PDE-5 Inhibitors: Current Status and Future Trends

Effect of daily tadalafil on reported outcomes in patients with erectile dysfunction and depressive symptoms: STROBE, a case-control study

Erectile dysfunction (ED) and depression are closely related. We sought to determine ED and depression were improved by tadalafil, a phosphodiesterase type 5 (PDE5) inhibitor, at 5 mg daily, in this case-control study.Participants were men aged 20 to 65 years with ED for >3 months, International Index of Erectile Function-5 (IIEF) score <21 points, and Zung Self-Rating Depression Scale (SDS) survey result >50 points who were willing to participate.On first visit (V1) and after 1 (V2) and 2 months (V3), clinical features were examined using IIEF-5 for diagnosing and evaluating ED, SDS for evaluating depression, and International Prostate Symptom Score and Quality of Life (IPSS/QoL) survey for examining lower urinary tract symptoms (LUTS). Tadalafil 5 mg was administered daily for 2 months.A total of 60 participants were an average age of 58.68 ± 6.71 years. Patient overall average IIEF was 8.76 ± 5.98, showing mild ED symptoms, and total average IPSS 13.74 ± 7.55 showed moderate LUTS. Average overall SDS index was 58.93 ± 9.21, indicating moderate-to-severe findings. Average change in IIEF among all patients revealed significant improvement from V1 to V2 (-2.69 ± 1.22, P = .03) and V1 to V3 (-4.38 ± 1.20, P < 0.01). IPSS also significantly improved from V1 to V3 (3.48 ± 1.37, P = .01), as did SDS index (V1, V2: 4.69 ± 1.89, P = 0.02), (V1, V3: 5.43 ± 1.89, P < .01). Patients with severe IIEF scores (group 1, n = 27) experienced significantly greater improvement in IIEF from V1 to V2 and V1 and V3, compared to those with mild-to-moderate IIEF scores. Both groups improved in SDS index from V1 to V2 and V1 to V3, with the greatest improvement between V1 and V3 for group 1 and V1 and V2 for group 2.Daily tadalafil 5 mg could be helpful for ED patients with depressive symptoms and improved LUTS and quality of life.

Phosphodiesterase Inhibitory Activity of the Flavonoids and Xanthones from Anaxagorea luzonensis

Five flavonoids, one isoflavone and five xanthones were isolated from Anaxagorea luzonensis. Of these eleven isolated compounds, 1,3,5-trihydroxy-4-prenylxanthone (3) was a relatively potent inhibitor of phosphodiesterase type 5 (PDE5), with an IC50 value of 3.0 μM. This is the first report showing that natural xanthones can exhibit promising PDE5 inhibitory activity. Moreover, this study revealed that the presence of the C-4 prenyl residue attached to the xanthone core is correlated with the significant PDE5 inhibitory activity.

Vasodilators, blood pressure-lowering medications, and age-related macular degeneration: the Beaver Dam Eye Study

OBJECTIVE

To examine the association of vasodilator and antihypertensive medication use with the incidence of age-related macular degeneration (AMD).

DESIGN

Longitudinal population-based study.

PARTICIPANTS

Persons 43 to 86 years of age living in Beaver Dam, Wisconsin, from 1988 through 1990.

METHODS

Examinations were performed every 5 years over a 20-year period. There were 9676 total person-visits over the course of the study. Status of AMD was determined from grading retinal photographs.

MAIN OUTCOME MEASURES

Incidence of AMD.

RESULTS

The 5-year incidence of early AMD over the 20-year period was 8.4%; for late AMD, it was 1.4%; for pure geographic atrophy (GA), it was 0.6%; for exudative AMD, it was 0.9%; and for progression of AMD, it was 24.9%. While adjusting for age, gender, and other factors, using a vasodilator (hazard ratio [HR], 1.72; 95% confidence interval [CI], 1.25-2.38), particularly oral nitroglycerin (HR, 1.81; 95% CI, 1.14-2.90), was associated with an increased risk of early AMD. Using an oral β-blocker was associated with an increased hazard of incident exudative AMD (HR, 1.71; 95% CI, 1.04-2.82), but not pure GA (HR, 0.51; 95% CI, 0.20-1.29) or progression of AMD (HR, 0.92; 95% CI, 0.67-1.28) over the 20-year period.

