This allows the smooth muscles in the penis to relax and fill with blood. When taken at the correct time and paired with sexual stimulation, the erection lasts long enough for successful intercourse. The mechanism of action for ED pills is simple: They inhibit the PDE5 enzyme which regulates the signals responsible for the smooth muscle tissue. However, some states require a live video consultation. If you are a Mayo Clinic patient, this could include protected health information. · a light-headed feeling, like you might pass out. Common sildenafil side effects may include: flushing (warmth, redness, or tingly feeling); headache, dizziness; heartburn, nausea, or upset stomach. abnormal vision (blurred vision, changes in color vision) runny or stuffy nose, nosebleeds; sleep problems (insomnia); or. The discount plan organization is Hippo Network LLC, One World Trade Center, Suite New York, NY , , help@, . 1M+ visitors in the past month.