Therapeutic range

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Hey guys! Okay so I am a little confused.... So when it comes to medications and therapeutic ranges I get confused. I had a question on a practice test and it said the INR was out of range I think specifically at 1.8 seconds. Now I thought maybe since it was out of the range they would get toxicity since it's above the 0.9-1.2. Another example is lithium if it's above the 2- toxicity. I was wondering how this works and why the INR 1.8 isn't toxic but the lithium over its range would be toxic ( or would it not be?). Thank you guys I am sorry I'm just slightly confused why that patient wouldn't be a high priority being over the therapeutic range for INR.

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Specializes in Medsurg/ICU, Mental Health, Home Health.

Hey there!

These are two completely different scenarios.

A serum lithium level is measuring the amount of lithium in the blood.

An INR isn't actually measuring the amount of a medication in the blood.
It's result that informs the provider of the amount of time it takes for blood to clot.

If a person is not taking warfarin/Coumadin, then his or her INR is expected to be in the range you suggest, this indicates normal clotting time.

Someone who is taking warfarin is taking in for the purpose of clot prevention, so we want their INR to be between 2 and 3 typically (often 2.5-3.5 if they have an artificial heart valve). 
 

so in this case, the INR is out of range because we want their patient to have a HIGHER INR.

 

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Thank you this helped a lot!

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