It is VERY difficult to get a manic person down off the moon......in fact, you can't do it yourself, and of course the manic person has no insight at all into his/her condition so it's like talking to a brick wall. (Or so my family says.)

I think the welfare check is OK but unless your friend is creating a public disturbance or acting out in ways that are dangerous to him and/or others, there's not much the authorities can (or will) do for him. Eventually, he will come down and that's when he'll need you the most, because mania louses up people's lives like nothing else and they are usually remorseful to a fault when they realize how destructive their behavior has been.