an α-blocker in patients with BPH and ED also appeared to improve both LUTS and ED severity.

CONCLUSIONS

Consistent evidence of improvements in LUTS has been shown with PDE5-Is, either alone or in combination with α-blockers. However, effects on urodynamics or objective measures of urinary flow are lacking. Further areas of research include investigation of mechanism of PDE5-Is, urodynamic studies, identification of new efficacy end points, head-to-head comparison with standard of care, potential benefit of add-on treatment, and long-term outcomes.

Mammalian Cyclic Nucleotide Phosphodiesterases: Molecular Mechanisms and Physiological Functions

The superfamily of cyclic nucleotide (cN) phosphodiesterases (PDEs) is comprised of 11 families of enzymes. PDEs break down cAMP and/or cGMP and are major determinants of cellular cN levels and, consequently, the actions of cN-signaling pathways. PDEs exhibit a range of catalytic efficiencies for breakdown of cAMP and/or cGMP and are regulated by myriad processes including phosphorylation, cN binding to allosteric GAF domains, changes in expression levels, interaction with regulatory or anchoring proteins, and reversible translocation among subcellular compartments. Selective PDE inhibitors are currently in clinical use for treatment of erectile dysfunction, pulmonary hypertension, intermittent claudication, and chronic pulmonary obstructive disease; many new inhibitors are being developed for treatment of these and other maladies. Recently reported x-ray crystallographic structures have defined features that provide for specificity for cAMP or cGMP in PDE catalytic sites or their GAF domains, as well as mechanisms involved in catalysis, oligomerization, autoinhibition, and interactions with inhibitors. In addition, major advances have been made in understanding the physiological impact and the biochemical basis for selective localization and/or recruitment of specific PDE isoenzymes to particular subcellular compartments. The many recent advances in understanding PDE structures, functions, and physiological actions are discussed in this review.

Tadalafil for the treatment of lower urinary tract symptoms secondary to benign prostatic hyperplasia: pathophysiology and mechanism(s) of action

BACKGROUND

The PDE5 inhibitor tadalafil is investigation for the treatment of lower urinary tract symptoms (LUTS) in men with benign prostatic hyperplasia (BPH). Several clinical studies of tadalafil and other PDE5 inhibitors have reported significant symptom reduction but limited urinary flow rate improvement. This manuscript reviews the published literature describing the pathophysiology of male LUTS, with an emphasis on mechanisms that may be modulated or improved by phosphodiesterase type 5 (PDE5) inhibition.

METHODS

Literature (through March 2010) was obtained via Medline searches and from the individual reviewers files. Articles were selected for review based on describing in vitro, preclinical, or clinical studies of pathological processes contributing to LUTS, or possible effects of PDE5 inhibition in the lower urinary tract.

RESULTS

Major mechanisms contributing to LUTS include: reduced nitric oxide/cyclic guanosine monophosphate signaling; increased RhoA kinase pathway activity; autonomic overactivity; increased bladder afferent activity; and pelvic ischemia. Tadalafil and other PDE5 inhibitors have demonstrated beneficial effects on smooth muscle relaxation, smooth muscle and endothelial cell proliferation, nerve activity, and tissue perfusion that may impact LUTS in men.

CONCLUSIONS

The pathophysiology of male LUTS is complex and not completely understood. LUTS may occur independently of BPH or secondary to BPH but in both cases involve obstructive or irritative mechanisms with substantial pathophysiological overlap. While the precise mechanism remains unclear, inhibition of PDE5 seems to have an effect on several pathways that may impact LUTS.

Phosphodiesterase-5 inhibitors for lower urinary tract symptoms secondary to benign prostatic hyperplasia: a systematic review and meta-analysis

OBJECTIVES

To evaluate the efficacy and safety of phosphodiesterase-5 (PDE-5) inhibitors for treating lower urinary tract symptoms secondary to benign prostatic hyperplasia.

