In my state, while someone with an MD or DO degree can prescribe whatever their heart desires, specialty nurse practitioners such as PMHNPs must stay in their own lane, as it were. I am allowed to prescribe any psychotropic medication that is on my collaborating formulary (which is pretty much everything because my collaborating physician is awesome), but I am not allowed to prescribe any general practice medications (BP, BG, etc) unless specifically directed to do so by my physician. While I understand that I'm smart enough to prescribe these medications, there's a reason we have FNPs and AGPCNPs and the like. They don't do what I do, and I don't do what they do. Besides, rarely is there a situation like a UTI, high A1c or other metabolic concern that is urgent to the point that it cannot wait for a primary care referral, and do I really want to be in front of the board of nursing d/t a patient's serious adverse reaction to a medication that I really shouldn't have been prescribing in the first place?
That being said, when I did clinical hours at a veterans home, there was one PMHNP and one AGPCNP full time, and one physician for the entire home. When one of the nurse practitioners was out or on vacation, the other would have to pick up and write the medications for the other. So unfortunately, there may not be a clear cut answer to your question, and the answer may be more situational than anything. Clear as mud, I know.