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TAKE HOME MESSAGE: The administration of phosphodiesterase 5 inhibitor commencing at the time of castration might preserve erectile function. OBJECTIVE: To determine if sildenafil citrate treatment could improve erectile function after castration. To determine if sildenafil citrate treatment reduces collagenisation and apoptosis in erectile tissue after castration. MATERIALS AND METHODS: In all, 60 Sprague-Dawley rats were studied; the rats were divided into the following groups: sham - no orchidectomy (S), control - orchidectomy only (O) and treatment - orchidectomy plus sildenafil treatment (V), with 10 rats per group. Erectile haemodynamics assessment was done at 7 days (S7, O7, V7) and at 28 days (S28, O28, V28) yielding a total of six groupings. Functional assessment measured the mean maximum intracavernosal pressure-mean arterial pressure (ICP/MAP) ratio. TUNEL assay was used to define apoptotic indices (AIs) and Masson's trichrome staining was used to evaluate smooth muscle-collagen (SM-C) ratios. RESULTS: The S28 group had the highest and the O7 group the lowest ICP/MAP ratio, at a mean (sd) of 70 (6)% and 36 (6)%, respectively. Both treatment groups, V7 [42 (12)%] and V28 [49 (13)%] showed statistically significant improvements over their corresponding control groups: O7 [36 (6)%] and O28 [37 (9)%] (P < 0.05). However, ICP/MAP values for V7 and V28 remained significantly below the S28 group (P < 0.001). There were no significant differences in ICP/MAP values between the 28-day and 7-day ICP/MAP ratios within each group (S, O, V). There were no significant differences in SM-C ratio between the O and V groups (O7 vs V7, P = 0.45; O28 vs V28, P = 0.16). There were no significant differences in AIs between the O and V groups (O7 vs V7, P = 0.54; O28 vs V28, P = 0.8). CONCLUSIONS: Daily treatment with sildenafil improved erectile function in rats after castration. ICP/MAP ratios increased significantly in the treatment groups compared with the control groups with the greatest erectile function occurring 28 days from administration. In this series of experiments the improved erectile function recovery with sildenafil after surgical castration cannot be explained by smooth muscle protection and decreased collagenisation. The improved erectile function with sildenafil after surgical castration cannot be explained by reduced apoptosis in erectile tissue.

What's known on the subject? and What does the study add? Tadalafil, a phosphodiesterase type 5 inhibitor, might be effective for not only erectile dysfunction but also lower urinary tract symptoms (LUTS). One of the mechanisms of tadalafil on LUTS is added in the study. OBJECTIVE • To determine if tadalafil, a phosphodiesterase type 5 inhibitor, decreases afferent nerve activity from the bladder with and without chemical stimulation by intravesical acrolein instillation. MATERIALS AND METHODS • Female Sprague-Dawley rats were used. Under urethane anaesthesia, single afferent fibres of the nerve primarily originating from the bladder were identified by electrical stimulation of the pelvic nerve and by bladder distension, and classified by conduction velocity as Aδ- or C-fibres. After measuring the baseline single afferent activities (SAA) during constant filling, two experiments were performed. • First, tadalafil was administrated intravenously (i.v.) at three doses, 0.01, 0.03 and 0.1 mg/kg cumulatively and SAA were repeatedly studied after each administration. • Second, in the presence of vehicle or tadalafil (0.1 mg/kg) i.v., the effect of intravesical instillation of acrolein (0.003%) was studied. RESULTS • In all, 39 single units were isolated (Aδ-fibres 21; C-fibres, 18) in 25 rats. • Tadalafil dose-dependently decreased SAA of both Aδ- and C-fibres during saline instillation. Intravesical acrolein facilitated SAA of both fibres after vehicle administration. • Pretreatment with tadalafil significantly inhibited the acrolein-induced hyperactivity of both fibres. CONCLUSION • Our study shows, using selective unifibre potential measurement, that systemic administration of tadalafil reduces mechanosensitive afferent activities of both Aδ- and C-fibres elicited by bladder distension in the rat, and also that tadalafil has an inhibitory effect on the increased activities of both fibres induced by intravesical acrolein instillation.

Study Type – Therapy (cohort) Level of Evidence 2b What’s known on the subject? and What does the study add? Phosphodiesterase type-5 (PDE5) inhibitors (tadalafil, vardenafil, and sildenafil) are well-known treatment options for men with erectile dysfunction and should be taken before anticipated sexual activity. Tadalafil is also approved for once daily use in men with erectile dysfunction. Recent 12-week studies in men with benign prostatic hyperplasia (BPH) have shown once daily use of tadalafil significantly reduced their urinary symptoms. This article is the first to report the long-term safety and maintenance of efficacy for once-daily use of tadalafil in men with urinary symptoms secondary to BPH. OBJECTIVE • To evaluate the 1-year safety of 5 mg of tadalafil once daily in men with lower urinary tract symptoms secondary to benign prostatic hyperplasia (BPH-LUTS); efficacy measures were included to evaluate the maintenance of efficacy after an additional year of treatment. PATIENTS AND METHODS • In total, 427 men who completed a 12-week, placebo-controlled, dose- finding study assessing once-daily tadalafil (2.5, 5, 10 or 20 mg) or placebo elected to continue into the open-label extension period. Safety and efficacy parameters were assessed after 1 month and every 3 months. RESULTS • In total, 299 patients (69.9%) completed the 1-year, open-label extension period. Treatment-emergent adverse events (TEAEs) were reported by 57.6% of patients, with most TEAEs being mild (44%) or moderate (45%) in severity; the most common TEAEs (≥2%) were dyspepsia, gastro-oesophageal reflux disease, back pain, headache, sinusitis, hypertension and cough. Twenty-two patients (5.2%) discontinued as a result of AEs. During the open-label extension period, mean prostate-specific antigen increased from 1.6 ± 1.3 ng/mL to 1.8 ± 1.4 ng/mL. • Mean post-void residual volume was 61.1 ± 60.4 mL at study entry and 42.2 ± 64.1 mL after the open-label extension period. Changes in the total International Prostate Symptom Score (IPSS), IPSS irritative and obstructive subscores, IPSS health-related quality of life and BPH Impact Index were maintained after 1 year. In sexually-active patients with erectile dysfunction, improvements in the International Index of Erectile Function–Erectile Function domain were maintained after 1 year. CONCLUSION • In men with BPH-LUTS, 5 mg of tadalafil once daily during 1 year of treatment was well tolerated and efficacy changes were maintained.

