Dosages and methods for treating pulmonary arterial hypertension with rodatristat

There is a daily dosage for treating pulmonary arterial hypertension (PAH) of two discrete dosage forms each having up to 600 mg of rodatristat ethyl or up to 1200 mg of rodatristat ethyl once per day. There are methods for treating PAH in human patients in need thereof via administration of the dosage forms. There is also a method for treating PAH via daily administration of an amount of a first compound of rodatristat ethyl and an amount of a second compound selected from among ambrisentan, sildenafil, tadalafil, bosentan, treprostinil, selexipag, macitentan, and a combination of two or more thereof. The combination results in an additive or synergistic reduction in symptoms or side effects of PAH compared to the two alone with a low risk for drug-drug interaction, such as with a C