My husband has had one (in the back of his neck). He said it wasn't fun by any means, but he was able to drive himself home. It was better than the constant debilitating headaches. He was really tired and slept most of the evening. It worked for him. He doesn't know what caused his headaches that eventually prompted the shot, but it worked.
Wish I had a concrete answer for you, but it depends how you tolerate pain and individual reaction.