"pharmacy schools require you to have pharmacy as your first choice. "
No we do not.
I have worked for 3 top Universities that offer MPharm and all have welcomed 5th choice Med applicants. Unis may require an additional Personal Statement focussed on Pharmacy, but we know that the vast majority of those applicants will probably not get an Med place and, especially given the changing face of Pharm, and the current staff shortages, turning down well qualified science-heads with a focus on patient care for a place on MPharm would be remarkably silly.