My Thor had ear mites last year.  I too got the drops, but it did not seem
to help.  I suspect this was because it was such a pain in the butt to
administer and I got more on the floor than in the guys ears (no one to
help me).  We then proceed on a course of Ivermec injectable (trade name
Ivormectin), which I presume is what you mean by shots.  In a nutshell we
had great success.  I also did a bit of research on this and got the
impression that this is quite a common form of treatment for ear mites.
 
Hope that helps.  And yes it is the same stuff they give to sheep and
cattle!
 
-David, Thor, Grover, Lady Penelope and foster Snuff.
[Posted in FML issue 2970]