Tadalafil (Page 8 of 11)

12.3 Pharmacokinetics

Over a dose range of 2.5 to 20 mg, tadalafil exposure (AUC) increases proportionally with dose in healthy subjects. Steady-state plasma concentrations are attained within 5 days of once per day dosing and exposure is approximately 1.6-fold greater than after a single dose. Mean tadalafil concentrations measured after the administration of a single oral dose of 20 mg and single and once daily multiple doses of 5 mg, from a separate study, (see Figure 4) to healthy male subjects are depicted in Figure 4.

4
(click image for full-size original)

Figure 4: Plasma tadalafil concentrations (mean ± SD) following a single 20 mg tadalafil dose and single and once daily multiple doses of 5 mg

Absorption — After single oral-dose administration, the maximum observed plasma concentration (C max ) of tadalafil is achieved between 30 minutes and 6 hours (median time of 2 hours). Absolute bioavailability of tadalafil following oral dosing has not been determined.

The rate and extent of absorption of tadalafil are not influenced by food; thus tadalafil tablets may be taken with or without food.

Distribution — The mean apparent volume of distribution following oral administration is approximately 63 L, indicating that tadalafil is distributed into tissues. At therapeutic concentrations, 94% of tadalafil in plasma is bound to proteins.

Less than 0.0005% of the administered dose appeared in the semen of healthy subjects.

Metabolism — Tadalafil is predominantly metabolized by CYP3A4 to a catechol metabolite. The catechol metabolite undergoes extensive methylation and glucuronidation to form the methylcatechol and methylcatechol glucuronide conjugate, respectively. The major circulating metabolite is the methylcatechol glucuronide. Methylcatechol concentrations are less than 10% of glucuronide concentrations. In vitro data suggests that metabolites are not expected to be pharmacologically active at observed metabolite concentrations.

Excretion — The mean oral clearance for tadalafil is 2.5 L/hr and the mean terminal half-life is 17.5 hours in healthy subjects. Tadalafil is excreted predominantly as metabolites, mainly in the feces (approximately 61% of the dose) and to a lesser extent in the urine (approximately 36% of the dose).

Geriatric — Healthy male elderly subjects (65 years or over) had a lower oral clearance of tadalafil, resulting in 25% higher exposure (AUC) with no effect on C max relative to that observed in healthy subjects 19 to 45 years of age. No dose adjustment is warranted based on age alone. However, greater sensitivity to medications in some older individuals should be considered [see Use in Specific Populations ( 8.5)].

Pediatric — Tadalafil has not been evaluated in individuals less than 18 years old [see Use in Specific Populations ( 8.4)].

Patients with Diabetes Mellitus — In male patients with diabetes mellitus after a 10 mg tadalafil dose, exposure (AUC) was reduced approximately 19% and C max was 5% lower than that observed in healthy subjects. No dose adjustment is warranted.

Patients with BPH — In patients with BPH following single and multiple-doses of 20 mg tadalafil, no statistically significant differences in exposure (AUC and C max ) were observed between elderly (70 to 85 years) and younger (≤60 years of age) subjects. No dose adjustment is warranted.

13 NONCLINICAL TOXICOLOGY

13.1 Carcinogenesis, Mutagenesis, Impairment Of Fertility

Carcinogenesis — Tadalafil was not carcinogenic to rats or mice when administered daily for 2 years at doses up to 400 mg/kg/day. Systemic drug exposures, as measured by AUC of unbound tadalafil, were approximately 10-fold for mice, and 14- and 26-fold for male and female rats, respectively, the exposures in human males given Maximum Recommended Human Dose (MRHD) of 20 mg.

Mutagenesis — Tadalafil was not mutagenic in the in vitro bacterial Ames assays or the forward mutation test in mouse lymphoma cells. Tadalafil was not clastogenic in the in vitro chromosomal aberration test in human lymphocytes or the in vivo rat micronucleus assays.

Impairment of Fertility — There were no effects on fertility, reproductive performance or reproductive organ morphology in male or female rats given oral doses of tadalafil up to 400 mg/kg/day, a dose producing AUCs for unbound tadalafil of 14-fold for males or 26-fold for females the exposures observed in human males given the MRHD of 20 mg. In beagle dogs given tadalafil daily for 3 to 12 months, there was treatment-related non-reversible degeneration and atrophy of the seminiferous tubular epithelium in the testes in 20 to 100% of the dogs that resulted in a decrease in spermatogenesis in 40 to 75% of the dogs at doses of ≥10 mg/kg/day. Systemic exposure (based on AUC) at no-observed-adverse-effect level (NOAEL) (10 mg/kg/day) for unbound tadalafil was similar to that expected in humans at the MRHD of 20 mg.

