Kanna extract is easy to eyeball, it has an absolutely huge dosage window. On my bottle with unknown strength they recommend 15-25mg but I didn't feel much (as expected from a SSRI though, when dosed acutely they lead to an increase in serotonin concentration but also immediate tachyphylaxis from autoreceptors being hit - imo the description of it being MDMA-like and hallucinogen is pure marketing but also I have a hefty serotonin tolerance acquired from prolonged antidepressant use) ... so I re-dosed. Again. And again.
There are no adverse effects to speak of and if you find the spot it's subtle but nice. A relaxing stimulation, slight anxiolysis and a light boost in confidence. Internet says the half life is 4-6 hours but it feels like an almost instant peak and fades off after some 15-45mins. Can lead to compulsive redose in higher doses, have yet to check out if there's a comedown - I notice slight increase in anxiety and tension after that time but I have generalized anxiety as well as I'm on venlafaxine - which isn't recommended to mix but this one here is mild.
Oh, kanna is good to overcome SSRI withdrawal, did this before and it worked but remember too that I was redosing often and plenty, went through a gram in a few days.