Mechanism of Action
Tadalafil is an inhibitor of phosphodiesterase type 5 (PDE5), the enzyme responsible for the degradation of cyclic guanosine monophosphate (cGMP). Pulmonary arterial hypertension is associated with impaired release of nitric oxide by the vascular endothelium and consequent reduction of cGMP concentrations in the pulmonary vascular smooth muscle. PDE5 is the predominant phosphodiesterase in the pulmonary vasculature. Inhibition of PDE5 by tadalafil increases the concentrations of cGMP resulting in relaxation of pulmonary vascular smooth muscle cells and vasodilation of the pulmonary vascular bed.
Studies in vitro have demonstrated that tadalafil is a selective inhibitor
of PDE5. PDE5 is found in pulmonary vascular smooth muscle, visceral smooth
muscle, corpus cavernosum, skeletal muscle, platelets, kidney, lung, cerebellum,
and pancreas.
In vitro studies have shown that the effect of tadalafil is more potent
on PDE5 than on other phosphodiesterases. These studies have shown that tadalafil
is > 10,000–fold more potent for PDE5 than for PDE1, PDE2, PDE4, and PDE7
enzymes, which are found in the heart, brain, blood vessels, liver, leukocytes,
skeletal muscle, and other organs. Tadalafil is > 10,000–fold more potent
for PDE5 than for PDE3, an enzyme found in the heart and blood vessels. Additionally,
tadalafil is 700–fold more potent for PDE5 than for PDE6, which is found in
the retina and is responsible for phototransduction. Tadalafil is > 9,000–fold
more potent for PDE5 than for PDE8, PDE9, and PDE10. Tadalafil is 14–fold more
potent for PDE5 than for PDE11A1 and 40–fold more potent for PDE5 than for PDE11A4,
two of the four known forms of PDE11. PDE11 is an enzyme found in human prostate,
testes, skeletal muscle and in other tissues. In vitro, tadalafil inhibits
human recombinant PDE11A1 and, to a lesser degree, PDE11A4 activities at concentrations
within the therapeutic range. The physiological role and clinical consequence
of PDE11 inhibition in humans have not been defined.
Pharmacodynamics
Effects on Blood Pressure When Administered with Nitrates
In clinical pharmacology studies, tadalafil (5 to 20 mg) was shown to potentiate
the hypotensive effect of nitrates. Do not use ADCIRCA in patients taking any
form of nitrates [see CONTRAINDICATIONS].
A double–blind, placebo–controlled, crossover study in 150 male subjects at
least 40 years of age (including subjects with diabetes mellitus and/or controlled
hypertension) assessed the interaction between nitroglycerin and tadalafil.
Subjects received daily doses of tadalafil 20 mg or matching placebo for 7 days
and then were given a single dose of 0.4 mg sublingual nitroglycerin (NTG) at
pre-specified timepoints following their last dose of tadalafil (2, 4, 8, 24,
48, 72, and 96 hours after tadalafil). A significant interaction between tadalafil
and NTG was observed at each timepoint up to and including 24 hours. At 48 hours,
by most hemodynamic measures, the interaction between tadalafil and NTG was
not observed, although a few more tadalafil subjects compared to placebo experienced
greater blood–pressure lowering effects at this timepoint. After 48 hours, the
interaction was not detectable. [see CONTRAINDICATIONS
and WARNINGS AND PRECAUTIONS].
Effects on Blood Pressure
Tadalafil 20 mg administered to healthy male subjects produced no significant
difference compared to placebo in supine systolic and diastolic blood pressure
(difference in the mean maximal decrease of 1.6/0.8 mm Hg, respectively) and
in standing systolic and diastolic blood pressure (difference in the mean maximal
decrease of 0.2/4.6 mm Hg, respectively). In addition, there was no significant
effect on heart rate.
Effects on Blood Pressure When Administered with Antihypertensives
Amlodipine — A study assessed the interaction between amlodipine
(5 mg daily) and tadalafil 10 mg. There was no effect of tadalafil on amlodipine
blood levels and no effect of amlodipine on tadalafil blood levels. The mean
reduction in supine systolic/diastolic blood pressure because of tadalafil 10
mg in subjects taking amlodipine was 3/2 mm Hg, compared to placebo. In a similar
study using tadalafil 20 mg, there were no clinically significant differences
between tadalafil and placebo in subjects taking amlodipine.
