Is there a list of language that the drug dosing suggestions will understand? If ordering Acetaminophen, CPS will understand "Take 1 Daily" but not "Take 1 as needed." What is the proper language for a provider to write in the Instructions field?
I have not tested this particular situation, but I suspect you need to include the frequency, probably before the "as needed". For example "Take 1 daily as needed" might work. The second set of instructions you have used, "Take 1 as needed." could be interpreted to allow pt to take an overdose if they decided they "needed" one every half hour.
I have noticed that I believe if you include something after the as needed you should use "as needed for..." For example, if I write "Take 1 daily as needed headache" I get an error, but if I instead use ""Take 1 daily as needed for headache" it will accept the prn instructions and just look at the dosing instructions to determine whether the dose is too high. This came up for me frequently because we have quick text to replace "prn" with "as needed" so if I would enter "prn headache" it would get converted to "as needed headache". Inserting "for" in the proper location would make the error go away.
I don't know the actual algorithm used or if this is available somewhere. Just some observations from my personal experience...