You may experience numbness and/or relief from your symptoms for up to six hours after the injection. Your usual symptoms may then return and may possibly be somewhat more intense than usual for a day or two. The beneficial effects of the steroids usually require 2-3 days to take effect, but can take as long as 10-14 days. In some patients, a second or third injection is required to achieve adequate pain relief. If your pain is not improved after a reasonable period of time, your doctor will want to investigate other possible sources for your pain and determine further evaluation and treatments.
Addiction to cortisone was the subject of the 1956 motion picture, Bigger Than Life , produced by and starring James Mason . Though it was a box-office flop upon its initial release,  many modern critics hail it as a masterpiece and brilliant indictment of contemporary attitudes towards mental illness and addiction.  In 1963, Jean-Luc Godard named it one of the ten best American sound films ever made.  John F. Kennedy needed to regularly use corticosteroids such as cortisone as a treatment for Addison's Disease . 
This is a rare complication that may occur if a small hole is made in the fibrous sac and does not close up after the needle puncture. These small holes are only made in less than 1% of epidural injections and usually heal on their own. The spinal fluid inside can leak out, and when severe, the brain loses the cushioning effect of the fluid, which causes a severe headache when you sit or stand. These types of headaches occur typically about 2-3 days after the procedure and are positional - they come on when you sit or stand and go away when you lie down. If you do develop a spinal headache, it is OK to treat yourself. As long as you do not feel ill and have no fever and the headache goes away when you lay down, you may treat yourself with 24 hours of bed rest with bathroom privileges while drinking plenty of fluids. This almost always works. If it does not, contact the radiologist who performed the procedure or your referring physician. A procedure (called an epidural blood patch) can be performed in the hospital that has a very high success rate in treating spinal headaches.