Angiotensin II receptor blockers (with and without other antihypertensives)
— A study assessed the interaction between angiotensin II receptor blockers
and tadalafil 20 mg. Subjects in the study were taking any marketed angiotensin
II receptor blocker, either alone, as a component of a combination product,
or as part of a multiple antihypertensive regimen. Following dosing, ambulatory
measurements of blood pressure revealed differences between tadalafil and placebo
of 8/4 mm Hg in systolic/diastolic blood pressure.
Bendroflumethiazide — A study assessed the interaction between
bendroflumethiazide (2.5 mg daily) and tadalafil 10 mg. Following dosing, the
mean reduction in supine systolic/diastolic blood pressure because of tadalafil
10 mg in subjects taking bendroflumethiazide was 6/4 mm Hg, compared to placebo.
Enalapril — A study assessed the interaction between enalapril
(10 to 20 mg daily) and tadalafil 10 mg. Following dosing, the mean reduction
in supine systolic/diastolic blood pressure because of tadalafil 10 mg in subjects
taking enalapril was 4/1 mm Hg, compared to placebo.
Metoprolol — A study assessed the interaction between sustained–release
metoprolol (25 to 200 mg daily) and tadalafil 10 mg. Following dosing, the mean
reduction in supine systolic/diastolic blood pressure because of tadalafil 10
mg in subjects taking metoprolol was 5/3 mm Hg, compared to placebo.
Effects on Blood Pressure When Administered with Alcohol
Alcohol and PDE5 inhibitors, including tadalafil, are mild systemic vasodilators. The interaction of tadalafil with alcohol was evaluated in three clinical pharmacology studies. In two of these, alcohol was administered at a dose of 0.7 g/kg, which is equivalent to approximately 6 ounces of 80–proof vodka in an 80–kg male, and tadalafil was administered at a dose of 10 mg in one study and 20 mg in another. In both these studies, all patients imbibed the entire alcohol dose within 10 minutes of starting. In one of these two studies, blood alcohol levels of 0.08% were confirmed. In these two studies, more patients had clinically significant decreases in blood pressure on the combination of tadalafil and alcohol as compared to alcohol alone. Some subjects reported postural dizziness, and orthostatic hypotension was observed in some subjects. When tadalafil 20 mg was administered with a lower dose of alcohol (0.6 g/kg, which is equivalent to approximately 4 ounces of 80–proof vodka, administered in less than 10 minutes), orthostatic hypotension was not observed, dizziness occurred with similar frequency to alcohol alone, and the hypotensive effects of alcohol were not potentiated.
Tadalafil did not affect alcohol plasma concentrations and alcohol did not
affect tadalafil plasma concentrations.
Effects on Blood Pressure When Administered with Alpha-Blockers
Alpha-blockers and PDE5 inhibitors, including tadalafil, are systemic vasodilators. In subjects receiving concomitant tadalafil (20 mg single dose) and doxazosin (8 mg daily), an alpha-1 adrenergic receptor blocker, there was an augmentation of the blood pressure–lowering effect of doxazosin. This effect was still present at 12 hours postdose and had generally disappeared at 24 hours. The number of subjects with potentially clinically significant standing–blood–pressure decreases was greater for the combination.
An additional study was performed with tadalafil (20 mg single dose) and doxazosin (4 and 8 mg daily) using ambulatory blood pressure monitoring. The augmentation appeared unrelated to dosing times and resulted in a greater number of outliers for the combination than had been observed in the previous study. Both of these studies had some symptomatology associated with these blood pressure changes.
A further study was carried out with doxazosin (up to 4 mg daily) added to tadalafil (5 mg daily) and there was again an augmentation of response. In this clinical pharmacology study there were symptoms associated with the decrease in blood pressure, including syncope.
An interaction study with tadalafil (20 mg single dose) and alfuzosin, also
an alpha-1 adrenergic receptor blocker, showed no clinically significant
effect on blood pressure.
In two clinical pharmacology studies in healthy volunteers, tadalafil (5 mg
daily, and 10 mg and 20 mg single dose) had no clinically significant effect
on blood pressure changes because of tamsulosin, a selective alpha-1a
adrenergic receptor blocking agent.
Effects on Cardiac Electrophysiology
The effect of a single 100 mg dose of tadalafil (2.5 times the recommended
dose) on the QT interval was evaluated at the time of peak tadalafil concentration
in a randomized, double–blinded, placebo, and active–controlled (intravenous
ibutilide) crossover study in 90 healthy males aged 18 to 53 years. The mean
change in QTc (Fridericia QT correction) for tadalafil, relative
to placebo, was 3.5 milliseconds (two–sided 90% CI=1.9, 5.1). The mean change
in QTc (Individual QT correction) for tadalafil, relative to placebo,
was 2.8 milliseconds (two–sided 90% CI=1.2, 4.4). In this study, the mean increase
in heart rate associated with a 100 mg dose of tadalafil compared to placebo
was 3.1 beats per minute.
