its not even that trigger, what if their friend has allergy to something in the drug, or even an undetected or unmentioned heart condition. i think encouaging this is wrong all together. you want to pull a prank on a friend, fine, just leave drugs out of it. you could end up doing something you regret
Do you want to try to find a quality doctor in Mexico when your friend's heart is beating out of his chest? I doubt it.
One of my mates put a viagra in another mates drink. It didn't really affect him that night. He was just chasing the birds a bit more than usual. Nothing prodding from his pants or anything. When we later confessed it turned out the next day he had a hard on for hours he couldn't get rid of. Some people take bad turns from it though, once the blood starts rushing more than usual, so I'd stay clear. You'd feel like shit if you end up having to take a friend to hospital.
This is a very dangerous prank. If someone slipped me Viagra I would DIE, I take a daily medication that contains nitrates, and this drug combined with Viagra could kill me. PDE5 inhibitors like Viagra can have major effects on your vision as well. DON'T DO IT!!!
It would be fing funny tho. slip him a pill when he is drunk as fuck just before you go to the lobby to find something to do and poor guy would be blasting tent all night long. And don't worry I'm sure you would check out your buddy's allergic reactions before pulling this prank.
There's no way for anyone to know what someone else is allergic to with 100% certainty. The person himself might have an allergy he isn't even aware of. If he's truly a friend I assume you wouldn't want to do anything in the name of fun that could causee himserious medical complications...or worse. Find another practical joke to pullon him. One that doesn't involve any mediations.