Effects of tadalafil on myocardial blood flow in patients with coronary artery disease.

OBJECTIVE: Erectile dysfunction and coronary artery disease share similar risk factors. Although phosphodiesterase-5 inhibitors used to treat erectile dysfunction do not adversely affect hemodynamic parameters in patients with coronary artery disease, their effects on myocardial blood flow are unknown. METHODS: In a randomized, double-blind, crossover study we examined the effects of tadalafil, 20 mg, compared with placebo on myocardial blood flow in patients with stable coronary artery disease (n=7, 52-73 years old). After tadalafil or placebo, myocardial blood flow was measured with positron emission tomography (nine-segment model) at rest, during maximal coronary hyperemia with adenosine, and during increased myocardial work with dobutamine. Abnormal flow was defined as myocardial blood flow <75% of maximum perfusion during adenosine plus placebo (46 normal/17 abnormal segments dentified). RESULTS: Compared with placebo, tadalafil had no significant effect on global myocardial blood flow at rest, during adenosine infusion, or during dobutamine infusion. Similarly, in normal and abnormal segments, tadalafil versus placebo had no significant effect on resting myocardial blood flow or on adenosine-induced increases in myocardial blood flow. In normal segments, myocardial blood flow with dobutamine plus tadalafil was greater than that with dobutamine plus placebo (1.79+/-0.56 versus 1.56+/-0.37 ml/g per min, P<0.01), and in abnormal segments, there was a trend for tadalafil compared with placebo to increase myocardial blood flow during dobutamine infusion (1.46+/-0.44 versus 1.36+/-0.36 ml/g per min, P=0.7). CONCLUSIONS: Tadalafil had no significant effect on global myocardial blood flow at rest, during adenosine infusion, or during dobutamine infusion. Compared with placebo, tadalafil significantly augmented myocardial blood flow during increased workload in normal regions, with a trend toward improving myocardial blood flow in poorly perfused regions.

The effect of tadalafil on the time to exercise-induced myocardial ischaemia in subjects with coronary artery disease.

OBJECTIVE: To investigate the effect of tadalafil on the time to exercise-induced myocardial ischaemia in subjects with coronary artery disease (CAD). Background CAD and erectile dysfunction (ED) share similar risk factors. It is important to know the cardiovascular effects of tadalafil in patients with CAD during physical exertion that is comparable with sexual activity. METHODS: A randomized, placebo-controlled, double-blind, two-period, crossover study comparing the effects of tadalafil 10 mg and placebo on the time to exercise treadmill test (ETT)-induced myocardial ischaemia in subjects with stable CAD (n = 23; age range: 53-75 years, all exhibited ST-segment depression >1.5 mm at screening ETT at > 5METS). Haemodynamic responses to sublingual nitroglycerin (NTG) were assessed before and after ETT. RESULTS: Compared with placebo, tadalafil did not significantly affect the time to ETT-induced ischaemia (13 min/31 s vs. 13 min/36 s, respectively). Before exercise, NTG evoked decreases in sitting systolic blood pressure (SBP) that were significantly greater when subjects received tadalafil compared with placebo, and after exercise, more subjects experienced a decrease in SBP <85 mmHg in response to NTG after taking tadalafil vs. placebo. When subjects received tadalafil compared with placebo, SBP was lower at rest (-7 mmHg; -12,-2), during ETT (-10 mmHg; -16, -3), and after ETT (-13 mmHg; -19, -7). CONCLUSION: Tadalafil did not significantly alter the time to ETT-induced ischaemia compared with placebo in subjects with CAD. Tadalafil reduced resting and exercise SBP. Due to the potential for hypotension, the concomitant use of nitrates and tadalafil is contraindicated.

The combined use of ibutilide as an active control with intensive electrocardiographic sampling and signal averaging as a sensitive method to assess the effects of tadalafil on the human QT interval.

