Thank you for posting this interesting topic @mgkahn
The European guideline for Hypertension 2018 will recommend to start 'combination drug' for treating hypertensive patients as the first line (But they will not revise the definition of hypertension, opposite to the American guideline).
So treatment pattern of combination drugs gets more importance (especially in hypertension).
I also prefer @Christian_Reich's solution
But we need to define 'what is combination?' as @hripcsa concerned
If treatment pathway only represent drug patterns in chronic diseases, I want to suggest 30-day rule (or 7-day rule).
In this rule,
- Only when A and B drug are concurrently used more than 30 days, it can be considered as combination. (Three or four combination is possible)
- If we remove drug era shorter than 30 days, we can remove many noises. If the patient starts A and B on the same day, and then stopped B 10 days after initiation, B drug would be ignored (The diagram shows that the patient use only A). If the patient stopped B 45 days after initiation, the single A drug use would be the second line of treatment.
And, How about using Sankey diagram? This diagram seems to be able to represent the reverse order of drug usage pattern and more flexible