METHODS

Randomized controlled trials were identified and extracted from MEDLINE, Embase, Cochrane Central, and relevant reference lists. The database search, quality assessment, and data extraction were independently performed by 2 reviewers. Heterogeneity was analyzed using the chi-square test and I(2) test. If lacking of heterogeneity, fixed-effects models were used for the meta-analysis, otherwise random-effects models were used.

RESULTS

A total of 5 studies (11 randomized controlled trials) were identified from the search strategy. Compared with placebo, short-term trials (≤12 weeks) indicated that PDE-5 inhibitors significantly improved the International Prostate Symptom Score (mean difference -2.60, 95% confidence interval [CI] -3.12 to -2.07; P < .00001), and statistical significance was observed in the International Prostate Symptom Score irritative and obstructive subscore, International Prostate Symptom Score quality of life and erectile function. However, no statistically significant difference was detected in maximal urinary flow rate (mean difference 0.21, 95% CI -0.21-0.64; P = .32) and postvoid residual urine volume (mean difference 0.09, 95% CI -4.71-4.89; P = .80). No statistically significant difference was found between the 2 groups in the incidence of serious adverse events (relative risk 0.52, 95% CI 0.25-1.07; P = .07), despite that adverse event with a greater incidence was detected in the PDE-5 group (relative risk 1.87, 95% CI 1.31-2.68; P = .0005).

CONCLUSIONS

As the first-line treatment of erectile dysfunction, the PDE-5 inhibitor is also effective and safe for lower urinary tract symptoms secondary to benign prostatic hyperplasia. It could be considered as the first-line treatment in the future for the treatment of patients with comorbid benign prostatic hyperplasia and erectile dysfunction.

Tadalafil administered once daily for lower urinary tract symptoms secondary to benign prostatic hyperplasia: a 1-year, open-label extension study

OBJECTIVE

• To evaluate the 1-year safety of 5 mg of tadalafil once daily in men with lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH-LUTS); efficacy measures were included to evaluate the maintenance of efficacy after an additional year of treatment.

PATIENTS AND METHODS

• In total, 427 men who completed a 12-week, placebo-controlled, dose- finding study assessing once-daily tadalafil (2.5, 5, 10 or 20 mg) or placebo elected to continue into the open-label extension period. Safety and efficacy parameters were assessed after 1 month and every 3 months.

RESULTS

• In total, 299 patients (69.9%) completed the 1-year, open-label extension period. Treatment-emergent adverse events (TEAEs) were reported by 57.6% of patients, with most TEAEs being mild (44%) or moderate (45%) in severity; the most common TEAEs (≥ 2%) were dyspepsia, gastro-oesophageal reflux disease, back pain, headache, sinusitis, hypertension and cough. Twenty-two patients (5.2%) discontinued as a result of AEs. During the open-label extension period, mean prostate-specific antigen increased from 1.6 ± 1.3 ng/mL to 1.8 ± 1.4 ng/mL. • Mean post-void residual volume was 61.1 ± 60.4 mL at study entry and 42.2 ± 64.1 mL after the open-label extension period. Changes in the total International Prostate Symptom Score (IPSS), IPSS irritative and obstructive subscores, IPSS health-related quality of life and BPH Impact Index were maintained after 1 year. In sexually-active patients with erectile dysfunction, improvements in the International Index of Erectile Function-Erectile Function domain were maintained after 1 year.

CONCLUSION

• In men with BPH-LUTS, 5 mg of tadalafil once daily during 1 year of treatment was well tolerated and efficacy changes were maintained.

Inhibition of cyclic nucleotide phosphodiesterases by methylxanthines and related compounds

Naturally occurring methylxanthines were the first inhibitors of cyclic nucleotide (cN) phosphodiesterases (PDEs) to be discovered. To improve potency and specificity for inhibition of various PDEs in research and for treatment of diseases, thousands of compounds with related structures have now been synthesized. All known PDE inhibitors contain one or more rings that mimic the purine in the cN substrate and directly compete with cN for access to the catalytic site; this review focuses on inhibitors that contain a nucleus that is closely related to the xanthine ring of theophylline and caffeine and the purine ring of cNs. The specificity and potency of these compounds for blocking PDE action have been improved by appending groups at positions on the rings as well as by modification of the number and distribution of nitrogens and carbons in those rings. Several of these inhibitors are highly selective for particular PDEs; potent and largely selective PDE5 inhibitors are used clinically for treatment of erectile dysfunction [sildenafil (Viagra™), tadalafil (Cialis™) and vardenafil (Levitra™)] and pulmonary hypertension [sildenafil (Revatio™) and tadalafil (Adenocirca)]. Related compounds target other PDEs and show therapeutic promise for a number of maladies.

