Sildenafil citrate 100 mg is a common dosage for treating erectile dysfunction (ED). Sildenafil citrate is the active ingredient in several medications, including Viagra and various generic versions. Sildenafil works by increasing blood flow to the penis in response to sexual stimulation, helping achieve and maintain an erection. It is usually taken about 30 to 60 minutes before sexual activity. The effects can last for up to 4-5 hours, but this can vary. Consult with a healthcare provider to determine if sildenafil citrate 100 mg is appropriate for you and to get personalized advice on usage.