I'm not overly familiar with the mechanics of codeine in overdose, but the toxicity of paracetamol (acetaminophen) can be estimated based on the mg/kg ingested,

I'm not overly familiar with the mechanics of codeine in overdose, but the toxicity of paracetamol (acetaminophen) can be estimated based on the mg/kg ingested, albeit with a cap at 110kg: > To avoid underestimating the potentially toxic paracetamol dose ingested by obese patients who weigh more than 110 kg, use a body-weight of 110 kg (rather than their actual body-weight) when calculating the total dose of paracetamol ingested (in mg/kg).[1] It strikes me as at least plausible that codeine could be behave in a similar way. [1] https://bnf.nice.org.uk/treatment-summary/poisoning-emergency-treatment.html https://bnf.nice.org.uk/treatment-summary/poisoning-emergenc...