Heart worm treatment

Question
My dog started HW treatment on May 1st.  We are doing the 3 injection plan.  She was adopted from a shelter. Her first week was hard on her as far as not wanting to eat, and drinking a lot of water.
My Question - are the 2 & 3 injections as hard on the dog?  Also, do they contain the same amt. of medicine as the first?

Thank you.

Gail

Answer
If the dog received Immiticide, the first dose is when the majority of the worms are killed right away.  That will cause the dying worms to fill the poulmonary arteries to the lungs. As the worms die, they release many toxins in the blood and that results in the dog not feeling well.  When we come back in 30 days, most of the worms have died off and are gone, so the follow up injections are easier on them.  The same amount of medication is used.