CONCLUSIONS

Use of vasodilators is associated with a 72% increase in the hazard of incidence of early AMD, and use of oral β-blockers is associated with a 71% increase in the hazard of incident exudative AMD. If these findings are replicated, it may have implications for care of older adults because vasodilators and oral β-blockers are drugs that are used commonly by older persons.

Synthesis and molecular modeling of novel tetrahydro-β-carboline derivatives with phosphodiesterase 5 inhibitory and anticancer properties

New derivatives based upon the tetrahydro-β-carboline-hydantoin and tetrahydro-β-carboline-piperazinedione scaffolds were synthesized. All compounds were evaluated for their ability to inhibit PDE5 in vitro, and numerous compounds with IC(50) values in the low nanomolar range were identified including compounds derived from l-tryptophan. Compounds with high potency versus PDE5 were then evaluated for inhibitory activity against other PDEs to assess isozyme selectivity. Compound 5R,11aS-5-(3,4-dichlorophenyl)-2-ethyl-5,6,11,11a-tetrahydro-1H-imidazo[1',5':1,6]pyrido[3,4-b]indole-1,3(2H)dione 14 showed a selectivity index of >200 for cGMP hydrolysis by PDE5 versus PDE11. Meanwhile, 6R,12aR-6-(2,4-dichlorophenyl)-2-ethyl-2,3,6,7,12,12a-hexahydropyrazino[1',2':1,6]pyrido[3,4-b]indole-1,4dione 45 demonstrated strong potency for inhibition of PDE11 with an IC(50) value of 11 nM, representing the most potent PDE11 inhibitor thus far reported. Docking experiments differentiated between active and inactive analogues and revealing the conformational, steric, and lipophilic necessities for potent PDE5 inhibition. Many derivatives, including potent PDE5 inhibitors, were able to inhibit the growth of the MDA-MB-231 breast tumor cell line with low micromolar potency.

Tolerability and pharmacokinetics of avanafil, a phosphodiesterase type 5 inhibitor: a single- and multiple-dose, double-blind, randomized, placebo-controlled, dose-escalation study in healthy Korean male volunteers

BACKGROUND

Avanafil is a selective phosphodiesterase type 5 inhibitor being developed for the treatment of erectile dysfunction.

OBJECTIVE

This study was conducted to meet Korean regulatory requirements for the marketing of avanafil. To this end, tolerability and pharmacokinetic properties of single and multiple oral doses of avanafil in healthy Korean male volunteers were assessed.

METHODS

A double-blind, randomized, placebo-controlled, parallel-group, dose-escalation study was conducted at the Asan Medical Center (Seoul, Korea). Subjects were randomized to receive either drug or placebo in blocks according to each dose. Subjects were randomly allocated to receive 50-, 100-, or 200-mg tablets of avanafil or placebo once daily for 7 days (avanafil:placebo, 8:2 in each dose group). Tolerability was assessed by monitoring vital signs and results of laboratory tests, 12-lead ECGs, and color discrimination tests. Blood samples of approximately 6 mL were collected in heparinized tubes before and 0.1, 0.33, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, and 24 hours after drug administration on days 1 and 7. Plasma concentrations of avanafil were measured using LC-MS/MS. Pharmacokinetic parameters of avanafil on days 1 and 7 were determined by noncompartmental analysis and compared among the 3 dose groups.

