I can tell you the U.S. requirements as I just went through this process 3 years ago when I built my new clinic.
The exterior of my building is block and brick so the dry wall for the exterior wall could be the standard dry wall.
On interior walls that connected to the adjacent rooms and hallway they required lead lined drywall which was quite expensive.
Also the large handicap accessable door is lead lined and expensive as far as doors go.
No special ceiling was required as I have only storage space in the attic.
With most Belize buildings using block for exterior and interior walls the lead lined drywall is prob not needed.
It's really not a big deal to provide the level of protection needed.http://www.medicalcenterforyou.com/