PDE-5-Inhibitoren

BACKGROUND: PDE5 inhibitors represent the gold standard in the medical therapy of erectile dysfunction (ED). Promising results have been published regarding further urological indications such as treatment of ureteral colic. The aim of the present study was to evaluate the functional effects of the PDE5 inhibitors sildenafil (SIL), vardenafil (VAR), and tadalafil (TAD) on tissue tension and cyclic nucleotide levels of human ureteral smooth muscle segments in vitro. METHODS: Relaxant responses of human ureteral smooth muscle were investigated in vitro using the organ bath technique. Cyclic nucleotides cAMP and cGMP were determined by specific radioimmunoassays. RESULTS: Relaxing effects of ureteral muscle tension were observed in the rank order VAR>SIL>TAD. While only VAR significantly elevated cGMP levels 3.3-fold over control, no increase for cAMP levels was observed. CONCLUSIONS: Our data provide evidence that cGMP is involved in the control of the normal function of the smooth musculature of the human ureter. Our findings suggest the potential of using selective inhibitors of PDE isoenzymes in the treatment of ureteral colic.     

Implications of PDE4 structure on inhibitor selectivity across PDE families

Phosphodiesterases (PDEs) control cellular concentrations of cyclic adenosine monophosphate (cAMP) or cyclic guanosine monophosphate (cGMP). PDE4 and PDE5 selectively hydrolyze cAMP and cGMP, respectively. PDE family members share approximately 25% sequence identity within a conserved catalytic domain of about 300 amino acids. Crystal structure analysis of PDE4's catalytic domain identifies two metal-binding sites: a high-affinity site and a low-affinity site, which probably bind zinc (Zn2+) and magnesium (Mg2+), respectively. Absolute conservation among the PDEs of two histidine and two aspartic acid residues for divalent metal binding suggests the importance of these amino acids in catalysis. Although active sites of PDEs are apparently structurally similar, PDE4 is specifically inhibited by selective inhibitors such as rolipram, while PDE5 is preferentially blocked by sildenafil. Modeling interactions of the PDE5 inhibitor sildenafil with the PDE4 active site may help explain inhibitor selectivity and provide useful information for the design of new inhibitors.     

Medikamentöse Therapie des benignen Prostatasyndroms mit Phosphodiesterase-5-Inhibitoren

Phosphodiesterase-5 (PDE5) inhibitors, such as sildenafil, tadalafil and vardenafil are first line treatment for erectile dysfunction (ED). These PDE5 inhibitors are known to increase cyclic guanosine monophosphate (cGMP) concentrations in the smooth muscle cells of the corpora cavernosa penis by inhibiting PDE5, leading to smooth muscle relaxation. This mode of action is also believed to result in prostatic smooth muscle relaxation and to improve lower urinary tract symptoms (LUTS). Randomized controlled trials have shown beneficial effects on LUTS and on objective parameters such as maximum urinary flow rate (tadalafil). Based on these data tadalafil was recently approved for treatment of patients with male LUTS; however, the mechanisms leading to improvement of symptoms are still under debate.     

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.     

Tolerability and safety profile of sildenafil citrate (Viagra) in Latin American patient populations

Safety data from 546 men with erectile dysfunction (ED) enrolled in three double-blind, placebo-controlled studies conducted in distinct regions of Latin America were pooled and analyzed. The most commonly reported adverse events of all causalities associated with sildenafil treatment were headache (19%), flushing (14%), dyspepsia (6%), and nasal congestion (4%), reflecting the inhibitory effects of sildenafil on cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5) in the peripheral vasculature, gastroesophageal sphincter, and nasal mucosa. Visual symptoms were reported in 5.5%, reflecting sildenafil's minor inhibitory effects on cGMP-specific PDE6 in the retina. These adverse events were generally transient and mild, and rarely resulted in discontinuation of sildenafil therapy. Thus, in this representative sample of Latin American men with ED, including those with concomitant stable cardiovascular disease, sildenafil treatment was well tolerated with an incident rate of adverse events similar to reports from other patient populations.     

