For me, they worked wonderfully. The Dr. said that it could take a week before I might have some relief. On more than one occassion, I felt much, much better that day.
Much, much better means that I could actually get up from sitting without worrying about muscle spasms and could get out of bed the next morning (using proper technique of course) without having to slide off the edge of the bed onto my knees then try to stand up and pray that my back muscles didn't spasm...
Oh, and I only needed to have two injections rather than three...
I had the first one a long time ago ('92ish)...the nurse had me sit on the table and lean forward, the numbing shot just about made me pass out...she had to catch me and lay me down on the table. Ironically she was talking to another nurse about having a patient pass out, fall on the floor and break his arm.
After that time (2001), I've always had it done with me lying on my side. The Dr. didn't like it as much, but I told him he had a choice, do it with me laying down or count on having to catch me before I hit the floor...he saw it my way