Silagra 100 mg contains Sildenafil citrate, which is a phosphodiesterase type 5 (PDE5) inhibitor. It works by increasing blood flow to the penis during sexual stimulation, helping men achieve and maintain erections.Common side effects of Silagra 100 mg may include headache, flushing, indigestion, nasal congestion, dizziness, and visual disturbances. These side effects are usually mild and temporary.