[codev]

That link shows some automated content brought in from healthnotes/aisle7 which is a Portland, Oregon based company. If you search Amazon UK for melatonin you'll find lots of supplement that are described as 'melatonin-like' but don't contain any active ingredients.

I buy it when I'm in the US which is fine for me as I take it for jet lag but I know GPs (family doctors) I talk to are often confused to learn they can prescribe melatonin and will often prescribe much more powerful and, in my opinion, dangerous hypnotics. I think that's probably because there's no patent on melatonin so not much marketing push to inform GPs of its uses - though I believe there's a patented slow release version of melatonin that might get a bit of marketing behind it.