Viagra 100 mg tablet is a medication used to treat erectile dysfunction in men. Erectile dysfunction, which is also called impotence, is a condition in which a man can't get or keep an erection when he's sexually active. This can cause stress, anxiety, and relationship problems. Sildenafil citrate is in the Viagra 50 mg tablet. Sildenafil citrate is a PDE5 (phosphodiesterase type 5) inhibitor. This medicine works by sending more blood to the penis, which makes it easier to get an erection. It is important to note that sexual stimulation is required for Viagra 100 mg tablets to be effective. The medication should be taken approximately 30 minutes to 1 hour before sexual activity and should not be taken more than once per day. While Viagra 150 mg tablet is generally safe and effective, it can cause side effects, so it is important to talk to a healthcare provider to see if this medication is right for you.