My problem with p.r.n. is not that it should not be ordered, and that many medicines should not be taken only when needed. For example instead of taking Tylenol routinely it is better to take it only when pain or fever arises. My problem is the way pharmacies label the p.r.n. orders.
If I write:
Xanax 1 mg. tid p.r.n. [t.i.d is another Latin obfuscation]
which means that 1 tablet of 1 mg Xanax can be taken up to three times a day but only if there is a need for it, the pharmacy will write on the label: take three a day as needed.
Writing it this way gives the impression to the patient that he should take three tablets of Xanax a day as [it is] needed.
It is a very subtle way of encouraging patients to take more medications than they should. This is especially true with anti-anxiety agents and narcotic pills where there is a tendency to take more medications than prescribed to begin with. As needed is interpreted tendentiously that they should take the maximum allowable dose.
Wouldn't it be better if the instruction reads: take up to three a day if needed.
If needed is much better than as needed when labeling prn orders.
Perhaps the ideal way would be: take up to three a day but only if needed.