Acetaminophen – can I take the daily limit all at once?

[luceluna]

I know that acetaminophen is harmful in large doses, but I don't understand why, exactly. In theory, could I take a day's worth (e.g. 3g) at once, if I don't take any more for the rest of the day?

Pls don't tell me just to do a CWE, I'm working with tablets that have 3 or more ingredients.

 

[4meSM]

To put it simply, your body metabolises paracetamol via 3 different routes, one of them produces a very toxic compound called NAPQI. If you take smaller doses through the day (the max is 1000mg every 4h IIRC) the liver is able to get rid of that toxic metabolite by attaching it to Glutathione (GSH), if you take too much at once two things will happen:
1) A bigger dose = larger amount of NAPQI produced
2) There won't be enough GSH reserves to get rid of all the NAPQI, so it will start damaging the liver.

NAPQI is very very hepatotoxic and it's known to cause liver failure, your liver is unlikely to fail from 3g at once (unless you have other risks factors and/or predispositions) but it would cause some damage for sure. Paracetamol overdose is very common unfortunately.

You can still do a CWE even if you have tablets with more than 3 ingredients, I don't see the issue there... Which tablets are you talking about?

 

[luceluna]

Thanks very much for that clear explanation. I appreciate it.

The tablets are an Australian brand, Mersyndol Forte: paracetamol 450mg, codeine 30mg, and doxylamine 5mg.

 

[4meSM]

Thanks very much for that clear explanation. I appreciate it.

The tablets are an Australian brand, Mersyndol Forte: paracetamol 450mg, codeine 30mg, and doxylamine 5mg.

Well you can at least get rid of the paracetamol, a CWE can be done relatively quickly (don't use too much water).

I'm not very familiar with doxylamine but those tablets contain doxylamine succinate which is a very water soluble salt. But even then, I don't think 30mg of doxylamine is particularly dangerous (assuming you were planning on taking 180mg of codeine). It may cause some minor side effects but you'll be fine (I have no personal experience with doxylamine).

 

[luceluna]

I want to retain the codeine AND the doxylamine, but it sounds like a CWE would achieve that.