Even if a word is technically correct, perceptions about the word can make it a bad choice.

I agree, I just find it strange that that is the perception of medicine that is a knockoff of an original, because that's very common, is widely sold, and generally has the exact same effect as the original.
A knockoff is also used for a cheaper copy of an original. Cheaper as in price, not necessarily quality, although that is often the case, it doesn't have to be. As is usually NOT the case when it regards medicine. The cheaper copy (knockoff) can usually be used interchangeably.

There are also knockoffs of Louis Vuitton products that are hard to identify even by experts. Louis Vuitton products are often not that expensive to make, so a knockoff can easily be cheaper, and have similar quality.
But disregarding how close it comes, it will always be considered cheap because it's a knockoff and not an original product.