You just changed the facts of our hypothetical malpractice case in a material way!
If the local drug store is out of Latisse, and I wish to use the EXACT same chemical identity (Lumigan) for cosmesis, there is no basis for malpractice…
The discussion in this thread re off-label use of Lumigan was never predicated on Latisse being out of stock; rather, it was predicated on saving money, pure and simple.