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12 CLINICAL PHARMACOLOGY

12.1Mechanism 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).

12.2Pharmacodynamics 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 is 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 20 mg at various times before NTG administration. Vardenafil 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 20 mg was 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 20 mg was 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 simulta… [Excerpted — this section continues on DailyMed.]

12.1Mechanism 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).

12.3Pharmacokinetics The pharmacokinetics of vardenafil are approximately dose proportional over the recommended dose range. Absorption Mean vardenafil plasma concentrations measured after the administration of a single oral dose of 20 mg to healthy male volunteers are depicted in Figure 8. Figure 8: Plasma Vardenafil Concentration (Mean ± SD) Curve for a Single 20 mg Vardenafil Dose Vardenafil is rapidly absorbed with absolute bioavailability of approximately 15%.

Maximum observed plasma concentrations after a single 20 mg dose in healthy volunteers are usually reached between 30 minutes and 2 hours (median 60 minutes) after oral dosing in the fasted state. Two food-effect studies were conducted which showed that high-fat meals caused a reduction in C max by 18% to 50%. Distribution The mean steady-state volume of distribution (Vss) for vardenafil is 208 L, indicating extensive tissue distribution.

Vardenafil and its major circulating metabolite, M1, are highly bound to plasma proteins (about 95% for parent drug and M1). This protein binding is reversible and independent of total drug concentrations. Following a single oral dose of 20 mg vardenafil in healthy volunteers, a mean of 0.00018% of the administered dose was obtained in semen 1.5 hours after dosing.

Metabolism Vardenafil is metabolized predominantly by the hepatic enzyme CYP3A4, with contribution from the CYP3A5 and CYP2C isoforms. The major circulating metabolite, M1, results from desethylation at the piperazine moiety of vardenafil. M1 is subject to further metabolism.

The plasma concentration of M1 is approximately 26% that of the parent compound. This metabolite shows a phosphodiesterase selectivity profile similar to that of vardenafil and an in vitro inhibitory potency for PDE5 28% of that of vardenafil. Therefore, M1 accounts for approximately 7% of total pharmacologic activity.

Excretion The total body clearance of vardenafil is 56 L/h, and the terminal half-life of vardenafil and its primary metabolite (M1) is approximately 4 to 5 hours. After oral administration, vardenafil is excreted as metabolites predominantly in the feces (approximately 91 to 95% of administered oral dose) and to a lesser extent in the urine (approximately 2 to 6% of administered oral dose). Pharmacokinetics in Specific Populations Pediatrics Vardenafil is not indicated for use in pediatric patients.

Vardenafil trials were not conducted in the pediatric population. Geriatric In a healthy volunteer study of elderly males (≥65 years) and younger males (18 to 45 years), mean C max and AUC were 34% and 52% higher, respectively, in the elderly males [see Use in Specific Populations ( 8.5 )]. Hepatic Impairment In volunteers with mild hepatic impairment (Child-Pugh A), the C max and AUC following a 10 mg vardenafil dose were increased by 22% and 17%, respectively, compared to healthy control subjects.

In volunteers with moderate hepatic impairment (Child-Pugh B), the C max and AUC following a 10 mg vardenafil dose were increased by 130% and 160%, respectively, compared to healthy control subjects. Vardenafil has not been evaluated in patients with severe (Child-Pugh C) hepatic impairment. [See Dosage and Administration ( 2.3 ), Warnings and Precautions ( 5.8 ), and Use in Specific Populations ( 8.6 ).] Renal Impairment In male volunteers with CL cr = 50 to 80 mL/min, the pharmacokinetics of vardenafil were similar to those observed in a control group with CL cr >80 mL/min.

In male volunteers with CL cr = 30 to 50 mL/min or CL cr <30 mL/min renal impairment groups, the AUC of vardenafil was 20 to 30% higher compared to that observed in a control group with CL cr >80 mL/min). Vardenafil pharmacokinetics have not been evaluated in patients requiring renal dialysis. [See Dosage and Administration ( 2.3 ), Warnings and Precautions ( 5.9 ), and Use in Specific Populations ( 8.7 ).]

12.2Pharmacodynamics 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 is 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 20 mg at various times before NTG administration. Vardenafil 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 20 mg was 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 20 mg was 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. Alpha-Blocker Simultaneous dosing of Va… [Excerpted — this section continues on DailyMed.]

14 CLINICAL STUDIES Vardenafil was evaluated in four major double-blind, randomized, placebo-controlled, fixed-dose, parallel design, multicenter trials in 2,431 men aged 20 to 83 (mean age 57 years; 78% White, 7% Black, 2% Asian, 3% Hispanic and 10% Other/Unknown). The doses of vardenafil in these studies were 5 mg, 10 mg, and 20 mg. Two of these trials were conducted in the general erectile dysfunction (ED) population and two in special ED populations (one in patients with diabetes mellitus and one in post-prostatectomy patients).