Cyclic nucleotide metabolism including nitric oxide and phosphodiesterase-related targets in the lower urinary tract

The clinical data on the use of the orally active phosphodiesterase (PDE) type 5 inhibitors sildenafil (VIAGRA™), vardenafil (LEVITRA™), and tadalafil (CIALIS™) for the treatment of male erectile dysfunction have boosted research activities on the physiology and pharmacology of the organs of the lower urinary tract (LUT). This includes both intracellular signal transduction in the prostate, urinary bladder (detrusor), and urethra, as well as central brain and spinal cord pathways controlling the function of the LUT. Such efforts provided the basis for the development of new therapeutic modalities into the management of dysfunctions/ syndromes of the LUT, some of which are already offered to the patients. The pharmacological treatment of the overactive bladder and the so-called benign prostatic syndrome, including LUT symptomatology and bladder outlet obstruction secondary to benign prostatic enlargement, has primarily focused on selective, orally available drugs acting by influencing intracellular regulatory mechanisms. These agents are regarded efficacious, have a fast onset of drug action in the target tissue and an improved effect-to-side-effect ratio. Better understanding of the functional significance of proteins related to cyclic nucleotide-dependent pathways, such as nitric oxide synthase, cytosolic and membrane-bound guanylyl cyclases, PDE isoenzymes and cyclic AMP- and cyclic GMP-binding protein kinases, the relative distribution in tissues of the LUT, and the consequences for urogenital function, seems to be of particular interest in order to identify new or more selective pharmacological approaches to manage disorders of the LUT. The present review focuses on cyclic nucleotide-related targets involved in the control of the function of the bladder, prostate, and urethra and the significance of those proteins in the process of evolving new pharmacological options for the treatment of LUT symptoms secondary to benign prostatic hyperplasia as well as dysfunctions of the storage and voiding capability of the urinary bladder.

Treatment of erectile dysfunction and lower urinary tract symptoms by phosphodiesterase inhibitors

To date, it is widely accepted that several disorders of the male and female urogenital tract, such as erectile dysfunction, bladder overactivity, urinary stone disease, the benign prostatic syndrome, as well as symptoms of female sexual arousal and orgasmic dysfunctions, can be therapeutically approached by influencing the function of the smooth musculature of the respective organs. To achieve a pronounced drug effect without significant adverse events, a certain degree of tissue selectivity is mandatory. Selective intervention in intracellular pathways regulating smooth muscle tone has become the most promising strategy to modulate tissue and organ function. Since the concept of taking a pill to relieve symptoms of lower urinary tract dysfunction is now widely accepted following the successes of phosphodiesterase 5 (PDE5) inhibitor treatment of erectile dysfunction, the treatment of urological diseases has focused on orally available drugs acting via influencing intracellular signaling pathways, thereby combining a high response rate with the advantage of an on-demand intake. Specifically, the use of isoenzyme-selective PDE inhibitors offers great opportunities in the medical treatment of various genitourinary diseases. These agents are regarded to be safe and to be efficacious, i.e., having a fast onset of drug action and an improved effect-to-side-effect ratio. As experience with this class of compounds and their use in urology is rapidly growing, basic and clinical research in this field will most likely expand the pharmacological armamentarium of innovative treatment options in the next few years. The purpose of this review is to summarize current, as well as potential, upcoming indications for the use of PDE inhibitors in the pharmacotherapy of male erectile dysfunction and lower urinary tract symptoms.

