Efficacy, safety and patient acceptance of sildenafil citrate as treatment for erectile dysfunction.

McMahon CG, Samali R, Johnson H.

Australian Centre for Sexual Health, St. Luke's Hospital Complex, Sydney, New South Wales, Australia.

PURPOSE: We assessed the efficacy and safety of sildenafil citrate as treatment for erectile dysfunction. MATERIALS AND METHODS: A total of 433 completely evaluated men with chronic erectile dysfunction were treated with sildenafil citrate. Response was assessed prospectively by baseline and followup physician interviews, and by a patient self-administered 15-item questionnaire on the domains of patient treatment response and satisfaction, partner treatment satisfaction, comparative previous treatment satisfaction, adverse effects, and patient and partner quality of life. RESULTS: Of the 304 men (70.2%) who completed the questionnaire 278 received sildenafil, including 186 who previously had undergone treatment for erectile dysfunction, principally involving intracavernous injection therapy. A response was elicited by a median dose of 100 mg. in 188 patients (67.6%) who achieved erection suitable for sexual intercourse. Those with psychogenic erectile dysfunction responded significantly better than those with organic dysfunction (p <0.001). Erection suitable for intercourse was attained by 30.8% of patients with erectile dysfunction after radical prostatectomy and 80% with cavernous veno-occlusive dysfunction. Of previous intracavernous injection responders 29.9% were refractory to sildenafil, while 33. 3% of previous intracavernous injection nonresponders responded to sildenafil. The sildenafil response was considered inferior to the intracavernous injection response by 43.6% of the men who previously responded to intracavernous injection, of whom 51.5% continued to receive intracavernous injection as the only treatment (19.5%) or as an alternative to sildenafil (32%). Adverse effects in 53.6% of cases were assessed as mild in 56.4%, moderate in 38.3% and severe in 5.3%. Multiple adverse effects were reported by 62.4% of patients, while 17 (6.1%) discontinued sildenafil as a direct result of intolerable adverse effects. The most common adverse effects were facial flushing in 33.5% of cases, headaches in 23.4%, nasal congestion in 12.6%, dyspepsia in 10.1% and dizziness in 10.8%. Baseline patient and partner quality of life scores significantly improved after sildenafil treatment (p <0.001), while significantly improved quality of life was noticed by 51.5% and 43.1%, respectively. CONCLUSIONS: Sildenafil citrate is effective oral first line treatment for erectile dysfunction. Although more than 50% of men reported adverse effects, most were considered mild and rarely resulted in treatment cessation. There was a trend in those on intracavernous injection who responded to sildenafil to continue intracavernous injection as the only therapy or as an alternative to sildenafil. Also, we noted that some cases refractory to sildenafil responded to intracavernous injection. These findings imply that intracavernous injection remains an effective erectile dysfunction treatment option.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10992364&dopt=Abstract sildenafil Viagra online



Sildenafil versus intracavernous injection therapy: efficacy and preference in patients on intracavernous injection for more than 1 year.

Hatzichristou DG, Apostolidis A, Tzortzis V, Ioannides E, Yannakoyorgos K, Kalinderis A.

Department of Urology, School of Medicine and Center for Sexual Dysfunction, Aristotle University of Thessaloniki, Thessaloniki, Greece.

PURPOSE: To our knowledge comparative data on the effectiveness of and patient preference for intracavernous injection therapy and sildenafil are still not available. We evaluated the efficacy of sildenafil as well as patient preference in a group of impotent men on intracavernous injection for more than a year. MATERIALS AND METHODS: Patients on intracavernous injection therapy for more than a year without neurological disease and/or a contraindication to sildenafil treatment were recruited for study. In phase 1 we determined the efficacy of 50 and 100 mg. sildenafil citrate at home. In phase 2 responders to sildenafil were asked to use the preferred dose orally for a month and choose intracavernous injection or sildenafil. In phase 3 patients were asked to continue either treatment for 3 more months. Patient preferences were reported at the end of phases 2 and 3. RESULTS: Of the 180 men recruited 155 with a mean age of 56.4 +/- 12.6 years on intracavernous injection for a mean of 26 +/- 9 months accepted and were included in our series. Overall 116 men (74.8%) responded to sildenafil during study phase 1. After 1 month of treatment 71 responders (61.2%) preferred to continue with the oral drug, 31 (26.7%) returned to intracavernous injection and 14 (12.1%) used each drug alternately. Three months later 74 of the 116 responders (63.8%) preferred oral treatment and 38 (32.8%) chose intracavernous injection, while 4 (3. 4%) continued to use each treatment alternately. CONCLUSIONS: Sildenafil is highly effective in intracavernous injection responders, although a certain group prefer to continue intracavernous injection. While sildenafil should be considered first line treatment, men with erectile dysfunction should be aware of all treatment options available because nonresponders to sildenafil may respond to intracavernous injection.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10992365&dopt=Abstract sildenafil Viagra online



