Why don't you discuss this with your veterinarian, instead of asking a bunch of nameless, faceless folks who don't necessarily know their backsides from a geyser, with regard to parasitology and veterinary medicine?

I DO know my backside from a geyser, even with regard to parasitology, and I would STILL suggest to the OP that she consult with her vet. Hopefully in a much more respectful and caring manner.

Killing off adult heartworms can kill the dog. If she has active microfilaria, this is not the time to start trying to self-medicate.

It also matters WHICH preventative she has been on, as well as her physical condition, age, level of activity, etc.

There is no such thing as Ivermec. There is ivermectin which comes in a 1% and a 0.27% strength (for swine) - also a 0.08% solution for sheep - and there is Ivomec, which is a brand name. Specifically Ivomec PLUS is absolutely the wrong thing to even think of giving. Ivomec PLUS could kill your dog, or at least make him/her very sick.

Any ivermectin product that has any active ingredient in it other than just plain ivermectin should not be administered to a dog.

Consult with your vet on treatment of active heartworm. While mixing up your own preventative from pure ivermectin products intended for livestock can be safe and effective, you cannot safely treat active heartworm infection on your own this way.

And only go the mix-it-yourself route if you are willing and able to understand the math involved. Otherwise, stick to the 0.27% swine Ivermectin and dose accordingly only for dogs over 20 lbs. That is:

1/10th cc for a dog from 20 to 100 lbs
2/10th cc for a dog from 101 to 200 lbs.

Or follow this guy's recommendations for using 0.08% ivermectin sheep dip - it seems close enough.

In any case this is NOT to be used with collies or other herding dogs with the genetic disposition to be killed by Ivermectin. Border collies are particularly susceptible, but other collies and herding dogs can have the sensitivity as well.

Otherwise - back to the vet for you for that as well.

This post was edited by zensojourner on Wed, Dec 17, 14 at 17:11