Ivermectin

Question
I am a foster for a cat rescue.  I just picked up two persian cats from a high-kill shelter.  My veterinarian comes to my home and she examined the two cats.  The cats ears appeared to be heavily infested with ear mites so the veterinarian swabbed their ears.  It was apparent from the swabs that the ears were also badly infected.  Since I already had Tresiderm, my veterinarian told me to apply it twice a day for two weeks.  When I got home later in the day, there was a message on my voicemail from the  veterinarian stating she had run the samples and the cats did indeed have ear mites.  She advised me to use Ivermectin and had left two packages of Ivermectin in her mailbox for me to pickup before leaving for a week-long veterinary conference.  By then I had already applied the first dose of Tresiderm.  My question is, how long do I have to wait to apply the Ivermectin and will that be a problem since the cats' ears are also heavily infected?  Also, do I continue with the Tresiderm after applying the Ivermectin?   

Thanks for your help.

Irene

Answer
I do not use Ivermectin in the ears.  I use it as an injection because the mites live all ver the skin , not just in the ears.  I suppose you can use it topically after the ears are cleaned.  Tresaderm does not really kill ear mites, but it stops the itching.