There were no treatment-related testicular findings in rats or mice treated with doses up to 400 mg/kg/day for 2 years.

13.2 Animal Pharmacology and/or Toxicology

Animal studies showed vascular inflammation in tadalafil-treated mice, rats, and dogs. In mice and rats, lymphoid necrosis and hemorrhage were seen in the spleen, thymus, and mesenteric lymph nodes at unbound tadalafil exposure of 2- to 33-fold above the human exposure (AUCs) at the MRHD of 20 mg. In dogs, an increased incidence of disseminated arteritis was observed in 1-and 6-month studies at unbound tadalafil exposure of 1- to 54-fold above the human exposure (AUC) at the MRHD of 20 mg. In a 12-month dog study, no disseminated arteritis was observed, but 2 dogs exhibited marked decreases in white blood cells (neutrophils) and moderate decreases in platelets with inflammatory signs at unbound tadalafil exposures of approximately 14- to 18-fold the human exposure at the MRHD of 20 mg. The abnormal blood-cell findings were reversible within 2 weeks after stopping treatment.

14 CLINICAL STUDIES

14.1 Tadalafil for Use as Needed for ED

The efficacy and safety of tadalafil in the treatment of erectile dysfunction has been evaluated in 22 clinical trials of up to 24-weeks duration, involving over 4,000 patients. Tadalafil, when taken as needed up to once per day, was shown to be effective in improving erectile function in men with erectile dysfunction (ED).

Tadalafil was studied in the general ED population in 7 randomized, multicenter, double-blinded, placebo-controlled, parallel-arm design, primary efficacy and safety studies of 12-weeks duration. Two of these studies were conducted in the United States and 5 were conducted in centers outside the U.S. Additional efficacy and safety studies were performed in ED patients with diabetes mellitus and in patients who developed ED status post bilateral nerve-sparing radical prostatectomy.

In these 7 trials, tadalafil was taken as needed, at doses ranging from 2.5 to 20 mg, up to once per day. Patients were free to choose the time interval between dose administration and the time of sexual attempts. Food and alcohol intake were not restricted.

Several assessment tools were used to evaluate the effect of tadalafil on erectile function. The 3 primary outcome measures were the Erectile Function (EF) domain of the International Index of Erectile Function (IIEF) and Questions 2 and 3 from Sexual Encounter Profile (SEP). The IIEF is a 4-week recall questionnaire that was administered at the end of a treatment-free baseline period and subsequently at follow-up visits after randomization. The IIEF EF domain has a 30-point total score, where higher scores reflect better erectile function. SEP is a diary in which patients recorded each sexual attempt made throughout the study. SEP Question 2 asks, “Were you able to insert your penis into the partner’s vagina?” SEP Question 3 asks, “Did your erection last long enough for you to have successful intercourse?” The overall percentage of successful attempts to insert the penis into the vagina (SEP2) and to maintain the erection for successful intercourse (SEP3) is derived for each patient.

Results in ED Population in U.S. Trials — The 2 primary U.S. efficacy and safety trials included a total of 402 men with erectile dysfunction, with a mean age of 59 years (range 27 to 87 years). The population was 78% White, 14% Black, 7% Hispanic, and 1% of other ethnicities, and included patients with ED of various severities, etiologies (organic, psychogenic, mixed), and with multiple co-morbid conditions, including diabetes mellitus, hypertension, and other cardiovascular disease. Most (>90%) patients reported ED of at least 1-year duration. Study A was conducted primarily in academic centers. Study B was conducted primarily in community-based urology practices. In each of these 2 trials, tadalafil 20 mg showed clinically meaningful and statistically significant improvements in all 3 primary efficacy variables (see Table 11). The treatment effect of tadalafil did not diminish over time.

