My friend is not affected at all by most drugs

my friend has taken a variety of drugs including alcahol, cocaine, ecstacy and ketamine but none of them have affected him at all. he has particularly had large amounts of alcahol at once but hasnt even started to shift from being sober and remains the same all night. he has once even dropped 3 200mg pills which showed no effect at all on him. he literally doesent feel any effect from drugs even in large doses. hes a large lad tall and built, maybe this is something to do with it but hes tried a variety of different drugs from different people and to this day has never felt any come up at all. i have also taken the same drugs at the same time and have been affected even when ive taken smaller doses so its not because the drugs are fake. any explanation??