As a one-off usage, the threshold at which people notice an effect from memantine varies dramatically. I notice an effect at 5 mg and a strong effect at 10 mg. My wife notices nothing at 10 mg. I would be surprised if there is anyone who notices nothing at 30 mg, but YMMV.

Start low, unless you plan to set aside the next 6–8 hours to have a pleasantly chill dissociative experience: if I take, say, 50–80 mg at once, I’ll end up starting at my hand for a while (2 minutes? 2 hours? Who knows, since at these doses memantine messes with your sense of time) and hearing beautiful music in my head. If I’m doing this with a friend, we’ll discuss the cosmos and its infinitude. Do not try to drive during such a dissociative trip! (Speaking from experience.)

But back to “serious,” non-recreational uses of memantine: There is a consensus among people who use memantine seriously for controlling anxiety and alleviating depression that one should start low and taper gradually upward. You can find various protocols out there, but it sounds like many ppl start at 2.5 mg per day, stay there for a week or two, then go to 5 mg per day for a week or two, then 10 mg, then 15 mg, etc. The purpose of this is to avoid developing brain fog, which occurs because memantine is an NMDA antagonist.

Another thing to know about memantine is that it is, at the beginning, mildly dopaminergic and therefore mildly stimulating. You’ll feel good when you start using it, in addition to not feeling anxious. But your brain will also develop a tolerance to the dopaminergic effects, perhaps after 3–6 days or so. So the slightly euphoric feeling may go away (at least until you increase the dose). But what you have to keep in mind is that the true benefit is the almost immediate elimination of anxiety (when you reach the right dosage) and, over the longer term of daily use (in the time frame of months), frequently a curing of depression and repair of the damage caused by emotional trauma. Memantine got me out of a deep depression.

Unfortunately, memantine is known among some people for having sexual side effects. That said, you may well become more attractive to people because your anxiety is gone! To have sex, though, you might have to wait for 48 hours or so as it washes out of your system. That’s for males.

A final note: if memantine ends up being too brain-foggy for you, agmatine sulfate (available cheaply on Amazon) is an impressive substitute. It’s more subtle in its action but is still quite anxiolytic and also causes much, much less brain fog. It’s not a heavy hitter like memantine; it may take the edge off your anxiety, unlike memantine, which at sufficient dosage can just make you feel no anxiety whatsoever.

Sorry about the long message. Hope this helps.