Recent heart or blood vessel problems. Many people have no side effects or only mild ones. They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. As with sildenafil, a high-fat meal or alcohol keep the body from absorbing it as quickly. Vardenafil usually works for 4 to 5 hours.About sildenafil (Viagra) Sildenafil is a medicine used to treat erection problems (erectile dysfunction). Sildenafil is also sometimes used to treat pulmonary hypertension (high . How does Viagra work? Viagra is used to treat erectile dysfunction (ED). It decreases ED symptoms by helping you get and keep an erection. What does Viagra do for ED? Viagra works to treat ED by helping you have and maintain an erection. The drug does this by improving blood flow into your penis when .