This project will assess the vascular responsiveness in leg muscles of boys with Duchenne
muscular dystrophy (DMD) to one single dose of tadalafil, a common vasodilator drug, using
non-invasive techniques (MRI or Doppler ultrasound). These findings will provide proof of
concept for a subsequent intervention study to demonstrate efficacy of longer-term tadalafil
to counter sympathetic vasoconstriction and slow disease progression in DMD. It will also
inform whether a group of patients do not respond to the drug.