I've never used ivermectin for treatment of demodectic mange, but the dosage I gave you came from a vet....I know that if you use too low of a dosage, it will not be effective for the mange. 1/10 mL/11 lb is actually the intestinal worming dosage....the heartworm dose is much less.
You can also use Revolution to treat it, but I suspect that would be more expensive.
http://www.critturs.com/mange7.html
This site quotes the "The Pill Book Guide to Medication for your Dog and Cat"
and says .27 cc/1 lb daily for 90 days....even higher than the dose I was told.
these are the numbers that I have:
Heartworm dose (monthly): .1 cc/ 100 lb
Intestinal worming dose (monthly): .1cc/11 lb.
Mange dose (daily for 3 months): 3 times worming dose, or .3cc/11 lb or 1 cc/35 lb. or 300 mcg/lb
I use the cattle ivermectin for my dogs for heartworm/intestinal parasites monthly at the .1 cc/11 lb dose regularly...have never had issues with it.