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 effects often last for 4 to 5 hours. It might work longer if you have mild to moderate erectile dysfunction. Vardenafil. See more.Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines. Common ones include: Flushing of the skin. You don’t need a health insurance plan to purchase Viagra, but prescriptions are usually cheaper with one. This site is intended only for U. Note that Viagra is only available in three doses: 25 mg, 50 mg, and mg. · Viagra is usually taken only when needed, 30 minutes to 1 hour before sexual activity. You may take it up to 4 hours before sexual activity. Stop taking sildenafil and . CHOOSE BRAND-NAME VIAGRA. The original little blue pill prescribed by doctors for over 20 years. Clinically proven to treat men with erectile dysfunction (ED) Ongoing . 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 effects often last for 4 to 5 hours. It might work longer if you have mild to moderate erectile dysfunction. Vardenafil. See more.Common ones include: Flushing of the skin. Side effects Side effects of oral ED medicines are often mild. Note that Viagra is only available in three doses: 25 mg, 50 mg, and mg. Should you choose to buy health insurance, take your time to shop and compare before making a purchase. Please expect up to 4 to 6 weeks for reimbursement. PPO vs. It might work longer if you have mild to moderate erectile dysfunction.