Table 11: Mean Endpoint and Change from Baseline for the Primary Efficacy Variables in the Two Primary U.S. Trials

Study A Study B
Placebo Tadalafil 20 mg Placebo Tadalafil 20 mg
(N=49) (N=146) p-value (N=48) (N=159) p-value
EF Domain Score
Endpoint 13.5 19.5 13.6 22.5
Change from baseline -0.2 6.9 <.001 0.3 9.3 <.001
Insertion of Penis (SEP2)
Endpoint 39% 62% 43% 77%
Change from baseline 2% 26% <.001 2% 32% <.001
Maintenance of Erection (SEP3)
Endpoint 25% 50% 23% 64%
Change from baseline 5% 34% <.001 4% 44% <.001

Results in General ED Population in Trials Outside the U.S. — The 5 primary efficacy and safety studies conducted in the general ED population outside the U.S. included 1,112 patients, with a mean age of 59 years (range 21 to 82 years). The population was 76% White, 1% Black, 3% Hispanic, and 20% of other ethnicities, and included patients with ED of various severities, etiologies (organic, psychogenic, mixed), and with multiple co-morbid conditions, including diabetes mellitus, hypertension, and other cardiovascular disease. Most (90%) patients reported ED of at least 1-year duration. In these 5 trials, tadalafil 5, 10, and 20 mg showed clinically meaningful and statistically significant improvements in all 3 primary efficacy variables (see Tables 12, 13 and 14). The treatment effect of tadalafil did not diminish over time.

Table 12: Mean Endpoint and Change from Baseline for the EF Domain of the IIEF in the General ED Population in Five Primary Trials Outside the U.S.

Placebo Tadalafil 5 mg Tadalafil 10 mg Tadalafil 20 mg
Study C
Endpoint [Change from baseline] 15.0 [0.7] 17.9 [4.0] 20.0 [5.6]
p=.006 p<.001
Study D
Endpoint [Change from baseline] 14.4 [1.1] 17.5 [5.1] 20.6 [6.0]
p=.002 p<.001
Study E
Endpoint [Change from baseline] 18.1 [2.6] 22.6 [8.1] 25.0 [8.0]
p<.001 p<.001
Study F a
Endpoint [Change from baseline] 12.7 [-1.6] 22.8 [6.8]
p<.001
Study G
Endpoint [Change from baseline] 14.5 [-0.9] 21.2 [6.6] 23.3 [8.0]
p<.001 p<.001

a Treatment duration in Study F was 6 months

Table 13: Mean Post-Baseline Success Rate and Change from Baseline for SEP Question 2 (“Were you able to insert your penis into the partner’s vagina?”) in the General ED Population in Five Pivotal Trials Outside the U.S.

Placebo Tadalafil 5 mg Tadalafil 10 mg Tadalafil 20 mg
Study C
Endpoint [Change from baseline] 49% [6%] 57% [15%] 73% [29%]
p=.063 p<.001
Study D
Endpoint [Change from baseline] 46% [2%] 56% [18%] 68% [15%]
p=.008 p<.001
Study E
Endpoint [Change from baseline] 55% [10%] 77% [35%] 85% [35%]
p<.001 p<.001
Study F a
Endpoint [Change from baseline] 42% [-8%] 81% [27%]
p<.001
Study G
Endpoint [Change from baseline] 45% [-6%] 73% [21%] 76% [21%]
p<.001 p<.001

a Treatment duration in Study F was 6 months

Table 14: Mean Post-Baseline Success Rate and Change from Baseline for SEP Question 3 (“Did your erection last long enough for you to have successful intercourse?”) in the General ED Population in Five Pivotal Trials Outside the U.S.

Placebo Tadalafil 5 mg Tadalafil 10 mg Tadalafil 20 mg
Study C
Endpoint [Change from baseline] 26% [4%] 38% [19%] 58% [32%]
p=.040 p<.001
Study D
Endpoint [Change from baseline] 28% [4%] 42% [24%] 51% [26%]
p<.001 p<.001
Study E
Endpoint [Change from baseline] 43% [15%] 70% [48%] 78% [50%]
p<.001 p<.001
Study F a
Endpoint [Change from baseline] 27% [1%] 74% [40%]
p<.001
Study G
Endpoint [Change from baseline] 32% [5%] 57% [33%] 62% [29%]
p<.001 p<.001

a Treatment duration in Study F was 6 months

In addition, there were improvements in EF domain scores, success rates based upon SEP Questions 2 and 3, and patient-reported improvement in erections across patients with ED of all degrees of disease severity while taking tadalafil, compared to patients on placebo.

Therefore, in all 7 primary efficacy and safety studies, tadalafil showed statistically significant improvement in patients’ ability to achieve an erection sufficient for vaginal penetration and to maintain the erection long enough for successful intercourse, as measured by the IIEF questionnaire and by SEP diaries.

