Megalis 20 mg is a medication used to treat erectile dysfunction (ED) in men. It contains tadalafil, which is a phosphodiesterase type 5 (PDE5) inhibitor. Tadalafil works by increasing blood flow to the penis during sexual stimulation, helping to achieve and maintain an erection. Megalis 20 mg contains 20 milligrams of tadalafil per tablet. This is considered a standard starting dose for most men with ED. However, your healthcare provider may adjust the dosage based on your individual response and tolerability.