If a family member is constantly a threat to themselves what are someone's options?

I have a friend who lives with a family member who is constantly self destructive. She can't be there 24/7 and when she is gone he takes the oppurtunity to self destruct. He attempts suicide, has some other psychiatric conditions, doesn't take meds consistently, or see therapist, nothing seems to help. What help can she get for him? Can he be institutionalized for a long period of time?