Effects on Exercise Stress Testing
The effects of tadalafil on cardiac function, hemodynamics, and exercise tolerance
were investigated in a single clinical pharmacology study. In this blinded crossover
trial, 23 subjects with stable coronary artery disease and evidence of exercise–induced
cardiac ischemia were enrolled. The primary endpoint was time to cardiac ischemia.
The mean difference in total exercise time was 3 seconds (tadalafil 10 mg minus
placebo), which represented no clinically meaningful difference. Further statistical
analysis demonstrated that tadalafil was similar to placebo with respect to
time to ischemia. Of note, in this study, in some subjects who received tadalafil
followed by sublingual nitroglycerin in the post–exercise period, clinically
significant reductions in blood pressure were observed, consistent with the
augmentation by tadalafil of the blood–pressure–lowering effects of nitrates.
Effects on Vision
Single oral doses of PDE inhibitors have demonstrated transient dose–related
impairment of color discrimination (blue/green), using the Farnsworth–Munsell
100–hue test, with peak effects near the time of peak plasma levels. This finding
is consistent with the inhibition of PDE6, which is involved in phototransduction
in the retina. In a study to assess the effects of a single dose of tadalafil
40 mg on vision (N=59), no effects were observed on visual acuity, intraocular
pressure, or pupillometry. Across all clinical studies with tadalafil, reports
of changes in color vision were rare ( < 0.1% of patients).
Effects on Sperm Characteristics
Three studies were conducted in men to assess the potential effect on sperm
characteristics of tadalafil 10 mg (one 6-month study) and 20 mg (one 6-month
and one 9-month study) administered daily. There were no adverse effects on
sperm morphology or sperm motility in any of the three studies. In the study
of 10 mg tadalafil for 6 months and the study of 20 mg tadalafil for 9 months,
results showed a decrease in mean sperm concentrations relative to placebo,
although these differences were not clinically meaningful. This effect was not
seen in the study of 20 mg tadalafil taken for 6 months. In addition there was
no adverse effect on mean concentrations of reproductive hormones, testosterone,
luteinizing hormone or follicle stimulating hormone with either 10 or 20 mg
of tadalafil compared to placebo.
Dose-Response Relationship
Dose-response relationships, between 20 mg and 40 mg, were not observed for
6-minute walk distance or pulmonary vascular resistance (PVR) in subjects with
PAH in the placebo-controlled study. Median change from baseline in 6-minute
walk distance was 32 meters and 35 meters at 16 weeks in subjects receiving
20 mg and 40 mg daily, respectively. Mean change from baseline PVR was -254
dynes*sec*cm-5 and -209 dynes*sec*cm-5 at 16 weeks in
patients receiving 20 mg and 40 mg daily, respectively.
Pharmacokinetics
Over a dose range of 2.5 to 20 mg, tadalafil exposure (AUC) increases proportionally with dose in healthy subjects. In PAH patients administered between 20 and 40 mg of tadalafil, an approximately 1.5-fold greater AUC was observed indicating a less than proportional increase in exposure over the entire dose range of 2.5 to 40 mg. During tadalafil 20 and 40 mg once daily dosing, steady-state plasma concentrations were attained within 5 days, and exposure was approximately 1.3-fold higher than after a single dose.
Absorption — After single oral-dose administration, the maximum
observed plasma concentration (Cmax) of tadalafil is achieved between 2 and
8 hours (median time of 4 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 ADCIRCA may be taken with or without food.
Distribution — The mean apparent volume of distribution following
oral administration is approximately 77 L, indicating that tadalafil is distributed
into tissues. At therapeutic concentrations, 94% of tadalafil in plasma is bound
to proteins.
Metabolism — Tadalafil is predominantly metabolized by CYP3A
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.
Elimination — Following 40 mg, the mean oral clearance for tadalafil
is 3.4 L/hr and the mean terminal half-life is 15 hours in healthy subjects.
In patients with pulmonary hypertension not receiving concomitant bosentan,
the mean oral clearance for tadalafil is 1.6 L/hr, and the mean terminal half-life
is 35 hours. 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).
