its not even that, to knowingly give someone a drug knowing that it can harm them when alcohol is mixed and knowing their friend will be drinking. even to slip someone a drug to begin with is wrong. i dont think people should be encouraging this kind of behaviour. but thats just my opinion.
I wouldn't do it at all, you don't know what this person could or could not be allergic to, and there have been reports of complications when men have taken it. Do you wanna ruin your freinds trip?