Efficacy Results in ED Patients with Diabetes Mellitus — Tadalafil was shown to be effective in treating ED in patients with diabetes mellitus. Patients with diabetes were included in all 7 primary efficacy studies in the general ED population (N=235) and in one study that specifically assessed tadalafil in ED patients with type 1 or type 2 diabetes (N=216). In this randomized, placebo-controlled, double-blinded, parallel-arm design prospective trial, tadalafil demonstrated clinically meaningful and statistically significant improvement in erectile function, as measured by the EF domain of the IIEF questionnaire and Questions 2 and 3 of the SEP diary (see Table 15).

Table 15: Mean Endpoint and Change from Baseline for the Primary Efficacy Variables in a Study in ED Patients with Diabetes

Placebo Tadalafil 10 mg Tadalafil 20 mg
(N=71) (N=73) (N=72) p-value
EF Domain Score
Endpoint [Change from baseline] 12.2 [0.1] 19.3 [6.4] 18.7 [7.3] <.001
Insertion of Penis (SEP2)
Endpoint [Change from baseline] 30% [-4%] 57% [22%] 54% [23%] <.001
Maintenance of Erection (SEP3)
Endpoint [Change from baseline] 20% [2%] 48% [28%] 42% [29%] <.001

Efficacy Results in ED Patients following Radical Prostatectomy — Tadalafil was shown to be effective in treating patients who developed ED following bilateral nerve-sparing radical prostatectomy. In 1 randomized, placebo-controlled, double-blinded, parallel-arm design prospective trial in this population (N=303), tadalafil demonstrated clinically meaningful and statistically significant improvement in erectile function, as measured by the EF domain of the IIEF questionnaire and Questions 2 and 3 of the SEP diary (see Table 16).

Table 16: Mean Endpoint and Change from Baseline for the Primary Efficacy Variables in a Study in Patients who Developed ED Following Bilateral Nerve-Sparing Radical Prostatectomy

Placebo Tadalafil 20 mg
(N=102) (N=201) p-value
EF Domain Score
Endpoint [Change from baseline] 13.3 [1.1] 17.7 [5.3] <.001
Insertion of Penis (SEP2)
Endpoint [Change from baseline] 32% [2%] 54% [22%] <.001
Maintenance of Erection (SEP3)
Endpoint [Change from baseline] 19% [4%] 41% [23%] <.001

Results in Studies to Determine the Optimal Use of Tadalafil — Several studies were conducted with the objective of determining the optimal use of tadalafil in the treatment of ED. In one of these studies, the percentage of patients reporting successful erections within 30 minutes of dosing was determined. In this randomized, placebo-controlled, double-blinded trial, 223 patients were randomized to placebo, tadalafil 10, or 20 mg. Using a stopwatch, patients recorded the time following dosing at which a successful erection was obtained. A successful erection was defined as at least 1 erection in 4 attempts that led to successful intercourse. At or prior to 30 minutes, 35% (26/74), 38% (28/74), and 52% (39/75) of patients in the placebo, 10, and 20 mg groups, respectively, reported successful erections as defined above.

Two studies were conducted to assess the efficacy of tadalafil at a given timepoint after dosing, specifically at 24 hours and at 36 hours after dosing.

In the first of these studies, 348 patients with ED were randomized to placebo or tadalafil 20 mg. Patients were encouraged to make 4 total attempts at intercourse; 2 attempts were to occur at 24 hours after dosing and 2 completely separate attempts were to occur at 36 hours after dosing. The results demonstrated a difference between the placebo group and the tadalafil group at each of the pre-specified timepoints. At the 24-hour timepoint, (more specifically, 22 to 26 hours), 53/144 (37%) patients reported at least 1 successful intercourse in the placebo group versus 84/138 (61%) in the tadalafil 20 mg group. At the 36-hour timepoint (more specifically, 33 to 39 hours), 49/133 (37%) of patients reported at least 1 successful intercourse in the placebo group versus 88/137 (64%) in the tadalafil 20 mg group.

In the second of these studies, a total of 483 patients were evenly randomized to 1 of 6 groups: 3 different dosing groups (placebo, tadalafil 10, or 20 mg) that were instructed to attempt intercourse at 2 different times (24 and 36 hours post-dosing). Patients were encouraged to make 4 separate attempts at their assigned dose and assigned timepoint. In this study, the results demonstrated a statistically significant difference between the placebo group and the tadalafil groups at each of the pre-specified timepoints. At the 24-hour timepoint, the mean, per patient percentage of attempts resulting in successful intercourse were 42, 56, and 67% for the placebo, tadalafil 10, and 20 mg groups, respectively. At the 36-hour timepoint, the mean, per-patient percentage of attempts resulting in successful intercourse were 33, 56, and 62% for placebo, tadalafil 10, and 20 mg groups, respectively.

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