Erectile dysfunction medications require a prescription from a licensed provider. Contact your medical provider if you experience any side effects during treatment. Medicines that block an enzyme called CYP3A4. This medication is taken with or without food an hour before sex. Generic versions of sildenafil, vardenafil and tadalafil are available. Follow-up support: Make sure you can get the help you need if questions or concerns arise after ordering. Payment options: Consider how you’d like to pay.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. Generic Viagra (sildenafil) is an alternative to the branded Viagra drug that can be used for treating erectile dysfunction (ED). It’s now sold by many manufacturers, including online. Generic sildenafil is covered by most Medicare and insurance plans, but some pharmacy coupons or cash prices may be lower. Get sildenafil for as low as $, which is 95% off the average retail price of $ for the most common version, by .