Other warning signs of an unsafe online pharmacy include outdated medication, no customer service, or suspiciously low prices. Oral medicine for ED also might not be safe or work well if you have: Very low blood pressure, called hypotension, or uncontrolled high blood pressure, called hypertension. Oral medicines for ED usually work well and cause few side effects. This allows the smooth muscles in the penis to relax and fill with blood. However, others work on a cash-pay basis and don’t partner with insurance companies. How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup. Your primary care doctor should always know what medications you’re taking, including ED pills prescribed by another provider.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 . By Ginger Skinner Last updated: June 14, If you’re looking for a less costly Viagra, you might want to ask your doctor about sildenafil. It’s the active . Cost Overdose Ask your doctor Q&A Drug Images What is Viagra? If you have erectile dysfunction (ED), your doctor may recommend that you take Viagra. It’s a .