For more on diagnosing and treating ED, read What to do About Erectile Dysfunction, a Special Health Report from Harvard Medical School. If you’ve been having difficulty getting or sustaining erections, talk about it with your doctor.This image may not be used by other entities without the express written consent of wikiHow, Inc. If Viagra is not covered, you may want to check to see if similar drugs that help treat erectile dysfunction, like Cialis or Levitra, are covered by your health insurance plan. Your doctor or other health care professional can recommend one for you based on these factors, other health conditions you have and any other medicines you take. It might work longer if you have mild to moderate erectile dysfunction. All rights reserved.Q&A Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a prescription drug that’s used in adult males* with . You can take the drug 30 minutes to 4 hours before you anticipate sexual activity. Based on how well you respond to this dosage and any side effects you have, your . If you’re looking for a less costly Viagra, you might want to ask your doctor about sildenafil. It’s the active ingredient in both branded Viagra and the drug Revatio, which is a lower .Vardenafil usually works for 4 to 5 hours. Sildenafil Viagra. All rights reserved. You’ll want to make sure to inquire about the potential side effects, contraindications or conditions that make Viagra untenable for you, such as a history of heart problems, stroke, liver or kidney disease, etc. An inherited eye disease that affects the retina. These medicines all work well for ED.