Combination therapy for erectile dysfunction: where we are and what's in the future

Penile erection occurs in response to visual, olfactory, imaginative, and tactile stimuli initiated within the brain and/ or on the periphery. Responses to these stimuli are mediated by efferent autonomic outflow originating in the sacral spinal cord and transmitted by the cavernosal and penile nerves. A number of neurotransmitters can play an integral role in corpus cavernosum smooth muscle relaxation, in part regulating penile erection through increased smooth muscle synthesis of the secondary messengers cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). In addition to directacting agents, there are indirect-acting smooth musclerelaxing agents. Phosphodiesterase (PDE) inhibitors such as sildenafil act indirectly and require sexual stimulation and endogenous nitric oxide production to activate the cGMP pathway effectively. In contrast, agents such as prostaglandin E₁ (PGE₁) act directly on the trabecular smooth muscle, binding to specific e-prostanoid receptors and increasing cAMP synthesis. For this reason the direct-acting agents do not require sexual stimulation for efficacy. Combination pharmacotherapy has been used experimentally to treat erectile dysfunction for 25 years, using combinations of cAMP synthesis augmentors, smooth muscle relaxants and PDE inhibitors, and α-blockers administered via intracavernosal injection. The present era of oral pharmacotherapy treatment has resulted in significant awareness in the field of sexual dysfunction; however, a single agent may not be ideal to sustain penile rigidity, especially if comorbidities and severity of erectile dysfunction are accounted for. The rationale for and recent reports on combination therapy are presented in this review.     

Molecular pharmacotherapeutic targeting of PDE5 for preservation of penile health

The molecular science of erection physiology has established that phosphodiesterase 5 (PDE5) serves an important biological role in the penis. Current research in the field has revealed this molecular effector to be relevant for penile erection, controlling the erectile response by degrading the second messenger product of the erection mediatory nitric oxide (NO) signaling pathway, 3', 5'-cyclic guanosine monophosphate. Accordingly, PDE5 has been targeted for sexual medicine purposes, and orally administered PDE5 inhibitors such as sildenafil, tadalafil, and vardenafil comprise a foremost intervention for erectile dysfunction (ED). New investigation of PDE5 regulation in the penis has suggested alternative roles for the enzyme and new therapeutic opportunities involving its molecular interactions. In particular, PDE5 function is altered under derangements of androgen deficiency, decreased NO bioactivity, and oxidative stress-associated inflammatory changes, thus contributing to an assortment of erectile disorders including hypogonadism-associated ED, recurrent ischemic priapism, penile vasculopathy, and penile fibrosis. This review provides a critical examination of the multifaceted role of the PDE5 regulatory system in the penis and its relevance for applying existing and emerging therapeutic strategies for erectile disorders.     

Testosterone and Erection: Practical Management for the Patient with Erectile Dysfunction

Although erectile dysfunction (ED) and testosterone deficiency syndrome are two independently distributed disorders, there is a degree of overlap between them. Testosterone replacement therapy, either alone or combined with other treatments such as a phosphodiesterase type 5 (PDE5) inhibitor, may therefore be useful in some men with ED. Corrective treatment of ED includes sex therapy, risk factor modification, chronic usage of PDE5 inhibitors, and testosterone replacement. Studies have shown that testosterone replacement in men with hypogonadism improves libido and erectile function in a significant proportion of cases. If corrective treatment fails or is not indicated, symptomatic treatments such as oral PDE5 inhibitors or intraurethral/intracavernous therapy are available. PDE5 inhibitors are an excellent first-line choice, although a significant proportion of men still fail to respond to monotherapy. Testosterone deficiency may be overlooked in some men with ED and, because this may be associated with lower expression of PDE5 in the penis, it could result in failure of PDE5 inhibitor therapy. Recent recommendations, therefore, suggest the need for combination therapy in some patients. In conclusion, all men presenting with ED should have their testosterone levels checked, and testosterone replacement should be considered in those with low levels. Testosterone replacement should also be considered in hypogonadal men with ED not responding to PDE5 inhibitors. If erections remain insufficient after 3 mo, a combination of testosterone and a PDE5 inhibitor may be beneficial.     

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.     

The future of erectile dysfunction (ED)

About 30-40 % of ED patients are non-responders to PDE 5 inhibitor monotherapy. Lifestyle modifications and physical activity with weight loss enhance PDE 5 inhibitor responsiveness. The same applies for combination therapies such PDE 5 inhibitors + L-Arginine 3.000mg, PDE 5 inhibitors + statins and PDE 5 inhibitors + Yohimbine. Combination of daily dosing with Tadalafil 5 mg and on demand application of sildenafil or vardenafil can improve responsiveness and erection hardness (personal experiences). Guanylate cyclase activators or RhoA-kinase inhibitors, either as monotherapy or in combination with PDE 5 inhibitors have shown in preclinical settings the potential to improve erectile function and represent targets for new ED drugs in the future. Immunophilin ligands were able to ameliorate erectile function after cavernous nerve injury due to pelvic surgery. Although having shown convincing efficacy both in animals and humans the centrally acting Melanocortin Receptor (MCR) Agonists were given up for ED treatment because of unfavorable side-effects.Promising targets for ED therapy in the future is gene therapy with several targets as well as stem cell therapy with adipose-derived or muscle-derived stem cells.     

