Viagra 100mg is a medication used to treat erectile dysfunction in men. The active ingredient in Viagra is sildenafil citrate, which works by relaxing the muscles in the blood vessels of the penis, allowing for increased blood flow and thus, an erection. Viagra 100mg is the highest dosage available and is typically prescribed to men who have severe erectile dysfunction. It is important to note that Viagra should only be taken as directed by a healthcare professional and may have potential side effects such as headaches, nausea, and vision changes. It should also not be taken by those with certain medical conditions or those taking certain medications.