What Happens During The Process Of Getting Rid Of Hookworms?

We found my dog a few months ago as a stray and he recently tested positive for hookworms. The vet gave us some medicine to give him and ever since he’s had crazy amounts of diarrhea lately. He has to go out every few hours and we just get a ton of poop.
I expected this for a couple of days since all the worms need to flush out, but it’s been 5 days and still the same. Is this typical? And when we give him his second shot to make sure the larvae that have hatched are killed will we have the same scenario or will it be better the second time around?
It’s been super hot here and he’s not drinking much water so I’m worried he’s dehydrated from all the loss of fluids. He’s been a bit more tired than usual though we did have him playing in the creek all weekend which wore him out. I just want to make sure that his current actions and symptoms are pretty normal… thanks for all the input!