I have epilepsy, i take MDMA, stupidly perhaps, but Id rather we keep this to your mate.... I dont need people preaching to me.
Most important point - Make sure your mate goes to his GP, they WONT care that he took MDMA, they will just want him to get checked out. Your brain is too important not to go the the GP -
One Seizure will NOT cause any long term damage.
He MUST avoid Cocaine, that crashes your Sodium levels, so that could cause a REALLY bad seizure. He should avoid MDMA, until he knows weather he has is epileptic or not.
Stimulants massively lower the seizure threshold, so he might not be epileptic, its just his natural threshold is lower than other peoples, but it doesnt mean he is epileptic.
Just make sure he visits a GP.