Your doctor may adjust your dose if needed. There are many other treatments for erectile dysfunction. You can take this medicine with or without food 30 minutes before sex, depending on the dose. These are commonly prescribed for an enlarged prostate or male pattern baldness. The drug works by stimulating enzymes within the body. Be sure to let your doctor and pharmacist know that you are taking these medications before you start taking sildenafil.Sildenafil comes as a tablet and suspension (liquid) to take by mouth. If you are taking sildenafil to treat erectile dysfunction, follow your doctor’s directions and the guidelines . 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 .