To my shame, when I lived in Canada and was earning my living as a web designer, I was asked to make a site promoting Viagra and other pharmaceutical products. I had never heard of the stuff so researched it and produced the website as requested. I then had to learn about website SEO to promote it. All skills which came in handy when I started promoting books.
Today I wouldn't dream of making such a website or using some of the spammy techniques I discovered in 1995-9. The chances are any of the products from such sites are fake. At the best they provide a placebo effect. At the worst they can harm.