Science, art and drug discovery: a personal perspective.

Campbell SF.

Pfizer Central Research, Sandwich, Kent CT13 9NJ, UK.

The research programme that started in 1985 led to the approval of Sildenafil (Viagra), in 1998, as the first oral treatment for male erectile dysfunction. The initial project objective was the design and synthesis of novel inhibitors of phosphodiesterase that would increase tissue levels of cGMP, and that could be beneficial for the treatment of cardiovascular conditions. Starting from zaprinast, a weak phosphodiesterase inhibitor, computer modelling guided rational medicinal chemistry to achieve significant increases in potency and selectivity for the 5-isoenzyme within a novel series of pyrazolopyrimidinones. Optimization of structure-activity relationships and pharmacokinetic properties led to sildenafil, which proved essentially devoid of cardiovascular activity in clinical trials. However, the emerging role of nitric oxide and cGMP in controlling blood flow in the penis suggested that sildenafil would have a beneficial effect on erectile function. This hypothesis was confirmed by extensive clinical trials in nearly 5000 patients and the Food and Drug Administration approved sildenafil in March 1998 for male erectile dysfunction. Sildenafil is now available in over 100 countries and more than 150 million tablets have been dispensed worldwide. The sildenafil research programme reflects a traditional approach to drug discovery, but pressures to improve productivity have prompted major investments in genome sciences and new technologies. The impact of these initiatives on the drug discovery paradigm will be discussed, particularly with respect to shortening time scales between identifying gene sequences and submitting innovative products for regulatory approval.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=10995589&dopt=Abstract sildenafil Viagra online



Sildenafil augments pelvic nerve-mediated female genital sexual arousal in the anesthetized rabbit.

Min K, Kim NN, McAuley I, Stankowicz M, Goldstein I, Traish AM.

Departments of Urology, Boston University School of Medicine, Boston, MA 02118, USA.

The NO-cGMP pathway has been implicated in clitoral and vaginal smooth muscle relaxation based on previous immunochemical, biochemical and physiologic studies. There are limited data from in vivo studies demonstrating enhancement of the genital sexual arousal response by pharmacologic agents influencing the NO-cGMP pathway. The goal of this study was to investigate if sildenafil, a phosphodiesterase type-5 inhibitor, facilitated female genital sexual arousal in an animal model in response to pelvic nerve stimulation (PNS). Using female New Zealand White rabbits, we measured the following parameters before, during and after PNS at 4, 16, and 32 Hz: a) hemoglobin concentration and oxygen saturation in female genital (vaginal, labial, clitoral) tissues by laser oximetry; b) clitoral blood flow by laser Doppler flowmetry; c) vaginal luminal pressure by a balloon catheter pressure transducer; d) vaginal lubrication by tampon. Sildenafil was administered intravenously (0.21 microg/kg, 0.42 microg/kg, 2.1 microg/kg) to achieve a systemic concentration of 5, 10 and 50 nM, respectively. After 20 minutes, physiologic measurements were repeated. Sildenafil (50 nM) caused a significant increase in genital oxyhemoglobin concentration and a significant decrease in genital deoxyhemoglobin concentration. Sildenafil also increased the duration of response following PNS, relative to genital hemoglobin concentration and mean clitoral blood flow. Sildenafil caused a decrease in vaginal luminal pressure and resulted in an increase in vaginal lubrication. These data indicate that the NO-cGMP pathway is involved in the physiologic mechanism of female genital arousal and that sildenafil facilitates this response in an in vivo animal model.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11002397&dopt=Abstract sildenafil Viagra online



Sildenafil in the treatment of erectile dysfunction after radical prostatectomy.