Study Type – Therapy (RCT) Level of Evidence 1b What’s known on the subject? and What does the study add? There is a positive effect of PDE5 inhibitors on several aspects of the men’s sex lives, chiefly erectile function, personal self-esteem, and satisfaction from their sex lives. To our knowledge, our study is the first study to evaluate the effects of PDE5 inhibitors on erectile variables simultaneously in a laboratory setting. In the present study, significant penile rigidities were obtained with PDE5 inhibitors in a short period, with no sexual stimulation, in laboratory conditions. Our findings might support the use of PDE5 inhibitors in the men who need penile rehabilitation. OBJECTIVE To investigate the effects of phosphodiesterase type 5 (PDE5) inhibitors on erectile variables during a period with no sexual stimulation in a laboratory setting double-blind study. PATIENTS AND METHODS In all, 80 men without erectile dysfunction (ED) but with lifelong premature ejaculation (PE) were included in the study. The men were divided equally in to four groups and received either placebo, vardenafil (10 mg), sildenafil (50 mg) or tadalafil (20 mg) in a double-blind study design. The men attended the laboratory following 3 days of sexual abstinence and placebo or one of the PDE5 inhibitors was ingested after ≥2 h of fasting and non-smoking. The men were then immediately placed in a silent room and real-time penile rigidity and tumescence monitoring with Rigiscan Plus (Rigiscan Plus® System, Osbon Medical Systems, Augusta, GA, USA) began. The men read some magazines or newspapers that contained no sexually stimulating material for 1.5 h. There was no interaction between the men and observer during the test period. Times to first measured and total durations of base and tip rigidities, and also total and per minute rigidity were evaluated. RESULTS The recorded base and/or tip rigidity ratios were 40% (eight of 20), 71% (12/17), 47% (nine of 19) and 70% (14/20) in men who took placebo, sildenafil, tadalafil and vardenafil, respectively (P= 0.126). The ratio of men who could obtain ≥60% base and/or tip rigidities were 10% (two of 20), 41% (seven of 17), 26% (five of 19) and 55% (11/20) in placebo, sildenafil, tadalafil and vardenafil groups, respectively (P < 0.05). The median time to first measured base rigidity was 58.0, 21.5, 54.5 and 57 min with placebo, sildenafil, tadalafil and vardenafil, respectively (P= 0032). The median total duration of recorded base rigidity was 4.0, 27.5, 10.0 and 11.5 min in men who took placebo, sildenafil, tadalafil and vardenafil, respectively (P= 0.013). The median total base rigidity (area under the curve) was 72.8, 699.0, 360.5 and 553.0 with placebo, sildenafil, tadalafil and vardenafil, respectively (P= 0.016). CONCLUSIONS Significant penile rigidities were obtained with PDE5 inhibitors during the short test period, with no sexual stimulation, in laboratory conditions. This finding might support the use of PDE5 inhibitors in men who need penile rehabilitation.

OBJECTIVES To explore the possible role of of 8-isoprostane F2α (8-IPF2α) in the aetiology of erectile dysfunction (ED), as the over-production of superoxide (O2-) derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase results in the formation of 8-IPF2α in vascular tissue, which has similar properties to thromboxane A2 (TXA2). TXA2 is vasoconstrictor and up-regulates the expression of NADPH oxidase and phosphodiesterase type 5 (PDE5). MATERIALS AND METHODS Cavernosal vascular smooth muscle cells (CVSMCs) were incubated with 8-IPF2α or the TXA2 analogue, U46619, ±sildenafil, iloprost (a stable prostacyclin [PGI2] analogue) or the nitric oxide (NO) donor NONOate for 16 h. The formation of O2- was then measured, PDE5 expression assessed using Western blotting and PGI2 and 8-IPF2α formation measured using enzyme-linked immunoassays. RESULTS 8-IPF2α promoted the formation of O2-, an effect inhibited by apocynin (an NADPH oxidase inhibitor) and up-regulated the expression of PDE5. Under identical incubation conditions, 8-IPF2α induced an increase in the formation of 8-IPF2α but reduced the formation of PGI2. All, these effects were reversed by sildenafil, iloprost, NONOate and picotamide. CONCLUSIONS These data show that O2- derived from NADPH oxidase influences the relative balance of PGI2 and 8-IPF2α in CVSMCs, which in turn alters the degree of PDE5 expression. This is a novel pathogenic mechanism underlying ED and a novel mechanism of action of sildenafil.

Study Type – Therapy (RCT) Level of Evidence 1b What’s known on the subject? and What does the study add? Phosphodiesterase type 5 inhibitors (PDE 5Is) improve erectile function and lower urinary tract symptoms (LUTS) caused by benign prostatic hyperplasia (BPH), however the exact effects on prostate tissue and its underlying mechanisms remain unclear. PDE 5Is enhanced the production of cyclic nucleotides in the plasma and prostate, and the distribution of PDE 5Is in the prostate was higher than in the plasma. OBJECTIVE • To evaluate the impact and distribution of a single phosphodiesterase type 5 inhibitor (PDE5 I) dose (udenafil or tadalafil) in prostate tissue and plasma in patients with benign prostatic hyperplasia (BPH). PATIENTS AND METHODS • Thirty BPH patients complaining of erectile dysfunction along with moderate-to-severe lower urinary tract symptoms (LUTS) who underwent transurethral resection of the prostate (TURP) were enrolled in the present study. • The patients were randomly divided into the three groups: group 1, TURP without PDE5 Is; group 2, 200 mg of udenafil given 1 h before TURP; and group 3, 20 mg of tadalafil given 1 h before TURP. • We evaluated the concentrations of PDE5-I, cAMP and cGMP in prostate tissues and plasma, and calculated the prostate tissue-to-plasma (T/P) ratio. RESULTS • The concentration of udenafil in prostate tissue and plasma was 2028.6 ± 360.8 ng/g and 463.7 ± 39.1 ng/mL, respectively, and the resulting T/P ratio was 4.4. The tadalafil concentration in prostate tissue and plasma was 385.7 ± 83.8 ng/g and 305.8 ± 41.1 ng/mL, respectively, and the T/P ratio was 1.3. • Udenafil and tadalafil significantly increased the cAMP and cGMP levels in plasma and prostate tissues. CONCLUSIONS • Udenafil and tadalafil significantly increased cAMP and cGMP levels and were more highly distributed in the prostate than plasma. The T/P ratio of udenafil was higher than tadalafil. • These findings may help in the assessment of the feasibility of using PDE5 Is to concurrently treat both LUTS and erectile dysfunction.

