I would not use an OTC meds for earmites. I used them years back when Mittens was a kitten and all it did was burn the skin on his ears and make the hair fall out on them. In the end I took him to the vet and they gave him an ointment in his ears and he's never had a problem since. It was only $16.00 for the treatment as well, so cost wise it's a good solution.
If you want to go natural I have heard that olive oil and a bit of oil of oregano placed on the ears will work, but I've never tried it so I couldn't say for sure.