Is my erectile dysfunction most likely temporary or chronic? Your health information should remain between your provider and yourself. Involve your sexual partner. Tadalafil Cialis. What you can do Take these steps to prepare for your appointment: Ask what you need to do ahead of time. An erection results from an increase in blood flow to the penis. These products are especially dangerous for anyone who takes nitrates.Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or alcohol. Its . The best way to take Viagra is either 1 hour before sex on an empty stomach or 2 hours after a meal to avoid a delay in effectiveness. Viagra works at its best within a few hours after it’s taken. In most people, the drug is most effective about 1 hour after it’s taken. Over time, Viagra is slowly removed from the body.