Study Type – Therapy (case series) Level of Evidence 4 OBJECTIVE To examine the early use of phosphodiesterase-5 inhibitor (PDE-5i; sildenafil citrate) in preventing subsequent erectile dysfunction (ED) after (monotherapy) prostate brachytherapy (PB, an accepted option for Gleason 6 or low-volume Gleason 7 prostate cancer), as PB is currently being offered more frequently in younger patients, and ED can be a side-effect often within the first 12 months after treatment. PATIENTS AND METHODS We examined a single-surgeon series of 69 patients who had been treated with PB from 2002 to 2005. All patients had a follow-up of ≥1 year; prospectively, and patients had baseline, 6- and 12-month assessments using the Sexual Health Inventory for Men (SHIM) and International Index of Erectile Function (IIEF)-6 scores. The 69 patients were divided into early treatment with PDE-5i (31) and not treated with PDE-5i (38), and their SHIM and IIEF-6 scores were compared at baseline, 6 and 12 months. Daily sildenafil (25–50 mg) was given immediately after PB for 12 months. Overall, for the entire group, the mean prostate-specific antigen (PSA) level was 6.8 ng/mL; 78% had Gleason 6 cancer and 20% had Gleason 7 (3 + 4) cancer. The mean age in the early PDE-5i group was 64.8 years, and was 66.0 years in the no-PDE-5i group. The mean radiation dose in the early PDE-5i group was 50.2 Gy, and 43.9 Gy in the other group (P= 0.08). RESULTS In the no-PDE-5i group, the mean baseline SHIM score of 17.1 decreased rapidly to 9.1 at 6 months (P= 0.01) and stayed at 9.3 at 12 months (P= 0.01). In the early PDE-5i group, the mean baseline SHIM score of 21.8 decreased slightly to 17.6 at 6 months (P= 0.2), and was maintained at 17.9 at 12 months (P= 0.2). Using the Wilcoxon rank-sum test, the 6- and 12-month SHIM scores in the two groups (P < 0.001). The IIEF-6 questionnaire confirmed the SHIM analysis. CONCLUSIONS After PB patients had a significant decline in SHIM/IIEF-6 scores at 6 and 12 months. Our results indicate a 50% decrease in the quality of their erections. This provides an opportunity to initiate early intervention with PDE-5i or perhaps vacuum constriction devices or intraurethral alprostadil. In this study, the early use of PDE-5i after PB maintained erectile function at both 6 and 12 months.

Study Type – Therapy (RCT) Level of Evidence 1b OBJECTIVE To determine, by post hoc analysis, the effects of tadalafil (a long-acting phosphodiesterase 5 inhibitor) on peak urinary flow (Qmax), bladder capacity, voiding efficiency and the obstructive symptoms of benign prostatic hyperplasia (BPH) in men with lower urinary tract symptoms secondary to BPH (BPH-LUTS), compared with placebo. PATIENTS AND METHODS After a 4-week placebo run-in period, 1058 men with BPH-LUTS were randomly allocated to receive once daily treatment with placebo or tadalafil (2.5, 5, 10, or 20 mg) for 12 weeks. Uroflowmetry, postvoid residual volume (PVR), and BPH symptom score measurements were assessed throughout the trial. RESULTS Increases in Qmax were numerically greater for tadalafil (2.5, 5, 10, and 20 mg with percentage changes of 15%, 16%, 17%, 22%, respectively) vs placebo (12%), but did not reach statistical significance. Age, baseline Qmax, erectile dysfunction history, sexual activity, and previous α-blocker therapy significantly influenced the Qmax response. Tadalafil was not associated with significant changes in PVR. Tadalafil had its greatest effects on bladder capacity and voiding efficiency in men with a Qmax of

Study Type – Aetiology (case control) Level of Evidence 3b OBJECTIVE To evaluate the effect of N(G)-nitro-l-arginine methyl ester (L-NAME)-induced hypertension (HT) on erectile function in the rat and determine if the phosphodiesterase (PDE)-5 inhibitor, sildenafil, can reverse the effects of nitric oxide (NO) deficiency, as HT is a risk factor for erectile dysfunction (ED) and the NO synthase (NOS) inhibitor L-NAME induces NO-deficient HT. MATERIALS AND METHODS Thirty-six adult Sprague-Dawley male rats were divided into three groups, i.e. a control, L-NAME-HT (40 mg/rat/day in the drinking water for 4 weeks), and sildenafil-treated L-NAME-HT (1.5 mg/rat/day sildenafil, by oral gavage concomitantly with L-NAME). The erectile response expressed as a ratio of intracavernosal pressure (ICP)/mean arterial pressure (MAP), evaluated after electrical stimulation of the right cavernous nerve. The isometric tension of corpus cavernosum smooth muscle (CCSM) was measured in organ-bath experiments. NOS expression was determined immunohistochemically for neuronal (n)NOS and by Western blot analysis for endothelial (e) and inducible (i) NOS protein. cGMP levels were evaluated by enzyme-linked immunosorbent assay. RESULTS The erectile response was diminished in the HT group. Nitrergic and endothelium-dependent relaxation was reduced, while the relaxation response to sodium nitroprusside and contractile response to phenylephrine were not altered in CCSM from L-NAME-treated rats. HT rats showed decreased expression of nNOS, whereas eNOS and iNOS protein expression was increased. Sildenafil partly restored endothelial and molecular changes in CCSM from HT rats, but did not reverse the decreased erectile response, even as cGMP levels returned to normal levels. CONCLUSIONS Sildenafil treatment did not correct the ED in L-NAME-treated HT rats. Under sustained high blood pressure, up-regulation of PDE5 expression failed to reverse the depletion of neuronal NO and/or impaired nNOS activity. However, endothelium-dependent relaxation was restored. Drug targeting of neuronal dysfunction might delay the onset of ED in HT.