OBJECTIVES: This study was designed to evaluate effects of tadalafil, a phosphodiesterase-5 inhibitor used for the treatment of erectile dysfunction (ED), on the QT interval. BACKGROUND: Cardiovascular disease is common in men with ED. Men with cardiovascular disease and ED may have decreased cardiac repolarization reserve. METHODS: Effects of tadalafil (100 mg by mouth), ibutilide (0.002 mg/kg intravenously), and placebo on the QT interval in healthy men were compared (placebo and tadalafil [n = 90], with a subset [n = 61] receiving all treatments; mean age 30 years, range 18 to 53 years). Electrocardiographic sampling was done for two days before treatment and on treatment days. The QT was corrected for RR interval with five correction methods, including an individual correction (QTcI). Plasma concentrations of tadalafil were measured to evaluate concentration-QT effect relationships. RESULTS: At the time corresponding to maximum plasma concentration of tadalafil, the mean difference in the change in QTcI between tadalafil and placebo was 2.8 ms; tadalafil was equivalent to placebo (a priori, upper limit of 90% confidence interval < 10 ms [actual = 4.4 ms]; post hoc, upper limit of 95% confidence interval < 5 ms [actual = 4.8]). The active control, ibutilide, significantly increased QTcI by 6.9 and 8.9 ms compared with tadalafil and placebo, respectively. Similar statistical results were obtained with four additional QT correction methods. No subject had a QTcI > or = 450 ms or an increase in QTcI > or = 30 ms with any treatment. CONCLUSIONS: Based on the a priori statistical test of equivalence, placebo and high-dose tadalafil produced equivalent effects on the QT interval. This study reliably discerned 5- to 10-ms changes in corrected QT in the ibutilide active control group.

Interaction between the phosphodiesterase 5 inhibitor, tadalafil and 2 alpha-blockers, doxazosin and tamsulosin in healthy normotensive men.

PURPOSE: Tadalafil, a phosphodiesterase type 5 inhibitor, is effective therapy for erectile dysfunction (ED). Men with ED have a high incidence of comorbid conditions including cardiovascular disease, diabetes mellitus and benign prostatic hyperplasia. Although phosphodiesterase type 5 inhibitors are safe when administered with most medications, sildenafil given with doxazosin and vardenafil given with terazosin evoke orthostatic hypotension in some patients. We examined the hemodynamic interactions of tadalafil with the alpha-blockers doxazosin and tamsulosin. MATERIALS AND METHODS: In separate double-blind, placebo controlled, randomized crossover studies (18 patients in each study) we evaluated the hemodynamic effects of doxazosin 8 mg with tadalafil 20 mg, and tamsulosin 0.4 mg with tadalafil 10 and 20 mg. Blood pressure (BP) and heart rate were recorded before dosing and for 24 hours after dosing. RESULTS: Tadalafil 20 mg augmented the hypotensive effect of doxazosin by producing a mean maximal decrease in standing systolic BP (SBP) that was significantly greater than placebo (a mean difference of 9.8 mm Hg). Analysis of BP outliers showed that the number of subjects with a standing SBP of less than 85 mm Hg was greater after doxazosin plus tadalafil (28%) versus doxazosin plus placebo (6%). In subjects on tamsulosin, tadalafil 10 and 20 mg produced mean maximal decreases in standing SBP that were similar to placebo (mean difference of 1.7 and 2.3 mm Hg, respectively). No subject taking tamsulosin had a decrease in standing SBP less than 85 mm Hg. CONCLUSIONS: Tadalafil augmented the hypotensive effects of doxazosin but had little hemodynamic interaction with tamsulosin. In patients taking tadalafil for ED, tamsulosin 0.4 mg may be given for the treatment of benign prostatic hyperplasia.

Absence of clinically important HERG channel blockade by three compounds that inhibit phosphodiesterase 5--sildenafil, tadalafil, and vardenafil.

Compounds that inhibit phosphodiesterase 5 (PDE5) have been developed for the treatment of erectile dysfunction. Because men with erectile dysfunction frequently have comorbid cardiovascular disease, they may have limited cardiac repolarization reserve and be at risk of arrhythmia if treated with medications that prolong ventricular repolarization. The human ether-a-go-go related gene (HERG) channel is important for repolarization in human myocardium and is a common target for drugs that prolong the QT interval. We studied the ability of three compounds that inhibit PDE5--sildenafil, tadalafil, and vardenafil--to block the HERG channel. Using a whole cell variant of the patch-clamp method, the HERG current was measured in a stably transfected human embryonic kidney cell line expressing the HERG channel. The compounds produced dose-dependent reductions in HERG current amplitude over a concentration range of 0.1 to 100 microM. The IC50 values were 12.8 microM for vardenafil and 33.3 microM for sildenafil. Because the maximum soluble concentration of tadalafil (100 microM) produced only a 50.9% inhibition of the HERG current amplitude, the IC50 value for tadalafil could not be determined with the Hill equation. Tadalafil had the weakest capacity to block the HERG channel, producing a 50.9% blockade at the maximum soluble concentration (100 microM), compared with 86.2% for vardenafil (100 microM) and 75.2% for sildenafil (100 microM). In conclusion, the concentrations of the PDE5 inhibitors required to evoke a 50% inhibition of the HERG current were well above reported therapeutic plasma concentrations of free and total compound. None of the three compounds was a potent blocker of the HERG channel.