The cyclic GMP-specific phosphodiesterase inhibitor, sildenafil, stimulates human sperm motility and capacitation but not acrosome reaction

Capacitation is the series of transformations that spermatozoa undergo in the female genital tract in order to bind to the zona pellucida, initiate the acrosome reaction, and fertilize an egg. Cyclic adenosine monophosphate (cAMP) plays an important role in this process and its levels are regulated by 2 key enzymes, adenylyl cyclase and cyclic nucleotide phosphodiesterase (PDE), the latter being involved in cAMP degradation. Evidence was provided for the involvement of PDE in sperm motility and capacitation. Of the 10 gene families of PDE that exist in mammalian tissues, the calcium-calmodulin-dependent (type 1) and the cAMP-specific (type 4) have been found in human spermatozoa. Using sildenafil, we investigated a highly potent cyclic guanosine monophosphate (cGMP)-specific PDE (type 5) inhibitor and whether this PDE is present in human spermatozoa and is involved in sperm functions. Sildenafil inhibited PDE activity of Percoll-washed spermatozoa with an IC50 of 97+/-3 and 33+/-3 microM when cAMP and cGMP, respectively, were used as substrates. Because the IC50 of sildenafil obtained for PDE type 5 is much lower (2 to 6 nM) than that obtained with sperm PDE, the data suggest that PDE type 5 represents only a small fraction of the whole PDE activity of spermatozoa. Sildenafil causes dose-dependent increases in sperm cAMP levels and capacitation, which are associated with an increase in the levels of tyrosine phosphorylation of 2 fibrous sheath proteins (p105/81). Sperm velocity, amplitude of lateral head displacement, and hyperactivation were increased at 30-180 minutes. Sildenafil did not trigger the acrosome reaction in capacitated spermatozoa. These results suggest that under our experimental conditions, sildenafil triggers human sperm motility and capacitation, probably via its inhibitory action on PDE activity other than type 5 with a resultant rise in cAMP levels.     

伐地那非治疗难治性勃起功能障碍的最新进展

5型磷酸二酯酶(phosphodiesterase 5,PDE5)在阴茎勃起功能中所起的作用越来越引起人们的关注。环磷酸鸟苷(cGMP)信号通路介导的一氧化氮平滑肌舒张效应是正常勃起功能的必要条件,这个信号通路的下调能引起勃起功能障碍(erectile dysfunction,ED)的许多病理状态,并导致一些慢性疾病的发生。本文回顾了伐地那非治疗ED患者的有效性和安全性。结果表明,伐地那非对于合并异常脂蛋白血症和高血压、糖尿病、抑郁症、前列腺切除术后、外伤性脊髓损伤、西地那非治疗无效、肾移植术后、慢性前列腺炎和早泄的ED患者安全有效,为这些难治性ED患者提供了一种合理的治疗选择。另外,伐地那非还能延长ED患者的勃起时间。     

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.     

磷酸二酯酶抑制剂在肺水肿、肺高压和急性肺损伤方面的研究新进展

背景磷酸二酯酶抑制剂（phosphodiesterase inhibitors,PDEIs）是一类抑制磷酸二酯酶（phosphodiesterases,PDEs）活性的药物,其主要作用是抑制PDEs的活性,降低细胞内第二信使环磷酸腺苷（cyclic adenosine monophosphate,cAMP）或环磷酸鸟苷（cyclic guanosine monophosphate,cGMP）的水解,因而提升cAMP或cGMP的浓度,产生多种生物学效应。选择性PDE3、PDE4、PDE5抑制剂早期多应用于心血管功能调整方面,近来扩展到其他治疗领域。目的介绍PDE3、PDE4和PDE5抑制剂在肺水肿、肺高压和急性肺损伤方面的研究新进展。内容肺血管内皮细胞和肺血管平滑肌细胞分别有PDE3、PDE4和PDE5分布,它们在维持血管内皮的完整性以及血管平滑肌的舒缩方面发挥着一定生物学作用。现对PDEIs通过抑制PDE活性,影响肺血管内皮细胞完整性以及肺微血管的舒缩功能,达到保护和维持肺内皮和肺血管功能的作用机制及研究新进展方面进行介绍。趋向通过了解PDEIs药物治疗的药理学基础,有望今后在临床治疗肺高压、肺水肿和肺损伤方面发挥更大的作用。     