OBJECTIVE To study the effects of the phosphodiesterase-5 inhibitor, vardenafil, on contraction and cyclic nucleotide levels in isolated detrusor preparations with and without mucosa, from control rats and rats with partial urethral obstruction (PUO) and intact mucosa. MATERIALS AND METHODS Female Sprague-Dawley rats were divided into groups subjected to PUO for 14 days (six), and sham-operated control rats (12). Detrusor preparations were mounted in organ baths and effects of increasing concentrations of vardenafil (1 nm to 100 microm) assessed on carbachol-activated (1 microm) preparations, and on contractions induced by transmural activation of nerves (electrical field stimulation, EFS). Levels of cGMP and cAMP were determined using radioimmunoassays. RESULTS Vardenafil caused concentration-dependent relaxations of carbachol-contracted detrusor, the mean (sd) of which at 100 microm was 91 (4)% in control and 100% in PUO rats. The -log 50% inhibitory concentration (IC(50)) was 4.41 (0.08) and 4.73 (0.05) (P < 0.01), respectively. Removing the mucosa increased the relaxant effect of vardenafil at 1-10 microm (P < 0.05) although -log IC(50) values were unaffected compared to the control. The cGMP levels ( pmol/mg protein) in control preparations increased from 2.5 (0.6) to 5.0 (0.8), and from 1.4 (0.2) to 7.2 (1.3) in obstructed bladders. In mucosa-denuded preparations the cGMP content increased from 0.6 (0.1) to 1.6 (0.4) in response to vardenafil. In control rats, the levels of cAMP increased from 12.8 (2.5) to 18.9 (0.9) (P < 0.05) after vardenafil. In mucosa-denuded preparations the cAMP levels after vardenafil increased from 16.5 (2.11) to 37.8 (3.4) (P < 0.01). In PUO bladders, the tissue content of cAMP increased from 12.6 (2.4) to 20.6 (3.4) (P < 0.01). Vardenafil concentration-dependently inhibited nerve-induced contractions in all groups studied. At 100 microm 19 (3)% of the control contraction remained, vs 8 (1)% for preparations from obstructed rats, and 11 (4)% in mucosa-denuded preparations. CONCLUSION In normal rats, vardenafil relaxed carbachol- and inhibited EFS-induced contractions of detrusor preparations with and without urothelium, and in PUO rats with urothelium. Relaxations were accompanied by increases in both cAMP and cGMP content. It is proposed that vardenafil-induced relaxation of rat detrusor, also in obstructed and mucosa-denuded preparations, is mediated via cAMP.

To investigate if sildenafil citrate can inhibit the functional and structural changes of the detrusor in a murine model of bladder outlet obstruction (BOO). Phosphodiesterase type 5 (PDE-5) inhibitors have recently been used for treating urinary symptoms associated with prostatic obstruction, but it is unclear whether PDE-5 inhibition acts on the prostatic urethra or the bladder.In 18 male Balb/CAN mice, partial BOO was created and the mice allowed to survive for 6 weeks. Half of the mice (nine) were treated with oral sildenafil citrate daily (10 mg/kg) by oral lavage (BOO + V), and half (nine) were not (BOO). Six mice were used as sham-operated controls and received no sildenafil. The mice were assessed by urodynamics at baseline and after 6 weeks, with a measurement of volume at first uninhibited non-voiding contraction (V(DO1)), bladder capacity (BC), and detrusor pressure during void (Pdet). At 6 weeks, bladders were harvested, fixed and sectioned, and stained with haematoxylin and eosin (HE) and trichrome stain. Detrusor muscle hypertrophy and fibrosis were evaluated on a scale of 1 (decreased) to 3 (increased), by two urologists and one pathologist unaware of the treatment group; the results were compared with those from normal controls.BOO mice had a significantly greater BC than control mice, with a mean (SD) of 153 (66) vs 58 (13) microL (P = 0.004). Treatment with sildenafil did not significantly alter BC. BOO caused an increase in Pdet compared to controls, with a mean (SD) of 25 (7) vs 12 (5) cm H2O. P(det) was not significantly different after treatment with sildenafil. The median V(DO1) as a percentage of BC was significantly lower in BOO than in control mice (20% vs 53%, P0.03) and increased significantly after sildenafil treatment (20% vs 44%, P = 0.04). BOO was associated with a greater bladder weight than in control mice, with a mean (SD) of 89 (32) vs 27 (6) mg (P = 0.001), which was decreased with sildenafil treatment, to 40 (14) vs 89 (32) mg (P = 0.013). BOO caused an increase in detrusor muscular hypertrophy vs control mice, with a median HE score of 3 vs 2 (P = 0.01) and an increase in fibrosis vs control mice, with a median trichrome score of 3 vs 2 (P = 0.01). BOO + V mice had reduced muscular hypertrophy and fibrosis, with a median HE score of 3 vs 2 (P = 0.01) and a median trichrome score of 3 vs 1 (P = 0.01).BOO mediates both functional and structural changes in the mouse bladder. Six weeks of obstruction caused an increase in BC, detrusor overactivity and voiding pressure, and mediated an increase in bladder weight, detrusor muscle hypertrophy and collagen deposition in the lamina propria and smooth muscle. Treatment with 6 weeks of oral sildenafil beginning at the time of BOO prevented the increase in detrusor overactivity without affecting voiding pressures, and prevented the increase in detrusor muscle hypertrophy and collagen deposition that otherwise occurred with BOO. It appears therefore that sildenafil citrate acts on the bladder rather than on the outlet.

OBJECTIVE To assess whether the longer half-life of tadalafil is associated with longer lasting or more severe side-effects than the other phosphodiesterase type 5 inhibitors (PDE-5Is), as clinical trials have shown that the efficacy and safety of the three available are similar, but tadalafil has a half-life four times longer than the other two drugs. PATIENTS AND METHODS Treatment-naive men beginning PDE5-I therapy were recruited from a specialist clinic. Data on the type and duration of drug-associated side-effects were collected prospectively. Levels of bother were assessed with a visual analogue scale (VAS). Differences in type, duration and bother of side-effect were compared between drugs. RESULTS In all, 409 men provided data; there were no differences between drugs in the proportion of men responding, or the overall prevalence of side-effects. The mean duration of side-effects with tadalafil was 14.9 h, compared to 3.9 and 7.7 h for sildenafil and vardenafil. Of men taking tadalafil, 30% had side-effects lasting >12 h. There were no differences in mean VAS scores between the drugs. Individual side-effects caused similar levels of bother, except for facial flushing, which was less bothersome. CONCLUSIONS Men taking tadalafil are at risk of prolonged side-effects, although levels of bother associated with these side-effects are not significantly greater than those seen with short-acting PDE5-Is.