RESULTS

Of the 32 healthy male subjects initially enrolled, 30 completed the study. The mean (SD) age, height, and weight of the participants were 23.4 (1.7) years, 175.0 (5.4) cm, and 70.3 (8.9) kg, respectively. Adverse events were reported by 20 of 25 subjects (80%) taking avanafil and by 4 of 6 (67%) taking placebo. No serious adverse events were reported, and there were no clinically relevant changes in vital signs, ECG recordings, physical examination findings, or color discrimination test results. All the adverse events resolved spontaneously. Avanafil reached a mean T(max) at 0.33 to 0.52 hour after dosing and then declined, with a mean apparent t1/2 of 5.36 to 10.66 hours. AUC and C(max) were proportional to dose, and the mean accumulation index on day 7 after a single daily dose of avanafil was 0.98.

CONCLUSION

Avanafil was generally well tolerated and had linear pharmacokinetic properties at daily doses of 50 to 200 mg over 7 days in these healthy Korean male volunteers. Korean National Study Registration Number: 3466.

Efficacy and Safety of Tadalafil 5 mg Administered Once Daily in Korean Men with Erectile Dysfunction: A Prospective, Multicenter Study

PURPOSE

The aim of this study was to evaluate the efficacy of a daily dose of tadalafil 5 mg as well as its safety for the cardiovascular system in men with erectile dysfunction.

MATERIALS AND METHODS

This study included a total of 162 men who were administered a daily dose of tadalafil 5 mg between April and December of 2009. A total of 127 men completed the 8-week clinical trial. The International Index of Erectile Function (IIEF)-5, blood pressure, and heart rate were measured before treatment with tadalafil (V1) and 4 (V2) and 8 weeks (V3) after treatment with tadalafil. Adverse effects were assessed at V1, V2, and V3. In cases in which the International Prostate Symptom Score (IPSS) was ≥8 at V1, maximal flow rate (Qmax) and postvoid residual volume (PVR) were measured.

RESULTS

The IIEF-5 values were 11.25±3.18, 14.56±3.79, and 16.91±3.56 at V1, V2, and V3, respectively, with significant improvement (V1 vs. V2, p<0.001; V1 vs. V3, p<0.001). The IPSS values were 10.59±5.56, 9.07±6.06, and 8.15±6.10 at V1, V2, and V3, respectively, and the differences were statistically significant (V1 vs. V2, p<0.001; V1 vs. V3, p<0.001). There were no significant differences in blood pressure or heart rate. Adverse effects were observed in 7 men (5.51%) at V2 and in 5 men (3.94%) at V3.

CONCLUSIONS

Tadalafil 5 mg administered once-a-day may be effective in improving erectile function. Adverse effects on the cardiovascular system may be minimal. In addition, it is believed that this may also be effective in improving voiding symptoms.

Factors associated with phosphodiesterase type 5 inhibitor treatment satisfactions: results of patient interrogation

INTRODUCTION

Phosphodiesterase type 5 (PDE5) inhibitor therapy is an efficacious means of treatment for erectile dysfunction (ED). PDE5 inhibitors supply penile erection by inhibiting the hydrolysis of cGMP and therefore relaxing the corpus cavernosum. In this study, retrospective evaluation of those patients who were admitted to our clinic with the complaint of ED and who were recommended on PDE5 inhibitor treatment in terms of follow-up results and patient satisfaction were aimed.

METHOD

The patients were called by phone and after informing about the study and taking the informed consent, patient satisfaction with the treatment, purposes of withdrawal, treatment alterations and partner satisfaction were investigated.

RESULTS

Interviews were made with 345 patients, who accepted to enroll in the study and the mean patient age was 56 +/- 11.2 years. Of the patients 66.4% were learned to be satisfied with the treatment. It was determined that 10.7% of the patients have never used the medication and 50% could not continue because of high drug cost. It was recognised that 50.2% of the patients who are not satisfied with the treatment tried another PDE5 inhibitor. The success rate of the treatment was found to be higher in the followed-up group than those losses to follow-up.