A multicenter, randomized, double-blind, crossover study to evaluate patient preference between tadalafil and sildenafil.

PURPOSE: To assess patient preference for erectile dysfunction treatment between either sildenafil or tadalafil, each administered with their respective dosing instructions, and to evaluate preference for either sildenafil or tadalafil dosing instructions during tadalafil therapy. METHODS: We conducted a randomized, double-blind, crossover study consisting of four treatment arms. Because the dosing instructions for sildenafil and tadalafil are different, a unique methodology using sham placebo arms was employed to maintain the blind. To assess drug preference, 219 patients were randomized to either sildenafil 50 mg or tadalafil 20 mg, with dosing instructions reflecting their respective product profiles. To assess dosing instruction preference during tadalafil therapy, 46 patients were randomized to tadalafil 20 mg with either tadalafil or sildenafil dosing instructions. After 12 weeks, patients were crossed-over. After 4 weeks of each treatment, all patients following sildenafil dosing instructions were offered the opportunity for an upward dose titration. In a double-blind fashion, all patients who requested an upward titration received additional capsules. To mimic the pattern of dose usage observed in clinical practice, the number of patients who received additional double-blind active medication was limited to 35% of patients taking sildenafil in each treatment period in each country. Following the crossover treatment period, patients chose their preferred double-blind treatment with dosing instructions to receive in the 12-week extension period. RESULTS: In the drug preference assessment, 132 of 181 (73%) evaluable patients chose to receive tadalafil (p < 0.001) during the extension period. In the dosing instruction preference assessment, 24 of 36 (67%) evaluable patients preferred tadalafil with tadalafil dosing instructions (p = 0.046). Sildenafil and tadalafil were well tolerated. CONCLUSIONS: In the doses utilized in this study, 73% of patients preferred tadalafil with tadalafil dosing instructions for the treatment of their erectile dysfunction over sildenafil with sildenafil dosing instructions. During tadalafil therapy, 67% of patients preferred tadalafil dosing instructions over sildenafil dosing instructions.

Update on clinical trials of tadalafil demonstrates no increased risk of cardiovascular adverse events.

INTRODUCTION: Cardiovascular disease and erectile dysfunction (ED) share similar risk factors and often occur concomitantly. Therefore, men with ED may be at increased risk for cardiovascular adverse events. AIM: The aim of this retrospective analysis was to evaluate the cardiovascular adverse events in clinical trials of tadalafil, an effective medication for the treatment of ED. METHODS: An integrated analysis of cardiovascular adverse events was performed on a database from 35 controlled clinical trials (placebo [N = 2,118] and tadalafil [N = 5,228]) and eight open-label trials of tadalafil (tadalafil [N = 6,939]). Some patients in controlled trials also received tadalafil in the open-label extension phase of four trials. Across all trials, the dose range of tadalafil was 2-25 mg, with the majority of patients receiving tadalafil 20 mg. This analysis represents an update of previous published results. RESULTS: In 35 controlled tadalafil clinical trials, the incidence of cardiovascular adverse events was low and comparable in tadalafil- and placebo-treated patients. The rate of myocardial infarction (MI) across all controlled and open-label studies was 0.33 per 100 patient-years in tadalafil-treated patients (N = 10,460, patient exposure = 5,088 patient-years). The MI rate in tadalafil-treated patients was comparable to that in placebo-treated patients (0.41 per 100 patient-years; N = 2,118; 489 patient-years), and to that in an age-standardized male population (0.6 per 100 patient-years). The cardiac mortality rate in tadalafil-treated patients across all studies (N = 10,460) was 0.12 per 100 patient-years which was not increased compared with the cardiac mortality rate of 0.26 per 100 patient-years reported in an age-standardized male population. CONCLUSIONS: In tadalafil clinical trials, the incidence of cardiovascular adverse events in patients receiving tadalafil was low and comparable to placebo. Tadalafil did not increase the rate of MI or cardiac mortality compared with reported rates from epidemiological studies. This favorable cardiovascular safety profile for tadalafil is important, because men with ED commonly have cardiovascular disease and may seek medical therapy for ED.

