I'm not so sure about that. Acute liver damage only tends to occur with acetaminophen
) overdose, as the liver normally has enough glutathione stashed away to effectively clear the drug
. It is only when these glutathione reserves are depleted by the huge dose of acetaminophen that the concentration of reactive metabolites becomes dangerously high. 4g acetaminophen at once would be quite harsh as the massive spike in drug levels puts a strain on the liver's antioxidant cache. 1g every 6 hours would be more manageable as this gives the liver more time to replenish the glutathione reserves. There is a risk of cumulative toxicity too though.
Chronic paracetamol use probably does slowly damage the liver over many years just through low-level radical damage, but this is probably no worse than drinking alcohol
, eating a high fat diet etc.
The biggest danger with chronic use of acetaminophen is that it causes gastric bleeding and ulcers in many users. This is a common side-effect of acetaminophen and many NSAIDs.
In the context of codeine
use it's also fortunately a totally avoidable problem. Anyone that has a chronic requirement for codeine but does not wish to also consume the acetaminophen could perform a relatively simple cold water extraction (CWE) to separate the codeine from the acetaminophen. It's bad to get into the habit of consuming large doses of something as toxic as acetaminophen when there is no medical reason to do so, even if it is still below a lethal threshold.