First line drugs for Functional class II-III PAH : cGMP Signaling Modulators: PDE-5 Inhibitors - Sildenafil, Tadalafil, Vardenafil cGMP Signaling Modulators: sGC Stimulator - Riociguat Endothelin Receptor Antagonists - Bosentan, Ambrisentan First line drugs for Functional class IV PAH: IP Receptor Agonists: Prostacyclin and Prostacyclin Analogs - Epoprostenol, Selexipag . L-type Ca2+ Channel Blockers like Nifedipine, Amlodipine: Use only in PAH patients with positive vasodilator testing.