I think the bottom line is even that the experts don't know everything. The Univ. of Arizona's work in this area is ongoing, meaning they add to it all the time. I remember many years ago how simple their website was. Not anymore!

Quinidine was popular 30 yrs ago... long before the new waves of sophisticated drugs arrived. Once the liver enzyme research heated up, and the new drugs became available, the QT and interaction data started to be compiled.

In fact the story behind how Seldane was discovered to be a deadly risk is pretty interesting. Seldane had been on the market for over 10 yrs and was losing its patent. Rugby generic already had it available and it was being dispensed. A professor at Georgetown Medical school discovered this cardiac sudden death thing by accident (meaning he wasn't looking for it). He started investigating this, and a brief period during which doctors were notified about this serious interaction and cardiac QT potential. They ignored the warning letters, and I remember a news show like 20/20 or Dateline going to pharmacies in NY with RXs for both Seldane and Erythromycin and none of the pharmacists caught it either, or called the doctors to change the combo. Since the parent company already had the active metabolite of Seldane ready to market (Allegra), it dropped its drug application for Seldane, which then made generics illegal in US. (generic Seldane is still available in other countries today however). And Allegra does not have this interaction potential either.

Some people genetically just cannot handle drug metabolism well. And it is difficult to predict still today. Not everyone who took Seldane with Erythromycin died...but many did, and it was attributed to "some other reason".

What I think the harmful potential of this drug combo is involves several potential areas for harm.
1)Used by people with genetic long QT situations, it is a risk. Something to watch and monitor and measure at the doctor's office. The FDA is putting the responsibility on the doctor.

2) people without genetic QT issues, can still have problems. The actual QT may occur when this drug combo is mixed with other medication. The Univ of Arizona has lists of high risk to low risk medications that when combined may affect heart rhythm. Anna Nicole Smith's son Daniel died from a combo of Lexapro and methadone...no overdoses, just a combo affecting his heart.

3) People without QT issues, can still have one if they become low in potassium and magnesium. Both these electrolytes affect conductivity in the heart. So throwing up alot, or having alot of diarrhea or not eating enough foods with adequate magnesium in them (very common in US)... can combine with this drug combo, to cause issues. Also many drugs may deplete potassium and magnesium. For example, diabetics excrete magnesium from the urine daily. Steroids deplete both electrolytes as well as diuretics.

4) this drug combo will interact with other drugs based on quinidine's effects on drug metabolism. That you have to look up on the charts, where quinidine is listed as a substrate inhibitor.

5) foods like grapefruit cannot be taken with this drug... because of its liver metabolism. Grapefruit paralyzes the GI lining which contains some of the Cytochrome P450 enzymes, so that a dose of drug appears higher in the blood than when grapefruit is not consumed.

So you see it is hard to predict what will happen. But for those who take many drugs, the risk increases. This is why having the charts is important. Some DNA testing sites have downloads for these enzyme systems, since they sell the tests. They also breakdown % based on ethnic race distribution if that is a factor. Some drugs are metabolized differently in Asians vs Africans vs Caucasians.

mrsD -

Great stuff! And I'll admit, I read the grapefruit ban in the PI sheet (as I do for every medication I'm on) despite the efforts of some drug makers to keep their FDA approved Prescribing Information unavailable to the public, but my doctor DID NOT mentioned it to me, although I've had to be off g.f. juice for a while now.

But I was particularly struck by your comments regarding the effects of sudden drops in electrolytes, whether from the flu or exercise on a hot day. My internist mentioned to me some time ago that's when people often O.D. from interactions at prescribed levels of drugs. (I know how wiped out my 14 year old son was after a hot hike - with water - until my wife had the good sense to give him a sports drink.)

I've been on a gram of magnesium a day for years, but only took Rx potassium when I was on Lasix. Sounds like this would be a great issue to publicize for the poly-medicated community, writ large.

Mike

There is a reference (out of print right now) on this.

But there are links to abbreviated data from that reference.
There is even a smart phone app for this subject now;

Here are the links:

http://www.chiro.org/nutrition/ABSTR...orticosteroids

http://itunes.apple.com/us/app/nutri...432547190?mt=8

Neither one of these is 100% inclusive, but the Drugs.com link has improved significantly in the past year... so it has food interactions too.

Depletions lead to drug interactions or failures. That is a bit different in thrust, but still very important.

Magnesium is thought to be low in at least 70% of people in the US.... it is significant even when no drugs are at fault.
And for any diabetic ...magnesium is ALWAYS significant.

Magnesium depletion was the major reason Propulsid was recalled...and Propulsid remains the best treatment to date for gastroparesis... a very sad situation for many many patients, that the doctors refused to follow FDA warning letters in its use! IMO.

I have a magnesium thread here:
http://neurotalk.psychcentral.com/showthread.php?t=1138

And I'll share some new info... CVS Epsom lotion is a nice product, very affordable and applies to skin providing some magnesium for muscles and cramping. I am using it now instead of some of my oral supplements. You might want to check it out: (unfortunately they don't provide dosing or quantity, but it seems to do the job when used on legs or arms for me.)

http://www.cvs.com/CVSApp/catalog/sh...new_crumb=true

I get it locally, and this link, has price changes every week it seems for "sales" stimulus etc.

Thanks Mrs. D and Mike,

I have a very young neurologist but fortunately he is very detailed. I got all the info regarding grapefruit, magnesium, EKG, etc. Also I spent considerable time going through the lengthy package insert. I am a little concerned about the effects of dehydration which occasionally happens to me but feel confident that I can increase hydration while taking it.

I am concerned because, although the package insert did not list it, I found a website that cautioned against taking Namenda, which I take, with Nuedexta. My neuro indicated that the nuedexta would increase the effectiveness of the namenda. I also found a caution for Adderall, which I am also taking. I believe the website listed Adderall as having potentially serious drug interactions.

I am confused. I am putting a hold on taking it until I can track down more information.

I am still interested in feedback from others who are taking nuedexta.

Teri

Can you give me the link where Adderall and Neudexta showed an interaction?

I did not find one at drugs.com

This is the interaction reported for Namenda + quinidine:
http://www.drugs.com/interactions-ch...981-0,1551-936
Has to do with the kidney.--and is listed as a minor interaction/potential.

I found the adderall interraction on drugs.com. I found it by going to ask.com and posing the question, "Can adderall be taken with nuedexta?"

Thanks again for your help!

I get this page for Adderall and Nuedexta:

http://www.drugs.com/drug-interactio...281-14874.html

I also searched Nuedexta separately by both drugs in the combo.
No interactions.

Of course drug interaction databases are not 100% reliable 100% of the time. And there are exceptions.

This one lists amphetamines with Nuedexta:
http://nervous-system.emedtv.com/nue...eractions.html
But offers no details.

Teri -

Your neurologist was quite correct, Neudexta would increase the effectiveness of Namenda. In fact, the potentiation of Namenda by Nuedexta is one of Nuedexta's best properties, if personal experience counts for anything.

Mike


ps Sorry I can't help you on the Adderall, which I would have loved to have been on years ago, but my then treating physicians passed on it because of my glaucoma. Instead they gave me Prozac, which landed me overnight in a monitored cardiac bed with SVT. Whereupon the UCLA Adult ADHD Clinic discharged me as "too hard." (Not that they ever checked my BP or pulse during any of my office visits.) So instead I joined the gym and signed up with a personal trainer in an effort to be more efficient at work. And here I am today, as a direct result of that last ill-fated call.