Companies can obtain market exclusivity without a patent. In the US, the FDA assigns 5 years of market exclusivity based on a NDA approval. If it's an orphan disease, it's 7 years. You can also bump up the exclusivity by 6 months if you get approved in a pediatric indication.
That said, there isn't much incentive for a company to do this. Let's say a company spend $200M getting FDA approval for melatonin. Considering the huge population that it would be used in, the FDA would require a very large trial to determine safety. Once launched, the drug company would need to recover that cost plus a profit, so suddenly melatonin goes from a few pennies per dose to several dollars. The push back from the public would probably kill any chance of making it a profitable venture.
What drug companies did do was create melatonin analogues. Rozerem by Takeda is a great example. It hasn't done that well.
As for omega-3s, GSK did get Lovaza approved by the FDA although they did have a patent on it (a specific form of omega-3s).
That is encouraging, sadly not aware of anything comparable in the UK, though was unaware of this avenue you mention and with that thank you.
Sad about the investment needed for the limited return window which would be enough time to promote the benifits intime for the market to mature just outside the window of opertunity.
Does make you wonder how many good useful medications are kept back due too fiscal investment to get the various approvals. Not aware of a universal World accepted standard of drug approval, certainly would make sense cost wise for the global return. But guess there is money in running trials as well.
There is an approved form of pharmaceutical melatonin in the UK (Circadin, 2mg modified release), but it's only licensed for use in adults aged over 55.
Any doctor can prescribe it off-label if they wish, although they might be hesitant in the non-insomniac population due to the relatively high cost (>50p per 2mg dose)
That said, there isn't much incentive for a company to do this. Let's say a company spend $200M getting FDA approval for melatonin. Considering the huge population that it would be used in, the FDA would require a very large trial to determine safety. Once launched, the drug company would need to recover that cost plus a profit, so suddenly melatonin goes from a few pennies per dose to several dollars. The push back from the public would probably kill any chance of making it a profitable venture.
What drug companies did do was create melatonin analogues. Rozerem by Takeda is a great example. It hasn't done that well.
As for omega-3s, GSK did get Lovaza approved by the FDA although they did have a patent on it (a specific form of omega-3s).