I used injectable ivermec for years, two problems, my supplier quit carring it, and It doesn't kill tape worms.
I switched to "zimecterin gold" Horse wormer.
1.5% ivermectin,7.75% praziquantel. I give a 100# dose to any and every dog on the place.(regardless of size).
One time had a bad deal, and gave a dog a 500# dose, she had no ill effects, never even went off feed. That was about 3 months ago. Maybe there will be a long term effect, but nothing yet.
A good point was made, about number of dogs.
The more dogs you have, the more it cost to take care of them.If you have one dog, you can afford to get the same stuff in a "pill", for around 20$a dose,from a vet.
When you are worming 20+ dogs, you want same protection, but at a reduced cost.I am paying 1.10$ per dose
Thats why most of us use "alternate" wormers. Duane