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Acetaminophen (Tylenol / Paracetamol)

Analgesicoral · predicted

Analgesic and antipyretic metabolized primarily by the liver via glucuronidation and sulfation. Hepatotoxic in overdose.

Projected serum levels — 500 mg, as needed (shown daily)

Acetaminophen (Tylenol / Paracetamol)
Acetaminophen (Tylenol / Paracetamol) modeled serum levels, 500 mg as needed (shown daily) over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 125 250 375 500 Day 0 Day 4 Day 8 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1

Maintenance schedule: 500 mg as needed (shown daily) (oral).

Modeled steady state after ~1 days: peak ≈ 277 mg, trough ≈ 0.000 mg body load. Population-based estimate over 15 days for a 500 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Analgesic
Route modeled
Oral
Model confidence
predicted
Half-life
2.3 h
Common dose
500 mg
Suggested maximum
4k mg/day
Reference dose range
325–4k mg (single dose)
Suggested cadence
as needed (shown daily)
Validated against
1k mg oral — Cmax 18 mg/L at 0.75 h

Documented interactions

  • danger
    Ethanol (Alcohol) + Acetaminophen (Tylenol / Paracetamol) Contraindicated

    Alcohol induces CYP2E1, increasing toxic NAPQI metabolite formation from acetaminophen. High risk of liver failure.

  • caution
    1,4-BDO (1,4-Butanediol) + Acetaminophen (Tylenol / Paracetamol) Potentiation

    1,4-BDO conversion to GHB consumes ADH/ALDH capacity. Heavy or chronic dosing pulls on the same hepatic oxidation systems acetaminophen relies on for safe clearance, increasing NAPQI accumulation…

  • moderate
    CBD (Cannabidiol) + Acetaminophen (Tylenol / Paracetamol) CYP inhibition

    CBD (Cannabidiol) reversible_inhibitor of UGT1A9 predicted to change Acetaminophen (Tylenol / Paracetamol) AUC by ~1.28x

  • watch
    Efavirenz (Sustiva) + Acetaminophen (Tylenol / Paracetamol) CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Acetaminophen (Tylenol / Paracetamol) AUC by ~0.87x

  • watch
    Rifampin + Acetaminophen (Tylenol / Paracetamol) CYP induction

    Rifampin inducer of CYP3A4 predicted to change Acetaminophen (Tylenol / Paracetamol) AUC by ~0.87x

Serum checks 9 modeled interaction pairings for acetaminophen (tylenol / paracetamol) across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. Efficacy and safety of paracetamol for spinal pain and osteoarthritis: systematic review and meta-analysis of randomised placebo controlled trials Machado GC et al. · BMJ, 2015 DOI

    Meta-analysis found paracetamol was ineffective for low back pain and provided only small, clinically insignificant benefits for osteoarthritis pain and disability.

  2. Acetaminophen-induced hepatotoxicity: a comprehensive update Yoon E et al. · Journal of Clinical and Translational Hepatology, 2016 DOI

    Review establishing acetaminophen overdose as the leading cause of acute liver failure in the US, detailing the NAPQI toxicity mechanism and NAC treatment.

  3. Paracetamol: not as safe as we thought? A systematic review of observational studies Roberts E et al. · Annals of the Rheumatic Diseases, 2016 DOI

    Systematic review found dose-response relationship between paracetamol use and adverse events including increased cardiovascular, GI, and renal risks at higher doses.

3 published studies referenced in the app, each with a plain-language summary.