Pharmacological management of erectile dysfunction

Application of Superb Microvascular Imaging in the Diagnosis of Vascular Erectile Dysfunction

To compare the difference between superb microvascular imaging (SMI) and color doppler flow imaging (CDFI) on vascular grading and blood flow display rate of the penile cavernous artery of vascular erectile dysfunction (ED), and to evaluate the length of time to obtain blood flow spectrum. 68 patients with ED were preformed for the examination of SMI and CDFI. The difference between the two techniques on vascular grading and blood flow display rate were compared. Hemodynamic parameters, namely peak systolic velocity (PSV), end diastolic velocity (EDV), and resistant index (RI) and the length of time obtained blood flow spectrum were compared. SMI was more sensitive to assess vascular grading and blood flow display rate than CDFI (P < 0.05). Hemodynamic parameters (PSV, EDV, and RI) measured by SMI and CDFI were well correlated (r = 0.981, P < 0.001; r = 0.879, P < 0.001; r = 0.937, P < 0.001). The duration of time necessary obtained the spectrums of grade 3 and grade 4 blood flow was shorter than that of grade 1 and grade 2, and SMI was comparatively shorter than CDFI (P < 0.05). In conclusion, SMI detected the blood flow of the penile cavernous artery better and maked the examination time shorter than CDFI, which can be considered as a more effective technique to diagnose vascular ED.

Association between sexual activity-related death and non-prescription use of phosphodiesterase type 5 inhibitors

In recent years, there has been an increase in the use of phosphodiesterase type 5 inhibitors (PDE5i) that are purchased from abroad without a doctor's diagnosis via the Internet or other means. We report six cases in which nonprescription use of PDE5i may have led to death. Among the four deceased individuals who were believed to have experienced sudden cardiac death, three (cases 1-3) had a history of cardiovascular disease, which is a contraindication, and the remaining case (case 4) involved combined use of multiple PDE5i. Sildenafil (0.063 µg/mL, 0.087 µg/mL) was detected in two of the four cases of sudden cardiac death. Tadalafil (0.096 µg/mL) was detected in one of the remaining two cases, and tadalafil (0.197 µg/mL) and vardenafil (0.011 µg/mL) were detected in the other case. Sildenafil (0.032 µg/mL), tadalafil (0.062 µg/mL), and ethanol were detected in a traffic accident case with a history of contraindications. In a case of asphyxiation by vomit aspiration, autopsy showed 90% stenosis in the anterior descending branch of the coronary artery, and sildenafil (0.063 µg/mL) was detected. To the best of our knowledge, this is the first report of postmortem blood levels of tadalafil and vardenafil likely contributing to the cause of death. Despite all the warnings about the dangers of using PDE5 inhibitors, cases of PDE5i contributing to death are still identified during autopsies. Therefore, raising public awareness of the risks of the risks associated with the imported drug use by individuals is necessary.

Accurate and sensitive determination of sildenafil, tadalafil, vardenafil, and avanafil in illicit erectile dysfunction medications and human urine by LC with quadrupole-TOF-MS/MS and their behaviors in simulated gastric conditions

The widespread use of phosphodiesterase-5 inhibitors has attracted broad attention of counterfeiters to develop illicit erectile products with inaccurate amounts, unknown toxicity, and purity of active ingredients. Correspondingly, intake of these products endangers consumer health and needs to be screened for precautionary actions to reduce this risk. Therefore, in this study, a sensitive and rapid analytical method has been developed for simultaneous determination of selected phosphodiesterase-5 inhibitors present in illicit erectile medications and human urine. Quantification of the analytes was performed by liquid chromatography coupled with quadrupole-time-of-flight tandem mass spectrometry system. The chromatographic separation was successfully achieved with a run period of 8 min. Low detection limits were obtained in the range of 1.63-9.81 ng/g with relative standard deviations below 7.72% obtained using the replicate measurements of lowest concentration in calibration plots. The analytical performance of the proposed method proved good linearity, low detection limits, good accuracy and precision with high percent recoveries for human urine samples. Developed method was successfully applied to real samples including four different brands of illicit erectile medications. The results obtained revealed the presence of high levels of sildenafil in analyzed samples. The behaviors of selected phosphodiesterase-5 inhibitors were also studied in simulated gastric conditions.

Sim1 Neurons Are Sufficient for MC4R-Mediated Sexual Function in Male Mice

Sexual dysfunction is a poorly understood condition that affects up to one-third of men around the world. Existing treatments that target the periphery do not work for all men. Previous studies have shown that central melanocortins, which are released by pro-opiomelanocortin neurons in the arcuate nucleus of the hypothalamus, can lead to male erection and increased libido. Several studies specifically implicate the melanocortin 4 receptor (MC4R) in the central control of sexual function, but the specific neural circuitry involved is unknown. We hypothesized that single-minded homolog 1 (Sim1) neurons play an important role in the melanocortin-mediated regulation of male sexual behavior. To test this hypothesis, we examined the sexual behavior of mice expressing MC4R only on Sim1-positive neurons (tbMC4Rsim1 mice) in comparison with tbMC4R null mice and wild-type controls. In tbMC4Rsim1 mice, MC4R reexpression was found in the medial amygdala and paraventricular nucleus of the hypothalamus. These mice were paired with sexually experienced females, and their sexual function and behavior was scored based on mounting, intromission, and ejaculation. tbMC4R null mice showed a longer latency to mount, a reduced intromission efficiency, and an inability to reach ejaculation. Expression of MC4R only on Sim1 neurons reversed the sexual deficits seen in tbMC4R null mice. This study implicates melanocortin signaling via the MC4R on Sim1 neurons in the central control of male sexual behavior.

An Empirical vs Risk-Based Approach Algorithm to Intracavernosal Injection Therapy: A Prospective Study

Introduction

Intracavernosal injection (ICI) therapy is widely used for the treatment of erectile dysfunction (ED). Its use in practice is largely empirical and has not been validated with evidence-based approaches.

Aim

To compare two strategies for ICI, specifically a risk-based approach and an empiric-based approach, and assess the efficacy, patient satisfaction, and complication rates of the two treatment approaches.

Methods

After obtaining approval from the institutional review board, a prospective database of patients enrolled in the ICI program at the Johns Hopkins Hospital (Baltimore, MD, USA) from May 2012 through May 2014 was amassed. Demographic information, treatment outcomes, and subjective patient evaluations of sexual function (International Index of Erectile Function erectile function domain [IIEF-EF], Quality of Erection Questionnaire [QEQ], Sexual Quality of Life [SQoL], and Erectile Dysfunction Inventory of Treatment Satisfaction [EDITS]) were obtained at baseline and at 3 and 6 months. Two approaches were compared. Group 1 received empiric ICI treatment initially with prostaglandin E₁ (PGE1) 10 μg irrespective of ED etiology or severity. After initial dosing with PGE1 in the clinic, adjustments were made to titrate or change formulations pending on patient results. Group 2 received a risk-based approach, in which an algorithm that factored in ED etiology and number of ED risk factors was used for a bimix (papaverine 30 mg/mL, phentolamine 1 mg/mL), a low-dose trimix (papaverine 30 mg/mL, phentolamine 1 mg/mL, PGE1 10 μg/mL), or a high-dose trimix (papaverine 30 mg/mL, phentolamine 2 mg/mL, PGE1 40 μg/mL). Dose titration was permitted in the two groups. Statistical analysis was carried out using t-test and χ² analysis.