Characteristics of photoreceptor PDE (PDE6): similarities and differences to PDE5

Phosphodiesterase 6 (PDE6) is highly concentrated in the retina. It is most abundant in the internal membranes of retinal photoreceptors, where it reduces cytoplasmic levels of cyclic guanosine monophosphate (cGMP) in rod and cone outer segments in response to light. The rod PDE6 holoenzyme comprises alpha and beta catalytic subunits and two identical inhibitory gamma subunits. Each catalytic subunit contains three distinct globular domains corresponding to the catalytic domain and two GAF domains (responsible for allosteric cGMP binding). The PDE6 catalytic subunits resemble PDE5 in amino-acid sequence as well as in three-dimensional structure of the catalytic dimer; preference for cGMP over cyclic adenosine monophosphate (cAMP) as a substrate; and the ability to bind cGMP at the regulatory GAF domains. Most PDE5 inhibitors inhibit PDE6 with similar potency, and electroretinogram studies show modest effects of PDE5 inhibitors on visual function-an observation potentially important in designing PDE5-specific therapeutic agents.     

Mechanisms of action of PDE5 inhibition in erectile dysfunction

A spinal reflex and the L-arginine-nitric oxide-guanylyl cyclase-cyclic guanosine monophosphate (cGMP) pathway mediate smooth muscle relaxation that results in penile erection. Nerves and endothelial cells directly release nitric oxide in the penis, where it stimulates guanylyl cyclase to produce cGMP and lowers intracellular calcium levels. This triggers relaxation of arterial and trabecular smooth muscle, leading to arterial dilatation, venous constriction, and erection. Phosphodiesterase 5 (PDE5) is the predominant phosphodiesterase in the corpus cavernosum. The catalytic site of PDE5 normally degrades cGMP, and PDE5 inhibitors such as sildenafil potentiate endogenous increases in cGMP by inhibiting its breakdown at the catalytic site. Phosphorylation of PDE5 increases its enzymatic activity as well as the affinity of its allosteric (noncatalytic/GAF domains) sites for cGMP. Binding of cGMP to the allosteric site further stimulates enzymatic activity. Thus phosphorylation of PDE5 and binding of cGMP to the noncatalytic sites mediate negative feedback regulation of the cGMP pathway.     

Interactions between cGMP- and cAMP-pathways are involved in the regulation of penile smooth muscle tone

Nitric oxide (NO)/cyclic GMP (cGMP)-mediated mechanisms have a pivotal function in reducing the tone of the penile smooth musculature during normal erectile responses. The cyclic AMP (cAMP) signaling pathway is also involved in the adjustment of smooth muscle contractility, and suggestions for interactions between cGMP- and cAMP-mediated mechanisms have been presented. Using activators of the cGMP- or the cAMP-pathway, as well as inhibitors of protein kinase A (PKA; cAMP-dependent kinase) and protein kinase G (PKG; cGMP-dependent kinase), the present study was undertaken to further delineate the functional relation between these pathways in the penis. In addition, the distribution of PKA and some cAMP-binding phosphodiesterases (cAMP-PDEs) were investigated in human erectile tissue. Functional experiments were performed on isolated human corpus cavernosum (HCC). The effects of an inhibitor of the PKA, Rp-8CPT-cAMPS (10 µM), or the PKG, Rp-8-pCPT-cGMPS (10 µM), on relaxation induced by the cumulative administration of sodium nitroprusside (SNP), forskolin, sildenafil or tadalafil (IC351) were studied in preparations of HCC precontracted with 1 µM norepinephrine (NE). Using immunohistochemical procedures, the presence of immunoreactivity for cAMP-PDEs PDE3, PDE4, and PDE4A, as well as for PKA was investigated in specimens of HCC from which preparations were also used in the functional experiments. Forskolin, SNP, sildenafil, and IC 351 dose-dependently reversed NE-induced tension of isolated HCC preparations. The relaxing effects of SNP were significantly attenuated by Rp-8-pCPT-cGMPS, but not by Rp-8CPT-cAMPS. In contrast, relaxation induced by forskolin, sildenafil and tadalafil were significantly reversed by both Rp-8-pCPT-cGMPS and Rp-8CPT-cAMPS. Abundant immunoreactivity for PDE3 and PKA was observed in the corpus cavernosum smooth muscle cells. Immunoreactivity for PDE4 was also detected in the smooth musculature and in the cytoplasm of endothelial cells lining the cavernous sinusoids, as well as in nerve fibres interspersing the trabecular stroma. The present results support the hypothesis of interactions between cGMP- and cAMP-mediated signals in the HCC, and suggest that the effects of inhibitors of PDE5 on isolated erectile tissue may also partly or indirectly include actions of the cAMP second messenger system. The exact mechanism by which such an interaction occurs is not clear, but it may involve altered activity of the cGMP-inhibited PDE3 brought about by a change in the intracellular levels of cGMP by the inhibition of PDE5. This will in turn lead to increasing levels of cAMP, facilitating the interaction of cAMP with the PKA. The immunoreactivity specific for PDE3, PDE4, PDE4A and PKA registered in HCC section is also in support of an important role for the cAMP/PKA-system for penile smooth muscle function.     