Efficacy and safety of on-demand oral tadalafil in the treatment of men with erectile dysfunction in Taiwan: a randomized, double-blind, parallel, placebo-controlled clinical study.

INTRODUCTION: Tadalafil is a phosphodiesterase type 5 inhibitor for the treatment of erectile dysfunction (ED). Past clinical trials have assessed its efficacy and safety in western populations. Tadalafil has not been investigated in a large clinical trial with a South-east Asian population. AIM: To assess the efficacy and safety of on-demand tadalafil for the treatment of ED in a 12-week, double-blind, placebo-controlled study in Taiwan. METHODS: Men with mild to severe ED of various etiologies were randomized to receive placebo, tadalafil 10 mg, or tadalafil 20 mg, taken as needed (maximum once daily). Efficacy assessments included the International Index of Erectile Function, the Sexual Encounter Profile (SEP) diary, and a Global Assessment Question (GAQ). RESULTS: Tadalafil significantly improved erectile function compared with placebo (P < 0.005, all measures). At endpoint, the patients receiving tadalafil reported a greater mean per-patient percentage of successful intercourse attempts (SEP question 3: 70.0%, 10 mg; 78.0%, 20 mg) than placebo-treated patients (42.8%) and a greater proportion of improved erections (GAQ: 92.3% and 84.6% vs. 54.5%). Most treatment-emergent adverse events were mild or moderate. The most common adverse events were back pain, dyspepsia, and myalgia. CONCLUSIONS: Tadalafil was an effective, well-tolerated therapy for men in Taiwan with ED of broad-spectrum severity and etiology.

Time course of the interaction between tadalafil and nitrates.

OBJECTIVES: This study was designed to determine the time course of nitrate interaction with tadalafil, a phosphodiesterase 5 (PDE5) inhibitor with a half-life (t(1/2)) of 17.5 h. BACKGROUND: The PDE5 inhibitors augment the blood pressure (BP)-lowering effects of nitrates, yet the time course of this interaction is unclear. Recent guidelines from the American College of Cardiology/American Heart Association recommend that nitrates be withheld for 24 h after taking sildenafil (t(1/2) = 4 h). METHODS: Male subjects (n = 150) received seven consecutive daily doses of placebo or tadalafil (20 mg). On day 7 and beyond, subjects received repeated doses of sublingual nitroglycerin (0.4 mg) after the last dose of placebo or tadalafil. After a 10- to 21-day washout period, subjects crossed over to either placebo or tadalafil, and nitrate dosing was repeated. RESULTS: In response to nitroglycerin at 4, 8, and 24 h, standing systolic BP fell below 85 mm Hg in more subjects on tadalafil compared with placebo (p < 0.05), with no difference in the response to nitroglycerin at 48, 72, and 96 h (p > 0.2). Similar observations were made for standing diastolic BP <45 mm Hg, decrease in systolic BP >30 mm Hg, and decrease in diastolic BP >20 mm Hg. Nitroglycerin also evoked greater mean maximal decreases in standing systolic BP at 8 and 24 h after taking tadalafil versus placebo (p < 0.02), with no significant difference at 48, 72, or 96 h (p > 0.49). CONCLUSIONS: The hemodynamic interaction between tadalafil and sublingual nitroglycerin lasted 24 h, but was not seen at 48 h and beyond. Similar to other PDE5 inhibitors, tadalafil should not be administered in combination with organic nitrates.

Cardiovascular effects of tadalafil.

