I had to get a steroid injection for sciatica recently. I wasn't too happy about it but my doctor felt that it was necessary. Now I'm glad that I had the injection because it has made a huge difference. It took over a week to experience the full effects, but once it kicked in, it worked very quickly. My sciatica pain just disappeared.
As far as I know, sciatica relief from steroid injections can last anywhere from six months to two years. I just hope I won't need an injection again.