Main Outcome Measures

The study design was powered for a non-inferiority comparison of the two approaches, in which the primary end point was a 15-point difference on the EDITS score or a 20% difference in the IIEF-EF score.

Results

One hundred seventy-five patients were enrolled (57 in group 1, 118 in group 2) with 3- and 6-month follow-up at 57% and 35%, respectively, and similar between groups. Baseline patient characteristics and sexual function questionnaire responses were similar between groups 1 and 2, although group 1 reported higher-quality erections at baseline (QEQ score = 14.3 vs 7.3, P = .05) and had a smaller proportion of patients with prostatectomy (54.4% vs 74.6%, P = .02). In the two groups, QEQ score (mean = 10.78 vs 56.76, P < .05), SQoL score (mean = 38.41 vs 50.25, P < .05), and IIEF-EF score (mean = 7.51 vs 18.48, P < .05) improved with treatment. However, at 3 and 6 months, there were no statistically significant differences in responses for IIEF, QEQ, SQoL, or EDITS scores and no difference in failure or medication switch rates between groups. There were no significant differences in complication rates, although at 3 months group 2 reported a higher incidence of priapism and pain (23% vs 7.4%, P = .08).

Conclusion

Empiric and risk-based strategies for ICI therapy resulted in significant improvements across multiple domains of sexual function. Complication rates, satisfaction, and efficacy overall were similar between the two approaches. Clinicians can be reassured that no one approach to ICI therapy for ED management appears inferior to another.

Erectile dysfunction: a need for greater awareness

Research has led to effective treatment regimes for erectile dysfunction (ED). Convincing evidence links vascular risk factors (hypertension, diabetes mellitus, hyperlipidaemia and smoking) with ED. This association is not surprising since the corpus cavernosum is a modified vascular tissue. This review presents a brief account of the aetiology, diagnosis and treatment of ED. There is a need to raise awareness of this condition and to make appropriate treatment available to patients.

[Medicinal therapy of benign prostate syndrome with phosphodiesterase-5 inhibitors]

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.

saRNA guided iNOS up-regulation improves erectile function of diabetic rats

PURPOSE

Promoter targeted saRNAs mediate sequence specific up-regulation of gene expression. We explored the therapeutic effect of RNA activation mediated iNOS gene activation on improving erectile function in a rat model of diabetes mellitus.

MATERIALS AND METHODS

An optimal saRNA sequence specific for iNOS promoter was cloned into an adenoviral vector, resulting in AdU6/shiNOS and AdU6/shControl. The corresponding viruses were used to transduce cultured rat cavernous smooth muscle cells. Streptozotocin induced diabetes models were established in rats and used to test the effects of intracavernous delivery of iNOS saRNA viruses on erectile function. iNOS expression in the cavernous smooth muscle cells or penile tissue of treated rats was assessed by reverse transcriptase-polymerase chain reaction and Western blot. Cyclic guanosine monophosphate was analyzed by enzyme-linked immunosorbent assay. Intracavernous pressure in response to cavernous nerve stimulation was measured using a data acquisition system on post-injection days 1, 3, 5, 7, 10 and 14.

RESULTS

Adenovirus mediated expression of iNOS saRNA caused sustained up-regulation of iNOS in cavernous smooth muscle cells. Intracavernous injection of AdU6/shiNOS activated iNOS expression in vivo and significantly increased peak intracavernous pressure in streptozotocin induced diabetic rats via nitric oxide/intracellular cyclic guanosine monophosphate activation.

CONCLUSIONS

Results show that saRNA mediated iNOS over expression in the penis can restore erectile function in streptozocin diabetic rats via the nitric oxide-cyclic guanosine monophosphate pathway.

What is the role of unripe Rubus coreanus extract on penile erection?

The effect of unripe Rubus coreanus extract on rabbit penile corpus cavernosum (PCC) was evaluated. Penises were obtained from healthy male New Zealand white rabbits (2.5-3.0 kg). The pre-contracted penis with phenylephrine (Phe, 10 μM) was treated with various concentrations of an extract of unripe R. coreanus (0.5, 1, 2, 3 and 4 mg/mL). The change in penile tension was recorded, cyclic nucleotides in the perfusate and the PCC were measured by radioimmunoassay, and the expression of neuronal nitric oxide synthase (nNOS) and endothelial nitric oxide synthase (eNOS) in the perfused PCC were measured by western blotting. The interaction between unripe R. coreanus and sildenafil was also evaluated. The PCC relaxation induced by the extracts of R. coreanus was in a concentration-dependent manner and enhanced sildenafil-induced PCC relaxation. The perfusion of penile cavernous tissue with the unripe R. coreanus extract increased cGMP and cAMP in the tissue and in the perfusate and the expression of eNOS and nNOS in the tissue. The unripe R. coreanus extract exerts a relaxing effect on penile cavernous tissue in part by activating the NO-cGMP system and it may improve erectile dysfunction (ED), which does not completely respond to sildenafil citrate.

The role of capillarisin from Artemisia capillaris on penile erection

The objective of this study was to evaluate the effect and mechanism of capillarisin from Artemisia capillaris (A. capillaris) on rabbit penile corpus cavernosum (PCC). The pre-contracted New Zealand White rabbit (2.5-3.0 kg) penis with phenylephrine (Phe; 10⁻⁵  M) was treated with various concentrations of ethanol extract of A. capillaris (0.1, 0.5, 1, and 2 mg/mL) and capillarisin, the active component of A. capillaris (10⁻⁷, 10⁻⁶, 10⁻⁵ and 10⁻⁴  M). Capillarisin was also applied to PCC tissues contracted with Phe, which were pre-incubated with phosphodiesterase type 5 inhibitors (PDE5 Is). Cyclic nucleotides in the perfusate were measured by radioimmunoassay. The tissues were pre-incubated with Nω nitro-l-arginine-methyl ester (L-NAME, 10⁻³  M) and 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10⁻⁵  M) to block nitric oxide (NO) synthase and guanylate cyclase, respectively. Capillarisin induced penile relaxation and enhanced PDE5 Is-induced relaxation. Capillarisin increased cGMP and cAMP in the perfusate. The application of capillarisin on PCC pre-treated with L-NAME and ODQ significantly inhibited the relaxation. Capillarisin exerts the relaxing effect on PCC by activating the NO-cGMP and adenylyl cAMP signaling pathways and may become an alternative medicine for patients who want to use natural products to improve erectile function or do not completely respond to PDE5 Is.

