Related Experiment Video

Updated: Apr 11, 2026

Pre-Chiasmatic, Single Injection of Autologous Blood to Induce Experimental Subarachnoid Hemorrhage in a Rat Model
09:14

Pre-Chiasmatic, Single Injection of Autologous Blood to Induce Experimental Subarachnoid Hemorrhage in a Rat Model

Published on: June 18, 2021

3.0K

[Fatal intracerebral haemorrhage possibly caused by interaction between paracetamol and warfarin]

Signe Vinsand Naver1, Maria Papina, Espen Jimenez Solem

  • 1Klinisk Farmakologisk Afdeling, Bispebjerg Hospital, Bispebjerg Bakke 23, 2400 København NV. signe.vinsand.naver@regionh.dk.

Ugeskrift for Laeger
|June 11, 2015
PubMed

Insights

A case report highlights a potential interaction between paracetamol (acetaminophen) and warfarin, leading to elevated INR levels and fatal intracerebral hemorrhage in an elderly patient. This underscores the importance of monitoring warfarin therapy during concomitant analgesic use.

Area of Science:

  • Pharmacology
  • Clinical Medicine
  • Neurology

Background:

  • Warfarin is a common anticoagulant used for atrial fibrillation and after aortic valve replacement.
  • Maintaining a stable International Normalized Ratio (INR) is crucial for patients on warfarin therapy.
  • Concomitant use of analgesics requires careful consideration due to potential drug interactions.

Observation:

  • An 83-year-old male on stable warfarin therapy self-medicated with high-dose paracetamol (acetaminophen) 4 g/day for two weeks.
  • The patient developed acute neurological deficits and was found to have an INR > 10.
  • A CT scan revealed an intracerebral hemorrhage, leading to the patient's death.

Findings:

  • High-dose, prolonged paracetamol (acetaminophen) use may potentiate warfarin's anticoagulant effect.
  • This interaction can lead to dangerously elevated INR levels.
  • The case suggests a possible pharmacokinetic or pharmacodynamic interaction between paracetamol and warfarin.

Implications:

  • Clinicians should exercise caution when prescribing or recommending paracetamol (acetaminophen) to patients on warfarin.
  • Close INR monitoring is recommended during and after concurrent use of high-dose paracetamol and warfarin.
  • Further research into the interaction mechanisms between paracetamol and warfarin is warranted to ensure patient safety.

More Related Videos

A Low Mortality Rat Model to Assess Delayed Cerebral Vasospasm After Experimental Subarachnoid Hemorrhage07:03

A Low Mortality Rat Model to Assess Delayed Cerebral Vasospasm After Experimental Subarachnoid Hemorrhage

Published on: January 17, 2013

14.9K
Double Direct Injection of Blood into the Cisterna Magna as a Model of Subarachnoid Hemorrhage10:34

Double Direct Injection of Blood into the Cisterna Magna as a Model of Subarachnoid Hemorrhage

Published on: August 30, 2020

11.8K

Related Concept Videos

Drug toxicity: Drug–Drug Interaction01:30

Drug toxicity: Drug–Drug Interaction

Drug–drug interactions can precipitate toxicity through multiple mechanisms. Absorption interactions alter how drugs enter the body, exemplified when ranitidine increases the absorption of basic drugs, while cholestyramine decreases the levels of propranolol. Protein binding interactions occur when drugs share the same binding sites on plasma proteins. Drugs like aspirin and warfarin, when bound in excess, can lead to increased free drug concentrations, enhancing the potential for...
372
Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants01:18

Anticoagulant Drugs: Vitamin K Antagonists and Direct Oral Anticoagulants

Oral anticoagulants are vital tools in preventing and treating blood clotting disorders. This diverse class of medications can be categorized as vitamin K antagonists, exemplified by warfarin, and direct thrombin inhibitors (DTIs), such as dabigatran, as well as factor Xa inhibitors, including rivaroxaban.
Warfarin, a prominent vitamin K antagonist family member, exerts its effect by inhibiting the enzyme VKORC1 (vitamin K epoxide reductase complex 1). By hindering this enzyme, warfarin...
2.8K
Anticoagulant Drugs: Low-Molecular-Weight Heparins01:30

Anticoagulant Drugs: Low-Molecular-Weight Heparins

Hemostasis is a crucial process that prevents excessive blood loss from damaged blood vessels. It involves various mechanisms such as vasoconstriction, platelet adhesion and activation, and fibrin formation. The importance of each mechanism depends on the type of vessel injury. In contrast, thrombosis is the abnormal formation of a blood clot within the blood vessels, leading to potential complications if the clot obstructs blood flow. Thrombosis can be caused by increased coagulability of the...
2.5K
Pharmacokinetics: Drug–Food and Drug–Viral Interactions01:26

Pharmacokinetics: Drug–Food and Drug–Viral Interactions

A drug interaction occurs when the concurrent use of another drug, food, or an external substance alters the pharmacological activity of a drug. This interaction can modify the action of the original drug, affecting its effectiveness and safety.Drug–food interactions are significant as they impact drug absorption, metabolism, and excretion. For example, grapefruit juice is a well-known disruptor of drug metabolism. It inhibits the cytochrome P450 3A4 enzyme, crucial for the metabolism of...
595
Venous Thrombosis III: Interprofessional Care01:29

Venous Thrombosis III: Interprofessional Care

Venous thrombosis requires effective prevention and treatment strategies to improve patient outcomes and reduce potential complications.Prevention StrategiesHealthcare providers must prioritize preventing venous thromboembolism (VTE) for all adult patients upon admission. Interventions depend on bleeding and thrombosis risk, medical history, current medications, diagnoses, planned procedures, and patient preferences. Patients on bed rest should change positions every two hours and, if not...
469
Drug toxicity: Idiosyncratic Reactions01:16

Drug toxicity: Idiosyncratic Reactions

Idiosyncratic drug reactions represent abnormal chemical responses that vary significantly among individuals, ranging from extreme sensitivity to low doses to insensitivity to high doses. These reactions often occur due to the drug's covalent binding with serum proteins, forming a foreign hapten that triggers an immunotoxicological response. The variability in drug reactions has a strong pharmacogenetic foundation, with genetic differences crucial in how individuals metabolize drugs. For...
195