Update/Question for Al

[MichelleS]

Hi everyone,

Just thought I'd give an update.

I posted earlier because over a five or six week period my INR jumped from 3.6 to 5.1 even though my doctor reduced my coumadin dosage a couple of times. (I started out at 60mgs per week - he had me decrease to 58 and then down to 56.)

When I tested at 5.1 I was instructed to hold an entire 8mg dose and retest the next morning. I didn't follow his instructions as the last time he had me do that I went from 4.6 to 1.8.

So I took 4mgs that night and my INR the next day was 3.3. Just about perfect. I was then told to go back to 8 mgs per day and test again on Tuesday. Between Friday and Tuesday I went back up to 4.3. NOW he's decreased my dosage from 8 to 7.5 mgs per day and have to go back again tomorrow (Monday) for another draw. The clinic phlebotomist is quickly becoming my best friend, I swear. : )

I know this is not at all dangerously high but I have to vent. Not withstanding the fact that my arm is majorly bruised from being used as a pin cushion I don't understand why they can't get my INR stable.

Nothing in my diet or exercise routine has changed so I still think it has to be because of the new med I'm taking (Actonel - plus I added Citracal+D) but they checked several sources and supposedly these shouldn't have caused my increased INR.

The information I found on Actonel said that "no specific drug-drug interaction tests were performed. Risenodrate is not metabolized and does not induce or inhibit hepatic microsomal drug-metabolizing enzymes. (Cytochrome P450).

Uh...could you translate that for me into layman's term, Al? : )

Thanks for listening, gang. Hope everyone is well.

Cheers,
Michelle

 

[JimL]

My 2 cents -- it sounds like the dosages adjustments are pretty good, in other words, small, conservative adjustments. I'm not sure if I understand correctly, but it sounds like your INR is being tested rather often. Are you still having a veinous draw?

My INR was 5.0 on Friday, and I'll go again next Friday. I've adjusted from 40mg to 39 or perhaps 38 for the week. But my test is a finger prick; I could have one of those a day without getting sore. I wouldn't want to have an arm draw on a regular basis.

 

[Guest]

Michelle,

As JimL noted, you are being tested too often. It sounds like your doctor does not understand how warfarin works. It takes about 3 days for the effect of warfarin to be seen. So testing every 3 days is like a puppy chasing its tail. You need to pick a dose and take it for one week without changing anything. Then test again.

Anyone who takes more than 5 mg per day should HARDLY EVER hold a dose for an INR that is below about 8. (AS you found out.)

If you have an INR under 5 it will HARDLY EVER lead to bleeding if you stay at that level for less than one month.

Because your doctor does not understand this, he is panicked by levels slightly out of range. When your phlebotomist gets to know you, it is because your doctor does not know warfarin.

Anybody who has followed my writings knows that this is the biggest complaint I get - the doctor is changing the dose and testing too often.

There are several enzymes in the Cytochrome P-450 system. Many drugs are metabolized by one or more of these (warfarin is).
Drugs that induce the enzymes (Fiorinal, Fioricet, Tegretol, Dilantin, Rifampin etc) cause warfarin to be metabolized faster than usual - so you need an increased dose if these are ADDED to warfarin and a DECREASED dose if these are stopped.

Drugs that inhibit these enzymes (amiodarone etc) require a DECREASED dose if they are added to warfarin and an INCREASED dose if they are stopped.

If you were taking the other drugs first (or started them at the same time as warfarin), then their effect is not noticed when you start warfarin because it is balanced for what is already there. But they have an effect if stopped.

These are among the most worrisome of the drug interactions. They can be huge. I've seen people have serious bleeds, seizures, and strokes because their doctor changed these without understanding what they were doing. Quite often, this is where I get called in.

I saw one man who had to start rifampin for a staph infection in his bones that required his warfarin dose to be adjusted from 28 mg per week to 170 mg per week to keep his INR constant. Then when it is stopped, it takes months of weekly testing and dosage adjusting to get the warfarin dose back down.