Effects of tetrandrine on cAMP and cGMP levels in rabbit corpus cavernosum in vitro

The aim of this study was to further investigate the relaxation mechanism of tetrandrine (Tet), a bis-benzylisoquinoline alkaloid isolated from the Chinese medicinal herb-root of Stephania tetrandra S Moore, on rabbit corpus cavernosum tissue in vitro. The effects of Tet on the concentrations of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in isolated and incubated rabbit corpus cavernosum tissue were recorded by means of (125)I radioimmunoassay. The basal concentration of cAMP in corpus cavernosum tissue was 5.67 +/- 0.97 pmol mg(-1). Tet increased the cAMP concentration in a dose-dependent manner (p < 0.05), but this effect was not inhibited by an adenylate cyclase inhibitor (cis-N-(2-phenylcyclopentyl)azacyclotridec-1-en-2-amine, MDL-12, 330A) (p > 0.05). The accumulation of cAMP induced by prostaglandin E(1) (PGE(1), a stimulator of cAMP production) was also augmented by Tet in a dose-dependent manner (p < 0.05). The basal concentration of cGMP in corpus cavernosum tissue is 0.44 +/- 0.09 pmol mg(-1). Tet did not affect this concentration of cGMP, neither in the presence nor the absence of a guanyl cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, ODQ) (p > 0.05). Further, sodium nitroprusside (SNP, a stimulator of cGMP production)-induced cGMP production was not enhanced by Tet (p > 0.05). Tet, with its relaxation mechanism, can enhance the concentration of cAMP in rabbit corpus cavernosum tissue, probably by inhibiting PDEs activity.

Chuanxiongzine relaxes isolated corpus cavernosum strips and raises intracavernous pressure in rabbits

It has been shown that there are many Chinese traditional herbals that can enhance sexual activity. Chuanxiongzine is a vasoactive ingredient that has been isolated and purified from Ligusticum chuanxiong Hort. In previous studies, it has been found that chuanxiongzine was effective in relaxing rabbit corpus cavernosum smooth muscle. We determined the effects of chuanxiongzine on relaxation of isolated corpus cavernosum strips in vitro and on increase of intracavernous pressure (ICP) in vivo in rabbits. Chuanxiongzine caused a concentration-dependent relaxation of phenylephrine precontracted isolated corpus cavernosum strips (EC₅₀ 1.58 × 10⁻⁴ mol l⁻¹), which were endothelium independent and NO independent. However, the guanylyl cyclase inhibitor 1-H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one significantly shifted the chuanxiongzine concentration–response relationship to the right. Although there was no significant difference in the level of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) in isolated corpus cavernosum strips treated with chuanxiongzine or vehicle, chuanxiongzine caused a significant rise in the level of cGMP and cAMP in isolated corpus cavernosum strips pretreated with the activator of adenylyl cyclase forskolin and the source of NO sodium nitroprusside. In an in vivo study, chuanxiongzine dose-dependently raised ICP after the intracavernous injection of its cumulative doses (0.5, 1, 2 and 5 mg kg⁻¹). The ICP increased from baseline to 19.1±3.7, 24.8±2.1, 30.2±4.8 and 39.7±6.1 mm Hg, respectively, and the duration of tumescence ranged from 8.5±2.8 to 22.9±7.3 min. Our results show that chuanxiongzine can relax isolated corpus cavernosum strips of rabbits in vitro and increase ICP of rabbits in vivo, which is neither endothelium dependent nor NO dependent, but may be partly mediated by the inhibition of cAMP phosphodiesterase or cGMP phosphodiesterase.

The relaxation mechanisms of tetrandrine on the rabbit corpus cavernosum tissue in vitro

The relaxation mechanisms of tetrandrine (Tet) on the rabbit corpus cavernosum tissue in vitro were investigated. Strips of rabbit corpus cavernosum were mounted in organ chambers. The effects of Tet were examined on isolated muscle strips pre-contracted with phenylephrine (PE) alone, in the presence of N(W)-nitro-L-arginine (LNNA, a nitric oxide synthase inhibitor), 1-H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one(ODQ, a guanylyl cyclase inhibitor), indomethacin (cyclooxygenase inhibitor), tetraethylammonium (TEA, Ca(2+)-activated K(+) channel blocker), 4-aminopiridine (4-AP, voltage dependent K(+) channel blocker) and glibenclamide (ATP sensitive K(+)channel blocker). The effects of Tet on KCl-induced contraction of isolated muscle strips were also investigated. The procedure of calcium absence-calcium addition was designed to observe the effect of Tet on the two components of the contractile responses to PE based on the source of Ca(2+) (extracellular vs. intracellular). Corpus cavernosum strips showed relaxation in response to Tet (10(-8) approximately 10(-3) mol L(-1)) in a concentration-dependent manner with an IC(50) of 3.73 x 10(-5) mol L(-1). However, they were not affected by LNNA, ODQ, indomethacin and K(+)-channel blockers. Tet (10 micromol L(-1), 30 micromol L(-1)) concentration dependently reduced the maximal contraction response of isolated strips induced by KCl to (73.0 +/- 3.8) and (41.5 +/- 3.4)%, respectively (p < 0.01). In the procedure of calcium absence-calcium addition, Tet 100 micromol L(-1) inhibited both intracellular calcium-dependent and extracellular calcium-dependent contraction induced by PE (20 micromol L(-1)) (p < 0.05). The inhibition ratios were (23.8 +/- 7.1) and (40.7 +/- 11.2)%, respectively. The results of the present study suggest that Tet possesses a relaxant effect on rabbit corpus cavernosum tissues, which is attributable to the inhibition of extracellular Ca(2+) influx and the inhibition of release of intracellular-stored Ca(2+), but not mediated by the release of nitric oxide, prostaglandins or by the activation of potassium channels.

Phosphodiesterase inhibition in heart failure

Drugs that inhibit cyclic nucleotide phosphodiesterase activity act to increase intracellular cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) content. In total, 11 families of these enzymes-which differ with respect to affinity for cAMP and cGMP, cellular expression, intracellular localization, and mechanisms of regulation-have been identified. Inhibitors of enzymes in the PDE3 family of cyclic nucleotide phosphodiesterases raise intracellular cAMP content in cardiac and vascular smooth muscle, with inotropic and, to a lesser extent, vasodilatory actions. These drugs have been used for many years in the treatment of patients with heart failure, but their long-term use has generally been shown to increase mortality through mechanisms that remain unclear. More recently, inhibitors of PDE5 cyclic nucleotide phosphodiesterases have been used as cGMP-raising agents in vascular smooth muscle. With respect to cardiovascular disease, there is evidence that these drugs are more efficacious in the pulmonary than in the systemic vasculature, for which reason they are used principally in patients with pulmonary hypertension. Effects attributable to inhibition of myocardial PDE5 activity are less well characterized. New information indicating that enzymes from the PDE1 family of cyclic nucleotide phosphodiesterases constitute the majority of cAMP- and cGMP-hydrolytic activity in human myocardium raises questions as to their role in regulating these signaling pathways in heart failure.

Relaxation mechanisms of neferine on the rabbit corpus cavernosum tissue in vitro

AIM

To investigate the relaxation mechanisms of neferine (Nef) on the rabbit corpus cavernosum tissue in vitro.

