Evaluating preference trials of oral phosphodiesterase 5 inhibitors for erectile dysfunction

More treatment options are available now for the treatment of erectile dysfunction (ED) than ever. Treatments include oral phosphodiesterase 5 (PDE5) inhibitors, intracavernosal injections, vacuum constriction devices, and penile implants. Clinicians, researchers, and patients are interested in making direct comparisons between the response of newer treatments and that of established and more developed therapies. Of the currently available treatment options for ED, the most commonly prescribed therapies are oral PDE5 inhibitors, which include sildenafil citrate (Viagra, Pfizer Inc), tadalafil (Cialis, Lilly ICOS), and vardenafil (Levitra, Bayer). However, most patient preference studies of these drugs conducted to date have serious design flaws that hinder interpretation of the data, and thus limit the utility of the results. To make an informed decision on the most appropriate treatment option available, physicians and their patients require a thorough understanding of the methodology of these studies. Clinical comparison or preference trials must establish internal and external validity if the data are to be used in a generalized patient population. We review preference studies that compared sildenafil, tadalafil, and vardenafil, and highlight study designs that can introduce bias. We propose that, like safety and efficacy trials, randomized controlled trials (RCTs) should be the gold standard for evaluating patient preference treatments for ED. We do not wish to discourage individual investigators from performing preference studies, but rather to highlight the features of current preference trials to help patients and clinicians alike become aware of potential biases from independent or industry-sponsored patient preference trials so that they can interpret the results accordingly. Key components of patient preference RCTs are reviewed: period and carryover effects, preference assessments, eligibility criteria, and data analysis. We discuss why these components of patient-preference RCTs are important for evaluating the validity and relevance of patient preference studies. The preference studies discussed in this brief review are summarized in , and the methodological problems with each study are indicated. We provide a recommendation for the design of such trials that can minimize bias and provide better data for physicians and their patients.     

长期低剂量PDE5抑制剂治疗勃起功能障碍的新进展

勃起功能障碍(ED)是一类常见的疾病,严重影响患者及其伴侣的生活质量,5型磷酸二酯酶(PDE5)抑制剂是治疗ED的首选药物,新近发现给予ED患者长期低剂量PDE5抑制剂同样安全有效,使得性生活更自然更方便,并为难治性ED患者提供了一种新的治疗选择,其机制在于改善阴茎血管内皮细胞的功能以及增加和(或)维持平滑肌细胞数量促进ED改善,但该方法是否能够使患者在服药结束后维持勃起功能依然是当前研究的热点。     

Evidence for contamination of herbal erectile dysfunction products with phosphodiesterase type 5 inhibitors

PURPOSE: We determined if pharmacological dosages of phosphodiesterase type 5 inhibitors (PDE5) inhibitors were present within a group of natural products marketed for the treatment of erectile dysfunction. MATERIALS AND METHODS: Seven herbal products marketed for the treatment of erectile dysfunction were purchased via the Internet or at local health food stores. Specimens were batched, relabeled and blindly analyzed for contamination with PDE5 inhibitors. High performance liquid chromatography and mass spectrometry were used to detect evidence of contamination with sildenafil, tadalafil or vardenafil. RESULTS: Of the 7 tested products 2 contained pharmacological dosages of sildenafil and tadalafil. Contamination with vardenafil was not identified. Mean dosages of sildenafil and tadalafil were 30.2 and 19.7 mg, respectively. CONCLUSIONS: A significant proportion of natural products marketed for erectile dysfunction contains PDE5 inhibitors. Although marketed as natural products devoid of adverse effects, these agents are known to have potentially fatal drug interactions with nitrates. Better regulation of the natural health products industry is urged.     

Phosphodiesterase type 5 inhibitors for erectile dysfunction

The cyclic nucleotide signalling pathway mediates the smooth-muscle relaxing effects of nitric oxide necessary for normal erectile function. Down-regulation of this pathway is central to the pathophysiology of many forms of erectile dysfunction (ED), which is often associated with other chronic diseases (e.g. hypertension, type 2 diabetes mellitus) and treatments (e.g. certain drugs, radical prostatectomy). Conversely, selective inhibition of the enzyme that catalyses the degradation of cGMP (phosphodiesterase type 5, PDE-5) promotes erectile responses to sexual stimulation. The successful launch and commercialization of the selective PDE5 inhibitor (PDE5I) sildenafil transformed the treatment of ED, not only by providing an effective, well tolerated oral ED therapy, but also by fostering greater candour about the problem among men. Sildenafil is highly effective in promoting erectile responses across a wide spectrum of severity and causes of ED, including patients with ED that is often refractory to treatment. The recent advent of vardenafil, which has the highest in vitro potency of all available PDE5Is, and tadalafil, which has a prolonged half-life that may enable couples to have sexual activity with less planning, represent further advances. Other PDE5Is offering further potential improvements are under active investigation.     

