Pfizer, the manufacturer of Viagra, has a patient assistance program you may qualify for. This medicine also works best when you take it an hour before sex on an empty stomach. Common ones include: Flushing of the skin. It works for up to 36 hours. It depends on the platform and insurance provider. As with sildenafil, a high-fat meal or alcohol keep the body from absorbing it as quickly.Oral medicines for ED usually work well and cause few side effects. The . Medications Prescribed: Viagra, Cialis, Cialis Daily, Levitra, tadalafil, .