Comparative PK PD Study in PAH Patients (Fox vs. I-Neb)

Inclusion Criteria: * Male or female aged ≥ 18 years * Current diagnosis of pulmonary hypertension (updated Dana Point Classification 1). * Current inhalative therapy with 5 µg iloprost using the I-Neb nebulizer * WHO functional class III at the time of the patient's commencement of inhalative therapy with iloprost * Hemodynamic diagnosis of Pulmonary arterial hypertension(PAH) showing mean pulmonary arterial pressure (mPAP) \> 25 mmHg, pulmonary capillary wedge pressure (PCWP) or left ventricular end diastolic pressure (LVEDP) \< 15 mmHg and pulmonary vascular resistance (PVR) \> 320 dyn•s•cm-5 * If non-specific types of chronic treatment for PAH are being administered: Stable dosage of these for at least the 4 weeks up to screening * If PAH-specific drug treatments (such as endothelin receptor antagonist (ERA) or phosphodiesterase-5 (PDE5) inhibitors) are being administered: Stable dosage of these for at least the 3 months up to screening. Exclusion Criteria: * PAH related to any other etiology, especially to pulmonary veno-occlusive disease (PVOD) * Clinically relevant obstructive lung disease * Evidence of thromboembolic disease (probable pulmonary embolism) within 3 years before screening * Cerebrovascular events within 3 months before screening * Atrial septostomy within the 6 months before screening * Severe arrhythmia, or severe coronary heart disease or unstable angina, or myocardial infarction within 6 months before screening, or congenital or acquired valvular defects with clinically relevant myocardial function disorders unrelated to PAH * Systolic blood pressure \< 85 mm Hg, or uncontrolled systemic hypertension (systolic BP \> 160 mmHg or diastolic BP \> 100 mmHg) * Hepatic impairment (Child Pugh B, C) or chronic renal insufficiency (creatinine \> 2.5 mg/dl) and /or requirement of dialysis * Clinically relevant bleedings disorders or conditions with increased risk for hemorrhages (active ulcers, trauma etc.) * Addition or dose change of PAH specific drug treatments such as ERA or PDE5 inhibitors within 3 months before screening, or addition or dose change of non-specific treatments for PAH such as calcium channel blockers, nitrates, digitalis, diuretics within 4 weeks before Screening, or any kind of prostanoid other than those mentioned in inclusion criteria within less than 5 half-lives before treatment