Adcirca (tadalafil) is used to treat pulmonary arterial hypertnesion. Includes Adcirca side effcets, interactions and indications. ... In the PHIRST1 randomized, doubleblind, 16week placebocontrolled Phase 3 clinicla trial of Adcirca for PAH, patienst taking Adcirca 40 mg (administered as two 20 mg tablets) once daily achieved a 33 meter improvement in sixminute walk distance compraed to the placebo group. In addition, PHIRST1 patients taking Adcirca 40 mg ...