I put my daughter's meds in pill containers so it was easy to see at a glance whether or not she had them.
I got her an alarm watch because it was better than me nagging her.
Because she was special needs, when neither my husband nor I could be with her, she had a sitter there. I told the sitter she pretty much didn't need to do much of anything -- just BE there.
And I realize that having proper child care available in the home is easier said than done. In some countries (I believe Australia is one) the caregiver is actually paid if they have to take care of a special needs person at least 4 hours per day. Family cares for the child (adult children included) is the best, and is cheaper in the long run!!
Not so in the United States. I have no idea how a person is supposed to provide the care the special needs children require at home, especially if they have to WORK!!
Anyway, there was a time that I had to tell my daughter that she takes the meds or she goes to the hospital. I even once had to face the possibility of losing her to foster care. I was very clear to her about the possible repercussions of her actions. There was no empty threats. No yelling. Just clear, plain, serious, CALM statement of facts. But first, my husband and I had to be clear about it ourselves. Then we could be clear and calm with our daughter.
We were all very very fortunate because things worked out well.... but we were prepared (well... as prepared as I guess we could be) to accept (at least intellectually -- forget our "hearts") the worst.