This sounds like the start of a horror movie where the drug works differently in some and they start to grow teeth where they don't belong like their eyes or feet. Not genitals, that movie already exists.
I had a similar thought and went looking for more info on how the drug is delivered, and if it's a matter of injecting it at the site where you want growth.
on the same line of thinking (but slightly more serious). There are bound to be all kinds of issues but I would imagine some form of braces would help with any alignment issues