METHODS

Strips of rabbit corpus cavernosum were mounted in organ chambers. The effects of Nef were examined on isolated muscle strips precontracted with phenylephrine (PE) alone, in the presence of N(W)-nitro-L-arginine (LNNA, a nitric oxide synthase inhibitor), 1-H-[1,2,4]oxadiazolo[4,3-alpha]quinoxalin-1-one (ODQ, a guanylyl cyclase inhibitor), indomethacin (cyclooxygenase inhibitor), tetraethylammonium (Ca(2+)-activated K(+) channel blocker), 4-aminopiridine (4-AP, voltage dependent K(+) channel blocker) and glibenclamide (ATP sensitive K(+) channel blocker). The effects of Nef on KCl-induced contraction of isolated muscle strips were also investigated. The procedure of calcium absence-calcium addition was designed to observe the effect of Nef on two components of the contractile responses to PE based on the source of Ca(2+) (extracellular vs. intracellular).

RESULTS

Corpus cavernosum strips relaxed in response to Nef (10(-9)-10(-4) mol/L) in a concentration-dependent manner with an IC(50) of 4.60 X 10(-6) mol/L. However, they were not affected by LNNA, ODQ, indomethacin or K(+)-channel blockers. Nef (10(-6) mol/L, 10(-5) mol/L) concentration dependently reduced the maximal contraction response of isolated strips induced by KCl to 79.3%+/-5.5% and 61.5%+/-3.2%, respectively (P < 0.01). In the calcium absence-calcium addition procedure, Nef 10(-5) mol/L inhibited both intracellular calcium-dependent and extracellular calcium-dependent contraction induced by PE (2 X 10(-5) mol/L) (P < 0.05). The inhibition ratios were 26.2%+/-5.4% and 48.3%+/-7.6%, respectively.

CONCLUSION

The results of the present study suggest that Nef possesses a relaxant effect on rabbit corpus cavernosum tissues, which is attributable to the inhibition of extracellular Ca2+ influx and the inhibition of release of intracellular stored Ca(2+), but not mediated by the release of nitric oxide, prostaglandins or by the activation of potassium channels.

Effects of plant extract neferine on cyclic adenosine monophosphate and cyclic guanosine monophosphate levels in rabbit corpus cavernosum in vitro

AIM

To further investigate the relaxation mechanism of neferine (Nef), a bis-benzylisoquinoline alkaloid extracted (isolated) from the green seed embryo of Nelumbo nucifera Gaertn in China, on rabbit corpus cavernosum tissue in vitro.

METHODS

The effects of Nef on the concentrations of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in isolated and incubated rabbit corpus cavernosum tissue were recorded using 125I radioimmunoassay.

RESULTS

The basal concentration of cAMP in corpus cavernosum tissue was 5.67 +/- 0.97 pmol/mg. Nef increased the cAMP concentration in a dose-dependent manner (P < 0.05), but this effect was not inhibited by an adenylate cyclase inhibitor (cis-N-[2-phenylcyclopentyl]azacyclotridec-1-en-2-amine, MDL-12, 330A) (P > 0.05). The accumulation of cAMP induced by prostaglandin E1 (PGE1, a stimulator of cAMP production) was also augmented by Nef in a dose-dependent manner (P < 0.05). The basal concentration of cGMP in corpus cavernosum tissue is 0.44 +/- 0.09 pmol/mg. Nef did not affect this concentration of cGMP, either in the presence or in the absence of a guanyl cyclase inhibitor (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one, ODQ) (P > 0.05). Also, sodium nitroprusside (SNP, a stimulator of cGMP production)-induced cGMP production was not enhanced by Nef (P > 0.05).

CONCLUSION

Nef, with its relaxation mechanism, can enhance the concentration of cAMP in rabbit corpus cavernosum tissue, probably by inhibiting phosphodiesterase activity.

Giving patients with erectile dysfunction the opportunity to try all three available phosphodiesterase type 5 inhibitors contributes to better long-term treatment compliance

INTRODUCTION

There are three phosphodiesterase type 5 (PDE5) inhibitors marketed, sildenafil, Vardenafil, and tadalafil for oral treatment of erectile dysfunction (ED). Although the treatment is simple and mostly effective, around 50% has ceased to use the medication within 2 years. One recently described way to improve the compliance is to let the patient try all the three PDE5 inhibitors and to prescribe the drug(s) he and his partner desires.

AIM

To study long-term compliance among patients who were treated according to this "three-drug regime."

MAIN OUTCOME MEASURES

Compliance and reasons for discontinuation after >2 years.

METHODS

The men who, during 2003, were enrolled in a treatment regime, where they had the opportunity to test all the three drugs and to chose the one(s) they preferred, were interviewed in 2006 by telephone concerning their ongoing ED treatment and the reason for discontinuation.

RESULTS

Of the 138 men, mean age 60 years (36-79 years), who had been enrolled and successfully treated with the three-drug regime, 127 (92%) could be reached. The mean follow-up time was 27 months (23-34 months). Of the 127 men, as many as 109 (86%) were still using PDE5 inhibitors. A few (8%) used more than two tablets per week. The majority (44%) used one to two tablets per week or one to two per month (43%), the others (5%) less often. The causes for discontinuation were varying. The most common reason (N = 7) was return of a satisfactory non-assisted erection. Seventy-five percent of the men used only one drug; the others switched between a short- and long-acting drug depending on the situation. It was not uncommon (25%) that the preference had changed during the 3 years of PDE5 inhibitor use.

CONCLUSION

To let patients with ED test the three available PDE5 inhibitors results in an unusually high compliance even under an extended period of time (>2 years).

Effects of neferine on cytosolic free calcium concentration in corpus cavernosum smooth muscle cells of rabbits

To study the relaxation mechanisms of neferine (Nef) on the corpus cavernosum smooth muscle (CCSM), the CCSM cells from New Zealand White rabbits were cultured in vitro. [Ca(2+)](i) was measured by fluorescence ion digital imaging system (FIDIS), using Fluo-2/AM as a Ca(2+)-sensitive fluorescent indicator. Nef (0.1, 1 and 10 micromol l(-1)) had no effect on the resting [Ca(2+)](i) (P > 0.05). In the presence of extracellular Ca(2+) (2.5 mmol l(-1)), Nef (0.1, 1 and 10 micromol l(-1)) inhibited [Ca(2+)](i) elevation induced by high K(+) and phenylephrine (PE) in a concentration-dependent manner (P < 0.05). In calcium free solution containing egtaic acid (EGTA), Nef (0.1 micromol l(-1)) had no inhibitory effects on [Ca(2+)](i) elevation induced by PE (P > 0.05). However, Nef (1 and 10 micromol l(-1)) inhibited [Ca(2+)](i) elevation induced by PE (P < 0.05). These data suggest that Nef inhibited [Ca(2+)](i) in CCSM cells via blocking voltage-dependent Ca(2+) channel, alpha(1)-adrenoceptor-operated Ca(2+) channel and Ca(2+) release from intracellular Ca(2+) pool. This inhibitory action on [Ca(2+)](i) might be one of the relaxation mechanisms of Nef on the CCSM.

Is sex only for the healthy and wealthy?

OBJECTIVE

To study reasons for Sildenafil (a phosphodiesterase type 5 inhibitor) treatment abortion in erectile dysfunction (ED), with special regard to the relation between cost and use.

METHODS

Men (N = 132) with ED, where treatment with Sildenafil was instituted between 1998 and 2000, were mailed a questionnaire in February 2003, regarding their current ED treatment, including frequency of use, reasons for change or discontinuation, effect on partner relations, and total income of the household.

