[Gnumed-devel] Fwd: Medications plug-in, refactored - *Managing* medications

[Busser, Jim]

Derived concepts:

1) "Time on therapy"

This can be computed by combinations of when the drug was started, and when the 
drug was last taken. When it was last taken can only be established through 
direct inquiry, for example:

- a patient could have restarted, out-of-praxis (or from their own supply), a 
drug which had either been discontinued
- a patient could have continued to take a drug whose duration was intended to 
have expired, and
- a patient could have stopped taking a drug which was intended to be adhered 
to up until and beyond the current encounter

2) "Time since therapy"

This is "negative time" and is represented, in those cases in which it applies, 
by the interval between

        Date discontinued and Today()

or, where the drug was not yet discontinued, and where applicable, by

        expired "Duration / Until" and Today()

Note: this is independent of knowing any "date started"

3) "Time remaining"

This is computable using a single input

        "Duration / Until" > today()

provided only that this was allowed to be stored as a "date until" instead of 
(currently) as an interval, which (currently) makes any meaning dependent on a 
start date which, in some cases, cannot be known. 

Sure, if the start date *is* known, great, however at any encounter the 
clinical question, and the question on the patient's mind, is nearly invariably

        how much *longer* (beyond today) do (I) need to take this medication?

And so, sure, when the start date is known, we can say "well, you already had X 
days, therefore take another Y days."

However I see a number of patients who were started out-of-praxis on medication 
days or even a couple of weeks or (in the case of chronic therapies, even 
prednisone) months before, and find myself unable to pin down start dates. And 
many of us have to manage, on a daily basis, without such information.

In such case, it can be enough to know that the patient has so far had "at 
least" a certain number of days or weeks or months, even though the actual 
might be much more. Sometimes even without knowing the historical total 
duration, it can be reasonable to say:

        Well, let's have you take "another … X days or Y weeks"

of antibiotics or prednisone, without the ability or need to precisely track 
down when they started.

-- Jim