If you have health insurance, confirm your coverage online or with a customer service representative. Along with other basic personal information such as your birth date and social security number , remember to have your health insurance ID number handy for when you log-in online or speak to a representative on the phone. Its effects often last for 4 to 5 hours. A newer form of the medicine that dissolves on the tongue might work faster than the pill that you swallow. Be prepared as well to submit to a full medical history and answer the following specific questions about why you are interested in taking Viagra: [3] X Trustworthy Source FamilyDoctor. How oral medicines differ Each oral medicine for ED has a slightly different chemical makeup.If you’re looking for a less costly Viagra, you might want to ask your doctor about sildenafil. It’s the active ingredient in both branded Viagra and the drug Revatio, . 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 .