OBJECTIVES To investigate whether vardenafil, a phosphodiesterase 5 (PDE-5) inhibitor, would protect the bladder from decompensatory changes in a 4-week rat bladder outlet obstruction (BOO) model, as evidence has been accumulating that PDE-5 inhibitors improve lower urinary tract symptoms (LUTS) in patients with benign prostatic hyperplasia (BPH). MATERIALS AND METHODS In all, 50 12-week-old female Sprague-Dawley rats were divided into five equal groups; group 1, sham operated vehicle control rats; group 2, BOO vehicle rats; group 3–5, BOO rats given oral vardenafil at 5, 20, 80 mg/L, respectively. Vardenafil was given in drinking water from the day of surgery. At 4-weeks after the introduction of BOO, vardenafil was washed-out by giving water for 24–48 h, and then the bladder was excised and dissected into four longitudinal strips for isometric organ-bath assay. Contractile responses of bladder strips to electrical field stimulation (EFS), carbachol and KCl was determined for each group. RESULTS BOO induced a significant increase in bladder weight in group 2 compared with group 1. Bladder weights of groups 3–5 were not significantly different from that of group 2. The contractile forces in response to EFS, carbachol and KCl in group 2 were 30.7–51.7% of those in group 1. Vardenafil treatment in groups 3–5 generally did not block the BOO-induced reduction of contractile force in the bladder strips. However, treatment with a high dose of vardenafil resulted in a significant increase in the contractile response to carbachol (78.4% group 5 vs 51.7% group 2). CONCLUSION Chronic treatment with a high dose of vardenafil protected the rat bladder from BOO-induced contractile dysfunction to carbachol.

Alpha(1)-adrenergic blockers (alpha(1)-blockers) are considered the most effective monotherapy for lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia. Phosphodiesterase type-5 (PDE-5) inhibitors are the first-line treatment for erectile dysfunction (ED). As LUTS and ED are strongly linked, co-prescription of both drug classes is likely to increase. Interaction studies have confirmed that tadalafil, a long-acting PDE-5 inhibitor, has only marginal effects on blood pressure when co-administered with the selective alpha(1)-blockers, alfuzosin or tamsulosin. alpha(1)-blockers show an incidence of ED similar to placebo; they may even have some benefit on sexual function in men with concomitant LUTS and sexual dysfunction, with the exception of tamsulosin which causes anejaculation. On the other hand, PDE-5 inhibitors have a beneficial effect on LUTS. These agents are likely to act via different mechanisms of action, providing the rationale for combining them to treat LUTS and ED. Indeed, alfuzosin and tadalafil show an additive relaxant effect on human detrusor muscle, human prostate tissue and human corpus cavernosum in vitro. A pilot study also suggests that daily intake of alfuzosin 10 mg and sildenafil 25 mg is well tolerated and may be more effective than monotherapy to improve LUTS and ED. Further research is warranted to establish the value of this combination therapy in LUTS and ED.

OBJECTIVE To investigate the effects of sildenafil on noradrenaline- and potassium-induced contractions of isolated human seminal vesicles (SVs), as premature ejaculation is a relatively common male sexual dysfunction that currently lacks an adequate therapy, and recent in vitro tests showed that sildenafil induces relaxation of rodent isolated SVs, but it is not known whether it also inhibits isolated human SV. MATERIAL AND METHODS Isolated strips of human SVs were suspended in an organ bath and cumulative concentration-response curves to either noradrenaline or KCl were constructed in the presence and absence of sildenafil to evaluate its inhibitory actions. RESULTS Sildenafil (25–100 µm) induced concentration-dependent inhibitory effects on the human SV contracted by either noradrenaline or KCl. These actions of sildenafil do not therefore appear to be mediated via a competitive antagonism of α-adrenoceptors and are consistent with its recognized ability to inhibit phosphodiesterase-5. CONCLUSIONS The present results show an important inhibitory action of sildenafil in the isolated human SV, supporting the therapeutic indication of this drug for treating premature ejaculation.

OBJECTIVES To compare treatment preference, efficacy, and tolerability of sildenafil citrate (sildenafil) and tadalafil for treating erectile dysfunction (ED) in men naive to phosphodiesterase 5 (PDE5) inhibitor therapy. PATIENTS AND METHODS This was an open-label, crossover study of sildenafil and tadalafil (taken as needed). After a 4-week baseline assessment, 367 men with ED (mean age 54 years) were randomized to receive sildenafil for 12 weeks followed by tadalafil for 12 weeks or vice versa (8-week dose optimization and 4-week assessment phases). During dose optimization, patients started taking 25- or 50-mg sildenafil or 10-mg tadalafil and could titrate to find their optimum dose (25-, 50- or 100-mg sildenafil; 10- or 20-mg tadalafil). After completing both 12-week periods, patients chose which treatment to continue during an 8-week extension. Efficacy was measured with the International Index of Erectile Function (IIEF) and Sexual Encounter Profile (SEP) diary. RESULTS Of the 291 men who completed both treatments, 85 (29%) chose sildenafil and 206 (71%) chose tadalafil (P < 0.001) for the 8-week extension. The IIEF erectile function domain scores were 14.2 at baseline, 23.9 at endpoint on sildenafil, and 24.3 at endpoint on tadalafil (P = 0.08, sildenafil vs tadalafil). The mean per patient percentage success scores for SEP2 (penetration) were: baseline (46%), sildenafil (post-baseline 82%) and tadalafil (post-baseline 85%; P = 0.06, sildenafil vs tadalafil), and for SEP3 (successful intercourse) were: baseline (19%), sildenafil (post-baseline 72%), and tadalafil (post-baseline 77%; P = 0.003, sildenafil vs tadalafil). The only treatment-emergent adverse events that were reported by > 5% of men were headache and flushing. CONCLUSIONS In men with ED who were naive to PDE5 inhibitor therapy, sildenafil and tadalafil were both effective and well tolerated. After treatment with sildenafil and tadalafil, 29% of men chose sildenafil and 71% chose tadalafil for ED therapy during an 8-week extension.

