Vardenafil

12 CLINICAL PHARMACOLOGY 12.1 Mechanism of Action Penile erection is a hemodynamic process initiated by the relaxation of smooth muscle in the corpus cavernosum and its associated arterioles. During sexual stimulation, nitric oxide is released from nerve endings and endothelial cells in the corpus cavernosum. Nitric oxide activates the enzyme guanylate cyclase resulting in increased synthesis of cyclic guanosine monophosphate (cGMP) in the smooth muscle cells of the corpus cavernosum. The cGMP in turn triggers smooth muscle relaxation, allowing increased blood flow into the penis, resulting in erection. The tissue concentration of cGMP is regulated by both the rates of synthesis and degradation via phosphodiesterases (PDEs). The most abundant PDE in the human corpus cavernosum is the cGMP-specific phosphodiesterase type 5 (PDE5); therefore, the inhibition of PDE5 enhances erectile function by increasing the amount of cGMP. Because sexual stimulation is required to initiate the local release of nitric oxide, the inhibition of PDE5 has no effect in the absence of sexual stimulation. In vitro studies have shown that vardenafil is a selective inhibitor of PDE5. The inhibitory effect of vardenafil is more selective on PDE5 than for other known phosphodiesterases (>15-fold relative to PDE6, >130-fold relative to PDE1, >300-fold relative to PDE11, and >1,000-fold relative to PDE2, 3, 4, 7, 8, 9, and 10). 12.2 Pharmacodynamics Effects on Blood Pressure In a clinical pharmacology study of patients with erectile dysfunction, single doses of vardenafil 20 mg caused a mean maximum decrease in supine blood pressure of 7 mmHg systolic and 8 mmHg diastolic (compared to placebo), accompanied by a mean maximum increase of heart rate of 4 beats per minute. The maximum decrease in blood pressure occurred between 1 and 4 hours after dosing. Following multiple dosing for 31 days, similar blood pressure responses were observed on Day 31 as on Day 1. Vardenafil may add to the blood pressure lowering effects of antihypertensive agents [see Drug Interactions (7) ] . Effects on Blood Pressure and Heart Rate when Vardenafil Hydrochloride Tablets are Combined with Nitrates A study was conducted in which the blood pressure and heart rate response to 0.4 mg nitroglycerin (NTG) sublingually was evaluated in 18 healthy subjects following pretreatment with vardenafil hydrochloride tablets 20 mg at various times before NTG administration. Vardenafil hydrochloride tablets 20 mg caused an additional time-related reduction in blood pressure and increase in heart rate in association with NTG administration. The blood pressure effects were observed when vardenafil hydrochloride tablets 20 mg were dosed 1 or 4 hours before NTG and the heart rate effects were observed when 20 mg was dosed 1, 4, or 8 hours before NTG. Additional blood pressure and heart rate changes were not detected when vardenafil hydrochloride tablets 20 mg were dosed 24 hours before NTG. (See Figure 1 ) Figure 1: Placebo-subtracted point estimates (with 90% CI) of mean maximal blood pressure and heart rate effects of pre-dosing with vardenafil 20 mg at 24, 8, 4, and 1 hour before 0.4 mg NTG sublingually Because the disease state of patients requiring nitrate therapy is anticipated to increase the likelihood of hypotension, the use of vardenafil by patients on nitrate therapy or on nitric oxide donors is contraindicated [see Contraindications (4.1) ] . Blood Pressure Effects in Patients on Stable Alpha-Blocker Treatment Three clinical pharmacology studies were conducted in patients with benign prostatic hyperplasia (BPH) on stable-dose alpha-blocker treatment, consisting of alfuzosin, tamsulosin or terazosin. Study 1: This study was designed to evaluate the effect of 5 mg vardenafil compared to placebo when administered to BPH patients on chronic alpha-blocker therapy in two separate cohorts: tamsulosin 0.4 mg daily (cohort 1, n=21) and terazosin 5 or 10 mg daily (cohort 2, n=21). The design