So buying them separately and mixing them in your mouth is legal? It's like combining 2 pieces of open-source software and selling them under one product.
Totally legal. You can have your doctor prescribe 50mg Naltrexone and 300mg Bupropion and you can take them at the same time every day. It's the same drugs in the same ratios. Contrave is not novel in any way. There's substantial prior art. And yet a patent was granted to cover this combination and prevent anyone else from taking two generic drugs and combining them into one pill.