Megalis 20 mg is used to improve erectile function in men who have difficulty achieving or maintaining an erection during sexual activity. It does not provide sexual stimulation but helps the body respond to sexual stimulation. The usual starting dose of Megalis is 10 mg, taken approximately 30 minutes to 1 hour before sexual activity. However, Megalis 20 mg is a higher dose and may be prescribed in cases where the lower dose is not as effective. The specific dosage should be determined by a healthcare provider.