PDE5A and Duchenne muscular dystrophy: Furthermore, phosphodiesterase 5 (PDE5) inhibitors, such as sildenafil and tadalafil, have also been tested clinically for the treatment of DMD, since it is hypothesized that these drugs may increase vascular perfusion in the skeletal muscle when motor demand increases, thereby preventing exercise-induced muscle ischemia, injury, and fatigue (Sander et al., 2000; Kobayashi et al., 2008; Kobayashi et al., 2012).