Zagaja GP, Mhoon DA, Aikens JE, Brendler CB.

Department of Surgery (Section of Urology), University of Chicago Medical Center, Chicago, Illinois, USA.

OBJECTIVES: To evaluate the efficacy of sildenafil for the treatment of erectile dysfunction after radical prostatectomy and to determine whether age, preservation of the neurovascular bundles (NVBs), or the interval between surgery and the initiation of sildenafil therapy influences the response to sildenafil. METHODS: We began this study in April 1998, immediately after the Food and Drug Administration approved sildenafil. We surveyed 170 men who had undergone radical retropubic prostatectomy, had not recovered natural erections sufficient for intercourse, and subsequently received sildenafil between 3 and 24 months postoperatively. The data were collected through a confidential mail survey conducted by a clinical nurse. The men used a dose of 50 mg sildenafil and increased this to 100 mg if they did not obtain an adequate response. RESULTS: In the 120 men who began taking sildenafil at least 12 months after surgery, the overall response rate was 29%. Results varied markedly by patient age and number of NVBs preserved. In men younger than 55 years in whom both NVBs had been preserved, the response rate was 80%. In contrast, no patient older than 55 years in whom only one NVB had been preserved reported an adequate response. Regardless of age, no patient in whom both NVBs had been excised reported success with sildenafil. Of the 50 patients who began taking sildenafil less than 9 months after surgery and who had not recovered natural sexual function, none reported erections adequate for intercourse using sildenafil. CONCLUSIONS: Sildenafil is an effective treatment for men with erectile dysfunction after radical retropubic prostatectomy, particularly in younger men in whom both NVBs have been preserved. It is ineffective in men in whom both NVBs have been excised, and it is also ineffective in older men in whom only one NVB has been preserved. Sildenafil appears ineffective in the first 9 months after prostatectomy.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11018620&dopt=Abstract sildenafil Viagra online



Efficacy of sildenafil in erectile dysfunction after radical prostatectomy.

Blander DS, Sanchez-Ortiz RF, Wein AJ, Broderick GA.

Division of Urology, University of Pennsylvania Health System, Philadelphia, USA. dbland mednet.swmed.edu

Radical retropubic prostatectomy (RRP) is an important cause of iatrogenic erectile dysfunction (ED). While sildenafil has been widely used since its introduction as a new treatment option for ED, its efficacy in post-RRP patients has not been extensively studied. We retrospectively compared the efficacy of sildenafil in post-RRP and non-surgical patients with ED (NSED) using a subset of questions from the International Index of Erectile Function (IIEF) and correlated results with their specific etiology of ED based on penile blood flow study (PBFS). A brief questionnaire regarding satisfaction with sildenafil was administered to 72 consecutive post-RRP patients (nerve sparing status unknown) and 32 consecutive NSED patients who had previously undergone PBFS with pharmacotesting as part of their evaluation for ED. PBFS diagnoses were arterial insufficiency (AI) for peak systolic velocity (PSV) < 25 cm/sec; venogenic (CVOD) for PSV > or = 35 cm/sec, mixed vascular for PV > 25 but < 35 cm/sec and resistive index (RI) < 0.9; a vascular normal diagnosis (neurogenic impotence) required excellent rigidity sustained for 20 min. Differences in the IIEF subscores for the different groups of patients were assessed. Success with sildenafil was defined as moderate or excellent improvement (3/4 or 4/4) with ability for penetration. No differences were found among the different subgroups of RRP patients with respect to IIEF scores or success rates with sildenafil. NSED patients had both significantly higher post-treatment IIEF scores (3.6/3.4 vs 2.5/2.2; t=4.50, P<0.0001) and success rates (63% vs 31%; t=3.11, P < 0.01) with sildenafil treatment than RRP patients. We found that sildenafil is significantly less effective in impotent RRP patients than in age-matched patients with ED (31% vs 63%). We had postulated that sildenafil would be least effective among RRP patients with excellent sustained rigidity to PGE1, as this subgroup is likely to have neurogenic impotence. We found that sildenafil response rates among subgroups of RRP patients were statistically similar regardless of PBFS diagnosis. IIEF scores for the RRP subgroups were similar but statistically lower than in men with ED and no history of RRP. While individuals with normal vascular responses to PGE1 have an increased likelihood of having neurogenic impotence, in RRP patients, we were unable to demonstrate any difference in efficacy of sildenafil, regardless of the PBFS diagnosis.

