What is Warfarin Toxicity?
Warfarin is a drug that combats vitamin K, often used to treat and prevent various diseases related to blood clotting and blockages in blood vessels. Interestingly, it was first sold as a rat poison but has been used as a medicine for over fifty years. There are also stronger versions of this drug, known as superwarfarins, which are used as pesticides and are a hundred times stronger than warfarin. These superwarfarins could potentially cause what’s known as “warfarin toxicity”.
Warfarin toxicity can occur in several ways: 1) A person intentionally takes too much of it; 2) They unintentionally take too much or become sick from it; 3) A child gets hold of it and ingests it by accident. Intentional overdoses are quite rare, with just 22 recorded cases in a 25-year survey at two major treatment centres. Unintentional overdosing or sickness can happen due to several factors like a change in diet, interactions with other medications, and even due to chronic liver disease spread through the body. The initial phase when a patient starts taking warfarin presents a heightened risk due to factors such as the patient’s existing health conditions, diet, and genetic quirks. Children may come into contact with warfarin and ingest it out of curiosity, or due to intentional harm from others, a condition known as Munchausen syndrome by proxy. Reports have also emerged of warfarin toxicity from mixing superwarfarins with illegal drugs to enhance their effects.
What Causes Warfarin Toxicity?
Interestingly, warfarin was first used to kill pests before we found a way to use it as a medication. However, some rats developed a resistance to warfarin, leading scientists to create stronger versions, known as superwarfarins, which are often used to control rats in homes and businesses. This, unfortunately, has increased the chances of humans coming into contact with these more potent forms.
The rate of human exposure to superwarfarins has been on the rise, with cases of exposure or poisoning jumping from approximately 5,000 in 1988 to over 13,000 in 1955. So, these more powerful versions of warfarin are something we need to be increasingly aware of and careful about.
Risk Factors and Frequency for Warfarin Toxicity
In 2014, a report from the American Association of Poison Control Centers showed that there were 1,766 cases of people accidentally taking the prescription medicine warfarin. Interestingly, 355 of these cases were small children under the age of 6. The majority of these cases, about 84%, were due to an accidental overdose. Although 16 serious medical issues arose from these incidents, thankfully, no one died.
In that same year, there were 181 recorded cases of exposure to a type of poison called superwarfarin rodenticides. The majority of these incidents, numbering 142, involved young children less than 6 years old. With 170 of these exposures being unintentional, no serious health issues or deaths were reported.
Signs and Symptoms of Warfarin Toxicity
When assessing someone for possible drug toxicity, it’s crucial to know several details. These would include the type of medication they’ve taken, any other substances they’ve consumed at the same time (including other drugs or alcohol), and any prescribed drugs they’re currently using. You would also need to know the dose strength, when they took the drug, and their reason for doing so. Additionally, it’s important to find out about any recent injuries, particularly head injuries.
In specific cases, such as warfarin toxicity, you should ask if the person is currently taking warfarin for any health condition. This affects how you should manage the situation because of the risk involved when reversing the INR. Look out for signs of abnormal bleeding such as nosebleeds or discolored urine or stools as well. It’s also necessary to obtain information about any existing medical issues that could influence the course of the toxicity, especially those related to alcohol use or potential liver disease.
Testing for Warfarin Toxicity
If you’re suspected of swallowing or being exposed to a harmful substance, your doctor will perform a comprehensive physical exam, checking your vital signs such as pulse and blood pressure. They are also likely to order an electrocardiogram, a test that measures your heart’s electrical activity, and a basic metabolic panel, a blood test that assesses your overall health. They will also test for acetaminophen concentration if they think you may have attempted self-harm. The doctor will also assess additional factors like the substance you may have eaten or drunk, whether you are pregnant or could experience complications, and any symptoms you may have.
If you are suspected of having too much warfarin (a type of blood thinner) in your blood, the doctor will run extra tests. They may check your prothrombin time (PT) and international normalized ratio (INR), which are tests that measure how long it takes your blood to clot. They will also likely examine your complete blood count (CBC), which measures the number of different types of cells in your blood, as well as a further detailed look at how your liver is functioning.
It’s crucial for the doctor to know about any recent changes in your prescription medications or any dietary supplements you may be taking, as well as if you made significant changes to your diet. All of these can impact how your body processes warfarin.
Finally, the doctor needs to understand how the poisoning occurred. Based on their findings, they might need to conduct additional checks on your mental health or your ability to carry out everyday activities.
Treatment Options for Warfarin Toxicity
If you take too much warfarin (a blood thinner), it can cause problems with your blood’s ability to clot, a condition known as warfarin toxicity. This can be particularly dangerous if you have a mechanical heart valve. Doctors measure this risk using a test called INR (International Normalized Ratio). If your INR is too high (over 3.0, or over 3.5 for those with a mechanical heart valve), it is considered warfarin toxicity.
The treatment for warfarin toxicity varies based on your specific situation. For instance, if you took too much warfarin but are not bleeding, doctors don’t usually recommend giving you blood products like Fresh Frozen Plasma (FFP) or Prothrombin Complex Concentrate (PCC), which can help your blood clot.
If you intentionally ingested warfarin (or a similar drug) and you’re not already on an anticoagulant (a drug that prevents clotting), doctors will want to check your clotting levels frequently, potentially every 12-24 hours at the start. If your INR remains normal after 36 hours and you’re not experiencing any signs of bleeding, doctors typically don’t need to do any further testing. If your INR is higher than 10 or you’re showing signs of bleeding, doctors might suggest taking Vitamin K, which can help your blood clot. Activated charcoal, which can limit the absorption of certain drugs like warfarin, may be an option if you arrive at the hospital within an hour of ingestion.
If your overdose on warfarin is causing active bleeding, this is a serious situation, and your medical team will take immediate steps to stop the bleeding and help your blood clot. They might give you a “clotting cocktail” that could include various blood products, Vitamin K, and an anti-bleeding drug like Tranexamic acid. Using these blood products is not without potential risks, such as the formation of dangerous blood clots. If the overdose has led to significant bleeding, it’s a good idea to have a hematologist (a blood specialist) or a toxicologist (a poison specialist) involved in your care.
If you accidentally take too much warfarin, your need for testing and evaluation will depend on your specific situation. For example, if you’re generally healthy and accidentally take a single dose of warfarin, you might not need any tests. But, if you’re pregnant or already on anticoagulants, doctors should measure your INR to see if you’re at risk for warfarin toxicity.
What else can Warfarin Toxicity be?
- Child abuse
- Nosebleeds (Epistaxis)
- Ectopic pregnancy
- GI bleeding (Bleeding in the digestive tract)
- Bleeding shock (Hemorrhagic shock)
- Shock due to severe fluid loss (Hypovolemic shock)
- Munchausen syndrome (A psychiatric disorder where someone pretends to be ill)
- Munchausen syndrome by proxy (A psychiatric disorder where someone pretends another person is ill)
- Bleeding after childbirth (Postpartum haemorrhage)
- Blood clot under the skin of the brain (Subdural hematoma)
- Bleeding in the space surrounding the brain (Subarachnoid haemorrhage)
- Haemophilia A (A blood clotting disorder)
- Haemophilia B (A blood clotting disorder)
- Bleeding in the eye (Vitreous haemorrhage)
