A dry powder inhalation treatment for pulmonary arterial hypertension includes a dose of dry particles comprising greater than 25 micrograms of treprostinil enclosed in a capsule. The dry particles can include treprostinil, a wetting agent, a hydrophobicity modifying agent, a pH modifying agent and a buffer. A method of treating a patient having pulmonary arterial hypertension includes providing a patient a dry powder inhaler, providing the patient at least one capsule for use in the dry powder inhaler, the capsule including at least 25 micrograms of treprostinil.