This app was mentioned in 2 comments, with an average of 1.50 upvotes
Yep not sure what the pi is bringing to the party other than making things more complicated. Something like https://play.google.com/store/apps/details?id=com.devicemagic.androidx.forms might work better for you - you can design a custom form, have the doctors complete it offline, and then maybe use a WiFi printer and sync the proscriptions to the server when there is internet.
I'd look to simplifying the task as much as possible to make it robust. Using phones as an interface may mean batteries die quickly, which may be a consideration, so have a paper backup!
This might work for you: Device Magic - https://play.google.com/store/apps/details?id=com.devicemagic.androidx.forms