was a randomized, double blind, cross-over study with four treatments: vardenafil 5 mg or placebo administered simultaneously with the alpha-blocker and vardenafil 5 mg or placebo administered 6 hours after the alpha-blocker. Blood pressure and pulse were evaluated over the 6-hour interval after vardenafil dosing. For blood pressure (BP) results see Table 2 . One patient after simultaneous treatment with 5 mg vardenafil and 10 mg terazosin exhibited symptomatic hypotension with standing blood pressure of 80/60 mmHg occurring one hour after administration and subsequent mild dizziness and moderate lightheadedness lasting for 6 hours. For vardenafil and placebo, five and two patients, respectively, experienced a decrease in standing systolic blood pressure (SBP) of >30 mmHg following simultaneous administration of terazosin. Hypotension was not observed when vardenafil 5 mg and terazosin were administered 6 hours apart. Following simultaneous administration of vardenafil 5 mg and tamsulosin, two patients had a standing SBP of <85 mmHg. A decrease in standing SBP of >30 mmHg was observed in two patients on tamsulosin receiving simultaneous vardenafil and in one patient receiving simultaneous placebo treatment. When tamsulosin and vardenafil 5 mg were separated by 6 hours, two patients had a standing SBP <85 mmHg and one patient had a decrease in SBP of >30 mmHg. There were no severe adverse events related to hypotension reported during the study. There were no cases of syncope. Table 2: Mean (95% C.I.) maximal change from baseline in systolic blood pressure (mmHg) following vardenafil 5 mg in BPH patients on stable alpha-blocker therapy (Study 1) Alpha-Blocker Simultaneous dosing of Vardenafil 5 mg and Alpha-Blocker, Placebo-Subtracted Dosing of Vardenafil 5 mg and Alpha-Blocker Separated by 6 Hours, Placebo-Subtracted Terazosin Standing SBP -3 (-6.7, 0.1) -4 (-7.4, -0.5) 5 or 10 mg daily Supine SBP -4 (-6.7, -0.5) -4 (-7.1, -0.7) Tamsulosin Standing SBP -6 (-9.9, -2.1) -4 (-8.3, -0.5) 0.4 mg daily Supine SBP -4 (-7, -0.8) -5 (-7.9, -1.7) Blood pressure effects (standing SBP) in normotensive men on stable dose of tamsulosin 0.4 mg following simultaneous administration of vardenafil 5 mg or placebo, or following administration of vardenafil 5 mg or placebo separated by 6 hours are shown in Figure 2. Blood pressure effects (standing SBP) in normotensive men on stable dose terazosin (5 or 10 mg) following simultaneous administration of vardenafil 5 mg or placebo, or following administration of vardenafil 5 mg or placebo separated by 6 hours, are shown in Figure 3. Figure 2: Mean change from baseline in standing systolic blood pressure (mmHg) over 6 hour interval following simultaneous or 6 hr separation administration of vardenafil 5 mg or placebo with stable dose tamsulosin 0.4 mg in normotensive BPH patients (Study 1) Figure 3: Mean change from baseline in standing systolic blood pressure (mmHg) over 6 hour interval following simultaneous or 6 hr separation administration of vardenafil 5 mg or placebo with stable dose terazosin (5 or 10 mg) in normotensive BPH patients (Study 1) Study 2: This study was designed to evaluate the effect of 10 mg vardenafil (stage 1) and 20 mg vardenafil (stage 2) compared to placebo, when administered to a single cohort of BPH patients (n=23) on stable therapy with tamsulosin 0.4 mg or 0.8 mg daily for at least four weeks. The design was a randomized, double blind, two-period cross-over study. Vardenafil or placebo was given simultaneously with tamsulosin. Blood pressure and pulse were evaluated over the 6­ hour interval after vardenafil dosing. For BP results see Table 3 . One patient experienced a decrease from baseline in standing SBP of >30 mmHg following vardenafil 10 mg. There were no other instances of outlier blood pressure values (standing SBP <85 mmHg or decrease from baseline in standing SBP of >30 mmHg). Three patients reported dizziness following vardenafil 20 mg. There were no cases of