User Tools

Site Tools


WikiTox Home Page

Poisoning monographs

General background

Teaching outlines

Topic structure


Problems for Discussion - 2 Anticoagulant Poisoning


A general practitioner calls about a 54-year-old male with an INR of 7.3. He has been on 6 mg of warfarin daily for 3 years. He was commenced on the warfarin following a mechanical mitral valve replacement for acute infective endocarditis. His INR is usually kept between 2.5 and 3.5. He is feeling well and has no cutaneous bleeding, haematemesis, haematuria or bruising. He says that he has been taking antibiotics for the last 2 weeks that another doctor prescribed him for a chest infection.

  1. What is the risk of an INR of 7.3?
  2. What are the common causes for a raised INR in a patient stabilised on warfarin?
  3. What is the appropriate management of this patient and is vitamin K indicated?
  4. What is the appropriate dose and route of administration of vitamin K?


A 37-year-old male presents 5 hours after ingesting 150 mg of warfarin. He is usually on 8 mg of warfarin daily for a mechanical aortic valve replacement (bicuspid) 10 years previously. He is asymptomatic and has an INR of 2.7. He is admitted overnight after a single dose of activated charcoal. His INR at midday the next day is 5.2.

Outline your management plan for this patient including frequency of INR and the use and dose of vitamin K.


A 47-year-old male presents to the emergency department with a large right haemothorax, haematuria and widespread bruising. He has an INR >15 and a haemoglobin of 70. He has been repeatedly ingesting concentrated liquid rodenticide over the last week.

  1. What is the initial management of this patient?
  2. What dose of vitamin K will be required and for how long?


A 2-year-old boy is brought in by his parents after eating some pellets from a box of rat killer. He was playing in the backyard and found the box of rat killer. He said he ate some pellets and it is estimated at about 5 pellets. He is brought to the emergency department within an hour of exposure. He is alert and well. There is nothing to find on examination. His INR is 1.1.

  1. What is the potential toxicity of the rat killer?
  2. Should the child be decontaminated?
  3. What is the value the INR in this child?
  4. How long should the child be observed and for how long should they be followed up?


Binks S, Davies P. Case of the month: “Oh! Drat!–A case of transcutaneous superwarfarin poisoning and its recurrent presentation”. Emerg Med J 2007; 24(4):307-8 PMID 17384395 Full text

/home/wikitoxo/public_html/data/pages/wikitox/problems_for_discussion_2_anticoagulant_poisoning.txt · Last modified: 2018/09/01 09:01 (external edit)