Question: how to code a prescription with "PRN"?

Sep 24, 2011

Question: I have a question about coding “prn” under a substanceAdministration class in CDA structure.  First, what coding system I should use to code it? Second, where should I put it? Frequency or indication of reason for taking the medication? If it should be interpreted as a type of frequency, how can I do it?

I asked Lloyd McKenzie for an answer to this one (thanks Lloyd):

Actually, you use neither of those.  ”PRN”, which translates to “as needed” is placing a precondition on the administration.  So “Administer this when x”.  Sometimes the statement is just PRN (as needed).  Sometimes it’s something like “PRN pain” (as needed for pain). So you use the precondition relationship.  If you don’t have a specific condition, you can leave the non-mandatory attributes in the Criterion class empty.  If you have a specific condition, then you can use the code or text attributes to describe it. Usually with PRN medications you’ll also want to specify maxDoseQuantity to indicate the maximum dose per period of time.  And you may choose to specify frequency as well.  E.g. “1 tablet every 2-4 hours PRN”