Clinical update on phosphodiesterase type-5 inhibitors for erectile dysfunction

Erectile dysfunction (ED) affects the sexual lives of millions of men. The first-line oral pharmacotherapy for most ED patients is phosphodiesterase type-5 (PDE-5) inhibitors, of which three are available. Sildenafil is the most widely prescribed oral agent for ED and has a very satisfactory efficacy–safety profile in all patient categories. Tadalafil and vardenafil were introduced in the European Union and in the United States in 2003 and 2004, respectively. The three PDE-5 inhibitors share many pharmacological and clinical characteristics, and each has unique features. This review, which is based on the contemporary literature on PDE-5 inhibitors, describes the chemical, pharmacological, and clinical features of sildenafil, vardenafil, and tadalafil. The first section reviews the pathophysiology of penile erection and PDE-5 inhibitor pharmacology. The second section summarizes data regarding efficacy and safety of the three drugs in treating ED in the general population as well as in selected patient categories.     

A meta-regression evaluating the effectiveness and prognostic factors of oral phosphodiesterase type 5 inhibitors for the treatment of erectile dysfunction

The effectiveness of phosphodiesterase type 5 inhibitors (PDE5-Is) for erectile dysfunction (ED) varies considerably among trials, but available studies investigating the factors that affect the effectiveness are few and findings are not consistent. A systematic search was performed in PubMed, Cochrane Library, and EMBASE to identify randomized controlled trials comparing PDE5-Is with placebo for the treatment of ED. The methodological quality of included studies was assessed by the Cochrane Collaboration''s tool for assessing risk of bias. The associations between prespecified study-level factors and effectiveness were tested by a random effects meta-regression model. This study included 93 trials with 26 139 patients. When all PDE5-Is were grouped together, Caucasian ethnicity was associated with 15.636% (95% confidence interval [CI]: 0.858% to 32.579%) increase in risk ratio (RR) for Global Assessment Questionnaire question-1 (GAQ-1), and 1.473 (95% CI: 0.406 to 2.338) score increase in mean difference (MD) for posttreatment International Index of Erectile Function-Erectile Function domain score (IIEF-EF), compared to Asian ethnicity. A one-score increase in baseline IIEF-EF was associated with −5.635% (95% CI: −9.120% to −2.017%) reduction in RR for GAQ-1, and −0.229 (95% CI: −0.425 to −0.042) score decrease in MD for posttreatment IIEF-EF. In conclusion, PDE5-Is are more effective in Caucasians than Asians, and in patients with more severe ED.     

Evolution of phosphodiesterase type 5 inhibitors in treatment of erectile dysfunction in Taiwan

Erectile dysfunction (ED) is a prevalent form of male sexual dysfunction. Phosphodiesterase type 5 (PDE5) inhibitor is the first-line treatment for ED. Numerous well-designed and -conducted clinical trials and postmarketing studies have established the safety and efficacy of PDE5 inhibitors for the treatment of ED. Ever since the first approval of sildenafil in 1998, PDE5 inhibitors have had several advances in their clinical use. More new agents with different pharmacokinetic profiles and new formulations were marketed. Conventional on-demand administration expanded to daily dosing. These advances provide more flexibility in clinical treatment of ED for patients and physicians. Moreover, clinical indications of PDE5 inhibitors extend from treatment of ED to pulmonary arterial hypertension and signs and symptoms of benign prostatic hyperplasia because of the distribution of PDE5 enzyme in human organs and tissues. The evolution of PDE5 inhibitors heralds a remarkable medical history from bench to clinical practice.     

