New oral therapies for the treatment of erectile dysfunction

Comparative evaluation of relaxant effects of three prangos species on mouse corpus cavernosum: Chemical characterization and the relaxant mechanisms of action of P. pabularia and (+)-oxypeucedanin

ETHNOPHARMACOLOGICAL RELEVANCE

Erectile dysfunction (ED) is the most common form of sexual dysfunction which has been the topic of great interest through the history by all cultures. It is now among the most treated health problems in men of all ages that develop under the influence of lifestyle factors and some diseases. Plants are extensively used to cure sexual dysfunction for centuries. Roots of Prangos sp. have been used to improve sexual performance in Anatolian traditional medicine and are rich of coumarin, furanocoumarin and their derivatives. Scientific research is necessary to support and validate the ethno-traditional uses of these plants.

AIM OF THE STUDY

The aim of this study is to investigate the effects of the root extracts of P. pabularia, P. uechtritzii and P. heyniae on erectile function and to isolate and identify the chemical compounds of the most active extract and reveal possible pharmacological mechanism of the major compound of the extract with the strongest relaxant effect in mouse corpus cavernosum (MCC).

MATERIALS AND METHODS

The roots of plants were extracted with chloroform, n-hexane and methanol. The compounds were isolated from the extract by column chromatography and structures were identified by NMR and MS. The relaxant effects of extracts (10^-7-10^-4 g/mL), (+)-oxypeucedanin (10^-7-10^-4 M) and Na₂S (10^-7-3 × 10^-3 M) were tested in MCC strips by DMT myograph. To investigate the mechanism, the synthesis inhibitors of aminooxyacetic acid (AOAA, 10^-2 M) and nitro-L-arginine methyl ester (L-NAME, 10^-4 M) were used, respectively. H₂S formation was evaluated basal and L-cysteine (L-cyst)-stimulated conditions by H₂S microsensor.

RESULTS

All extracts relaxed MCC in a concentration dependent manner. The maximum relaxing effects were achieved with chloroform extracts. Chloroform extract of P. pabularia (Pp-CE) was more potent than the others. Pp-CE-induced relaxations were significantly decreased by AOAA and L-NAME. (+)-Oxypeucedanin, the major compound of Pp-CE, induced relaxant responses and this effect was inhibited by AOAA, but not L-NAME. The relaxation of (+)-oxypeucedanin was found to be similar in view of E_max to positive control H₂S donor Na₂S. (+)-Oxypeucedanin increased L-cyst-stimulated H₂S formation. Augmentation of H₂S synthesis with (+)-oxypeucedanin was inhibited by AOAA.

CONCLUSIONS

Pp-CE has the strongest effect on relaxation of MCC and this result supports the traditional aphrodisiac use of P. pabularia root extract in Anatolia. The pharmacological mechanisms of Pp-CE to relax MCC involve NO and H₂S formation. (+)-Oxypeucedanin could be responsible for the H₂S-mediated relaxations of Pp-CE in MCC.

Potent and selective xanthine-based inhibitors of phosphodiesterase 5

Inhibitors of PDE5 are useful therapeutic agents for treatment of erectile dysfunction. A series of novel xanthine derivatives has been identified as potent inhibitors of PDE5, with good levels of selectivity against other PDE isoforms, including PDE6. Studies in the dog indicate excellent oral bioavailability for compound 21.

Can written information material help to increase treatment motivation in patients with erectile dysfunction? A survey of 1188 men

Although erectile dysfunction (ED) prevalence is high, patients and physicians often have problems discussing this issue. This study examines whether written information material increases motivation to seek treatment in patients with ED. For the study, persons were able to order information material about sexual problems within the context of a public campaign. From a total of 70,000 responders, 8000 persons were asked to fill out an epidemiological questionnaire. The response rate yielded 18.4%, the data of 1188 men with ED were analyzed. As a result of the information material, 28.3% of the untreated men intended to seek treatment and 38.5% of the men who had not spoken with their physician about their problem, planned to do so now. Nearly all responders were satisfied with the information material. These data reflect the usefulness of written information for men with ED. It not only serves as an informational source for patients but may also encourage them to seek treatment.

