acetaminophen

[Ibis]

Can anyone explain how the half life of acetaminophen relates to the "daily limit"
Example. If I take 3g 12 hours later 500mg remain so does that mean I can take another 3g and still adhere to limit.

 

[serotonin2A]

The "daily limit" means the maximum amount you can safely take in a 24 hour period. If you take 3 g and then take another 3 grams 12 hours later you would have exceeded the limit you listed.

Edited to add the following:
I thought I should mention that the problem with taking high doses of acetaminophen is that a certain percentage is metabolized to a toxic compound called NAPQI. So the reason for having a recommended maximal daily dose of acetaminophen isn't because a certain blood level of acetaminophen is toxic, it is to limit the amount of NAPQI that the liver is exposed to per day. So it doesn't matter how much acetaminophen is left in the body after 12 hours--if you take another dose, more NAPQI will be generated.

 

[Ibis]

Thank you for the update, so I guess then what I am asking is more related to napqi.
it seems some have more tolerance to it. I hear people are fatal at 6g but others can 6g for a week, off three
for like two years with no problem. No damage to liver.

 

[serotonin2A]

Thank you for the update, so I guess then what I am asking is more related to napqi. it seems some have more tolerance to it. I hear people are fatal at 6g but others can 6g for a week, off three for like two years with no problem. No damage to liver.

Chemical sensitivity varies from person to person. Toxicology is based on averages. The toxic dose level of a chemical is typically measured by giving it to animals and looking for the dose that kills 50% of the population (the LD50 dose). But by definition half of the people who take a LD50 dose would survive.

The maximal daily dose of acetaminophen is set so that it is too low to produce fatalities (it is intentionally below the LD). The problem is that there is no way to predict where you will fall on the curve, so it is impossible to predict whether a higher dose will be safe.

 

[endotropic]

Two points to help you stay safe:
(1) using acetaminophen alongside alcohol greatly increases the toxicity
(2) a safe acute dose of acetaminophen might be toxic when taken repeatedly for a number of weeks