CONCLUSION

Therapy with PDE5 inhibitors is an effective means of ED treatment. The importance of doctor-patient communication should be considered, and the patient should be advised for adaptation to follow-up program. High drug cost is a significant predictor of patient compliance to treatment continuation.

Long-acting oral phosphodiesterase inhibition preconditions against reperfusion injury in an experimental lung transplantation model

OBJECTIVES

Ischemia-reperfusion injury remains a devastating complication of lung transplantation. Phosphodiesterase inhibitors have been shown to precondition tissues against ischemia-reperfusion injury. Little is known, however, about the utility of phosphodiesterase inhibition in reperfusion injury after lung transplantation. We evaluated the long-acting phosphodiesterase-5 inhibitor, tadalafil, in an ex vivo lung transplant model.

METHODS

New Zealand White rabbits (4 kg), were given oral tadalafil (n = 11) 24 hours before lung harvest and compared with rabbits given oral vehicle alone (n = 11). Lungs were recovered with Perfadex solution (Vitrolife, Kungsbacka, Sweden) and cold stored for 18 hours. After storage, lung blocks were reperfused with donor rabbit blood in an ex vivo apparatus. Pulmonary artery pressures were recorded with serial arterial and venous blood gas sampling and animals served as their own controls. Phosphodiesterase-5 and protein kinase G tissue activity assays confirmed drug effects. Luminol chemiluminescence assay was used to measure reactive oxygen species and levels of endothelial and inducible nitric oxide synthase were measured.

RESULTS

Extended cold storage, followed by reperfusion produced a consistent reproducible decrease in oxygenation and increase in pulmonary pressure. Tadalafil-treated animals exhibited greater Pao(2) throughout the course of reperfusion (P = .001) Mean pulmonary artery pressure was lower in tadalafil-treated animals (22 vs 40 mm Hg; P = .04). Phosphodiesterase-5 activity was decreased (143 +/- 8 vs 205 +/- 32 mP; P < .001) with protein kinase G activity increased (25 +/- 12 vs 12 +/- 2.4 fU/microg; P = .01) in the experimental group confirming that oral pretreatment resulted in active phosphodiesterase inhibition in the lung tissue. Reactive oxygen species (as measured by luminol activity) were decreased in tadalafil-treated animals (7.8 +/- 1.5 vs 10.2 +/- 1.2 relative light units; P = .003).

CONCLUSIONS

Our experimental model demonstrates that oral donor pretreatment with a long-acting phosphodiesterase inhibitor is an effective strategy for improving pulmonary performance after reperfusion. Importantly, phosphodiesterase enzymes and their downstream effectors may play a critical role in reperfusion injury after lung transplantation.

Initially obscure hepatotoxicity attributed to sildenafil

We describe a patient with a hepatotoxic reaction, presenting with general malaise, severe jaundice, and pruritus. This turned out to be caused by the, at first unrevealed, use of sildenafil. The injury seems to be hepatocanalicular, characterized by a hepatocellular liver test pattern, combined with extensive cholestasis on liver biopsy. One should bare in mind that the use of sildenafil may not be readily disclosed by the patient nor his doctor.

Centrally acting mechanisms for the treatment of male sexual dysfunction

The development of pharmacologic therapy for erectile dysfunction (ED) has been possible because of incremental growth in our understanding of the physiology of normal erections and the complex pathophysiology of ED. Although the oral phosphodiesterase type 5 (PDE5) inhibitors have provided safe, effective treatment of ED for some men, a large proportion of men who have ED do not respond to PDE5 inhibitors or become less responsive or less satisfied as the duration of therapy increases. Also, men who are receiving organic nitrates and nitrates, such as amyl nitrate, cannot take PDE5 inhibitors because of nitrate interactions. The current options for treatment beyond PDE5 inhibitors are invasive, unappealing to some patients, and sometimes ineffective. The search for other options by which ED can be treated has branched out and now encompasses centrally acting mechanisms that control erectile function. Drugs available in Europe include apomorphine. This article focuses on the mechanism of centrally acting agents and reviews clinical data on potential new centrally acting drugs for men who have ED.