Population pharmacokinetics — In patients with pulmonary hypertension
not receiving concomitant bosentan, the average tadalafil exposure at steady-state
following 40 mg was 26% higher when compared to those of healthy volunteers.
The results suggest a lower clearance of tadalafil in patients with pulmonary
hypertension compared to healthy volunteers.
Geriatric patients
In healthy male elderly subjects (65 years or over) after a 10 mg dose, a lower oral clearance of tadalafil, resulting in 25% higher exposure (AUC) with no effect on Cmax was observed relative to that in healthy subjects 19 to 45 years of age.
Renal impairment
In clinical pharmacology studies using single-dose tadalafil (5 to 10 mg),
tadalafil exposure (AUC) doubled in subjects with mild (creatinine clearance
51 to 80 mL/min) or moderate (creatinine clearance 31 to 50 mL/min) renal impairment.
In subjects with end-stage renal disease on hemodialysis, there was a two-fold
increase in Cmax and 2.7- to 4.1-fold increase in AUC following single-dose
administration of 10 or 20 mg tadalafil, respectively. Exposure to total methylcatechol
(unconjugated plus glucuronide) was 2- to 4-fold higher in subjects with renal
impairment, compared to those with normal renal function. Hemodialysis (performed
between 24 and 30 hours post-dose) contributed negligibly to tadalafil or metabolite
elimination [see DOSAGE AND ADMINISTRATION
and WARNINGS AND PRECAUTIONS].
Hepatic impairment
In clinical pharmacology studies, tadalafil exposure (AUC) in subjects with
mild or moderate hepatic impairment (Child-Pugh Class A or B) was comparable
to exposure in healthy subjects when a dose of 10 mg was administered. There
are no available data for doses higher than 10 mg of tadalafil in patients with
hepatic impairment. Insufficient data are available for subjects with severe
hepatic impairment (Child-Pugh Class C) [see DOSAGE
AND ADMINISTRATION and WARNINGS AND PRECAUTIONS].
Patients with diabetes mellitus
In male patients with diabetes mellitus after a 10 mg tadalafil dose, exposure (AUC) was reduced approximately 19% and Cmax was 5% lower than that observed in healthy subjects. No dose adjustment is warranted.
Race
Pharmacokinetic studies have included subjects from different ethnic groups, and no differences in the typical exposure to tadalafil have been identified. No dose adjustment is warranted.
Gender
In healthy female and male subjects following single and multiple-doses of tadalafil, no clinically relevant differences in exposure (AUC and Cmax) were observed. No dose adjustment is warranted.
Drug interaction studies
Tadalafil is a substrate of and predominantly metabolized by CYP3A. Drugs that inhibit CYP3A can increase tadalafil exposure.
Ritonavir
Ritonavir (500 mg or 600 mg twice daily at steady state), an inhibitor of CYP3A,
CYP2C9, CYP2C19, and CYP2D6, increased tadalafil 20–mg single-dose exposure
(AUC) by 32% with a 30% reduction in Cmax, relative to the values for tadalafil
20 mg alone. Ritonavir (200 mg twice daily), increased tadalafil 20-mg single-dose
exposure (AUC) by 124% with no change in Cmax, relative to the values for tadalafil
20 mg alone. Ritonavir inhibits and induces CYP3A, the enzyme involved in the
metabolism of tadalafil, in a time-dependent manner. The results suggest the
initial inhibitory effect of ritonavir on CYP3A may be mitigated by a more slowly
evolving induction effect so that after about 1 week of ritonavir twice daily,
the exposure of tadalafil is similar in the presence of and absence of ritonavir
[see DOSAGE AND ADMINISTRATION and WARNINGS
AND PRECAUTIONS, and DRUG
INTERACTIONS]. Although specific interactions have not been studied,
other HIV protease inhibitors would likely increase tadalafil exposure.
Other Cytochrome P450 inhibitors
CYP3A (e.g., ketoconazole) — Ketoconazole (400 mg daily), a selective and potent inhibitor of CYP3A, increased tadalafil 20 mg single-dose exposure (AUC) by 312% and Cmax by 22%, relative to the values for tadalafil 20 mg alone. Ketoconazole (200 mg daily) increased tadalafil 10–mg single-dose exposure (AUC) by 107% and Cmax by 15%, relative to the values for tadalafil 10 mg alone.
Although specific interactions have not been studied, other CYP3A inhibitors,
such as erythromycin, itraconazole, and grapefruit juice, would likely increase
tadalafil exposure.
