Yes, ivermectin for treating ear mites is a good thing.  The dose range is
0.2mg/kg up to 0.5mg/kg.  High doses of ivermectin (1mg/kg) are apparently
safe.  This is given as an SC injection that is repeated in 2-3 weeks.
Some bad cases may even require a third dose (after another 2-3 weeks).
 
Yes, it can be diluted with propylene glycol and put directly into the ears
(Acarexx ear drops).  The bad thing about ear drops or ivomec into the ears
is it is hard to get into the ears because of the small size of the ear
canal.
 
Yes, you can even give it orally, but it does taste bad.  Thus the
injection is usually the best way to go.
 
The heartworm preventive dose of ivermectin is lower.  It is only
0.006mg/kg once a month.  This is usually given orally.
 
Hope that clears up the confusion,
Jerry Murray, DVM
[Posted in FML issue 3423]