The inside of the outer ear flap (not inside the ear canal) is an excellent area for many pets. Drugs have been formulated to cross the skin barrier and you can potentially be exposed if you come in contact with them. Wear gloves to avoid being exposed to the drug.
Be sure the ear where you are going to apply the medication is clean and dry.
Most trans-dermal medications will come in per-dose syringes.
Be sure you gently rub the gel into the skin as you don't want a glob or a clump because it will easily dislodge if the pet shakes the head after administering. Don't let your pet rub or scratch that ear for a few minutes. You have to ask your vet if the medication he/she puts your pet on comes in trans-dermal medication. This method is good when you can't give your pet oral medication. The risk is that it could be insufficiently absorbed causing low drug levels and treatment. Your vet and pharmacist will ensure that your pet receives the proper amount of medication.
Now is a good time to feed the pet or go for a walk because the pet needs a distraction.
Here is a video to show how to do it.
Professional Pet Sitting Services offered in the Upper to Mid-Pinellas County Area