PDE5A and Duchenne muscular dystrophy: To determine whether PDE5 inhibition can alleviate exercise-induced skeletal muscle ischemia in DMD patients, an open-label, crossover trial with tadalafil or sildenafil was initiated in 2012 to assess exercise-induced attenuation of reflex sympathetic vasoconstriction (i.e., functional sympatholysis) in 10 boys with DMD and 10 healthy-matched male controls.