It is very unfortunate they limit the different prescription. For my mom's case, she has more urgent medication like anti-biotic drops and lubricant drops for her eyes, which is a lot more expensive and needs doctor's prescription in order to get it, however, Vit C for her is a nice to have option to speed up the healing process. So they give her the medication ones.
Moreover, my mom's Steven Johnson Syndrome case has got most doctors a little on the edge for giving her medication, even Vitamins.
They always encourage my mom to consume natural products for supplements if possible.
While my dad, there is no medication that can really help him except paracetamol and Vit B12, so he gets Vit B12 supplies.
Sometimes it is also based on the doctors there to decide which to prescribe and which not, for there are a lot of other patients that needs them.