United Therapeutics Corp., of Silver Springs, Md., reported revenue of $389 million in the first quarter. Sales of top-selling pulmonary arterial hypertension (PAH) drug Remodulin (treprostinil injected) were $126.8 million while fellow PAH drugs, Tyvaso (treprostinil inhaled) and Adcirca (tadalafil), registered sales of $94.6 million and $97.6 million, respectively.