Ivermectin is a great HW med. I use ‘Agrimectin injectable heart worm for cows’ from the farm co-op. 1cc orally per 100# of dawg once a month on the food. Cheap.I adopted a dog once long ago that had heart worms. GSD that had to go thru the heartworm treatments. She eventually died an old dog but with cancer. Since this dog, my dogs have been heartworm meds once a month. I’m not sure of how safe they are and actually have my doubts about big pharma dog meds. The pills have gone up in price too to where they are not affordable to a lot of folks. There is not any relief in site either according to my vet. The prices are not going down and generics are not available