A sister who cares,   If he has threatened to stab you or others, or admitted he is thinking of that, you can get him forced into a hospital, because he may fit the criteria of being a danger to himself or others.  Read the book, "I Am Not Sick, I Don't Need Help!" by Dr. Xavier Amador.  Because if your brother wanted to get better, he would be taking his meds.  Only he has the ability to make himself be the best he can be, you can't do it for him or give him anything, only love and trust.  Instead of badgering him to take meds, use "motivational interviewing," as Amador suggests, to get him to see that he'll achieve his goals if he stays in treatment.   It's a tough call, you say when he feels better he stops taking his meds.  But if he has outbursts, you need to get him committed involuntarily.   Best wishes, Chris