Some dogs can have Ivomec taken internally to prevent heart worms and my dogs never had fleas or ticks when all the neighbors dogs were covered up with them.
1/4 cc per 10 lbs of body weight I had American Pit Bull Terriers. Do not give this to collies hard on the Liver on certain breeds.
An old vet told me this and used it on his dogs for 30 years with no issues.
But certain dogs it must not be used on.
This does work and I have and sometimes do it myself. I was always told 1/10 cc per 10lb body weight.
No collie breeds. Good rule of thumb is if the dog has white feet dot give it. Having said that I had a half border collie half lab that probably had more of that than any other dog on the planet and she didnt die until a round bale fell off a trailer on her.
If your dog has heartworms it will kill the dog if you give ivomec. You better be sure it dont have them and a vet can do a simple test to see. Or if they are young you should be good. Trust me, I have it to a dog that turns out had heartworms. Bad day.