ecstasy - never (but have a bad story on an old friend from highschool who did it too much and seizures hit him hard).
lsd - a few times in my teens. looking back i shudder, coming down off acid was the WORST feeling i've ever had, worse than a grand mal. so i tried a 'lighter' version of hallucinogenics at christmas, shrooms. would take that experience back too. fun at first, you could take over the world, and then...)

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coke - unfortunately yes (tho there was a lot of great times). my first grand mal was two days after a big coke and drinking night with my best friend. turned out it wasn't a true part of my epilepsy (mine was due to a lesion), but it sure as hell didn't help. silver lining was that i was at home in bed when it happened.
marijuana - i became a regular smoker (and loved hash) at 16, very into it. even grew it. then in my mid-20's, roughly within a year of grand mals starting, one hoot would turn into a simple partial. over the years i've given it a break, then tried again 'just to see.' seizure every time. i understand that weed helps some with seizures, but it can also be a
bad trigger.
in addition to all that, the withdrawal. hard enough for someone w/o epilepsy, and a million times harder/riskier for one with. deciding to hit heavy drugs is, imo, about the same wrong decision as dropping ur meds.
i am a designer too (graphic/publishing), and tho i don't touch drugs anymore, i wouldn't try and work even if i did. you may do your best work one night, then be found dead in the morning. we all love you (and understand you more than your other, younger friends), and it sounds unanimous - please don't do it.