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Question about PRN meds


Hello, I'm a new nurse (3 months), and I'm a bit confused with prn medication administration. For example, if a med, say lorazepam, is ordered TID, does that automatically mean that there has to be an 8 hour space between the doses?

Also, let's say someone gets a certain medication ordered @ hs, and then they have a prn order for that same med TID (let's use lorazepam again), and the person requests it again a couple of hours after hs, states hs dose was ineffective.....can I give it again that early?

Sorry if this post is hard to understand, but I would like some insight.


I am also a new nurse and we also get a ton of prn orders that are confusing. And when I ask other nurses, they all do something different.If a patient had lorazapam ordered tidd, hs, and prn I would want clarification from dr or pharm before giving more than once in an 8 hour span.


Specializes in acute care med/surg, LTC, orthopedics. Has 5 years experience.

TID is three times/day not necessarily 8 hours apart, it could be 0800, 1700 and 2100 for example. Using your Lorazepam at hs example, if he's got a prn order then yes he can receive another dose if ineffective.

I can't emphasize enough how important nursing judgment is, which is what you will have to use to decide if/when a med is appropriate for your patient.

Normally if a patient has the same med TID and prn, you may notice the TID doses are on the lower end of the dosage scale.

Where I work any order TID is given a time by pharmacy.

MJB, I'm talking about PRN meds.

classicdame, MSN, EdD

Specializes in Hospital Education Coordinator.

JC is now looking for the MD's to write WHEN prn is appropriate. For instance, Tylenol 325 mg every 4 hours prn pain

tyvin, BSN, RN

Specializes in Hospice / Psych / RNAC.

With my experience when the order is written TID then you can give it every 8hr's; so yes you wait until there has been at least an 8hr interval (3x8=24). I try to catch those type of orders and get the doc to change it to q hr's because it is muddy water.

Now if there is a PRN for a routine med and the routine med is ineffective; yes you can give the PRN according to what the orders say. So if they get the routine you don't have to wait 8hr's; wait at least 1hr before giving the PRN and of course document accordingly. But if it says TID wait 8hrs before giving another PRN dose. Now if this person is always requesting the PRN med then you need to look at possibly upping the routine dose since it is always ineffective.

As a rule if a PRN is given everyday for >7 days then it needs to be looked at to possibly resolve why the PRN is being given everyday. In most cases the orders are changed to reflect the needs of the patient.


Specializes in acute care med/surg, LTC, orthopedics. Has 5 years experience.

TID, BID, OD times are normally set as per the facility's convenience corresponding with med pass times. The only instance pharm sets the times is when the MARs are computer generated otherwise we write them in ourselves. Many OD meds which are usually given with the am med pass for convenience can feasibly be given at any time of day. A good example are SSRI, MAOI, tricyclics which can be given either am, noon or hs depending on whether they cause the patient somnolence or insomnia - and also whatever the patient's own time is as they normally come with these meds. I have often crossed out a time, wrote in a different time with the notation "pt's own time."

The Tylenol example provided by a PP is a good example of using nursing judgment. Your patient may have an order for Tylenol, Tramacet and Percocet... are you going to give all of them potentially frying your poor patient's liver with all that Acet? No, you're going to stop and think. That's why monkey's can't do our job.

You can also ask for the doc to write for a MDD (Maximum Daily Dose) Many do this routinly for many meds. APAP and Benzo's this I see often. But they usually figure how much a person can have in a 24 hour period and divide it up between the routine and PRN dosing. If you have just a TID the last lost is usually like 2100 but if you have both a TID AND a HS you move up the TID so the last one is at 1700 and the HS at 2100. So like 0800, 1300 and 1700 for the TID and 2100 for the HS. Then the PRN on top of that--again keeping in mind the MDD.

tyvin, BSN, RN

Specializes in Hospice / Psych / RNAC.

My experience with these docs who use the TID etc...without writing it in hr's is that they prefer that the med actually not be given except for the intervals written. There are many docs who won't give Tylenol or percocet q 4 hrs as is usually the time but prefer the 6 and 8 hr time line.

Also; if you use up the med at the first part of the day what happens later when it's exhausted and there is no more doses to give because you gave the 3 dose in the day time? Like I said when I see these orders I clarify with the doc and get it in hr's. Many times I ended up re-writing it q 8hrs instead of TID because many docs prefer it that way.

What I suggest to you is ask the doc or your charge for clarification.


Specializes in ER/Ortho.

I am a new nurse and this is how I do it.

All of my prn orders have a time reference. (q 8 hrs prn). If the patient needs the drug prior to the 8 hours then I cannot give another dose unless I call the Dr and he orders a one time additional dose. If the patient has a scheduled dose of a med, and then asked for a prn of the med at the same time I would hold the prn. If it were a few hours after the prn dosage it would depend on the medication involved and on the status of the patient. Again nursing judgment....If ever in doubt ask before giving.