How does Viagra work?
Viagra was the first FDA-approved medication used to treat erection problems in men. When a man cannot get or maintain an erection for sexual activity, it’s called erectile dysfunction. Viagra works by blocking an enzyme called PDE-5, which boost the amount of nitric oxide in the system. Nitric oxide causes the muscles in the penis to relax, increasing blood flow and facilitating an erection.
Viagra stays in your bloodstream for 4 to 6 hours, making it much easier to achieve an erection for sexual intercourse. http://www.edquestions.com/viagra/how-does-viagra-work/