A placebo-controlled exploratory study investigating the efficacy and safety of the phosphodiesterase type 5 inhibitor UK-369,003 for the treatment of men with storage lower urinary tract symptoms associated with a clinical diagnosis of overactive bladder

OBJECTIVES

To evaluate the efficacy and safety of the phosphodiesterase type 5 inhibitor, UK-369,003 modified release (MR), for the treatment of storage lower urinary tract symptoms (LUTS) in men with and without erectile dysfunction (ED).

PATIENTS AND METHODS

This was a multicentre, double-blind, placebo-controlled, parallel-group study conducted across 50 centres in North and South America, Europe and Australia. In all, 310 men aged ≥ 18 years with a clinical diagnosis of overactive bladder (OAB; voiding frequency ≥ 8 times/24 h, urgency episode frequency once or more per 24 h and a mean voided volume of <300 mL) and maximum urinary flow rate of >5 mL/s in a voided volume of >150 mL were stratified into two groups (with or without ED) and randomized to one of five treatment groups (10, 25, 50 or 100 mg UK-369,003; or placebo once a day) for 12 weeks. The primary study endpoints were those derived from the bladder diary that recorded the number of voluntary urinary voids, volume of urine per void, leaks and urgency episodes over a 72-h period, before baseline and again at 2, 4 and 12 weeks. Secondary efficacy measures included the International Prostate Symptom Score (total and storage and voiding subscores), International Index of Erectile Function-Erectile Function domain (IIEF-EF), questions 5 and 6 of the Quality of Erection Questionnaire (QEQ), the Overactive Bladder Questionnaire Short Form, the Patient Perception of Bladder Condition, the International Consultation on Incontinence Questionnaire-Male LUTS, and the patient-reported treatment impact questionnaire.

RESULTS

Overall, there were no clinically relevant treatment differences in voiding frequency, mean voided volume, urgency episode frequency, or nocturia frequency for any dose of UK-369,003 MR compared with placebo. In the subset of patients with ED there were improvements in the IIEF-EF and QEQ scores in all UK-369,003 treatment groups compared with placebo.

CONCLUSIONS

These data provide no evidence of efficacy for UK-369,003 in the treatment of storage LUTS in men (based on classic OAB eligibility criteria). However, although the endpoints on these classic OAB efficacy variables were negative, there is evidence to suggest a greater preference, satisfaction and willingness to use UK-369,003 again for all treatment groups compared with placebo.

A placebo-controlled study investigating the efficacy and safety of the phosphodiesterase type 5 inhibitor UK-369,003 for the treatment of men with lower urinary tract symptoms associated with clinical benign prostatic hyperplasia

OBJECTIVES

To evaluate the efficacy and safety of the phosphodiesterase type 5 inhibitor UK-369,003 for the treatment of lower urinary tract symptoms (LUTS) associated with benign prostatic hyperplasia (BPH) in men with and without erectile dysfunction (ED).

PATIENTS AND METHODS

This was a multicentre, double-blind, placebo- and active-controlled, parallel-group study conducted across 45 centres in North and South America, Europe, and Australia. In all, 418 men aged ≥ 40 years with a clinical diagnosis of BPH, an International Prostate Symptom Score (IPSS) of ≥ 13, and maximum urinary flow rate (Q(max) ) of 5-15 mL/s for a voided volume of > 150 mL were stratified into two groups (with and without ED) and randomized to one of seven treatment groups, i.e. UK-369,003 at 10, 25, 50 or 100 mg modified release (MR), UK-369,003 40 mg immediate release (IR), tamsulosin 0.4 mg prolonged release, or placebo, for 12 weeks. The primary study endpoint was the change in total IPSS after 12 weeks of treatment. Secondary efficacy measures were IPSS storage and voiding subscores, Q(max) , International Index of Erectile Function-Erectile Function domain, questions 5 and 6 of the Quality of Erection Questionnaire, the International Consultation on Incontinence Questionnaire-Male LUTS, the patient-reported treatment-impact questionnaire, and a bladder diary in which patients recorded the number of voluntary urinary voids, volume of urine voided per micturition, leaks, and urgency episodes.

