Defendex is safe for most pets to use. However, only use a little bit because it is very concentrated. This is how we approach Demodectic mange.
Demodectic mange is an opportunistic infection because the immune system is weak. I would bathe with Defendex shampoo once or twice weekly for 4-6 weeks or a couple of weeks past having a negative skin scraping. I would also use Derma-IonX orally to help heal and soothe the skin as well as rebuilding the immune system. Giving digestive enzymes, probiotics, MSM, vitamin C, and fish oil will all help in that goal. Derma-IonX also helps the body to better utilize the supplements for faster results. It can also be sprayed onto the skin to give relief in between baths. I would also suggest that you give water that is free of chlorine or fluoride for drinking or bathing. Feeding a grain-free diet for a while could be beneficial as well.
Please let us know how you progress or if you have any other questions.