Acetaminophen overuseage

[bananaface]

Does anyone else regularly ask people about their acetaminophen useage when they are counseling on acetaminophen containing drugs? I started asking not just on new prescriptions, but on refills where people claim they are already familiar with the medication.

Some people know that excessive doses acetaminophen causes liver damage. But, almost nobody in the lay public realizes what doseages of acetaminophen are safe. They assume that because medications are prescribed or because acetaminophen is available OTC that they cannot be anywhere near a dangerous dose.

Quite a few people are using acetaminophen over the counter without realizing that their medication(s) already contain(s) acetaminophen. Some others are taking two prescription drugs that add up to more than a safe daily dose, without realizing it. And, there are the people whose doctors have written for doses that have the potential to cause liver damage when taken at the max prescribed dose (ie: 1-2 Vicodin q4-6hprn). It's a pretty big problem.

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[bgreet]

Just curious, what is the max daily dosage usually?

 

[pharmer]

Max dose taken daily should not exceed 4g (adults) and 2.6g (kids). When I get a script for Loratab, Darvocet N-100, etc many times they are written with take 1-2 q 4h prn pain. The patient, if s/he followed the order as written, could essentially take more than the max dose of APAP. I Always let the pt know the max amount they can take safely and tell them not to exceed that amount eventhough their RX is written as if they could. I also always tell them to avoid other procucts with APAP and that if they do need additional prn pain meds that IBU is usually ok.

Pharmer

 

[bananaface]

Also, any single adult dose should also not exceed 1g aka 1000mg. A dose is anything taken in the same 4-6 hour period. So, someone could take 500mg and then any time in the next 4 hours they could take up to 500mg more. But if they initially took 1g they would need to wait 4-6 hours before taking any more.

For adults using acetaminophen long term, a maximum dose of 2.6g per day or less is recommended. Doses of 3g-4g have caused liver damage in one year of use in some patients.

Many people cannot convert between grams and milligrams. And, milligrams are generally used in OTC and Rx labeling. So, it is a good idea to tell people that 4g is the same as 4000mg (or 2.6g = 2600mg). If they are just taking one source of acetaminophen it is easy to do the math for them and tell them how many tablets are safe in a 24 hour period. ie:
650mg/tab = max 6/24hr (4/24hr if long term)
500mg/tab = max 8/24hr (5/24hr if long term)
325mg/tab = max 12/24hr (8/24hr if long term)

 

[PharmDMD]

Also keep in mind pre-existing conditions that increase risk for hepatotoxicity such as alcoholism, hepatitis, enzyme inducing agents (common ones--rifampin, phenytoin, CBZ and even St. John's Wort). Max Doses less than 4g are recommended in these scenarios.

Patient counseling regarding warning signs of yellow skin or eyes (jaundice), dark urine, light colored stools, abdominal pain or swelling, nausea, vomitting, loss of appetite and that these symptoms should be reported to you and their health care provider.


Good topic !! 🙂

Harold DelasAlas, Pharm.D.
UH college of Pharmacy Alumni '04
UTMB School of Medicine '08

 

[Seaglass]

Actually, as a physician, I write on my inpatient orders that APAP dose is not to exceed 4g in 24h and such since so many are on Percs, Tylenol PRN fever. etc. So some of us are aware of the problem and attempt to make a note of it.

C

 

[GravyRPH]

As part of my consultant pharmacist duties, I make sure none of my residents have orders that would pontentially push them over the 4g limit. If they are , I recommend the physicain either reduce the frequency, even if it's prn, or list the max warning (as above) as part of the sig. They've always followed one of the two rec's. I prefer the former, but the latter is acceptable.

 

[bgreet]

Come to think of it I know a lot of customers that are overdosing on APAP. (I'm just a technician) I tried to inform that pharmacist that was on duty of some of the customers that were exceeding the 4gm limit (and some WAY over this limit) and he basically didn't care. *Shrug*