Cytochrome P450 inducers
CYP3A (e.g., rifampin, bosentan) — Rifampin (600 mg daily), a CYP3A
inducer, reduced tadalafil 10 mg single–dose exposure (AUC) by 88% and Cmax
by 46%, relative to the values for tadalafil 10 mg alone.
Bosentan (125 mg twice daily), a substrate of CYP2C9 and CYP3A and a moderate inducer of CYP3A, CYP2C9 and possibly CYP2C19, reduced tadalafil (40 mg once per day) systemic exposure by 42% and Cmax by 27% following multiple-dose co-administration.
Although specific interactions have not been studied, other CYP3A inducers, such as carbamazepine, phenytoin, and phenobarbital, would likely decrease tadalafil exposure.
Cytochrome P450 substrates — Tadalafil is not expected to cause clinically
significant inhibition or induction of the clearance of drugs metabolized by
cytochrome P450 (CYP) isoforms.
CYP1A2 (e.g., theophylline) — Tadalafil (10 mg once per day) had no
significant effect on the pharmacokinetics of theophylline. When tadalafil was
administered to subjects taking theophylline, a small augmentation (3 beats
per minute) of the increase in heart rate associated with theophylline was observed.
CYP2C9 (e.g., warfarin) — Tadalafil (10 mg and 20 mg once per day) had
no significant effect on exposure (AUC) to S– warfarin or R–warfarin, nor did
tadalafil affect changes in prothrombin time induced by warfarin.
CYP3A (e.g., midazolam, lovastatin or bosentan) — Tadalafil (10 mg and
20 mg once per day) had no significant effect on exposure (AUC) to midazolam
or lovastatin. Tadalafil (40 mg once per day) had no clinically significant
effect on exposure (AUC and Cmax) of bosentan, a substrate of CYP2C9 and CYP3A,
or its metabolites.
Aspirin — Tadalafil (10 mg and 20 mg once per day) did not potentiate
the increase in bleeding time caused by aspirin.
P-glycoprotein (e.g., digoxin) — Coadministration of tadalafil
(40 mg once per day) for 10 days did not have a significant effect on the steady-state
pharmacokinetics of digoxin (0.25 mg/day) in healthy subjects.
Combined oral contraceptives — At steady-state, tadalafil (40 mg once
per day) increased ethinylestradiol exposure (AUC) by 26% and Cmax by 70% relative
to oral contraceptive administered with placebo. There was no significant effect
of tadalafil on levonorgestrel.
Antacids — Simultaneous administration of an antacid (magnesium hydroxide/aluminum
hydroxide) and tadalafil (10 mg) reduced the apparent rate of absorption of
tadalafil without altering exposure (AUC) to tadalafil.
H2 antagonists (e.g., nizatidine) — An increase in
gastric pH resulting from administration of nizatidine had no significant effect
on tadalafil (10 mg) pharmacokinetics.
Animal Toxicology and/or Pharmacology
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 1– to 17–fold the human exposure (AUCs) at the MRHD of 40 mg. In dogs, an increased incidence of disseminated arteritis was observed in 1– and 6-month studies at unbound tadalafil exposure of 0.5– to 38–fold the human exposure (AUC) at the MRHD of 40 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 4– to 10–fold the human exposure at the MRHD of 40 mg. The abnormal blood–cell findings were reversible within 2 weeks upon removal of the drug.
Reproductive Toxicology Studies
Reproduction studies have been performed in rats and mice at exposures up to 17 times the MRHD of 40 mg and have revealed no evidence of impaired fertility or harm to the fetus because of tadalafil. In addition, there was no evidence of teratogenicity, embryotoxicity, or fetotoxicity when tadalafil was given to pregnant rats or mice at exposures up to 7 times the MRHD during the period of major organ development.
In a rat prenatal and postnatal development study at doses of 60, 200, and 1000 mg/kg, a reduction in postnatal survival of pups was observed. The no-observed-effect-level (NOEL) for maternal toxicity was 200 mg/kg/day and for developmental toxicity was 30 mg/kg/day. This gives approximately 8- and 5-fold exposure multiples, respectively, of the human AUC for the MRHD of 40 mg. Tadalafil and/or its metabolites cross the placenta, resulting in fetal exposure in rats.
Tadalafil and/or its metabolites were secreted into the milk in lactating rats at concentrations approximately 2.4–fold greater than found in the plasma.