OBJECTIVE To evaluate the safety and efficacy of sildenafil citrate for treating erectile dysfunction (ED) in patients with combat-related post-traumatic stress disorder (PTSD). PATIENTS AND METHODS In all, 266 combat-exposed war veterans with ED (aged 37–59 years) were recruited. They met the Diagnostic and Statistical Manual of Mental Disorders-IV criteria for PTSD according to the Structured Clinical Interview for Patients, Investigator Version. The patients were also evaluated with the Clinician-Administered PTSD Scale, both to establish the diagnosis of PTSD and to measure symptom severity. Only patients with psychogenic ED were included in the study. Patients with comorbid conditions (diabetes mellitus, hypercholesterolaemia, hypertension, Peyronie’s disease) and smokers of more than five cigarettes daily were excluded. The patients were randomly divided into a group of 133 who received 100 mg of on-demand sildenafil 0.75–2 h before sexual stimulation, and 133 who received placebo. Patients were asked to use ≥16 doses or attempts at home. The efficacy of the treatments was assessed every four attempts during treatment, and at the end of the study, using responses to the 15-question International Index of Erectile Function (IIEF), Sexual Encounter Profile diary questions 2 and 3, Erectile Dysfunction Inventory of Treatment Satisfaction questionnaire, patients’ event logs of sexual activity, and a Global Assessment Question about erections. RESULTS Sildenafil did not produce significantly and substantially greater improvement than placebo in each of the primary and secondary outcome measures (P = 0.08). A normal EF domain score (≥26) at endpoint was reported by 13 (9.8%), and 11 (8.3%) of patients on the sildenafil and placebo regimens, respectively (P = 0.09). Patients treated with sildenafil had no statistically significantly greater improvement in the five sexual function domains of the IIEF questionnaire than those treated with placebo (P = 0.08). The incidences of treatment-emergent adverse events were significantly greater in the sildenafil arm than in the placebo group (P = 0.01). CONCLUSIONS Sildenafil is no better than placebo in treating PTSD-emergent ED. Further randomized clinical trials are warranted in combat veterans and other populations with PTSD to better elucidate the role of phosphodiesterase type 5 inhibitors in treating PTSD-emergent ED.

OBJECTIVE To evaluate the indications for penile prosthesis implantation in the treatment of erectile dysfunction (ED) before and after the introduction of sildenafil. PATIENTS AND METHODS Penile prosthesis implantation was indicated in 144 men with ED at our institution between 1992 and 2007; 83 (55.6%) accepted the procedure, 55 (38.2%) refused it and six (4.2%) accepted but eventually had no surgery. Sixty-seven patients were operated primarily, and the remainder were referred cases with complications after or dissatisfaction with primary operations done elsewhere. Thirty-two were operated before the introduction of sildenafil (BS) and 35 after (AS). RESULTS In the BS group the most frequent aetiology was vascular disease, with 11(34%) vs two (6%) in the AS group. The most frequent aetiology in the AS group was previous radical pelvic surgery (radical prostatectomy, sigmoidectomy, etc.) with 17 (49%) vs none in the BS group. There were no significant differences in complication rates in both groups. Satisfaction rates in patients with malleable and inflatable devices were 36 (86%) and 17 (85%), respectively. CONCLUSIONS After the introduction of oral therapy for ED there were some changes in the aetiology of refractory ED; ED after radical prostatectomy is gaining acceptance as the main reason for a penile implant.

OBJECTIVES To examine the safety of tadalafil as used in general practice in England, and to compare the mortality rate due to ischaemic heart disease (IHD) in tadalafil users with that in the male population in England. PATIENTS AND METHODS Patients in this observational cohort study were identified from dispensed prescriptions for tadalafil issued by general practitioners (GPs) from February 2003 to November 2004. Demographic and outcome data (clinical events) were requested from patients’ GPs using a postal questionnaire. A standardized mortality ratio (SMR) was calculated using indirect standardization for deaths from IHD in the cohort (where age was known) over a 1-year observation period compared to that in the English male population (2003). A sensitivity analysis was carried out to investigate the effects of missing data for age and cause of death. RESULTS Clinical information was obtained for 16 129 patients (median age 60 years, interquartile range 52–67); the age was not specified for 3212 (19.9%) patients. At least a third of the patients had diabetes mellitus and 29% had hypertension. Comparison of the mortality rate due to IHD for the patients of known age with that in the English male population provided an SMR of 0.57 (95% confidence interval 0.38–0.83) indicating fewer observed deaths in the cohort than expected. The results of the sensitivity analyses investigating the effect of missing data for age and cause of death produced similar SMR estimates. One confirmed case of non-arteritic anterior ischaemic optic neuropathy (NAION) was reported during tadalafil therapy in a patient with other risk factors for this condition. CONCLUSION The results from this prescription-event monitoring study suggest that tadalafil is generally well tolerated when used in general practice in England. The most frequently reported adverse clinical events were in keeping with clinical trial data and include headache, dyspepsia and back pain. There was no evidence of a greater mortality rate due to IHD in the tadalafil cohort than in the general male population. However, these results are limited by the use of an external comparator group and might be explained by a ‘healthy cohort effect’. One event of NAION was reported, and although a causal relationship was not established it indicates that NAION occurs rarely in patients prescribed tadalafil.

OBJECTIVE To evaluate the efficacy, tolerability, and treatment satisfaction after initiating treatment with sildenafil 50 mg and later titrating to 100 mg, compared with continuing treatment with sildenafil 50 mg, in men with erectile dysfunction (ED). PATIENTS AND METHODS A multicentre, parallel-group trial was conducted in two 4-week periods. In period 1, patients received 50-mg doses of sildenafil single-blinded for 4 weeks. In period 2, patients were randomized to double-blind, placebo-controlled treatment with sildenafil 50 mg or sildenafil 100 mg for 4 weeks. All patients were aged ≥18 years with a documented clinical diagnosis of ED (score of ≤25 on the International Index of Erectile Function, IIEF, Erectile Function, EF, domain), and met the prescribing criteria for sildenafil 50 mg and 100 mg. RESULTS Of 492 enrolled patients (mean age 53 years, sd 11), 476 (97%) completed period 1 and 473 (96%) completed period 2. Patients receiving sildenafil 50 mg in period 1 had an increase in the mean (sd) baseline EF domain score from 12.8 (5.2) to 22.5 (6.6) (P