JNJ-10280205 and JNJ-10287069: novel PDE5 inhibitors as clinical candidates for erectile dysfunction

Phosphodiesterase 5 (PDE5) inhibitors are efficacious in treating patients with erectile dysfunction. New PDE5 inhibitors with different selectivity and pharmacokinetic profiles have been vigorously pursued. Here we report two novel, potent, and selective PDE5 inhibitors, JNJ-10280205 and JNJ-10287069, with Ki values of 0.05 and 0.12 nM, respectively. Both compounds displayed superior selectivity against PDE1-4 and -6 when compared to sildenafil. In the anesthetized dogs, JNJ-10280205 and JNJ-10287069 exhibited similar efficacy as sildenafil in enhancing erectile functions, with no significant effect on cardiovascular parameters. Pharmacokinetic studies showed that JNJ-10287069 had better oral bioavailability than JNJ-10280205 in several animal species. In vitro study suggested that cytochrome P450 (CYP) 3A4 played a major role in the metabolism of both compounds. The compounds inhibited some of the CYP450 enzymes and the human ether-a-go-go (HERG) channel at much higher concentrations than that required to inhibit PDE5, thus, no cross inhibition would be expected at therapeutic doses. Both compounds are suitable clinical candidates.

The efficacy of sildenafil for the treatment of erectile dysfunction in male peritoneal dialysis patients

BACKGROUND

The aim of this study was to evaluate the safety and effectiveness of sildenafil in male peritoneal dialysis patients with erectile dysfunction.

METHODS

Sixteen peritoneal dialysis patients were recruited to this prospective, randomized, double-blind, placebo-controlled, crossover study of sildenafil during a period of 8 weeks. Efficacy was assessed by using the International Index of Erectile Function and a Global Assessment Question. Penile arterial supply was assessed by means of Doppler ultrasound in all patients, and adverse events were recorded.

RESULTS

Three patients failed to complete the study (1 patient received a renal transplant, 1 patient died unrelated to the study, and 1 patient withdrew for personal reasons). In the remainder, there was a significant improvement in erectile function with sildenafil compared with placebo (P = 0.01) and the baseline assessment (P = 0.002). There were also significant improvements in intercourse satisfaction (P = 0.002) and overall satisfaction (P = 0.005) compared with baseline. In response to the Global Assessment Question, 75% of patients reported improvement in erections. Only 1 adverse event was reported: a headache, which resolved after the third dose of sildenafil.

CONCLUSION

Sildenafil caused a significant improvement in erectile function in peritoneal dialysis patients, with a success rate at least as high as that reported in other patient groups. The drug was well tolerated, with few adverse events.

The etiology of erectile dysfunction and contributing factors in different age groups in Turkey

BACKGROUND

The aim of the present study was to determine the pathophysiological factors which cause erectile dysfunction (ED), as well as the risk factors in different age groups in Turkey.

METHODS

A total of 948 patients with ED who were admitted to three andrology clinics were evaluated in terms of etiological factors. They underwent a multidisciplinary diagnostic evaluation. Erectile dysfunction was classified as primarily organic, primarily psychogenic, mixed or unknown in etiology.

RESULTS

Psychogenic ED was diagnosed in 65.4% of the patients and organic ED was diagnosed in 34.6% of patients overall. In patients under 40 years, the rate of psychogenic ED was 83% and the rate of organic ED was 17%, but in the patients over 40 years, the rate of psychogenic ED was 40.7% and the rate of organic ED was 59.3%. The causes of organic ED were identified as arteriogenic ED, 40.5%; cavernosal factor (venogenic) ED, 10%; neurogenic ED, 12.5%; endocrinologic ED, 1.8%; mixed type ED, 11.8%; and drug induced ED, 4.5%.

CONCLUSION

Our data represent a higher ratio of ED in patients under 40, which are mostly psychogenic, This finding potentially results from local social and cultural differences.

Tadalafil

black triangle Tadalafil is a selective phosphodiesterase type 5 inhibitor that is effective in men with mild-to-severe erectile dysfunction (ED), including those with diabetes mellitus. black triangle The improvement in the erectile function domain score on the International Index of Erectile Function (IIEF) and the percentage of sexual intercourse attempts marked by successful vaginal penetration and completion was significantly greater with on-demand (not more than once daily) tadalafil 10 or 20 mg than placebo in trials of 12 weeks' duration. Improvement in scores on other domains of the IIEF and the percentage of positive responses to a Global Assessment Question measuring erection improvement were also significantly greater with on-demand tadalafil than placebo. black triangle The adverse events associated with tadalafil were generally mild to moderate and decreased in frequency with continued administration. The most commonly reported adverse events were headache and dyspepsia. The incidence of cardiovascular adverse events was not significantly different in tadalafil or placebo recipients.

Trazodone for erectile dysfunction: a systematic review and meta-analysis

OBJECTIVE

To determine the efficacy and safety of trazodone in the treatment of erectile dysfunction (ED) in a meta-analysis.