RESULTS

The response rate was 69%. Nearly every second man (47%) still used Sildenafil at least twice per month. The remaining 53% had aborted oral ED treatment: 10% due to return of normal erections, 43% due to (either alone or in combination): cost of treatment, impaired health, loss of efficacy, change to another ED treatment, or side-effects. Cost was the most common cause (48%) for discontinuation. In low-income households, rationing of treatment or abortion due to the cost was reported significantly (P < 0001) more often (86%) than in high-income households (35%).

CONCLUSION

Just under half of all the patients (47%) used Sildenafil for more than 2 years after initiation of treatment. The cost of the treatment is an important factor for patient compliance in households with a low income, despite the fact that the treatment is highly effective and improves the partner relationship.

Sexual sequelae of general medical disorders

That sexual symptoms can signal serious underlying disease confirms the importance of sexual enquiry as an integral component of medical assessment. Data on sexual function are sparse in some medical specialties. However, increased scientific understanding of the central and peripheral physiology of sexual response could help to identify the pathophysiology of sexual dysfunction from disease and medical interventions, and also to ameliorate or prevent some dysfunctions. Many common general medical disorders have negative effects on desire, arousal, orgasm, ejaculation, and freedom from pain during sex. Chronic disease also interferes indirectly with sexual function, by altering relationships and self-image and causing fatigue, pain, disfigurement, and dependency. Current approaches to assessment of sexual dysfunction are based on models that combine psychological and biological aspects.

Efficacy and Safety of Tadalafil in Men with Erectile Dysfunction with a High Prevalence of Comorbid Conditions: Results from MOMENTUS: Multiple Observations in Men with Erectile Dysfunction in National Tadalafil Study in the US

INTRODUCTION

Limited efficacy and safety data exist from open-label clinical trials of phosphodiesterase 5 inhibitors in men with erectile dysfunction (ED) and multiple comorbid (MCM) conditions, historically a difficult group to treat.

AIM

A multicenter study (Multiple Observations in Men with Erectile Dysfunction in National Tadalafil Study in the US) assessed efficacy and safety of tadalafil in men with ED and MCM conditions.

MAIN OUTCOME MEASURES

The primary end point was change from baseline in the erectile function (EF) domain of the International Index of Erectile Function. Secondary end points included the Sexual Encounter Profile, Global Assessment Questions, and Sexual Self-Confidence and Spontaneity Domains of the Psychological and Interpersonal Relationship Scales.

METHODS

This was an open-label, multicenter study in men with ED. Tadalafil 20 mg was administered as needed prior to sexual activity, up to once/day, for 12 weeks following a 4-week ED-treatment-free period. The MCM group was 155 of 1,911 men enrolled in this study. Men in the MCM group met eligibility criteria but could not be included in other predefined groups: (i) Caucasian; (ii) Black American; (iii) Hispanic (groups 1-3, < or =65 years, no diabetes or depression); (iv) depression, < or =65 years, no diabetes; (v) diabetes, < or =65 years, no depression; (vi) >65 years, no diabetes or depression; and (vii) ED subsequent to traumatic spinal cord injury.

RESULTS

Mean baseline EF domain score in MCM (mean age 65 +/- 9 years) was 12.2 +/- 6.5; 52% of subjects had severe ED; 72% diabetes mellitus; 67% cardiovascular disease (including hypertension); 49% hyperlipidemia; 38% depression; 84% had two or more comorbidities. At end point, there was a significant (P < 0.001) mean change of 7.6 from baseline in mean EF domain score. Among men with severe ED, 22% achieved an EF domain score > or =26. Most common adverse events were headache 5.2%; flushing 3.9% and nasal congestion 3.2%; 3% discontinued use because of an adverse event.

CONCLUSIONS

In this open-label clinical trial of older men with ED and MCMs, tadalafil 20 mg significantly increased all efficacy end points and was well-tolerated.

Antidepressants and sexual dysfunction

OBJECTIVE

Many patients with depression suffer from sexual dysfunction and sexual dysfunction is a recognized side-effect of antidepressants. The aim of this review was to examine the prevalence of psychosexual dysfunction associated with antidepressants, and to review treatment options which are specific to the affected component of sexual functioning and antidepressants.

METHOD

Comprehensive literature review using Medline and Cochrane databases.

RESULTS

Up to 70% of patients with depression may have sexual dysfunction. Tricyclic antidepressants, selective-serotonin reuptake inhibitors and venlafaxine are most and the non-serotonergic antidepressants and duloxetine least likely to produce sexual dysfunction. Pharmacological treatment options include antidepressants less likely associated or 'antidotes' to reverse sexual dysfunction.

CONCLUSION

Sexual dysfunction may be a preventable or treatable side-effect of antidepressants. Patients need routinely to be asked about sexual function to identify problems early. If sexual dysfunction is ignored it may maintain the depression, compromise treatment outcome and lead to non-compliance.

Does the clinical efficacy of vardenafil correlate with its effect on the endothelial function of cavernosal arteries? A pilot study

OBJECTIVE

To investigate whether the results of the ultrasonographic (US) measurement of post-occlusive changes in the diameters of cavernosal arteries after administering phosphodiesterase type 5 (PDE-5) inhibitor vardenafil could be associated with the response to vardenafil in patients with erectile dysfunction (ED), as currently there are no reliable methods for predicting the success rate of oral PDE-5 inhibitors.

PATIENTS AND METHODS

The study included 122 men with ED; after a complex evaluation, the endothelial function of the cavernosal arteries was assessed in all patients before and 1 h after oral ingestion of vardenafil (20 mg), using our modification of the US assessment of post-occlusive changes in the diameter of cavernosal arteries. After the evaluation, all patients received vardenafil 20 mg on demand for 4 weeks. A successful response was defined using two endpoints, i.e. the normalization of the International Index of Erectile Function Erectile Function domain score (> or = 26) and positive answers to both Sexual Encounter Profile questions 2 and 3 on > or = 75% of occasions, based on the diary data collected.

RESULTS

In all patients the mean (sd) initial percentage increase in the cavernosal artery diameter (PICAD) in responders and nonresponders was not statistically different, at 49 (24) and 43 (26), respectively (P = 0.168), but PICAD values after vardenafil were significantly greater in responders, at 73 (16) vs 55 (23) (P < 0.001). Analysis of data from patients with different causes of ED showed statistically significant differences in PICAD between responders and nonresponders only in those with arteriogenic ED. The sensitivity and specificity of a PICAD of > or = 50% after taking vardenafil 20 mg for predicting a positive response to the same dose of the drug in patients with arteriogenic ED were 94.9% and 91.3%, respectively.

CONCLUSION

The results of the US assessment of post-occlusive changes in the diameter of cavernosal arteries after vardenafil administration are significantly associated with the clinical efficacy of the drug in patients with arteriogenic ED.