syncope. Table 3: Mean (95% C.I.) maximal change from baseline in systolic blood pressure (mmHg) following vardenafil 10 and 20 mg in BPH patients on stable alpha-blocker therapy with tamsulosin 0.4 or 0.8 mg daily (Study 2) Vardenafil 10 mg Placebo-subtracted Vardenafil 20 mg Placebo-subtracted Standing SBP -4 (-6.8, -0.3) -4 (-6.8, -1.4) Supine SBP -5 (-8.2, -0.8) -4 (-6.3, -1.8) Blood pressure effects (standing SBP) in normotensive men on stable dose of tamsulosin 0.4 mg following simultaneous administration of vardenafil 10 mg, vardenafil 20 mg or placebo are shown in Figure 4. Figure 4: Mean change from baseline in standing systolic blood pressure (mmHg) over 6 hour interval following simultaneous administration of vardenafil 10 mg (Stage 1), vardenafil 20 mg (Stage 2), or placebo with stable dose tamsulosin 0.4 mg in normotensive BPH patients (Study 2) Study 3: This study was designed to evaluate the effect of single doses of 5 mg vardenafil (stage 1) and 10 mg vardenafil (stage 2) compared to placebo, when administered to a single cohort of BPH patients (n=24) on stable therapy with alfuzosin 10 mg daily for at least four weeks. The design was a randomized, double blind, 3­ period cross-over study. Vardenafil or placebo was administered 4 hours after the administration of alfuzosin. Blood pressure and pulse were evaluated over a 10-hour interval after dosing of vardenafil or placebo. For BP results see Table 4 . Table 4: Mean (95% C.I.) maximal change from baseline in systolic blood pressure (mmHg) following vardenafil 5 and 10 mg in BPH patients on stable alpha-blocker therapy with alfuzosin 10 mg daily (Study 3) Vardenafil 5 mg Placebo-subtracted Vardenafil 10 mg Placebo-subtracted Standing SBP -2 (-5.8, 1.2) -5 (-8.8, -1.6) Supine SBP -1 (-4.1, 2.1) -6 (-9.4, -2.8) One patient experienced decreases from baseline in standing systolic blood pressure >30 mm Hg after administration of vardenafil 5 mg tablet and vardenafil 10 mg tablet. No instances of standing systolic blood pressure <85 mm Hg were observed during this study. Four patients, one dosed with placebo, two dosed with vardenafil 5 mg tablets and one dosed with vardenafil 10 mg tablets, reported dizziness. Blood pressure effects (standing SBP) in normotensive men on a stable dose of alfuzosin 10 mg following administration of vardenafil 5 mg, vardenafil 10 mg, or placebo separated by 4 hours, are shown in Figure 5. Figure 5: Mean change from baseline in standing systolic blood pressure (mmHg) over 6 hour interval following 4 hr separation administration of vardenafil 5 mg (stage 1), vardenafil 10 mg (stage 2) or placebo with stable dose alfuzosin 10 mg in BPH patients (Study 3) Blood pressure effects in normotensive men after forced titration with alpha-blockers: Two randomized, double blind, placebo-controlled clinical pharmacology studies with healthy normotensive volunteers (age range, 45-74 years) were performed after forced titration of the alpha-blocker terazosin to 10 mg daily over 14 days (n=29), and after initiation of tamsulosin 0.4 mg daily for five days (n=24). There were no severe adverse events related to hypotension in either study. Symptoms of hypotension were a cause for withdrawal in 2 subjects receiving terazosin and in 4 subjects receiving tamsulosin. Instances of outlier blood pressure values (defined as standing SBP <85 mmHg and/or a decrease from baseline of standing SBP >30 mmHg) were observed in 9/24 subjects receiving tamsulosin and 19/29 receiving terazosin. The incidence of subjects with standing SBP <85 mmHg given vardenafil and terazosin to achieve simultaneous T max led to early termination of that arm of the study. In most (7/8) of these subjects, instances of standing SBP <85 mmHg were not associated with symptoms. Among subjects treated with terazosin, outlier values were observed more frequently when vardenafil and terazosin were given to achieve simultaneous T max than when dosing was administered to separate T max by 6 hours. Ther