Treating erectile dysfunction by endothelial rehabilitation with phosphodiesterase 5 inhibitors

A large body of evidence has accumulated demonstrating that a common pathway in conditions such as hypertension, atherosclerosis, hypercholesterolemia, diabetes mellitus, and erectile dysfunction (ED) is endothelial dysfunction. Although a complete pharmacological cure for ED is currently unavailable, the phosphodiesterase 5 (PDE5) inhibitors sildenafil, vardenafil, and tadalafil are efficacious oral therapy for ED. Results from recent studies suggest that regular treatment with a PDE5 inhibitor may lead to enhanced erectile function (EF) beyond that observed with on-demand usage, possibly through improvement of endothelial function. Such an effect may be viewed as rehabilitation of damaged erectile tissue. The present review focuses on several recent studies which provide evidence for the beneficial effect of regular PDE5 inhibitor administration on the improvement of EF by rehabilitation of vascular endothelium.     

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.     

Evaluation and diagnostic testing of erectile dysfunction in the era of phosphodiesterase type 5 inhibitors

The diagnosis and treatment of erectile dysfunction has changed dramatically since the availability of safe and effective oral therapies. Unfortunately, not all men can be adequately treated in this way, and might require more invasive testing to diagnose and treat the specific cause of their dysfunction. This review looks at the tests and strategies available for men who cannot be treated by oral therapy alone.     

Incidence rate of prostate cancer in men treated for erectile dysfunction with phosphodiesterase type 5 inhibitors: retrospective analysis

The purpose of this study was to determine the incidence rate of prostate cancer among men with erectile dysfunction (ED) treated with phosphodiesterase type 5 inhibitors (PDE-5i) over a 7-year period vs. men with ED of the same age and with similar risk factors who were not treated with PDE-5i. In a retrospective review of electronic medical records and billing databases between the years 2000 and 2006, men with ED between the ages of 50 and 69 years and no history of prostate cancer prior to 2000 were identified. These individuals were divided into two groups: 2362 men who had treatment with PDE-5i, and 2612 men who did not have treatment. Demographic data in each group were compared. During the study period, 97 (4.1%) men with ED treated with PDE-5i were diagnosed with prostate cancer compared with 258 (9.9%) men with ED in the non-treated group (P<00001). A higher percentage of African Americans were treated with PDE-5i vs. those who were not (10.5% vs. 7.1% P<0.0001). The PDE-5i group had lower documented diagnosis of elevated prostate-specific antigen (10.0% vs. 13.1% P=0.0008) and higher percentage of benign prostatic hyperplasia (38.4% vs. 35.1% P=0.0149). Men with ED treated with PDE-5i tended to have less chance (adjusted odds ratio: 0.4; 95% confidence intervals: 0.3–0.5; P<0.0001) of having prostate cancer. Our data suggest that men with ED treated with PDE-5i tended to have less of a chance of being diagnosed with prostate cancer. Further research is warranted.     

Daily use of phosphodiesterase 5 inhibitors for erectile dysfunction and lower urinary tract symptoms

Erectile dysfunction is a prevalent disorder that not only affects men with the disorder but also their partners. Significant improvements in the sexual health of these couples have been achieved with the introduction of phosphodiesterase 5 (PDE5) inhibitors. Currently PDE5 inhibitors are used on an on-demand basis. New evidence regarding the effects of PDE5 inhibitors on the underlying pathophysiologic processes that cause erectile dysfunction have sparked interest in the continuous dosing of these medications. We will discuss the biological background and the available clinical evidence for the continuous use of phosphodiesterase inhibitors in erectile dysfunction. Lastly, we will discuss the emerging clinical data for the use of daily PDE5 inhibitors in men with lower urinary tract symptoms.     

PDE5 inhibitors beyond erectile dysfunction

The phosphodiesterase type-5 (PDE5) inhibitors sildenafil, vardenafil and tadalafil are widely used first-line therapy for erectile dysfunction (ED). Since the advent of sildenafil in 1998, more than 40 million men worldwide have been successfully treated with these compounds. The safety and high tolerability of PDE5 inhibitors make them an attractive tool to investigate further physiological functions of PDE5, for example the modulation of intracellular cyclic GMP (cGMP) pools. As cGMP is a key component of intracellular signaling this may provide novel therapeutic opportunities beyond ED even for indications in which chronic administration is necessary. The approval of sildenafil for the treatment of pulmonary hypertension in 2005 was a notable success in this area of research. A number of other potential new indications are currently in various phases of preclinical research and development. In recent years, extensive but very heterogeneous information has been published in this field. The aim of this review is to summarize existing preclinical and clinical knowledge and critically discuss the evidence to support potential future indications for PDE5 inhibitors.     

