Viagra, the brand name for Sildenafil, is a drug used to treat male sexual function problems (impotence or erectile dysfunction-ED). Out of all the pharmaceutical drugs that have entered the market in the last 30 years, Viagra is the most controversial one. Viagra works by increasing blood flow to the penis by relaxing the walls of the blood vessels to help a man get and sustain an erection. It activates within 20 minutes, and the effects last for about two hours. In Mereja Health kick-off segment, Behailu Tadesse sat down with Dr. Yared Wasihun to discuss the medical uses, mechanism of action and adverse effects of Viagra. Dr. Yared also discussed who should only take Viagra.