A comparative review of apomorphine formulations for erectile dysfunction : recommendations for use in the elderly

Erectile dysfunction (ED) is a common medical condition that affects the sexual life of millions of men worldwide. First-line oral therapy for ED includes the use of phosphodiesterase type 5 inhibitors (sildenafil, tadalafil and vardenafil) and sublingual apomorphine. Apomorphine is a dopamine D(1) and D(2) receptor agonist that has been approved for marketing in Europe. Different apomorphine formulations have been tested, such as sublingual, subcutaneous and intranasal. However, the sublingual formulation has shown the best results in terms of efficacy, safety and tolerability, especially the 2mg and 3mg doses. Although clinical studies of the efficacy and tolerability of apomorphine sublingual (SL) have included older patients, who are more likely to have ED, no study has specifically assessed the efficacy and tolerability of different doses of apomorphine SL in aging men. Therefore, a MEDLINE search was conducted from January 1987 to November 2005 to identify studies of the efficacy, safety (in particular cardiovascular safety) and tolerability of different apomorphine formulations and doses as treatments for ED in the subcohort of aging men. On the basis of the most recent peer-reviewed publications, the first part of this article critically evaluates data regarding the epidemiology of ED in the aging population. The second part of the article focuses on the mechanism of action and pharmacokinetics of apomorphine both in the general and the elderly population. Finally, a critical analysis of the efficacy and safety of different apomorphine formulations and doses for the treatment of ED is reported. Apomorphine represents a first-line oral treatment for ED. Available formulations include only sublingual administration. Few studies have assessed the efficacy and safety of apomorphine in the elderly population. However, in clinical practice, older patients with multiple vascular risk factors and systematic vascular damage show poor overall response to apomorphine SL for the treatment of ED.

Role of the brain in the control of erection

In contrast to the spinal control of erection, relatively little is known about the brain control. In the present review, we have outlined the role of brain structures involved in penile erection and provided a synopsis on the brain circuit of erection. Findings from both animal and human studies are discussed. Evidence suggests that the most important structures are the frontal lobe, cingulate gyrus, amygdala, thalamus and hypothalamus. Within the brain circuit of erection, the thalamus serves as a gate-controller in which all relevant information is evaluated and further processed to higher and lower centres.

Tyrosine-612 in PDE5 contributes to higher affinity for vardenafil over sildenafil

Despite close structural similarity, vardenafil (Levitra) is 32-fold more potent than sildenafil (Viagra) to inhibit cGMP-binding cGMP-specific PDE (PDE5); this is due to differences between their heterocyclic rings. In co-crystals with PDE5, one of the rings of vardenafil or sildenafil interacts with Tyr(612), a catalytic site AA, via (1) a hydrogen bond with a water molecule and (2) hydrophobic bonds. For mutant PDE5(Y612F), which ablates hydrogen-bonding potential, vardenafil or sildenafil inhibition was strengthened (2.2- or 3.0-fold, respectively), implying that the Tyr(612) hydroxyl is a negative determinant for these inhibitors. For mutant PDE5(Y612A), which ablates both hydrogen bonding and hydrophobic-bonding potential, vardenafil inhibition was weakened much more than sildenafil inhibition (122- and 26-fold, respectively), suggesting that hydrophobic bonds involving Tyr(612) are stronger for vardenafil than for sildenafil.

Inhibitors of cyclic nucleotide phosphodiesterase 3 and 5 as therapeutic agents in heart failure

Cyclic nucleotide phosphodiesterases (PDE) 3 and 5 regulate cAMP and cGMP signalling in cardiac and smooth muscle myocytes. Important advances in the understanding of the roles of these enzymes have recently been made. PDE3 inhibitors have inotropic and vasodilatory properties, and although they acutely improve haemodynamics in patients with heart failure, they do not improve long-term morbidity and mortality. Although combination therapy with beta-adrenergic receptor antagonists or selective inhibition of specific PDE3 isoforms might result in a more favourable long-term outcome, more clinical data are needed to test this proposition. The role of PDE5 inhibitors in the treatment of cardiac disease is evolving. PDE5 inhibitors cause pulmonary and systemic vasodilation. How these drugs will compare with other vasodilators in terms of long-term outcomes in patients with heart failure is unknown. Recent studies also suggest that PDE5 inhibitors may have antihypertropic effects, exerted through increased myocardial cGMP signalling, that could be of additional benefit in patients with heart failure.

Effects of tetrandrine on cytosolic free calcium concentration in corpus cavernosum smooth muscle cells of rabbits

AIM

To study the relaxation mechanisms of tetrandrine (Tet) on the corpus cavernosum smooth muscle.

METHODS

The corpus cavernosum smooth muscle cells from New Zealand white rabbits were cultured in vitro. [Ca(2+)](i) was measured by Fluorescence Ion Digital Imaging System, using Fluo-2/AM as a Ca(2+)-sensitive fluorescent indicator.

RESULTS

Tet (1, 10 and 100 micromol/L) had no effect on the resting [Ca(2+)](i) (P>0.05). In the presence of extracellular Ca(2+) (2.5 mmol/L), Tet (1, 10 and 100 micromol/L) inhibited [Ca(2+)](i) elevation induced by high K(+) and phenylephrine (PE) in a concentration-dependent manner (P>0.05). In calcium free solution containing egtaic acid, Tet (1 and 10 micromol/L) had no inhibitory effects on [Ca(2+)](i) elevation induced by PE (P>0.05). However, Tet (100 micromol/L) inhibited [Ca(2+)](i) elevation induced by PE (P>0.05).

CONCLUSION

Tet inhibited the Ca(2+) influx from the extracellular site via voltage-activated Ca(2+) channel and alpha(2)-adrenoceptor-operated Ca(2+) channel. At a high concentration, Tet might inhibit the cytosolic calcium pool release in cultured corpus cavernosum smooth muscle cells. This inhibitory action on [Ca(2+)](i) might be one of the relaxation mechanisms of Tet on the corpus cavernosum smooth muscle.

Prescribing all phosphodiesterase 5 inhibitors to a patient with erectile dysfunction--a realistic and feasible option in everyday clinical practice--outcomes of a simple treatment regime

OBJECTIVE

In clinical practice, to apply and evaluate outcomes of a treatment regime, in which the patient had the opportunity to try all the available phosphodiesterase 5 (PDE5) inhibitors.

METHODS

Patients eligible for treatment with PDE5 inhibitors were prescribed 8 tablets with a shorter-acting substance (four tablets sildenafil 100mg and four tablets vardenafil 20mg) and eight tablets with a long-acting substance (tadalafil 20mg). Outcomes of the regime were recorded.

RESULTS

Of the 186 patients, 64 (34%) had not been treated previously (naïve), and 122 (66%) were undergoing treatment for their erectile dysfunction. The overall treatment response was 89% (165 of 186 patients); 78% (n=145 of 186 patients) tested all three substances. No significant difference in choice between long- and shorter-acting medications in the overall material was observed. Two thirds of the naïve patients (n=64) preferred a shorter-acting substance (p<0.01). Every fifth man requested both a shorter- and a long-acting medication to accommodate his need.

CONCLUSION

If patients are given the opportunity in clinical practice to try all three available PDE5 inhibitors, the overall response rate is very high, almost 90%. No significant difference in patient preference between long- and shorter-acting drugs was observed. Treatment choice was based mainly on efficacy or duration of effect.

Experimental study of verapamil on the relaxation of isolated human corpus cavernosum tissues

AIM

To evaluate the relaxant effect of verapamil on human corpus cavernosum in vitro and to assess the drug's potential as a treatment for erectile dysfunction (ED).