METHODS

The data sources used were Medline and the Cochrane Library databases (January 1966 to May 2002), bibliographies of retrieved articles and review articles, and conference proceedings and abstracts. Trials were eligible for inclusion in the review if they included men with ED, compared trazodone with a control, were randomized, of > or = 7 days' duration and assessed clinically relevant outcomes. Two reviewers independently evaluated study quality and extracted data in a standardized fashion.

RESULTS

Six trials (comprising 396 men) met the inclusion criteria; they consisted of heterogeneous populations, were small, brief and in some cases methodologically weak. Three of the six trials showed an apparently clinically meaningful benefit of trazodone for ED compared with placebo, the differences being statistically significant in two. In pooled results, trazodone monotherapy appeared more likely than placebo to lead to a 'positive treatment response', although this difference was not statistically significant (37% vs 20%; relative benefit increase, 1.6; 95% confidence interval, CI, 0.8-3.3). Subgroup analyses suggested that men with psychogenic ED might be more likely to benefit from trazodone than those with mixed or physiological ED. The efficacy of trazodone also appeared greater at higher doses (150-200 vs 50 mg/day). Men randomized to trazodone were not significantly more likely than those receiving placebo to withdraw for any reason or for an adverse event, or to have specific adverse events, but wide CIs could not exclude a greater risk of these adverse outcomes with trazodone. Specific adverse events with trazodone included dry mouth (19%), sedation (16%), dizziness (16%) and fatigue (15%).

CONCLUSION

Trazodone may be helpful in men with ED, possibly more so at higher doses, and in men with psychogenic ED. Future high-quality trials should compare trazodone with placebo and other therapies in men with depression and psychogenic ED.

Design, synthesis and biological activity of beta-carboline-based type-5 phosphodiesterase inhibitors

The SAR of a series of beta-carboline derived type 5 phosphodiesterase inhibitors has been explored and we have discovered compounds with excellent levels of PDE5 potency and selectivity over PDE6. However, the series exhibits low levels of selectivity over PDE11, a phosphodiesterase with unknown function.

A solid-phase approach towards the synthesis of PDE5 inhibitors

PDE5 inhibitors based upon the xanthine scaffold 8 have been expediently synthesized using a solid-phase route. Attachment of the xanthine scaffold 8 using the Rink chloride linker 4 and N-1 functionalization using Mitsunobu chemistry is described. A library of compounds was produced in multi-milligram quantities with excellent purities and acceptable yields. The compounds were tested for their PDE5 inhibitory activity.

Erectile dysfunction and the effects of sildenafil treatment in patients on haemodialysis and continuous ambulatory peritoneal dialysis

BACKGROUND

Sexual dysfunction, including erectile dysfunction, is common in patients with uraemia. Despite successful treatment of male sexual dysfunction with sildenafil in non-uraemic population, its efficacy in dialysis patients is unknown.

PATIENTS AND METHODS

In this study, 35 male HD patients (mean age 48+/-12 years) and 15 male CAPD patients (mean age 44+/-12 years) were included. In the baseline period, haemoglobin, serum urea, and albumin, Kt/V, several hormonal parameters, Beck depression scale, and penile Doppler blood flow, (peak systolic velocity after intracavernous papaverine administration) were measured. The international index of erectile function (IIEF) form was used to evaluate erectile dysfunction. Sildenafil was given to patients with erectile dysfunction at a dose of 50-100 mg/day twice a week.

RESULTS

The percentage of erectile dysfunction was similar between patients on HD (71%) and those on CAPD (80%). Patients with erectile dysfunction were significantly older and had lower free-testosterone serum levels and penile blood flow than those without. In linear regression analysis for baseline IIEF score, penile blood flow was the only independent variable associated with erectile dysfunction. IIEF score increased to a similar extent after sildenafil treatment in both HD patients (from 8.10+/-5.54 to 21.70+/-9.61, P<0.001) and CAPD patients (from 9.90+/-3.87 to 21.60+/-10.18, P=0.011). Changes in IIEF scores after sildenafil treatment were associated with baseline penile blood flow as an independent variable by linear regression analysis. Adverse events observed during sildenafil treatment were dyspepsia in two patients and headache in one patient.

CONCLUSION

The rate of erectile dysfunction is high in dialysis patients. Penile blood flow is the most important factor for predicting both the development of erectile dysfunction and the response to sildenafil therapy in such patients. Oral sildenafil is an effective, reliable, well-tolerated treatment for uraemic patients with erectile dysfunction.