OBJECTIVE To evaluate prospectively and compare the clinical response and the change in nucleotides correlating with haemodynamic changes in the cavernosal arteries after an intracavernosal injection (ICI) with vasoactive agents with or without oral sildenafil in men with erectile dysfunction (ED). PATIENTS AND METHODS In all, 80 patients with ED were prospectively evaluated by clinical assessments, measuring nucleotides in blood plasma and haemodynamics in cavernosal arteries. All patients had colour Doppler ultrasonography (CDU) twice with an interval of 5 h. First, each patient had CDU after ICI with trimix (0.25 mL) or prostaglandin E1 (PGE1, 5 µg), and the second CDU was after ICI trimix given 1 h after oral placebo (group I), sildenafil 25 mg (group II) or 100 mg (group III) and after ICI with PGE1 at 1 h after oral placebo (group IV) or 100 mg sildenafil (group V). Levels of cGMP and cAMP in peripheral venous and penile cavernosal blood plasma were measured at 15 min after ICI. RESULTS The mean peak systolic velocity (PSV) at 5, 10, 15 min, and resistive index at 10 min in the second CDU after ICI with trimix, were significantly increased in group III. The mean (sem) levels of cavernosal cGMP were significantly increased in group III and V, from 1130.1 (313.5) to 2056.7 (580.4) and 1017.0 (214.2) to 1905.2 (915.0) fmol/mL, respectively. cAMP was significantly increased in group V, from 9533.1 (2068.4) to 12150 (3684.2) fmol/mL. CONCLUSIONS The haemodynamic changes and cGMP and cAMP production in the cavernosum were improved by trimix plus sildenafil more than with than PGE1 plus sildenafil or one ICI with trimix or PGE1. The results suggest that ICI with trimix and sildenafil is the best combination for a pharmacological erection test.

OBJECTIVE To evaluate the effect of low-dose sildenafil for rehabilitating erectile function after nerve-sparing radical prostatectomy (NSRP), as the delay to recovery of erectile function after NSRP remains under debate. PATIENTS AND METHODS Forty-three sexually active patients had a NSRP; at 7–14 days after surgery they had a Rigiscan® (Dacomed Corporation, Minneapolis, MN, USA) measurement of nocturnal penile tumescence and rigidity (NPTR). To support the recovery of spontaneous erectile function, 23 patients with preserved nocturnal erections received sildenafil 25 mg/day at night. A control group of 18 patients were then followed but had no phosphodiesterase-5 inhibitors. The International Index of Erectile Function (IIEF)-5 questionnaire was completed 6, 12, 24, 36 and 52 weeks after NSRP. RESULTS Of the 43 patients, 41 (95%) had one to five erections during the first night after catheter removal. In the group using daily sildenafil the mean IIEF-5 score decreased from 20.8 before NSRP to 3.6, 3.8, 5.9, 9.6 and 14.1 at 6, 12, 24, 36 and 52 weeks after NSRP, respectively. In the control group the respective scores were 21.2, decreasing to 2.4, 3.8, 5.3, 6.4 and 9.3. There was a significant difference in IIEF-5 score and time to recovery of erectile function between the groups (P

To test the hypothesis that a variable dosage of the oral phosphodiesterase type 5 (PDE5) inhibitor sildenafil (25, 50, 100 mg) or vardenafil (5, 10, 25 mg) determined according to results obtained from nocturnal penile tumescence and rigidity (NPTR, RigiScan), given nightly for 1 year, can improve spontaneous erectile function (EF) in men with mild-to-moderate arteriogenic erectile dysfunction (ED); this regimen was compared with a fixed daily dosage of sildenafil 25 mg or vardenafil 5 mg.In a prospective open-label, parallel-group trial 154 men with ED were randomized either to fixed low-dose sildenafil 25 mg or vardenafil 5 mg (group 1) or to the lowest erectile dosage of sildenafil (25, 50 or 100 mg) or vardenafil (5, 10 or 20 mg) (group 2) provoking an erectile event as measured by NPTR nightly for 1 year. The EF domain of the International Index of Erectile Function (IIEF) was assessed before and 1 year after the beginning of treatment, and at 4 weeks after ending treatment.After 1 year, 27 of 63 (64%) evaluable men in group 1 had an EF domain score in the normal range, vs 46 of 61 (75%) men in group 2. After the subsequent 4-week wash-out phase, both groups continued to have improved EF domain scores; 22 of 63 (35%) men in group 1 still had a score in the normal range, whereas 38 of 61 (62%) in group 2 had a normal score. The EF domain score in group 1 and 2 improved significantly after 1 year of treatment, from 13.6 to 18.9, and 15.1 to 23.9, respectively (P0.01). After the subsequent 4-week wash-out phase, men from both groups maintained this significant level of EF, at 17.1 and 22.4, respectively (P0.05).Nightly PDE5-inhibitor treatment 1 year in a dosage determined by NPTR measurements results in better EF than giving a fixed dosage of sildenafil (25 mg) or vardenafil (5 mg). This improvement persisted for4 weeks beyond the end of treatment. The results from this open-label, randomized trial warrant verification under double-blind, placebo-controlled conditions.

OBJECTIVE To evaluate the effect of sildenafil citrate on each item of the 14-item Self-Esteem And Relationship (SEAR) questionnaire, which is used to measure self-esteem, confidence, satisfaction with sexual relationship, and overall relationship satisfaction in men with erectile dysfunction (ED). PATIENTS AND METHODS Data were combined from two 12-week, double-blind, placebo-controlled, flexible-dose sildenafil trials having identical protocols, one conducted in the USA and the other in Mexico, Brazil, Australia and Japan. All men had ED and were aged >or=18 years. Response categories of each SEAR item used a 4-week reference period and were based on a five-point scale (1, almost never/never; 2, a few times; 3, sometimes; 4, most times; 5, almost always/always). The difference (sildenafil vs placebo) in the change from baseline to week 12 was evaluated with a Wilcoxon rank sum test using ridit analysis, and an analysis of covariance model that included treatment group, centre, study and baseline item score. RESULTS Compared with the 274 patients receiving placebo, the 279 receiving sildenafil reported significantly greater mean and median improvements (P < 0.001) in each of the 14 SEAR items. The probability of increased psychosocial benefit from baseline to week 12 was higher with sildenafil for each SEAR item, and ranged from 0.60 ('My partner was unhappy with the quality of our sexual relations'[item reverse-scored]) to 0.72 ('I was satisfied with my sexual performance'). Across all items, the mean (sd) probability was 0.67 (0.04) that a randomly selected patient in the sildenafil group would have a more favourable change relative to a randomly selected patient in the placebo group. CONCLUSIONS Sildenafil produced substantial and meaningful improvements at the item-specific level. This analysis complements previously published work on self-esteem, confidence and relationship satisfaction.

