Arts on prescription is distinct from arts in health in the "prescription" aspect. Arts in health programming can take place in communities or healthcare settings; as can arts on prescription programs. The difference is whether someone is referred to the program.
For example, a Dance for Life class may have a flyer up in a neurologist's office. This would be considered arts in health. However, if you meet with a link worker or your provider and they say, "Since your Parkinson's diagnosis, I've been concerned for your social wellbeing. You mentioned being interested in dance before, would you like to attend this Dance for Life class?" That would be arts on prescription!
And just remember, as clinical services, the creative arts therapies (visual arts, music, dance-movement, theater) are not included in arts in health or arts on prescription!