Your point of view is shared by several others.
According to http://en.wikipedia.org/wiki/Epidural_steroid_injection, steroids are not FDA approved for epidural administration. That would cause me concern.
However, many people claim to be helped.
Your "15mg morphine" may be just fine for you (your doctor wouldn't give it to you if he didn't concur). However, the problem is that 15mg may become 20mg, 20 becomes 40 etc.
It's all about risk vs reward. If you are 85 years old, who cares if your 15mg becomes 20mg. But, if you are 25 years old, you could become one of those people who say they have to take a handful of pills just to keep withdrawals at bay.
I do want to "throw out a thought" here, for you to consider. You say you are on 15mg morphine. Have you ever considered non-narcotic pills? The reason I ask is that 15mg is a relatively "low" dose, so you are not in excruciating pain. Maybe there are some non-steroidal, non-narcotic meds that may be safe and effective for you?
Generally, the drugs are not unknown, but corticosteroids.
What is your diagnosis, what treatment is being fostered on you, and why?