I have noticed that Kratom reduces, and sometimes kills my positive effects from phenibut. Also, the phenibut makes kratom work better the next day, but last a fraction of the amount of time, so I find myself dosing the kratom nearly all day or I feel bad. I am a daily kratom user but actually trying to reduce it to every week or every two weeks.
I have found that 2g every other week is the best way to do phenibut. I did it twice a week for a while and it was getting to where it made me feel the bad the day after.