RESULTS

The mean change in the IPSS from baseline at week 12 for UK-369,003 100 mg MR and 40 mg IR was -2.91 and -2.50 better than placebo, respectively. There was increasing efficacy with increasing dose of the MR formulation. For UK-369,003 100 mg MR, Q(max) improved by 2.10 mL/s compared with 0.84 mL/s in the placebo group.

CONCLUSIONS

UK-369,003 had clinically meaningful efficacy and was well tolerated in men with LUTS associated with BPH. The Bayesian statistical analysis gave high posterior probabilities for true differences between UK-369,003 100 mg MR and placebo. There was greater preference, satisfaction and willingness to use UK-369,003 again for all treatment groups compared with placebo.

Vardenafil decreases bladder afferent nerve activity in unanesthetized, decerebrate, spinal cord-injured rats

BACKGROUND

Phosphodiesterase type 5 inhibitors (PDE5-Is) improve storage symptoms in benign prostatic hyperplasia patients, despite a lack of effect on peak urinary flow rate. Moreover, vardenafil improves urodynamic parameters in spinal cord-injured (SCI) patients with neurogenic detrusor overactivity (NDO). SCI rats also display NDO characterized by nonvoiding contractions (NVCs) during bladder filling, resulting in an increased bladder afferent nerve firing (BANF).

OBJECTIVE

We postulated that vardenafil could improve urodynamic parameters by reducing BANF. The effect of vardenafil has been investigated on intravesical pressure by cystometry experiments while recording BANF in response to bladder filling.

DESIGN, SETTING, AND PARTICIPANTS

Complete T7-T8 spinalization was performed in 15 female adult Sprague-Dawley rats (250-275 g).

MEASUREMENTS

At 21-29 d postspinalization, fine filaments were dissected from the L6 dorsal roots and placed across a bipolar electrode. Bladder afferent nerve fibers were identified by electrical stimulation of the pelvic nerve and bladder distension. SCI rats were decerebrated before cystometry experiments. Bladders were filled to determine the maximal bladder filling volume (BFV) for each rat. Then, after bladder stabilization at 75% of maximal BFV, saline (n=7) or vardenafil 1 mg/kg (n=8) was delivered intravenously. NVCs and BANF were recorded for 45 min.

RESULTS AND LIMITATIONS

In all SCI rats, BANF was already present and regular at resting conditions (26.2±4.1 spikes per second). During bladder filling, intravesical pressure (IVP) slowly increased with transient NVCs superimposed. Concomitantly, BANF progressively increased up to 2.4-fold at maximal BFV (2.08±0.24 ml). After stabilization at submaximal BFV, BANF was increased by 186±37%. Vardenafil injection induced an immediate decrease in NVCs compared to saline (p<0.001) and BANF (52% decrease vs 28% in saline after 45 min; p<0.001).

CONCLUSIONS

Systemic vardenafil reduced both NVCs and BANF in unanesthetized, decerebrate, SCI rats. These findings provide new insights into the mechanism of action by which PDE5-Is improve storage symptoms in SCI patients.

[Treatment of the lower urinary tract symptoms secondary to benign prostatic hyperplasia by phosphodiesterase type 5 inhibitors. Review article]

CONTEXT

In aging males, there is an increased prevalence of lower urinary tract symptoms (LUTS) related to benign prostatic hyperplasia (BPH) and erectile dysfunction (ED) whose affect significantly their quality of life. LUTS would represent for ED an independent risk factor. Some treatment of LUTS have undesirable effects on the erectile function. The phosphodiesterase type 5 inhibitors (IPDE 5) revolutionized the treatment of ED. Several recent clinical studies evaluated the effect daily treatment by IPDE 5 on the LUTS secondary to BPH among patients with or without ED.

MATERIALS AND METHODS

we searched Medline for the peer-reviewed articles in English published, pertaining to findings of potential interest supporting a role of IPDE5 in LUTS due to BHP. The keywords used were: benign prostatic hyperplasia; cyclic nucleotide phosphodiesterase type 5; lower urinary tract symptoms; erectile dysfunction.

