Viagra 200 mg is the highest dose that can be used for the treatment of erectile dysfunction (ED). The lower doses of Viagra include Viagra 25 mg, Viagra 50 mg, Viagra 100 mg, and Viagra 150 mg. It is generally used in cases where the lower dosages fail to work properly. Also popularly known as the blue pill, it increases the blood flow to the penis, thereby promoting a hard erection for an extended period. An erection is known to last for a period of 4 to 5 hours when appropriate stimulation is provided along with the medication.