[Jeff]

a) Cannot answer specifically without breeching patient confidentiality - but most local or national guidelines allow some concessions to individual patient preferences.
e.g.Cox2 for elderly patient willing to accept risks in exchange for the ability to walk up the stairs rather than crawl.

b) Where there is no licenced treatment. e.g. Aricept and Lewy Body Dementia
Use of many medicines in children

Jeff