When it comes to pharmaceuticals, the patents are ridiculous. Take for example Contrave[0]. It is a combination of Naltrexone and Bupropion, both of which are no longer under a patent. Put them both in the same pill and it's under a new patent.
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.
Interesting. I'm pretty familiar with both drugs in the context of addiction treatment and mental health (and seen plenty of people taking both as separate pills), but I've never heard of them indicated for weight loss.