If you prefer, you may contact the U. The ability to develop and maintain an erection is largely governed by sexual arousal, a complex process that involves the brain, hormones, emotions, nerves, muscles, and blood vessels. It might work longer if you have mild to moderate erectile dysfunction. Sildenafil Viagra. Its effects often last for 4 to 5 hours.The original little blue pill prescribed by doctors for over 20 years. Clinically proven to treat men with erectile dysfunction (ED) Ongoing commitment to product quality and safety . Viagra comes as an oral tablet in different dosages. Discuss with your doctor what’s an appropriate dose for you. For daily use, Goldstein said, the generic form, sildenafil, . The recommended dosage of Viagra for erectile dysfunction (ED) is 50 mg, taken as needed about 1 hour before sexual activity. You can take it 30 minutes to 4 hours before .