Take this erectile dysfunction pill exactly as prescribed. Vidalista 20 mg has specific potential side effects if not used as directed. Do not chew or crush the tablet before swallowing it with a full glass of water. Take it by mouth, whole. Taking a medication pill as directed, even if it means taking it on an empty stomach, is perfectly safe. 30-60 minutes before sexual activity is the ideal time to take a 20mg dose of Vidalista. You will have a hard erection for three to four hours after taking Vidalista 20 mg. Avoid taking two doses of the medicine at the same time.