It still works for me, but I am not a regular user. Kratom has several alkaloids other than Mitragynine that influence the effect, but it is difficult to say in what way. Also, fermentation of the leaves may transform some Mitragynine into 7-Hydroxymitragynine, which also changes the effects. Regarding extracts, my experience is that the "full spectrum" extracts are more "straight to zzz" than the extracts that contain mostly Mitragynine and less of the other alkaloids (sometimes called "Mit