OBJECTIVE To evaluate differential gene expression in penile tissue after treatment with the phosphodiesterase 5 (PDE5) inhibitor tadalafil, as of the three clinically available PDE5 inhibitors (sildenafil, tadalafil, and vardenafil) used for the treatment of erectile dysfunction (ED), tadalafil has a long half-life and low incidence of side-effects. MATERIALS AND METHODS In all, 32 adult rats were divided into two groups. The control group received 0.5 mL of drinking water alone, while the tadalafil group was treated with tadalafil at a dose of 0.27 mg/kg. At 4 h after treatment with water or tadalafil the rats were killed and the penile tissue was removed. The total RNA was isolated from the penile tissue from both groups and differentially expressed genes were identified by cDNA microarray analysis. To validate the expression data from the microarray analysis, quantitative real-time polymerase chain reaction (PCR) and immunohistochemistry were used. RESULTS In all, 153 genes were differentially expressed between the control group and the tadalafil group. We validated the microarray results by quantitative PCR for the insulin-like growth factor binding protein 6 (IGFBP-6) gene and the neuronal calcium sensor 1 (NCS-1) gene, both of which were up-regulated in the tadalafil group, and for the natriuretic peptide receptor 1 (NPR-1) gene that was down-regulated in this group. Immunohistochemistry showed localization of the NCS-1 protein in sinusoid trabeculae of the corpus cavernosum in control and tadalafil-treated rats. CONCLUSIONS There was differential expression in 153 genes after tadalafil treatment. Some of these genes such as IGFBP-6, NPR-1 and NCS-1, might result in new targets in the treatment of ED.

OBJECTIVE To survey patient satisfaction, using validated questionnaires, in a group of men with erectile dysfunction who had used and responded to both sildenafil citrate and intracavernosal injection (ICI) therapy. PATIENTS AND METHODS In all, 300 patients on ICI therapy were mailed questionnaire packets containing a survey enquiring about the patients' medical history, and two sets of the International Index of Erectile Function (IIEF) and the Erectile Dysfunction Inventory of Treatment Satisfaction (EDITS) sexual function surveys. If patients were using sildenafil alternating with ICI they were asked to complete the IIEF and EDITS questionnaires for each therapy. To identify only patients who had an adequate response to each agent, a score of >/=22 on the EF domain of the IIEF for sildenafil and ICI was required for inclusion in the final analysis. RESULTS In all, 178 packets were evaluable; 123 men (69%) responded to ICI but not sildenafil, and 11 (6%) responded only to sildenafil and not ICI, leaving 37 patients who responded to both; these patients comprised the study population. There was no difference in EF domain score of the IIEF between the treatments; EDITS scores were significantly higher for ICI therapy than for sildenafil (P < 0.001). CONCLUSIONS In patients who alternate the use of sildenafil and ICI therapy, satisfaction appears to be higher with ICI, although the erectogenic performance is similar. This suggests that patient satisfaction does not depend solely on erection performance, and that patients might benefit from various treatment options.

To evaluate the efficacy of vardenafil in patients previously unresponsive to sildenafil.A multicentre, double-blind, 12-week, flexible-dose, placebo-controlled trial was conducted, involving 463 men agedor = 18 years with moderate-to-severe erectile dysfunction (ED) and who were unresponsive to sildenafil (by history). After a 4-week treatment-free run-in, patients received placebo or vardenafil 10 mg with the option to maintain current dose or to titrate by one dose level (5, 10 or 20 mg) based on efficacy and tolerability at 4 and 8 weeks. Outcome measures were the erectile function (EF) domain score of the International Index of Erectile Function, two Sexual Encounter Profile diary questions (vaginal penetration and maintenance of erection until successful completion of intercourse), and the Global Assessment Question (GAQ).There was significantly better EF with vardenafil than with placebo throughout the study. The least-square mean EF domain scores increased from 9.3 at baseline to 17.6 at the 'last' observation carried forward (LOCF) analysis with vardenafil (P0.001). Overall least-square mean per-patient success rates more than doubled for penetration (30.3% to 62.3%) and quadrupled for successful intercourse (10.5% to 46.1%) with vardenafil. Improved erections (positive response to the GAQ) were reported by 61.8% of patients receiving vardenafil and 14.7% of those receiving placebo at LOCF (P0.001). Normal EF (domain scoreor = 26) was achieved by 30% of patients receiving vardenafil and 6% receiving placebo at LOCF (P0.001). Adverse events were infrequent and representative of the phosphodiesterase-5 inhibitor profile.Vardenafil is an effective and generally safe treatment for ED, even in men unresponsive to sildenafil (by history).

Associate Editor Michael G. Wyllie Editorial Board Ian Eardley, UK Jean Fourcroy, USA Sidney Glina, Brazil Julia Heiman, USA Chris McMahon, Australia Bob Millar, UK Alvaro Morales, Canada Michael Perelman, USA Marcel Waldinger, Netherlands OBJECTIVES To determine whether a long-term single daily oral dose of a longer half-life phosphodiesterase-5 (PDE5) inhibitor, tadalafil, has a similar effect to that of the shorter half-life PDE5 inhibitors sildenafil and vardenafil, and can prevent the fibrosis and resultant corporal veno-occlusive dysfunction (CVOD) occurring after cavernosal nerve (CN) injury. MATERIALS AND METHODS Male rats (10 per group) had either a sham operation, unilateral CN resection (CNR) or bilateral CNR, and were left untreated or given retrolingually 5 mg/kg per day of tadalafil. After 45 days, CVOD was assessed via cavernosometry, and the underlying corporal tissue changes were examined by immunohistochemistry and histochemistry (followed by quantitative image analysis), Western blots, and ad hoc methods. RESULTS Tadalafil treatment normalized the low response to papaverine and high drop rate in the intracavernosal pressure measured by cavernosometry after CNR compared with sham-operated rats. Tadalafil also normalized the increase in penile shaft collagen content, and the reduction in corporal smooth muscle cell (SMC) content, SMC/collagen, and replication index, and improved the lower collagen III/I ratio and the increase in apoptotic index, caused by CNR, compared with sham operation. There were no effects of tadalafil on increased transforming growth factor β1, inducible nitric oxide synthase and xanthine oxidoreductase levels. CONCLUSIONS A long-term single daily dose of tadalafil prevented CVOD and the underlying corporal fibrosis in the rat caused by CN damage, as effectively as the previously reported continuous treatment with vardenafil or sildenafil, through a cGMP-related mechanism that appears to be independent of inducible nitric oxide synthase induction.