Sildenafil citrate, a selective phosphodiesterase type 5 inhibitor: urologic and cardiovascular implications

Erectile dysfunction (ED) occurs in varying degrees in an estimated 20 to 30 million American men and is associated with adverse effects on quality of life; particularly personal well-being, family and social interrelationships. Research into ED has focused primarily on the physiologic mechanisms of corpus cavernosum smooth muscle relaxation, and penile erection as the end result of smooth muscle relaxation. These processes are mediated by cholinergic, nonadrenergic, noncholinergic (NANC, e.g., nitric oxide), vasoactive intestinal peptide (VIP), and potentially calcitonin gene-related peptide (CGRP) containing nerves. Release of nitric oxide following sexual stimulation from non-adrenergic, non cholinergic nerves and vascular endothelium activates guanylyl cyclase and induces intracellular cGMP synthesis. In turn, cGMP results in lowering intracellular concentrations, inhibits contractility of the penile smooth muscle, and induces an erectile response. Phosphodiesterase type 5 (PDE 5) is the predominant enzyme responsible for cGMP hydrolysis in trabecular smooth muscle. Activation of PDE 5 terminates NO-induced, cGMP-mediated smooth muscle relaxation, and subsequent penile flaccidity. Sildenafil citrate is a potent PDE type 5 reversible and selective inhibitor which blocks cGMP hydrolysis effectively. FDA approval of sildenafil citrate as the first oral agent for ED in males has resulted in significant interest. We discuss the clinical and pharmacologic properties of sildenafil citrate as well as the urologic and cardiac implications.     

Erectile dysfunction in the cardiac patient

Erectile dysfunction (ED) often is caused by endothelial dysfunction and may be a sign that a patient has vascular disease elsewhere in the body. Risk factors for coronary artery disease such as lipid abnormalities, smoking, diabetes, and hypertension also are risk factors for ED. Oral therapy for ED, such as sildenafil, inhibits phosphodiesterase-5 (PDE-5) and the breakdown of cyclic guanosine monophosphate. PDE-5 inhibitors have been shown to be safe and effective for the therapy for ED, but remain contraindicated in patients receiving organic nitrates. These agents are mild vasodilators and are being investigated for their treatment potential for patients with pulmonary hypertension, heart failure, and endothelial dysfunction.     

Use of combined intracorporal injection and a phosphodiesterase-5 inhibitor therapy for men with a suboptimal response to sildenafil and/or vardenafil monotherapy after radical retropubic prostatectomy

OBJECTIVE: To report experience with combined therapy using intracorporal injection (ICI) of alprostadil and oral phosphodiesterase 5 (PDE-5) inhibitors for the minimally invasive treatment of erectile dysfunction (ED) after radical prostatectomy (RP), as PDE-5 inhibitors are effective but a few patients may have a suboptimal response. PATIENTS AND METHODS: In a retrospective study, 34 men (aged 46-66 years) had a nerve-sparing retropubic RP and subsequent ED. Patients were titrated on sildenafil citrate or vardenafil to maximum doses. All had a suboptimal response after a maximum of eight doses of oral therapy and were then treated with ICI therapy using 15 or 20 microg alprostadil. Erectile function was assessed with the Sexual Health Inventory for Men (SHIM). RESULTS: Of the 32 patients who continued combined therapy, 22 (68%) had an improvement in erectile function after ICI therapy, as assessed by the SHIM score. On follow-up, 36% of these patients used ICI therapy only intermittently, instead of regularly, as they felt that this was adequate enough for good results. CONCLUSIONS: PDE-5 oral pharmacotherapy is the most commonly used effective therapy for ED but may not be as effective in patients who have radical surgery; the addition of testosterone patches may have side-effects or be considered a risk in patients with a history of prostate cancer. The use of ICI therapy as an adjunct or maintenance therapy to their oral medication may be another alternative in these patients.