You experience sudden vision loss. It works thanks to its active ingredient, Sildenafil citrate. A: Viagra 50mg tablet is meant for use only in men. Keep away from children and pets. If it’s time for your next dose, then skip the missed dose and continue with your regular dose schedule.A Comparison of mg Viagra Prices in India. The best way to see the major cost difference between U.S. Viagra and Indian Viagra is to do a side-by-side comparison. . Other Options for the Treatment of Erectile Dysfunction. Unbranded Sildenafil. Sildenafil is the active ingredient that powers Viagra. However, the drug itself is available without the . How Sildenafil works. Sildenafil is a phosphodiesterase-5 (PDE-5) inhibitor. It works by relaxing the blood vessels in your penis, thereby increasing blood flow into the penis on .