Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. This increased blood flow can cause an erection. Sildenafil treats PAH by relaxing the blood vessels in the lungs to allow blood to flow easily. There is no single "fastest cure" for erectile dysfunction (ED), as the most effective treatment depends on the underlying cause and can include prescription medications like sildenafil (Viagra) and tadalafil (Cialis), which can provide quick results, as well as lifestyle changes such as quitting smoking, exercising, and losing weight to improve blood flow.