Effect of Niaspan on INR

[Georgia]

I've been on Niaspan for cholesterol since December. After about 2 months the dosage has settled at 1500 mg. I checked all lists and information I could find and nothing said anything about effect on inr or interaction with coumadin.

In February my inr soared; from my normal 3.5 to 5.8. After a couple weeks of messing around and unnecessary bloodwork (while I tried to avoid see-sawing) it came down. My dosage settled in at 4 mg/day - down from 6 mg/day.

This whole thing makes sense to me, as niaspan is processed in the liver; but I wonder why it's not listed as an interaction or a warning? I think a reduction of 1/3 in coumadin my dose is a LOT.

Al, have you seen similar results in your practice? Thanks.

 

[Yaps]

I take niaspan..and last week my inr was 5.9.. I wonder if you are on to something....Thanks , love the pup

 

[Guest]

There are no reports in the National Library of Medicine's database of anyone being harmed by this combination. There was a theoretical report in 1998 but no actual cases.

There are lots of different liver enzymes that metabolize different drugs mainly based on their 3 dimensional shape. Just because two drugs are metabolized by the liver does not mean that they will automatically interact.

I'd say that this is not a true interaction.