Hopefully i can clear up some of the confusion around here. Escitalopram or lexapro is a very clean drug thats action is mostly serotonergic, unlike some other ssris like zoloft/sertraline which has dopamine reuptake inhibition also, or prozac which resembles an snri (norepinephrinergic activity) like pristiq/esvenalfaxine that grey owl is taking.
So, if the question was about ssri's you would have to look at each individual one as the mileage does vary, however, in this case lexapro is the truest selective sri. So how could this interact with kava, well kava has little serotonergic effects, mostly downstream, meaning via the changes in other catecholamines. Kavain is an NRI (like some classical TCA's, think amitryptilline) which would have sedative effects, concentration and focus effects along with some anxiolysis. Also, kava's various lactones have MAO-B inhibition, unlike MAO-A, this means it's mostly dopaminergic (think selegiline). In fact it has been shown to raise dopamine levels in the nucleus accumbens, a area of the brain related to reward and addiction ( in the mesocorticolimbic pathway). Kava's main actions seem to be via calcium channel blockade and sodium blockade to a lesser extent. This has effects on all catecholamines and glutamate (the brains major excititory neurotransmitter). Also, there seems to be no direct gabaergic effects (gaba is the brains major inhibitory nt) but kava inhibits gaba transaminase to some degree, an enzyme which degrades gaba ( similar to the anti-convulsant and mood stabilizer valproic acid). This inhibition would increase gaba levels and thus reduce anxiety, cause sedation, myorelaxation etc.
so with all that being said and the pharmacology of lexapro taken into account, i would say there will be no significant interaction, and any interaction that is suggested is erring on the side of caution, in medicine we combine several serotonergics often, and more so happening at the liver level, ie increasing or decreasing the clearance of the drug. I would suggest taking them at seperate times and for circadian rhythm purposes take lexapro in the morning, but in terms of serotonin syndrome that would be hard to induce with kava's relative lack of 5-HT activity.
hopefully that helps. oh ya this isn't medical advice. sorry for the poor grammar I was in a hurry but wanted to lend a hand.
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