Phosphodiesterase-5 inhibitors for lower urinary tract symptoms in men

OBJECTIVE

To review the efficacy of phosphodiesterase-5 (PDE-5) inhibitors for the treatment of lower urinary tract symptoms in men.

DATA SOURCES

MEDLINE and International Pharmaceutical Abstracts were searched (1970-August 2007) using the terms phosphodiesterase inhibitor, sildenafil, vardenafil, tadalafil, lower urinary tract symptoms, and benign prostatic hypertrophy.

STUDY SELECTION AND DATA EXTRACTION

English-language clinical trials, case reports, and background material were evaluated for safety and efficacy data. References of reviewed articles were examined and used to identify additional sources.

DATA SYNTHESIS

Erectile dysfunction (ED) and lower urinary tract symptoms have numerous shared risk factors and are common in aging men. PDE-5 inhibitors may relax urinary tract smooth muscle tissue, which has led to interest in their utility for lower urinary tract symptoms. Six 12 week clinical trials were identified. Three uncontrolled trials (N = 168) examined the effects of on-demand sildenafil ED dosing on lower urinary tract symptoms. The 2 largest trials found that, the greater the ED response, the larger the reduction in lower urinary tract symptoms. A single prospective placebo-controlled trial (N = 369) studied sildenafil 100 mg daily in men with ED and lower urinary tract symptoms. Lower urinary tract symptoms improved significantly in the sildenafil group; patients with the worst lower urinary tract symptoms experienced the greatest benefits. An open-label trial (N = 62) compared daily sildenafil 25 mg, alfuzosin 10 mg, or sildenafil 25 mg plus alfuzosin 10 mg on ED and lower urinary tract symptoms. Combination therapy resulted in greater improvements in ED and lower urinary tract symptoms and urinary flow than did either drug alone. The effects of daily tadalafil 20 mg were studied in 281 men with lower urinary tract symptoms independent of ED. Tadalafil produced statistically significant but clinically modest improvements in lower urinary tract symptoms when compared with placebo.

CONCLUSIONS

PDE-5 inhibitors consistently produced modest reductions in lower urinary tract symptoms. Further studies are needed to fully elucidate the efficacy, cost effectiveness, safety, and appropriate place in therapy of PDE-5 inhibitors. At this time, data are insufficient to routinely recommend chronic use of PDE-5 inhibitors for lower urinary tract symptoms in men.

Role of the soluble guanylyl cyclase alpha1-subunit in mice corpus cavernosum smooth muscle relaxation

Soluble guanylyl cyclase (sGC) is the major effector molecule for nitric oxide (NO) and as such an interesting therapeutic target for the treatment of erectile dysfunction. To assess the functional importance of the sGCalpha(1)beta(1) isoform in corpus cavernosum (CC) relaxation, CC from male sGCalpha(1)(-/-) and wild-type mice were mounted in organ baths for isometric tension recording. The relaxation to endogenous NO (from acetylcholine, bradykinin and electrical field stimulation) was nearly abolished in the sGCalpha(1)(-/-) CC. In the sGCalpha(1)(-/-) mice, the relaxing influence of exogenous NO (from sodium nitroprusside and NO gas), BAY 41-2272 (NO-independent sGC stimulator) and T-1032 (phosphodiesterase type 5 inhibitor) were also significantly decreased. The remaining exogenous NO-induced relaxation seen in the sGCalpha(1)(-/-) mice was significantly decreased by the sGC-inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one. The specificity of the impairment of the sGC-related responses was demonstrated by the unaltered relaxations seen with forskolin (adenylyl cyclase activator) and 8-pCPT-cGMP (cGMP analog). In conclusion, the sGCalpha(1)beta(1) isoform is involved in corporal smooth muscle relaxation in response to NO and NO-independent sGC stimulators. The fact that there is still some effect of exogenous NO in the sGCalpha(1)(-/- mice suggests the contribution of (an) additional pathway(s).