RESULTS

Generally, daily treatment with IPDE 5 improves the LUTS secondary to BPH as well as in both the storage and voiding domains of the international prostate symptom score (IPPS) and in quality of life questionnaire. It was not observed adverse events.

CONCLUSION

The first results of the use of IPDE 5 in the LUTS treatment secondary to the HBP seem promising. However, a direct comparison of efficacy of IPDE 5 and alpha-blockers or 5-alpha-reductase inhibitors is not yet available. The mechanism(s) of action(s) of these compounds in this indication remain difficult to affirm even if new hypotheses can be formulated.

Phosphodiesterase 5 inhibitors for lower urinary tract symptoms secondary to benign prostatic hyperplasia: a systematic review

OBJECTIVE

• To review the evidence in support of the effectiveness of phosphodiesterase 5 inhibitors in lower urinary tract symptoms (LUTS) caused by benign prostatic hyperplasia (BPH).

METHODS

• Relevant studies were identified by performing a literature search using MEDLINE® and The Cochrane Library®. The criteria used during the search included randomized, placebo-controlled trials of treatment for LUTS secondary to BPH using the International Prostate Symptom Score as an outcome measure.

RESULTS

• Four trials that included a total of 1928 patients met the inclusion criteria. All four studies showed a statistically significant difference in the International Prostate Symptom Score, quality of life and erectile function in favour of phosphodiesterase 5 inhibitors. • No study showed a statistically significant improvement of the maximum urinary flow. • Meta-analysis of the results was not possible because of heterogeneity across the studies.

CONCLUSIONS

• Phosphodiesterase 5 inhibitors used in the clinical setting can significantly improve LUTS secondary to BPH, erectile function and quality of life. Maximum urinary flow improvement is not statistically significant. • Future research should focus on pathophysiological principles and cost analysis.

Expression of cAMP-dependent protein kinase isoforms in the human prostate: functional significance and relation to PDE4

OBJECTIVES

To investigate the expression of isoforms of the cyclic AMP (cAMP)-dependent protein kinase (cAK) in the transition zone of the human prostate and the functional significance of the enzyme in the control of prostate smooth muscle.

METHODS

Using Western blot analysis and immunohistochemistry, the expression and distribution in the prostate of cAKIalpha, cAKIbeta, cAKIIalpha, and cAKIIbeta in relation to alpha-actin and the phosphodiesterase PDE4 (types A and B) were investigated. The effects of the cAK inhibitor Rp-8-CPT-cAMPS on the reversion of the adrenergic tension of isolated prostate tissue induced by forskolin, rolipram, sodium nitroprusside (SNP), and tadalafil were examined by means of the organ bath technique.

RESULTS

Immunosignals specific for cAKIalpha, cAKIIalpha, and cAKIIbeta were observed in the smooth musculature and glandular structures of the prostate. Double stainings revealed the colocalization of alpha-actin and PDE4 with the cAK isoforms. The expression of the cAK isoforms was confirmed by Western blot analysis. The relaxation of the tension induced by norepinephrine brought about by forskolin, rolipram, SNP, and tadalafil was significantly attenuated by Rp-8-CPT-cAMPS.

CONCLUSIONS

The colocalization of smooth muscle alpha-actin and PDE4 with cAK, as well as the results from the organ bath experiments, provide further evidence for a pivotal role of the cAMP-dependent signaling in the regulation of prostate smooth muscle contractility. Compounds interacting with the cAMP/cAK pathway might represent a new therapeutic avenue to treat symptoms of benign prostatic hyperplasia and lower urinary tract symptomatology.

Nitric oxide/cyclic guanosine monophosphate signalling mediates an inhibitory action on sensory pathways of the micturition reflex in the rat

BACKGROUND

Overactive bladder can be associated with a hyperexcitability of bladder afferent C-fibres. Several studies have suggested that nitric oxide (NO) or its downstream signalling could modulate the micturition reflex (MR) by reducing the excitability of bladder afferents.

