What mg did you take, and are you on any other supplements or medications? It could just be an interaction issue. Everything I've heard/read indicates that magnesium is safe, and that if you take too much at once your body will let you know (I've only heard of people getting tummy troubles, but shakiness/dizziness could be an indicator too I suppose).
Also, for anyone who's interested: I've been on this regimen now (30 mL Amino Fuel, 1 tsp glutamine powder, and 250 mg magnesium in the morning and another right before bed) since November, and I feel 99.99% back to my old self. In fact, the only reason I feel like it's not 100% is because I simply have the memory of the panic attacks--kind of a PTSD thing, I suppose--and occasionally I get little mild twinges of anxiety, which makes me paranoid another episode will happen. But it never does.
I was able to plan my wedding and get married--and the only stress I felt was normal wedding stress. No anxiety attacks, no depression. I actually had FUN planning, and our wedding day was everything I could have possibly imagined and more (last year I was dreading it, thinking for sure I'd be in full-blown panic mode the entire day). I'm now enjoying life with my new husband and our wonderful daughter. I have my life back, and it's even better now because I appreciate every day so much more.
To anyone reading who's debating trying this--if you aren't on any meds (I think you have to be off them at least six weeks), do the regimen. Give it a month--though I felt the difference immediately--and I'm positive you'll see enough improvement to want to stick with it.
I'm also exercising now (p90x3, which is awesome considering I'm a total couch potato) and that's helped a lot as well. I actually feel *better* than before my anxiety even started, before I even took the Abilify that messed me up in the first place.
I'm almost at the six-month mark at which Hanino, the OP, cut down his dosages to every other day (and I believe, eventually, a couple times a week)--I haven't decided yet how or if I'll cut back my own doses, but I'll keep updating as often as I can, for others who come across this thread. It helped me so much and I would be remiss to not pay it forward.
Best of luck to everyone,
Taylor