To determine the effects of tadalafil on the cardiovascular system, safety assessments were performed on a database of >4000 subjects who received tadalafil in >60 clinical pharmacology, phase 2, phase 3, and open-label studies. In healthy subjects, tadalafil resulted in small changes in blood pressure, which are not believed to be clinically relevant. Daily administration of tadalafil 20 mg for 26 weeks in healthy male subjects or patients with mild erectile dysfunction resulted in blood pressure changes similar to those observed after placebo administration. In patients with coronary artery disease (CAD), tadalafil administration before nitrate administration resulted in small decreases in blood pressure. The resulting mean maximal change in standing systolic blood pressure (SBP) after coadministration of sublingual nitroglycerin in patients with chronic stable angina was -36 mm Hg for tadalafil 5 mg, -31 mm Hg for tadalafil 10 mg, and -28 mm Hg for placebo. In addition, a larger number of men had a standing SBP <85 mm Hg after coadministration of sublingual nitroglycerin and tadalafil 5 mg (p <0.001 vs placebo) or tadalafil 10 mg (p <0.01 vs placebo) compared with coadministration with placebo. In patients with chronic stable angina taking doses of isosorbide mononitrate on a long-term basis, the mean maximal change in standing SBP was -23 mm Hg for placebo, -23 mm Hg for tadalafil 5 mg, and -26 mm Hg for tadalafil 10 mg. In a study of older subjects (>or=55 years of age) with no overt evidence of CAD, the resulting mean maximal change in standing SBP after coadministration of sublingual nitroglycerin was -25 mm Hg for tadalafil 10 mg, -29 mm Hg for sildenafil 50 mg, and -25 mm Hg for placebo. Cardiac mortality rates in tadalafil studies are consistent with the expected rate in this male population. Across all studies, the incidence rate of myocardial infarction was low in tadalafil-treated patients (0.43 per 100 patient-years) compared with patients who received placebo (0.6 per 100 patient-years), and the incidence rate was comparable to that observed in the age-standardized male population (0.60 per 100 patient-years). The incidence rate of presumed thrombotic strokes in tadalafil studies (0.27 per 100 patient-years) is comparable to the expected rate in this patient population. The data presented herein suggest that tadalafil can be safely used by healthy subjects and by patients with cardiovascular diseases. As with sildenafil, the use of tadalafil is contraindicated in patients receiving nitrate therapy because of the potential for significant hypotensive effects.

Cardiovascular effects of tadalafil in patients on common antihypertensive therapies.

Tadalafil is a potent, selective, reversible phosphodiesterase 5 inhibitor under investigation for the treatment of erectile dysfunction (ED). Because some oral agents for ED have vasodilator properties, interaction studies were performed between tadalafil and commonly prescribed antihypertensive agents. In addition, cardiovascular safety assessments were made from a safety database of phase 3 studies comparing patients who were and who were not receiving antihypertensives. In patients receiving concomitant antihypertensive therapy, tadalafil administration may result in a reduction in blood pressure, which is, in general, mild and not likely to be of clinical concern. In the phase 3 studies, no statistically significant differences were observed between tadalafil and placebo in the mean changes in blood pressure from baseline in patients taking >or=2 antihypertensive agents. The incidence rates of cardiovascular events were comparable between patients who were and were not treated with concomitant antihypertensive therapy, with the exception of events recorded as hypertension, which would be expected to occur periodically in this patient population despite treatment. Hypotension or postural hypotension was not reported in any tadalafil-treated patient, compared with 1 report of each in the placebo-treated patients. Syncope was reported in 1 tadalafil-treated patient (0.1%) who was not on concomitant antihypertensive medication and in 2 patients (1.9%) who received placebo with concomitant antihypertensive agents. The data presented herein suggest that tadalafil is safe in patients receiving >or=1 concomitant antihypertensive agent.

Effects of tadalafil on erectile dysfunction in men with diabetes.

OBJECTIVE: To evaluate the efficacy and safety of tadalafil taken as needed before sexual activity by men with diabetes and erectile dysfunction (ED). RESEARCH DESIGN AND METHODS: Men with type 1 or type 2 diabetes and a minimum 3-month history of ED were randomly allocated to one of three groups: placebo (n = 71), tadalafil 10 mg (n = 73), or tadalafil 20 mg (n = 72) taken up to once daily for 12 weeks. Changes from baseline in mean scores on the erectile function domain of the International Index of Erectile Function (IIEF) and changes from baseline in the proportion of "yes" responses to question 2, "Were you able to penetrate?," and 3, "Were you able to complete intercourse?," of the Sexual Encounter Profile were coprimary outcome measures. RESULTS: A total of 191 (88%) of 216 patients completed the study. Treatment with tadalafil significantly improved all primary efficacy variables, regardless of baseline HbA(1c) level. Therapy with tadalafil also significantly improved a number of secondary outcome measures, including changes in other IIEF domains, individual IIEF questions, and percentage of positive responses to a global assessment question measuring erection improvement. Treatment with tadalafil did not alter mean HbA(1c) levels. Tadalafil was well tolerated, with headache and dyspepsia being the most frequent adverse events with active treatment. CONCLUSIONS: Tadalafil therapy significantly enhanced erectile function and was well tolerated by men with diabetes and ED.