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What is LD50 and what does it mean?

LD50 or median lethal dose, a toxicology term meaning the dose amount of a toxic substance required to kill 50% of a tested population. Typical units for LD50 values are milligrams or grams of material per kilogram of body weight (mg/kg or g/kg, recall that 1 kg = 2.2 pounds). The larger the LD50 means it takes a large quantity of the material to cause toxic response and the lower the LD50 the more toxic – Table salt mg/kg 3000 and warfarin (rat bait) is 50–500 mg/kg.

Most people have heard that if a rat eats a substance that makes it sick, the rat will avoid that substance in the future (something many of us learn about with alcohol…). Therefore, one has to be clever in designing a rat poison.

Warfarin is a particularly effective rat poison even though it is not what one normally considers highly toxic. It doesn’t work like traditional poisons, so rats will eat a bait containing a sub-lethal dose and then come back for more.

Curiously, warfarin is widely prescribed for medical use in humans (“the dose makes the poison”)! Which one of these medical conditions can not be treated effectively with warfarin?

Trivia Question

Atrial fibrillation (irregular heartbeat)
Deep vein thrombosis
Pulmonary embolism
Breast cancer
a molecule
The correct answer is Breast cancer –  Wafarin is an anticoagulant (blood-thinning drug). By reducing the ability of your blood to clot, you can prevent diseases that involve the formation of potentially deadly blot clots. Of course, if you take too much warfarin like Mr. Rat, then you can develop fragile capillaries and die of massive internal (or external) hemorrhaging (oooh, how pleasant).Informative sites and 

So the important takeaway from this information, always read and follow all Labels and MSDS (Material Safety Data Sheets), call 911 or Poison Control 1-800-222-1222 if you suspect someone has ingested something toxic, this includes animals as well. So in laymans terms – LD50 is based upon what was ingested compared to the body weight of the person or animal.



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