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Cyclic nucleotide phosphodiesterase type 5 activity limits blood flow to hypoperfused myocardium during exercise.

Traverse JH, Chen YJ, Du R, Bache RJ.

Department of Medicine, Division of Cardiology, University of Minnesota Medical School, Minneapolis, MN 55455, USA.

BACKGROUND: Nitric oxide (NO) causes vasodilation by stimulation of guanylate cyclase in vascular smooth muscle to produce cGMP. The resultant vasodilator effect is regulated by a family of cGMP phosphodiesterases (PDEs). Sildenafil, a selective inhibitor of PDE5 used for treatment of erectile dysfunction, has been found to cause relaxation of isolated epicardial coronary artery segments. The present study examined the effects of sildenafil on coronary blood flow and hemodynamics during exercise in normal and ischemic heart. METHODS AND RESULTS: In chronically instrumented normal dogs, sildenafil 2 mg/kg PO caused a slight but significant increase in left anterior descending (LAD) coronary blood flow during resting conditions, with a nonsignificant trend toward increased coronary flow during treadmill exercise. Exercise in the presence of LAD stenosis that decreased distal coronary pressure to 57+/-2 mm Hg reduced LAD flow during exercise from 69+/-8 to 41+/-7 mL/min (P:<0. 05), with hypoperfusion most severe in the subendocardium. At the same distal coronary pressure, sildenafil increased LAD flow in the ischemic region to 50+/-11 mL/min (P:<0.05). Increase in ischemic region blood flow produced by sildenafil was uniform across the LV wall, given that no change occurred in the transmural distribution of perfusion. CONCLUSIONS: Inhibition of PDE5 with sildenafil caused vasodilation of coronary resistance vessels with an increase of blood flow into an ischemic myocardial region during exercise in the presence of coronary artery stenosis.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11113052&dopt=Abstract sildenafil Viagra online



Effect of the selective phosphodiesterase type 5 inhibitor sildenafil on erectile dysfunction in the anesthetized dog.

Carter AJ, Ballard SA, Naylor AM.

Discovery Biology Department, Pfizer Central Research, Sandwich, United Kingdom.

PURPOSE: The effects of sildenafil, a highly selective inhibitor of cyclic guanosine monophosphate-specific phosphodiesterase type 5, on erectile function in the anesthetized dog were evaluated. MATERIALS AND METHODS: In pentobarbital-anesthetized dogs, increases in intracavernosal pressure in the corpus cavernosum and penile blood flow were induced by pelvic nerve stimulation over a frequency range of 1 to 16 hertz. The effects of increasing doses of sildenafil on electrically stimulated intracavernosal pressure, penile blood flow, blood pressure, and heart-rate were evaluated. In parallel experiments, the effects of the nitric oxide synthase inhibitor N omega-Nitro-L-Arginine (L-NOArg) on these same parameters also were assessed. RESULTS: The effects of nerve stimulation on intracavernosal pressure and blood flow to the penis were blocked by L-NOArg, 0.1-3 mg./kg., in a dose-related manner, confirming the important role of nitric oxide in producing erections. Sildenafil, 1-100 microg./kg administered intravenously, had no direct effect on intracavernosal pressure but potentiated the increase in intracavernosal pressure induced by nerve stimulation. This potentiation occurred at sildenafil plasma concentrations consistent with its relaxation effect on isolated human cavernosal tissue and its inhibition of phosphodiesterase type 5 in vitro. Sildenafil had no significant effect on blood pressure or heart rate. CONCLUSIONS: By inhibiting cyclic guanosine monophosphate-specific phosphodiesterase type 5, sildenafil augments the neuronal mechanism responsible for penile erection. This mechanism explains the significant improvements reported in the rigidity and duration of erections seen in patients with erectile dysfunction who have been treated with oral sildenafil.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=9628657&dopt=Abstract sildenafil Viagra online