First, was the medicine you purchased from a veterinarian or from over the counter? If it was from over the counter, you might try going to see the vet. I know it's expensive, but the doctor knows best, and can give you a prescription for powerful medication.
Having said that, I do make my own ear mite medication out of olive oil (yes, the kind you can buy at the store) and 100% pure pharmaceutical grade essential oils--tea tree oil and lemon oil. You can find these easily on the web for good prices, and a little goes a LONG way. One ounce of olive oil plus ten drops of tea tree oil and five drops of lemon oil. Shake well before each use. Put a couple of drops in each ear and rub it in. The essential oils are antiviral and antibiotic; the mites also hate the smell of them. The olive oil is soothing to irritated skin. There should be no harmful side effects; however, every person and animal is different, if you notice any negative effects (i.e., swelling, infection, redness, etc.) stop use immediately and talk to your veterinarian.
Best course of action: Go to the vet. If you cannot, or try this remedy first and it doesn't work, go to the vet.