Learn pharmacokinetics
Paracetamol pharmacokinetics simulator
One-compartment model with linear elimination. Pick a preset or enter your own values; everything recalculates as you type.
How paracetamol moves through the body
Paracetamol, called acetaminophen in North America, is absorbed quickly from the small intestine. Peak levels arrive about 30 to 60 minutes after a tablet on an empty stomach, a little later after food.
Its half-life is short, around 2 to 3 hours, so levels drop substantially before the next six-hourly dose and build-up between doses is small. That is why regular dosing keeps pain under control better than waiting for pain to return.
Most of the drug is conjugated in the liver. A small fraction becomes a toxic metabolite, NAPQI, which is normally neutralised by glutathione. In overdose that defence is overwhelmed, which is why the daily maximum matters so much.
Looking for paracetamol abroad? See its brand names in every country.
Learn the concepts
Half-life
What elimination half-life means, how to calculate it from clearance and volume, and why it decides dosing frequency.
Steady state
Why repeated doses build up, why steady state takes about five half-lives, and what accumulation ratio means.
Area under the curve (AUC)
What AUC measures, how it relates to dose, bioavailability and clearance, and why vancomycin dosing now targets AUC.
Bioavailability
Oral bioavailability (F), first-pass metabolism, and why IV and oral doses of the same drug differ.
Loading dose
When and why a larger first dose is used, and how to calculate it from volume and target concentration.
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