METHODS

Preparations of the human corpus cavernosum were obtained from recently deceased young men who had had normal erectile function. The isometric tension and detailed curves were recorded when contractions induced by 10 micromol/L phenylephrine were reduced by different doses of verapamil or the vehicle control (sterile water). The tension of human corpus cavernosum preparations are described as a percentage of their top tension before adding verapamil or the vehicle. ANOVA and least significant difference tests were used for statistical analysis.

RESULTS

Doses of 1 micromol/L, 10 micromol/L and 100 micromol/L verapamil resulted in relaxation of (35.28+/-7.96)%, (55.91+/-6.41)%, (85.68+/-4.16)% after 30 min, respectively. The vehicle control at the same time point produced relaxation of (-0.06+/-10.57)% (P<0.05).

CONCLUSION

Verapamil is significantly effective in relaxing normal human corpus cavernous smooth muscle induced by phenylephrine in vitro and the relaxant effect depends on the concentration of verapamil.

Phosphodiesterase-5 Inhibition: the Molecular Biology of Erectile Function and Dysfunction

This article discusses the role of phosphodiesterase-5 (PDE-5) inhibition in the molecular biology of erectile function and dysfunction. Commercially marketed PDE-5 inhibitors are highly specific for PDE-5, and in the face of continuing cyclic GMP (cGMP) synthesis,elevate cellular cGMP. This elevation results from direct competitive inhibition of PDE-5 and from blocking the negative feedback regulation of the enzyme. Elevation of cGMP activates cGMP-dependent protein kinase, which mediates the effects of the cGMP-signaling pathway to decrease smooth muscle tone and dilate penile vascular smooth muscle. By exploiting features of PDE-5 regulatory mechanisms that modulate PDE-5 function, the inhibitors enhance their own potencies.

Therapie der organogen bedingten erektilen Dysfunktion

Erectile dysfunction is a common disease of men. It is associated with various comorbidities and has a prevalence of about 50% in the 7th decade. Erectile dysfunction often affects the quality of life of the patient and his partner, and it is very important to offer adequate therapy that respects the individual circumstances of each patient. The mandatory diagnostic work-up includes a medical and psychosexual history, a physical examination and routine laboratory tests. Besides psychotherapy, oral pharmacotherapy with oral PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) is the most effective therapy for erectile dysfunction and is superior to centrally acting drugs (yohimbine). In cases of failure or contraindication of oral pharmacotherapy, local pharmacotherapy is the second-line therapy. The third-line options are vacuum erectile devices and penile implants, and these have a high patient satisfaction. New therapeutic strategies such as anti-serotoninergic substrates and growth hormone offer a promising future for the therapy of erectile dysfunction but remain to be evaluated.

Urologic complications of sexual trauma among male survivors of torture

OBJECTIVES

To describe the urologic and sexual complications of male survivors of sexual torture, including prevalence, sequelae, diagnosis, and treatment.

METHODS

Through chart reviews, we identified all male survivors of torture who had been treated for physical and/or psychological symptoms due to sexual trauma at the Boston Center for Refugee Health and Human Rights at Boston Medical Center between January 1, 2001 and January 1, 2002. Of the 72 men seen, 20 (28%) were survivors of sexual trauma. Our study focused on genital trauma leading to urologic and/or sexual dysfunction. Therefore, all cases of male genital trauma that had been referred to the urology department (3 of 20) were selected for this review.

RESULTS

The patients presented with chronic genital and erectile pain, lower urinary tract symptoms, and sexual dysfunction. The diagnostic workup included history, physical examination, and ultrasonography. Treatment included steroid injections for chronic pain and oral erectogenic agents for sexual dysfunction.

CONCLUSIONS

The apparent prevalence and severity of the physical and mental sequelae to sexual trauma make it an important area for screening when treating survivors of torture. Our study is the first of its kind to document urologic complications of sexual torture in a foreign-born U.S. cohort of tortured men, including prevalence, diagnosis, and treatment. The proposed use of steroid injections in the clinical treatment of these patients has not been previously reported.

Sildenafil: efficacy, safety, tolerability and mechanism of action in treating erectile dysfunction

Sildenafil citrate is marketed under the trademark name Viagra and is widely used to treat male erectile dysfunction; therapeutic uses of this medication for other diseases related to vascular dysfunction are emerging. When used as recommended, the drug has a strong clinical efficacy and safety profile in a broad spectrum of the male population. Its widespread use and effects of long-term exposure to the drug due to particular treatment regimens or inappropriate use mandate an ongoing update of its molecular mechanism, pharmacological profile and associated safety issues. This review focuses on biochemical and pharmacological features of sildenafil, the active component in Viagra, interaction of sildenafil with phosphodiesterase 5, pharmacokinetic parameters, action in smooth muscle, side effects, safety profile and prospects for other uses.

Treatment for Erectile Dysfunction Based on Patient-Reported Outcomes

Erectile dysfunction (ED) is a common medical condition linked both to aging and to many medical conditions such as diabetes mellitus and cardiovascular disease. Although a common condition, treatment for ED has in the past been conducted by a few specialists, mostly urologists and sex therapists. The revolutionary introduction of oral therapy, and the massive amount of research into sexual dysfunction that followed, has led to paradigm shift in the treatment of ED. This is no longer something done by a few for a few; it involves all disciplines of medicine and more patients are being treated by a greater number of physicians. Several medications administered by different routes are available for treating ED but oral pharmacotherapy represents the first-line option. Phosphodiesterase (PDE) type 5 inhibitors are the most widely prescribed oral agents and they have a satisfactory efficacy-safety profile in patients of all categories. An alternative for men who do not respond to PDE5 inhibitors is intracavernosal injection therapy with alprostadil, a prostaglandin analogue. Other alternatives include sublingual apomorphine and intraurethral alprostadil. Both agents have a less satisfactory efficacy profile than PDE5 inhibitors and a low compliance rate. The aim of ED treatment is to restore an erection satisfactory for the sexual needs of the patient. Thus, the patient-reported outcome is the gold standard in efficacy evaluation. There are now three PDE inhibitors available, all with satisfactory efficacy-safety profiles, but with different pharmacokinetic properties. The availability of three different agents has initiated studies aiming to evaluate them regarding patient preference. However, the results are rather conflicting with some studies suggesting that tadalafil has the best patient preference, while others fail to demonstrate a clinically significant difference between the three agents. However, there is a tendency for younger men to choose tadalafil because it gives them a broader window of opportunity, while older men tend to prefer vardenafil or sildenafil. These data could be used when making a decision on which PDE5 inhibitor to prescribe, although another option is to let the patient try all three available agents and make his own choice.

Safety and Tolerability of Oral Erectile Dysfunction Treatments in the Elderly

Erectile dysfunction (ED) is a common medical condition that affects the sexual life of millions of men worldwide. It is generally accepted that sexual function tends to decline with aging, which is often associated with a higher prevalence of sexual problems, including ED and loss of libido. As the mean age of men seeking medical help for sexual dysfunction continues to increase, it is important to assess the safety and tolerability of currently available medical treatments in elderly men, who often share other co-morbidities that should be carefully evaluated when any type of ED therapy is considered. With this aim in mind, a MEDLINE search was conducted from 1 January 1998 to 31 May 2004 to identify studies assessing the efficacy, safety and tolerability of treatments for ED in the elderly. Particular care was taken to assess the cardiovascular safety of oral drugs for ED in this subset of patients, who often have multiple cardiovascular risk factors which contribute to a complicated clinical scenario. The most important conclusion of the paper is that the high efficacy, reliability, safety and tolerability of oral ED treatments makes them appropriate first-line therapies for elderly patients with ED.