Vardenafil was dosed without regard to meals on an as needed basis in men with ED, many of whom had multiple other medical conditions. The primary endpoints were assessed at 3 months. Primary efficacy assessment in all four major trials was by means of the Erectile Function (EF) Domain score of the validated International Index of Erectile Function (IIEF) Questionnaire and two questions from the Sexual Encounter Profile (SEP) dealing with the ability to achieve vaginal penetration (SEP2), and the ability to maintain an erection long enough for successful intercourse (SEP3).

In all four fixed-dose efficacy trials, vardenafil showed clinically meaningful and statistically significant improvement in the EF Domain, SEP2, and SEP3 scores compared to placebo. The mean baseline EF Domain score in these trials was 11.8 (scores range from 0 to 30 where lower scores represent more severe disease). Vardenafil (5 mg, 10 mg, and 20 mg) was effective in all age categories (<45, 45 to <65, and ≥65 years) and was also effective regardless of race (White, Black, Other).

14.1Trials in a General Erectile Dysfunction Population In the major North American fixed-dose trial, 762 patients (mean age 57, range 20 to 83 years; 79% White, 13% Black, 4% Hispanic, 2% Asian and 2% Other) were evaluated. The mean baseline EF Domain scores were 13, 13, 13, 14 for the vardenafil 5 mg, 10 mg, 20 mg and placebo groups, respectively. There was significant improvement (p <0.0001) at 3 months with vardenafil (EF Domain scores of 18, 21, 21, for the 5 mg, 10 mg, and 20 mg dose groups, respectively) compared to the placebo group (EF Domain score of 15).

The European trial (total N=803) confirmed these results. The improvement in mean score was maintained at all doses at 6 months in the North American trial. In the North American trial, vardenafil significantly improved the rates of achieving an erection sufficient for penetration (SEP2) at doses of 5 mg, 10 mg, and 20 mg compared to placebo (65%, 75%, and 80%, respectively, compared to a 52% response in the placebo group at 3 months; p <0.0001).

The European trial confirmed these results. Vardenafil demonstrated a clinically meaningful and statistically significant increase in the overall per-patient rate of maintenance of erection to successful intercourse (SEP3) (51% on 5 mg, 64% on 10 mg, and 65% on 20 mg, respectively, compared to 32% on placebo; p <0.0001) at 3 months in the North American trial. The European trial showed comparable efficacy.

This improvement in mean score was maintained at all doses at 6 months in the North American trial.

14.2Trial in Patients with ED and Diabetes Mellitus Vardenafil demonstrated clinically meaningful and statistically significant improvement in erectile function in a prospective, fixed-dose (10 and 20 mg vardenafil), double-blind, placebo-controlled trial of patients with diabetes mellitus (n=439; mean age 57 years, range 33 to 81; 80% White, 9% Black, 8% Hispanic, and 3% Other). Significant improvements in the EF Domain were shown in this study (EF Domain scores of 17 on 10 mg vardenafil and 19 on 20 mg vardenafil compared to 13 on placebo; p <0.0001).

Vardenafil significantly improved the overall per-patient rate of achieving an erection sufficient for penetration (SEP2) (61% on 10 mg and 64% on 20 mg vardenafil compared to 36% on placebo; p <0.0001). Vardenafil demonstrated a clinically meaningful and statistically significant increase in th… [Excerpted — this section continues on DailyMed.]

13 NONCLINICAL TOXICOLOGY

13.1Carcinogenesis, Mutagenesis, Impairment of Fertility Carcinogenesis Vardenafil was not carcinogenic in rats and mice when administered daily for 24 months. In these studies systemic drug exposures (AUCs) for unbound (free) vardenafil and its major metabolite were approximately 400-and 170-fold for male and female rats, respectively, and 21-and 37-fold for male and female mice, respectively, the exposures observed in human males given the Maximum Recommended Human Dose (MRHD) of 20 mg. Mutagenesis Vardenafil was not mutagenic as assessed in either the in vitro bacterial Ames assay or the forward mutation assay in Chinese hamster V 79 cells.

Vardenafil was not clastogenic as assessed in either the in vitro chromosomal aberration test or the in vivo mouse micronucleus test. Impairment of Fertility Vardenafil did not impair fertility in male and female rats administered doses up to 100 mg/kg/day for 28 days prior to mating in male, and for 14 days prior to mating and through day 7 of gestation in females. In a corresponding 1-month rat toxicity study, this dose produced an AUC value for unbound vardenafil 200 fold greater than AUC in humans at the MRHD of 20 mg.