Paracetamol ist das meistverkaufte rezeptfreie Schmerzmittel in Deutschland und weltweit in nahezu jeder Hausapotheke zu finden. Es lindert Schmerzen und senkt Fieber – schnell, wirksam und meist gut verträglich. Doch hinter der vermeintlichen Harmlosigkeit verbirgt sich ein ernstes Risiko: Paracetamol ist die häufigste Ursache für medikamentös bedingtes akutes Leberversagen in der westlichen Welt.
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If paracetamol overdose is suspected: call NHS 111 or go to A&E immediately — even with no symptoms. This article does not replace medical advice.
Paracetamol (also known as acetaminophen) is the world's best-selling painkiller and the most widely recommended analgesic in pregnancy and for children. Despite its apparent harmlessness, paracetamol is at the same time the most common cause of drug-induced acute liver failure in the UK. This paradox is explained by the narrow window between the therapeutic and toxic dose.
| Property | Details |
|---|---|
| Active substance | Paracetamol (acetaminophen, APAP) |
| ATC code | N02BE01 (anilides) |
| Drug class | Non-opioid analgesic / antipyretic (not an NSAID!) |
| Available forms | Tablets, effervescent tablets, suspension, suppositories, infusion solution, sachets |
| Half-life | approx. 1.5–2.5 hours |
| Max. daily dose (adults) | 4,000 mg (4 g) — in at-risk patients: 2,000 mg (2 g) |
| Max. OTC pack size | 32 tablets (16 × 500 mg or 32 × 500 mg depending on pack) |
| Onset of action | approx. 30–60 minutes |
| Special feature | Not an NSAID — no anti-inflammatory action |
The precise mechanism of action of paracetamol remains incompletely understood despite decades of research — a pharmacological curiosity for such a well-established medication. Unlike NSAIDs such as ibuprofen, paracetamol inhibits cyclooxygenase (COX) in peripheral tissues only very weakly. Instead, it acts predominantly in the central nervous system: it inhibits COX-2 in the brain and spinal cord, reducing prostaglandin synthesis there. Influences on the endocannabinoid and serotonergic systems are also discussed.
This is the most important clinical difference: paracetamol has no relevant anti-inflammatory action. For pain arising primarily from inflammation — joint inflammation, sports injury with swelling, inflamed gums — ibuprofen is pharmacologically the better choice. Paracetamol's strengths lie where gastric tolerability matters, where cardiac or renal risk limits NSAIDs, and wherever pain is not inflammatory in nature — headaches, fever, period pain.
Standard dosage for adults: 500–1,000 mg every 4–6 hours, maximum 4,000 mg per day. In at-risk patients (liver disease, regular alcohol consumption, low body weight, malnutrition), the limit is a maximum of 2,000 mg per day. At least 4–6 hours must elapse between individual doses.
In children, paracetamol is strictly dosed by body weight: 10–15 mg per kilogram body weight as a single dose, every 4–6 hours, maximum 60 mg/kg body weight per day. The most important rule: never give paracetamol suppositories and suspension at the same time — this leads to double-dosing.
| Body weight | Age (approx.) | Single dose suppository | Single dose suspension (120 mg/5 ml) |
|---|---|---|---|
| 3–4 kg | Newborns | 60–75 mg | Medical supervision only |
| 5–8 kg | 3–12 months | 60–125 mg | 2.5–5 ml |
| 8–12 kg | 1–3 years | 125–250 mg | 5–10 ml |
| 12–20 kg | 3–6 years | 250 mg | 10–15 ml |
| 20–30 kg | 6–9 years | 250–500 mg | 15–20 ml |
| 30–43 kg | 9–12 years | 500 mg | 20 ml (or 500 mg tablet) |
Paracetamol has one clear advantage in use: it can be taken with or without food — as a non-NSAID, it does not irritate the stomach lining. The most important rules:
Record all medications and dosing times in your digital medication plan.
This is the pharmacological core that every paracetamol user must understand. Paracetamol is broken down in the liver via several pathways. The dangerous pathway: a small portion of the active substance is converted by the enzyme CYP2E1 into a highly toxic intermediate — NAPQI (N-acetyl-p-benzoquinoneimine). Normally, NAPQI is immediately neutralised by the body's own antioxidant glutathione and excreted.
In overdose, so much NAPQI is produced that the liver's glutathione stores become depleted. The unneutralised NAPQI then binds covalently to liver cell proteins, destroying liver cells irreversibly. The insidious aspect: this destruction occurs with a delay of 24–72 hours. During this time, those affected often still feel relatively well or have only mild symptoms — while the liver is already being massively damaged.
The critical dose of 7.5–10 g applies to a healthy adult with normal glutathione reserves. With several risk factors, this threshold may be considerably lower. Risk factors include: regular alcohol consumption (induces CYP2E1 and depletes glutathione), pre-existing liver disease (hepatitis, cirrhosis), malnutrition or eating disorders (low glutathione reserves), and use of medications that induce CYP2E1 (isoniazid, rifampicin). For these at-risk groups, the maximum daily dose is 2,000 mg.
| Stage | Timeframe | Symptoms |
|---|---|---|
| Stage 1 | 0–24 hours | Nausea, vomiting, upper abdominal pain — or symptom-free! |
| Stage 2 | 24–72 hours | Liver enzymes rise, right upper abdominal pain, jaundice begins |
| Stage 3 | 72–96 hours | Liver failure: jaundice, coagulopathy, altered consciousness, organ failure |
| Stage 4 | From day 4 | Recovery or death / liver transplant |
When used as directed, paracetamol is one of the lowest-side-effect analgesics. Unlike NSAIDs, it does not damage the gastric lining, does not raise blood pressure, and does not significantly impair kidney function. In rare cases: allergic skin reactions, blood count changes (thrombocytopenia), and bronchospasm in patients with analgesic-induced asthma.
One important long-term problem: with too-frequent use (more than 10 days per month), there is a risk of medication overuse headache (MOH). This is a paradoxical phenomenon: the painkiller itself causes headaches when taken too often. Anyone who notices they need paracetamol for headaches ever more frequently should speak to their doctor.
This is the most common paracetamol problem in practice: patients take a cold and flu remedy (e.g. Lemsip, Night Nurse, Day Nurse, Sudafed, Beechams) and additionally take paracetamol tablets for a headache. Many of these combination products contain paracetamol as one of their active substances — without this being prominently visible on the front of the packaging. The maximum daily dose of 4 g can thus be unknowingly exceeded. Always check the ingredients of all other medications before taking paracetamol. brite's interaction check detects such duplications automatically.
| Substance / medication | Interaction | Recommendation |
|---|---|---|
| Alcohol | Depletes glutathione, increases NAPQI production — massively elevated liver risk | No alcohol. With chronic use: max. 2 g/day |
| Combination products (Lemsip, Night Nurse, Day Nurse, Beechams, Sudafed) | Often contain hidden paracetamol — duplication! | Always read the package leaflet; calculate total dose |
| Warfarin | Paracetamol can enhance warfarin's anticoagulant effect | Monitor INR more frequently |
| Carbamazepine, phenytoin, rifampicin, isoniazid | Induce CYP2E1 → more toxic NAPQI produced | Reduce daily dose to max. 2 g! |
| Metoclopramide / domperidone | Accelerate gastric emptying → faster onset of action | Can be used therapeutically (e.g. in migraine) |
| Colestyramine | Reduces paracetamol absorption | At least 1 hour apart |