Thalamus and penile erection

Penile erection is a complex neurovascular event. The neuronal system involved is often divided into a spinal (generator) and supraspinal (controller) network. Little is known about the supraspinal control. The recent finding of changes in penile erection following deep brain stimulation of the thalamus in two patients has raised the question as to what extent the thalamus is involved in erectile function. The thalamus has generally been regarded as a group of relay nuclei that served as a 'gate' for sexual information from the spinal cord towards higher centres. Recent evidence, however, suggests a more integrated regulatory function. Our review of the literature from 1960 until 2003 revealed 13 reports describing original data (preclinical and clinical). Various thalamic regions, varying from the midline thalamus to the posterior thalamus, have been reported to be activated during erection. The majority of the reports, however, showed that mainly the mediodorsal (MD) nucleus and the centromedian-parafascicular nucleus (Cm-Pf complex) are involved in penile erection. MD is the second largest nuclear aggregation located within the medial part of the thalamus. Anatomically, the MD is closely related to the Cm-Pf complex. The Cm-Pf complex is one of the most important relay stations in which the anterolateral spinothalamic pathway is further processed. This pathway is thought to transmit peripheral sexual sensations. On the whole, the present data on the role of the thalamus in erection are far from complete and future experiments are required to delineate its involvement.

Vardenafil: structural basis for higher potency over sildenafil in inhibiting cGMP-specific phosphodiesterase-5 (PDE5)

Phosphodiesterase-5 (PDE5) inhibitors act by competing with the substrate, cGMP, for the catalytic site of the enzyme. Two commercialized PDE5 inhibitors, sildenafil and vardenafil, are being used to treat erectile dysfunction. These two compounds differ in the heterocyclic ring system used to mimic the purine ring of cGMP. They also differ in the substituent (ethyl/methyl) of a piperazine side chain. Although these are the only two structural differences, vardenafil has more than 20-fold greater potency than sildenafil for inhibiting purified PDE5. The molecular structural basis for the difference in potency of the two compounds was investigated by synthesizing an analog of sildenafil ("methyl-sildenafil") that contained the sildenafil ring system but with the appended ethyl group found in vardenafil, and an analog of vardenafil ("demethyl-vardenafil") that contained the vardenafil ring system but with the appended methyl group found in sildenafil. The IC50 of methyl-sildenafil for inhibiting PDE5 indicated that it was 64 times less potent than demethyl-vardenafil, which was similar to the finding that, based on IC50, sildenafil was 40 times less potent than vardenafil. Similarly, the EC50 of methyl-sildenafil for inhibiting [3H]vardenafil binding to PDE5 indicated that it was 84 times less potent than demethyl-vardenafil, while the EC50 for sildenafil indicated that it was 31 times less potent than vardenafil. It is concluded that the methyl/ethyl appended group on the piperazine moiety plays very little role in the difference in potency between sildenafil and vardenafil for inhibiting PDE5, whereas the differences in the ring systems play a critical role in higher potency of vardenafil over sildenafil.

REVIEW: Review of Phosphodiesterases in the Urogenital System: New Directions for Therapeutic Intervention

INTRODUCTION

With the success of Phosphodiesterase (PDE) type 5 inhibitors (i.e., sildenafil, tadalafil, vardenafil) in the treatment of erectile dysfunction (ED), PDEs are considered attractive targets for drug intervention in the urogenital tract.

AIM

To review the role of PDEs, which exist as a superfamily of enzymes comprising 11 distinct families, in the urogenital system, focusing on anatomical locations, functions and dysfunctions, potential disorders that could be treated, and any promising new selective PDE inhibitors under development.

METHODS

Included are (i) abstracts from 2001, 2002, and 2003; (ii) a MEDLINE search from 1996 through December 2003; and (iii) a pipeline search for therapeutics in development. Data from animal experiments are presented when there is a paucity of human data, but with the caveat that the distribution of PDE isozymes in a specific tissue can vary between species.

RESULTS

PDE mRNA and protein have been localized throughout the normal human urogenital tract. Double-blind, placebo-controlled studies suggest possible new clinical roles for sildenafil, including prophylaxis to preserve penile smooth muscle and erectile function after radical prostatectomy, and treatment of ejaculatory delay secondary to serotonergic reuptake inhibitor antidepressant therapy. Open-label studies suggest a potential clinical role for: vinpocetine (a PDE1 inhibitor) in the treatment of incontinence and low-compliance bladder; and sildenafil in the treatment of premature ejaculation, prostate-related lower urinary tract symptoms, and in women who have had unsuccessful in vitro fertilization. Several new orally administered PDE5 inhibitors are in early clinical development for the treatment of ED. Potential indications for PDE inhibitors that are suggested by preclinical data include Peyronie's disease, ureteral colic, male and female birth control, and prevention of preterm labor.

CONCLUSIONS

Drug selectivity and differential PDE tissue distribution allow for potential targeted intervention for numerous disorders related to the urogenital tract.

Pharmacotherapy for Erectile Dysfunction

INTRODUCTION

Advances in understanding of the biochemistry and physiology of penile erection have led to breakthroughs in pharmacotherapy of erectile dysfunction.

AIM

To provide recommendations/guidelines concerning state-of-the-art knowledge for the putative molecular and cellular mechanisms of action of centrally and peripherally acting drugs currently utilized in pharmacotherapy of erectile dysfunction.

METHODS

An international consultation in collaboration with the major urology and sexual medicine associations assembled over 200 multidisciplinary experts from 60 countries into 17 committees. Committee members established specific objectives and scopes for various male and female sexual medicine topics. The recommendations concerning state-of-the-art knowledge in the respective sexual medicine topic represent the opinion of experts from five continents developed in a process over a two-year period. Concerning the Pharmacotherapy for Erectile Dysfunction Committee there were 25 experts from 10 countries.

MAIN OUTCOME MEASURE

Expert opinion was based on grading of evidence-based medical literature, widespread internal committee discussion, public presentation and debate.

RESULTS

Selective and potent oral PDE5 inhibitors have significantly more affinity than cGMP and form broader molecular interactions with multiple amino acids, thereby blocking access to cGMP in the catalytic sites of the PDE5 enzyme. PDE5 inhibitors, which vary as to biochemical potency, selectivity and pharmacokinetics, lead to cGMP elevation and relaxation facilitation of penile corpus cavernosum smooth muscle cells following sexual stimulation. Various centrally acting drugs influence sexual behaviour. In particular, the dopaminergic substance apomorphine is a central enhancer that acts in the paraventricular nucleus of the hypothalamus as a dopamine (D2) receptor agonist, induces and increases penile erection responses via disinhibition, following sexual stimulation.

CONCLUSIONS

There is a need for more research in the pharmacotherapeutic development of central and peripheral agents for safe and effective erectile dysfunction treatment.