Sildenafil treats erectile dysfunction by increasing blood flow to the penis during sexual stimulation. Sildenafil belongs to a group of medicines called phosphodiesterase 5 PDE5 inhibitors. You could also ask your pharmacist for advice on other ways to help you remember to take your medicine. It comes as standard tablets, chewable tablets, and as a liquid that you swallow. However, the dose is usually not more than 80 mg 3 times a day. Sildenafil comes as a tablet and suspension liquid to take by mouth.swelling in your hands, ankles, or feet; shortness of breath; seizure (convulsions); or. a light-headed feeling, like you might pass out. Common Viagra side effects may include: flushing (warmth, redness, or tingly feeling); headache, dizziness; abnormal vision (blurred vision, changes in color vision) runny or stuffy nose, nosebleeds;.  · For oral dosage form (tablets): Adults up to 65 years of age—50 milligrams (mg) as a single dose no more than once a day, 1 hour before sexual intercourse. . 1 day ago · Both Viagra and sildenafil are available in mg, mg, and mg doses. REX MD currently has a out of 5-star rating on Trustpilot as of November About 84% of the over 3, reviews.