Efficacy of phosphodiesterase type 5 inhibitors in patients with erectile dysfunction after nerve-sparing radical prostatectomy: a systematic review and meta-analysis

BackgroundNerve-sparing radical prostatectomy (NSRP) had to be performed because approximately 94% of patients are diagnosed with localized prostate cancer (PCa). Although NSRP is generally done to improve functional outcomes, erectile dysfunction (ED) is one of the most prevailing complications after radical prostatectomy (RP). Phosphodiesterase type 5 inhibitors (PDE5-Is) are the most well-known treatment agent for postoperative ED. This study aimed to assess the efficacy of PDE5-Is in patients with ED after NSRP.MethodsIn this systematic literature review, randomized controlled trials on the efficacy and safety of PDE5-Is in patients who underwent NSRP were searched in MEDLINE, EMBASE, and the Cochrane Controlled Trials Register using the OVID platform. This study was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses and Cochrane Review Methods. The quality of the evidence of the outcome data was evaluated using the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) approach.ResultsA total of 14 trials involving 2,822 patients were included. Significant improvements in the International Index of Erectile Function—Erectile Function (IIEF) domain score [mean difference (MD) =4.93; 95% confidence interval (CI): 4.14–5.71; P<0.00001] and erectile function recovery events [odds ratio (OR) =2.06; 95% CI: 1.45–2.94; P<0.0001] were observed after PDE5-I treatment. A higher positive response to Sexual Encounter Profile (SEP) question 2 (OR =2.27; 95% CI: 1.80–2.86; P<0.00001) and question 3 (OR =2.78; 95% CI: 1.97–3.91; P<0.00001) was also found after PDE5-I treatment. However, the incidence of treatment-emergent adverse events (TEAEs) was higher after PDE5-I treatment than after placebo treatment (OR =2.91; 95% CI: 1.84–4.61). Furthermore, the incidence of headache (OR =3.38; 95% CI: 2.40–4.75) and flushing (OR =9.44; 95% CI: 4.30–20.70) was also significantly higher after PDE5-I treatment (P<0.00001). In terms of the quality of the evidence of the outcome data, inconsistency problems were detected in all outcomes and imprecision problems in most outcomes.DiscussionPDE5-I treatment was more effective to placebo treatment in patients with ED after NSRP. No clinically serious complications were found in spite of the incidence of TEAEs being higher after PDE5-I treatment.     

PDE5抑制剂治疗ED的不良反应及防治措施

5型磷酸二酯酶抑制剂(PDE5i)是目前治疗勃起功能障碍(ED)的一线药物,随着PDE5i临床应用增多,其不良反应的发生亦趋增多,可累及全身多个系统,大多数为轻到中度,偶有严重、罕见的并发症,其发生概率和严重程度与剂量、用药频率和个体差异相关,因此需个体化用药。对患有严重心血管疾病、癫痫及精神疾病、过敏性疾病的患者应谨慎或避免用PDE5i。     

Testosterone undecanoate improves erectile dysfunction in hypogonadal men with the metabolic syndrome refractory to treatment with phosphodiesterase type 5 inhibitors alone

At least 30–35% of men with erectile dysfunction (ED) fail to respond to treatment with phosphodiesterase type 5 (PDE‐5) inhibitors. Testosterone (T) has effects not only on sexual desire, but also on the anatomical and physiological substrate of erection. This study analysed the effects of T administration to men unsuccessfully treated for ED with PDE‐5 inhibitors only. Twenty‐nine men aged 36–75 years (mean 59 years) with ED were studied. They suffered from ED for a mean of 2.7 years and had subnormal plasma T levels (total T <3.5 ng ml^?1). They received parenteral testosterone undecanoate for 102 weeks. Changes of the domains of the International Index of Erectile Function (IIEF) were assessed. After 6 weeks of T treatment, the sexual desire domain of IIEF had improved (from 4.1 ± 1.4 to 7.2 ± 1.7) and erectile function as measured by IIEF started to improve, reaching a plateau after 30 weeks (from 9.1 ± 2.1 to 26.5 ± 2.3). Features of the metabolic syndrome also improved. There were no adverse effects of T administration. Addition of T to treatment of hypogonadal men unsuccessfully treated with PDE‐5 inhibitors only, appeared useful and acceptably safe.