Its effects often last for 4 to 5 hours. Oral medicines for ED usually work well and cause few side effects. These include a heart attack, stroke or a serious heart rhythm disorder in the past six months. Common ones include: Flushing of the skin. Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines.Ways to save on Viagra. Below, we discuss four ways you can save on Viagra, whether you have insurance or not. 1. Check your insurance coverage. Insurance companies are . Best subscription service for Viagra and generic Viagra: Rex MD Viagra Although erectile dysfunction (ED) may be an upsetting diagnosis for some, many people find their . Viagra (sildenafil) is a prescription drug that’s used to treat erectile dysfunction (ED). The drug comes as a tablet you’ll take by swallowing. It’s usually taken as needed about 1 hour.