Clinical Studies
ADCIRCA for Pulmonary Arterial Hypertension
A randomized, double-blind, 16 week placebo-controlled study was conducted in 405 patients with pulmonary arterial hypertension, defined as a resting mean pulmonary artery pressure (mPAP) ≥ 25 mmHg, pulmonary capillary wedge pressure (PCWP) ≤ 15 mmHg, and pulmonary vascular resistance (PVR) ≥ 3 Wood units via right heart catheterization. Allowed background therapy included bosentan (maintenance dosing up to 125 mg twice daily) and chronic anticoagulation. The use of prostacyclin or analogue, L-arginine, phosphodiesterase inhibitor, or other chronic PAH medications were not permitted.
Subjects were randomly assigned to 1 of 5 treatment groups (tadalafil 2.5, 10, 20, 40 mg, or placebo) in a 1:1:1:1:1 ratio. Subjects had to be at least 12 years of age and had a diagnosis of PAH that was idiopathic, related to collagen vascular disease, anorexigen use, human immunodeficiency virus (HIV) infection, associated with an atrial-septal defect, or associated with surgical repair of a congenital systemic-to-pulmonary shunt of least 1 year in duration (for example, ventricular septal defect, patent ductus arteriosus). Patients with a history of left-sided heart disease, severe renal insufficiency, or pulmonary hypertension related to conditions other than specified in the inclusion criteria were not eligible for enrollment.
The mean age of all subjects was 54 years (range 14 - 90 years) with the majority of subjects being Caucasian (81%) and female (78%). PAH etiologies were predominantly idiopathic PAH (61%) and related to collagen vascular disease (24%). More than half (53%) of the subjects in the study were receiving concomitant bosentan therapy. The majority of subjects had a World Health Organization (WHO) Functional Class III (65%) or II (32%). The mean baseline 6-minute walk distance (6-MWD) was 343 meters. Of the 405 subjects, 341 completed the study.
The primary efficacy endpoint was the change from baseline at week 16 in 6-MWD (see Figure 2). In the ADCIRCA 40 mg treatment group, the placebo-adjusted mean change increase in 6-MWD was 33 meters (95% C.I. 15-50 meters; p=0.0004). The improvement in 6-MWD was apparent at 8 weeks of treatment and then maintained at week 12 and week 16.
Figure 2: 6-Minute Walk Distance (meters) Mean Change from
Baseline, with 95% Confidence Intervals
Placebo-adjusted changes in 6-MWD at 16 weeks were evaluated in subgroups (see
Figure 3). In patients taking only ADCIRCA 40 mg (i.e., without concomitant
bosentan), the placebo-adjusted mean change in 6-MWD was 44 meters. In patients
taking ADCIRCA 40 mg and concomitant bosentan therapy, the placebo adjusted
mean change in 6-MWD was 23 meters.
Figure 3: Placebo-adjusted Mean Change in 6-Minute Walk Distance
(meters) of ADCIRCA 40 mg, with 95% Confidence Intervals
There was less clinical worsening (defined as death, lung transplantation, atrial septostomy, hospitalization because of worsening PAH, initiation of new PAH therapy [prostacyclin or analog, endothelin receptor antagonist, PDE5 inhibitor], or worsening WHO functional class) in the ADCIRCA 40 mg group compared to the placebo group and the groups that used lower doses of ADCIRCA.
Table 2: Number (percent) with Clinical Worseninga
| |
|
ADCIRCA |
Placebo
N=82 |
2.5 mg
N=82 |
10 mg
N=80 |
20 mg
N=82 |
40 mg
N=79 |
| Total with clinical worsening |
13 (16) |
10 (12) |
7 (9) |
8 (10) |
4 (5) |
| Death |
1 |
0 |
1 |
0 |
0 |
| Hospitalization for worsening PAH |
2 |
2 |
3 |
0 |
1 |
| New PAH therapy |
0 |
1 |
0 |
2 |
1 |
| Worsening WHO class |
11 |
10 |
6 |
6 |
3 |
| a Subjects may be counted in more
than one category |
The Kaplan-Meier plot of times to clinical worsening is shown below in Figure 4.
Figure 4: Kaplan-Meier Plot of Time to Clinical Worsening
Long-Term Treatment of Pulmonary Arterial Hypertension
Patients (N=357) from the placebo-controlled study entered a long-term extension study. Of these, 311 patients have been treated with tadalafil for at least 6 months and 182 for 1 year (median exposure 356 days; range 2 days to 415 days). The survival rate in the extension study was 96.5 per 100 patient years. Without a control group, these data must be interpreted cautiously.
Last updated on RxList: 6/15/2009