the bug seems to be only related to ecig and caffeinated chew gum only, I cant seem to repro any problems with other drugs, hopefuly someone will confirm.

this fix might work since it will pass the medications to be handeled by consumed() function directly, but it will bypass all medications iuse_functions in general.
It is important to note that items that dosnt have a use_action should be consumed(if satisfies other conditions), and the ones that have a use_action should pass into the use action code section so it can be invoked.
on that note, items that have a use action(in this case the ecig and caffeinated gum) but dosnt achieve its purpose suggests that it has a problem related to its iuse function, therefore iuse::ecig() and iuse::chew() in iuse.cpp for this case.

Well it should work on any drug with a use action and effects outside the use action. For example cocaine gives you a high as part of the use action, but as part of the comestible it gives you stimulants. In my tests anyway, I found using coke did not give stimulants but consuming coke did.

Also as part of player::consume_med, it will invoke the item's use function if it has a use:

if( target.type->has_use() ) {
    amount_used = target.type->invoke( *this, target, pos() );
    ...