Credelio (lotilaner) for Cats

I am using this product for a couple of feral cats within my colony that cannot be handled (re: to do topical flea applications). I am so very glad that a monthly oral is even available now. I used at the dosage stated on the box (1 pill indicated for a large weight range). However, both cats experienced side affects - 1 hid/was unusually quiet for the day, the other threw up and obviously felt poorly for 36-48 hrs. The product has allowed me to get on top of a flea infestation, and the completely scabbed up neck on the latter cat is now much improved and he no longer scratches incessantly. It's time for the second dose. This time I will calculate the dose needed for efficacy based on estimated weight, and will give partial pills, then I will watch them both closely.