OBJECTIVES

To evaluate the role of the NO/cyclic guanosine monophosphate (cGMP) signalling pathway on the MR in a model of bladder hyperactivity (BHA) associated with C-fibre activation in the rat.

DESIGN, SETTING, AND PARTICIPANTS

Adult female Sprague Dawley rats were used.

MEASUREMENTS

Cystometry was performed in anaesthetised rats. The effects of 0.1 mg/kg of sodium nitroprusside (SNP), an NO donor; 10 mg/kg of 8Br-cGMP, a cGMP analogue; 3 mg/kg of sildenafil and 1 mg/kg of vardenafil, two phosphodiesterase type 5 inhibitors (PDE5-I); 10 mg/ml of L-N(G)-nitroarginine methyl ester (L-NAME), an NO synthase inhibitor; and 1 mg/kg of LY-83583, a guanylate cyclase inhibitor, were investigated on BHA during intravesical capsaicin (30 micromol/l) instillation. All drugs were delivered intravenously except for L-NAME, which was intravesically administered.

RESULTS AND LIMITATIONS

SNP, 8Br-cGMP, and PDE5-I increased the intercontraction interval (ICI), while SNP and PDE5-I increased the micturition pressure threshold (MPT). L-NAME and LY-83583 decreased MPT, and L-NAME decreased ICI. 8Br-cGMP decreased the maximum intravesical pressure (MP), contrary to L-NAME and LY-83583. SNP and PDE5-I had no effect on MP. SNP increased the voided volume (VV). PDE5-I and 8Br-cGMP also increased VV, although not significantly. In contrast, L-NAME tended to decrease VV. Although 8Br-cGMP decreased the baseline intravesical pressure, LY-83583 increased it. Neither SNP nor PDE5-I nor L-NAME had any effect on baseline pressure.

CONCLUSIONS

Compounds activating the NO/cGMP pathway inhibited BHA, whereas compounds inhibiting the NO/cGMP pathway increased it. These results indicate that the NO/cGMP signalling pathway is involved in the regulation of the MR, with an action that seems more predominant on the sensory rather on the motor component of the MR in a rat model of BHA associated with C-fibre afferent activation.

Signalling pathways involved in sildenafil-induced relaxation of human bladder dome smooth muscle

BACKGROUND AND PURPOSE

The mechanism(s) of action responsible for the beneficial effects of phosphodiesterase 5 (PDE5) inhibitors including sildenafil on lower urinary tract symptoms suggestive of benign prostate hyperplasia are unclear. In particular, the role of the NO-cGMP signalling pathway in regulating human bladder dome smooth muscle relaxation is questionable. Thus, we assessed the ability of a PDE5 inhibitor, sildenafil, to relax such tissue, and identified the signalling pathways involved in this relaxation.

EXPERIMENTAL APPROACH

Human bladder samples were obtained from 20 patients with no overactive bladder undergoing cystectomy for bladder cancer. Detrusor strips were mounted isometrically in Krebs-HEPES solution. Concentration-response curves for sildenafil (10 nM-30 microM) were generated in the presence of various inhibitors on carbachol-induced pre-contraction.

KEY RESULTS

Sildenafil relaxed carbachol-pre-contracted human detrusor strips, starting at 3 microM. This effect was not modified by NO donors, S-nitroso-N-acetylpenicillamine (10 microM) or sodium nitroprusside (300 nM), but was significantly inhibited by inhibition of guanylate cyclase (with ODQ, 10 microM) or adenylyl cyclase (with MDL-12,330A, 10 microM), by the ATP-sensitive potassium channel inhibitor, glibenclamide (10 microM), or inhibition of the large (with iberiotoxin, 30 nM) or small (with apamin, 100 nM) conductance calcium-activated potassium channels.

CONCLUSIONS AND IMPLICATIONS

Sildenafil-induced relaxation of human detrusor smooth muscle involved cGMP-, cAMP- and K(+) channel-dependent signalling pathways, with a minor contribution from NO. The effect of this sildenafil-induced relaxation on the clinical benefit of PDE5 inhibitors on urinary storage symptoms in men deserves further investigation.