It's really difficult to get someone to go to the doctor when they don't want to. When I was a teen I lived through a similar situation with my dad. He became impossible to live with and it turned out he had uncontrolled diabetes. His blood sugar was so high it would normally put someone into a coma but it turned him into an enraged person who had an alternative reality to Mum and me.
I would try to find a time when he's doing better with his moods and calmly explain that you are worried about his health. Try not to get into the giving of examples of his behaviour being wrong or who is at fault. He's only likely to get into an argument with you and blame you. It is okay to say that you thought the previous tablets were having some benefits to him and that he might benefit from another sort that doesn't have the bad side effects that these ones do.
Focusing on the positives might be easier for him to take and hopefully he'll be interested in making the family dynamic better.
Talking about it with my dad when he was medicated and stable again, he couldn't honestly see that what he was doing was unreasonable at the time. For example he would get enraged with a minute when someone said "good morning" to him. He'd almost wind himself up and say things like "Why is a good morning, it's not", "Why would say something to me that's not true" etc. In his head we were out to get him or always moaning about things. The more he thought we were trying to force him to see the doctor, the more he was determined not to! He nearly attacked the doctor in hospital,for standing too close to him. Ordinarily he isn't a violent person so it was out of character but felt justified to him. Everyone was in a conspiracy against him, in his head. Once stable he could realise that he wasn't processing the world properly.
Also be aware that it's very damaging to you and the kids mental health living like that, so it might not be possible for you to accept that you have to get used to living with him as he is. It's also possible for his mental state to deteriorate. Blaming people around him, can also be the first step in justification for violence to start.
There are other options he might like to explore other than the doctor, like mental health charities.
Could you get a trusted close friend or family member to encourage him to seek professional help?