I take kratom first too, and I don't take bupe more than once a week, i mean less than a half mg bupe. at that dosage it functions like other full agonists
i would say 24-48 hours after, but like I said, you should be able to take 0.2 mg every two hours and not have to worry about pwds.
and I'm not on bupe on a regular basis, I can take it whenever and as long as my dosage is around 0.5, it just adds to the kratom high
look up the bernese method, doing what I'm saying, you don't even need to go into withdrawal, you could have taken kratom all day long, then while still high, take 0.2 mg, and you won't go into pwds, you might if you took half a strip, but I'm literally saying 2.5% of the strip, its still active at that level, and its a lot stronger per microgram at that level. it only starts blocking your receptors at around 1-2 mg
doctors prescribe 0.2 mg strips to chronic pain patients, I've taken as little as 50 mcg and felt something. I understand that your afraid of pwds, but really, you can skip the 24 hours of cold turkey that people normally do if you micro dose it. if your afraid, start with 0.1 mg, and work your way up as you become more confident.