Sildenafil

Sildenafil (Viagra, Pfizer, Inc.) is a new orally effective therapy for the treatment of men with erectile dysfunction (ED). It is a specific and selective inhibitor of phosphodiesterase Type 5 (PDE5), an enzyme which is an important modulator of smooth muscle relaxation in the corpus cavernosum. In the presence of a sexual stimulus, inhibition of PDE5 results in improved smooth muscle relaxation within the sinusoids of the corpus cavernosum and the penile arteries. This results in improved erections in men with ED. In clinical trials, sildenafil has been found to be effective in improving the erections of large numbers of men with ED secondary to a range of causes. The presence of PDE5 in other tissues such as vascular smooth muscle results in side effects such as headache, flushing, indigestion and nasal congestion. These side effects are dose-dependent and well-tolerated. The introduction of sildenafil in many countries around the world has revolutionised the assessment and treatment of men with ED.

Male infertility and erectile dysfunction in spinal cord injury: a review

OBJECTIVE

To review the pathophysiology, evaluation, and management of erectile dysfunction and infertility in spinal cord injury (SCI).

STUDY SELECTIONS

Studies that covered various treatment options and their contraindications, complications, or side effects, including sildenafil (Viagra), intracavernosal injection therapy, topical medications and a urethral delivery system, a vacuum erection device, and penile prostheses. Other studies covered the effects of SCI on reproduction: spermatogenesis and testicular function, and seminal constituents. In addition, assisted reproductive techniques were compared: external vibratory stimulation, electroejaculation, testicular sperm aspiration, and intracytoplasmic sperm injection.

CONCLUSION

Goal-directed therapy is the mainstay of treatment of erectile dysfunction in men with or without SCI. The choice of therapy is often defined more by the needs of the patient's sexual relationship than by his erectile dysfunction. The majority of men with SCI are infertile because of a combination of ejaculatory dysfunction, impaired spermatogenesis, and poor semen quality. Although many technological advances have evolved to overcome ejaculatory dysfunction, the sperm density, motility, and function remain poor. Until these parameters are improved, men with SCI will have to pursue more financially and emotionally taxing procedures. Further studies to elucidate the cellular and molecular mechanisms of diminished sperm quality are needed. Addressing the issues of erectile dysfunction and male infertility may help to preserve the relationship between the patient and his partner.

Overall cardiovascular profile of sildenafil citrate

Sildenafil, a selective inhibitor of phosphodiesterase type 5 (PDE5), is the first in a new class of orally effective treatments for erectile dysfunction. During sexual stimulation, the cavernous nerves release nitric oxide (NO), which induces cyclic guanosine monophosphate (cGMP) formation and smooth muscle relaxation in the corpus cavernosum. Sildenafil facilitates the erectile process during sexual stimulation by inhibiting PDE5 and thus blocking the breakdown of cGMP. Sildenafil alone can cause mean peak reductions in systolic/diastolic blood pressure of 10/7 mm Hg that are not dose related, whereas the heart rate is unchanged. Sildenafil and nitrates both increase cGMP levels in the systemic circulation but at different points along the NO-cGMP pathway. The combination is contraindicated because they synergistically potentiate vasodilation and may cause excessive reductions in blood pressure. Erectile dysfunction is a significant medical condition that shares numerous risk factors with ischemic heart disease, and hence a substantial overlap exists between these patient groups. From extensive clinical trials, the most commonly reported cardiovascular adverse events in patients treated with sildenafil were headache (16%), flushing (10%), and dizziness (2%). The incidences of hypotension, orthostatic hypotension, and syncope and the rate of discontinuation of treatment due to adverse events were <2% and were the same in patients taking sildenafil and those taking placebo. Retrospective analysis of the concomitant use of antihypertensive medications (beta blockers, alpha blockers, diuretics, angiotensin-converting enzyme inhibitors, and calcium antagonists) in patients taking sildenafil did not indicate an increase in the reports of adverse events or significant episodes of hypotension compared with patients treated with sildenafil alone. In clinical trials, the incidence of serious cardiovascular adverse events, including stroke and myocardial infarction, was the same for patients treated with sildenafil or placebo. Concurrent disease states, such as renal or hepatic impairment, or concomitant use of inhibitors of the cytochrome P450 isozyme CYP3A4 could increase systemic exposure to sildenafil. Since the US market launch in April 1998, monitoring of spontaneous adverse event reports in association with sildenafil has demonstrated a pattern that is generally consistent with the experience observed during clinical development, with the exception of infrequent reports of priapism. In conclusion, extensive clinical testing has shown that overall treatment with sildenafil for up to 1 year is well tolerated and is associated with a low incidence of adverse events that result in discontinuation of treatment in <3% of patients.