The natural progression and remission of erectile dysfunction: results from the Massachusetts Male Aging Study

PURPOSE

Erectile dysfunction affects more than 150 million men and is strongly associated with cardiovascular disease. A 1992 National Institutes of Health consensus development panel identified erectile dysfunction progression and spontaneous remission as priorities for investigation, but there are few data describing the natural course of the disorder following its initial presentation. This analysis estimates the frequency of erectile dysfunction progression and remission among aging men, and assesses the relation of progression/remission to demographics, socioeconomic factors, comorbidities and modifiable lifestyle characteristics.

MATERIALS AND METHODS

Data from the Massachusetts Male Aging Study, a longitudinal study of men (401) 40 to 70 years old, were analyzed to assess erectile dysfunction severity following initial presentation of symptoms. Logistic regression was used to estimate the odds of erectile dysfunction progression/remission as a function of covariates.

RESULTS

A total of 141 subjects (35%) exhibited erectile dysfunction remission (95% CI: 30%, 40%). Of 323 subjects with minimal or moderate baseline erectile dysfunction 107 (33%) exhibited erectile dysfunction progression (95% CI: 28%, 38%). The 78 subjects with complete erectile dysfunction were considered ineligible for progression and 45 (58%) of these exhibited complete erectile dysfunction at followup. Age and body mass index were associated with progression and remission, while smoking and self-assessed health status were associated with progression only.

CONCLUSIONS

Natural remission and progression occur in a substantial number of men with erectile dysfunction. The association of body mass index with remission and progression, and the association of smoking and health status with progression, offer potential avenues for facilitating remission and delaying progression using nonpharmacological intervention. The benefits of such interventions for overall men's health may be far-reaching.

Counseling Patients About Sexual Issues

In recent years, the frequency of antidepressant drug-induced sexual dysfunction has increased, along with the use of new drugs for the treatment of erectile dysfunction and premature ejaculation. It has thus become common for pharmacists to counsel patients about sexual issues. Pharmacists must not only become knowledgeable about these drugs and their indications, but they must also become skilled and comfortable with counseling patients and answering questions from both patients and other health care providers. In addition to therapeutic information, pharmacists' discussions with patients should take into account factors that contribute to treatment nonadherence and treatment failure. Patient education is essential to ensure optimum outcomes for pharmacologic treatments for both erectile dysfunction and premature ejaculation. Improper use of phosphodiesterase-5 inhibitor drugs for erectile dysfunction accounts for most nonresponsiveness and discontinuation of treatment. Drug-induced sexual dysfunction is common with some psychotropic drugs. Up to 50% of men will experience delayed ejaculation, and at least 30% of men and women will experience anorgasmia from antidepressant drugs with serotonin agonist activity. Trazodone is the drug most commonly associated with the rare but very serious adverse effect of priapism. The pharmacist who is both competent and comfortable discussing sexual function and dysfunction with patients can make positive contributions to their therapeutic outcomes as well as their quality of life.

Treatment of erectile dysfunction in multiple sclerosis

Erectile dysfunction in men with multiple sclerosis (MS) is a very common symptom that often leads to a reduced quality of life. It is related to neurological dysfunction, psychological factors, side effects of medication or generalized MS symptoms, such as fatigue or micturition problems, usually in combination. The question of sexual dysfunction should always be broached during routine follow-up, regardless of age and social status. The possibility that erection problems can be a side-effect of drugs commonly used in MS must also be remembered. There are several effective pharmacological treatments, such as phosphodiesterase inhibitors and prostaglandin E(1) (alprostadil). The contraindications and side effects should be familiar to the MS doctor. Dose titration in the initial stages is recommended to avoid priapism. In the future, combinations of impotence drugs may be tested.