Have you used oral Ivomec before for heart worm prevention? Have you talked to your vet about using products they carry for heart worm prevention?
Ok. Thanks for helping to clarify things. IN this situation, your little one most likely either has scabies or demodex. I would really encourage having him seen by your vet to make sure the correct diagnosis is made. The reason for this is that that determines the best course and duration of therapy. Also it determines how we can determine if the situation is cured. The 1% injectable ivermectin has ivermectin in it and it is the same drug used in heart guard, the oral heart worm prevention. So, yes, it has heart worm preventative effects to it.
But, the difficult thing here is safety for that little of a dog. In all reality, this drug can be easily overdosed due to its concentration and the size of your little one.
Here is a link on scabies.
Here is a link on demodex.
Ivermectin is considered off lable as far as its use for both of these in dogs.