A Pharmacokinetics Study for Pediatric Participants With Pulmonary Arterial Hypertension

During Period I, tadalafil will be administered orally, once daily, at a low dose for
approximately 5 weeks followed by a high dose for approximately 5 weeks. Dose levels are
calculated based on body weight cohorts. Heavy weight cohort >=40 kg, middle weight cohort
>=25 kg to <40 kg. Light weight cohort<25 kg. Participants who complete Period 1 may continue
taking tadalafil in Period 2 for at least 2 years. Starting dose will not exceed the maximum
weight range dose established in Period 1 and after the first 3 months of Period 2, the dose
may be adjusted based on available safety and efficacy information.

Inclusion Criteria:

- Currently have a diagnosis of PAH that is either:

- idiopathic (including hereditary), related to collagen vascular disease, related
to anorexigen use, associated with surgical repair, of at least 6 month duration,
of a congenital systemic to pulmonary shunt (for example, atrial septal defect,
ventricular septal defect, patent ductus arteriosus).

- Have a history of the diagnosis of PAH established by a resting mean pulmonary artery
pressure ≥25 mm Hg, pulmonary artery wedge pressure ≤15 mm Hg, and a pulmonary
vascular resistance (PVR) ≥3 Wood units via right heart catheterization. In the event
that a pulmonary artery wedge pressure is unable to be obtained during right heart
catheterization, participants with a left ventricular end diastolic pressure <15 mm
Hg, with normal left heart function, and absence of mitral stenosis on
echocardiography can be eligible for enrollment

- Have a World Health Organization (WHO) functional class value of I, II or III at the
time of enrollment

Exclusion Criteria:

- Have pulmonary hypertension related to conditions other than specified above,
including but not limited to chronic thromboembolic disease, portal pulmonary
hypertension, left-sided heart disease or lung disease and hypoxia

- History of left-sided heart disease, including any of the following:

- clinically significant (pulmonary artery occlusion pressure [PAOP] 15 to 18 mm
Hg) aortic or mitral valve disease (that is, aortic stenosis, aortic
insufficiency, mitral stenosis, moderate or greater mitral regurgitation)

- pericardial constriction

- restrictive or congestive cardiomyopathy

- left ventricular ejection fraction <40% by multigated radionucleotide angiogram
(MUGA), angiography, or echocardiography

- left ventricular shortening fraction <22% by echocardiography

- life-threatening cardiac arrhythmias

- symptomatic coronary artery disease within 5 years of study entry as determined
by the physician

- History of atrial septostomy or Potts Shunt within 3 months before administration of
study drug

- Unrepaired congenital heart disease