Weird phenytoin levels (dilantin)

[kirsten]

Five minutes ago I was going to write a post about how sick I am of feeling sick. I figured it was the phenytoin I was taking that was making me feel ill. I have absolutely no appetite, I've lost a ton of weight in the last two weeks, and I'm completely home-bound and unable to work.

I did levels on Monday and my phenytoin levels are half what they should be despite being on the proper dose. I'm taking 300mg, split between morning and night. I am having tonic clonics, myoclonics, absences/partials (no way of knowing because I'm always alone.) The neuro will be calling me later but I know many of you have been taking dilantin, and of course, all of you know what happens to you when you're having seizures all the time. So first of all, do you have any idea why I wouldn't be absorbing the phenytoin I'm taking? Second of all, the cognitive problems, confusion, seizures, general feeling of dizziness and tiredness--do they sound to you like phenytoin issues or seizure issues? Third of all, if any of you have had problems with phenytoin levels, is there something that can be done to change things? Do you simply have to change meds? The neuro didn't expect the phenytoin to be good for me. It was merely a hoop we were jumping through to get my medical insurance to cover neurontin, which they don't usually pay for. Because I've been feeling so ill since the phenytoin, I feel desperate to go off it and move on to neurontin, but I'm worried that I might be being too hasty. I know if I tell the neuro I'm sick of the phenytoin woes, he will switch me, but I want to do the best thing.

 

[Dolores]

Kirsten, I was told by a number of doctors that Dilantin is one of the drugs for which the generic (phenytoin) may not be a viable substitute. Generics, while they have the same active drug, are not required to have the same amount of the drug. The scary thing with phenytoin is that the amount of the drug can vary between 85% & 125%. By the nature of the drug itself, the amount of Dilantin/Phenytoin in your system increases and decreases in a very non-linear manner. So if you switch to a new batch of drug or the pharmacy changes providers, the amount of actual drug you are getting can vary by 40%. The nature of Dilantin/Phenytoin has caused my levels to spike to over 20 so that I start to overdose and, when I was trying to readjust them, fall to close to 10. I prefer to be on the higher side of average since I have had seizures when my levels fell too low but never when they were too high. All that being said, for me Dilantin controls my T/Cs so I chose to monitor these issues rather than try something diffferent.

Taking generic phenytoin rather than Dilantin may be the reason your levels are so low even though you have been taking the same dose.

 

[kirsten]

Thanks for the info, Delores. It gets a bit confusing on my side of the world because we don't get dilantin here. We get something called Epaneutin. I have no clue how well regulated the levels are with that particular brand. But my neuro has called me today and he reckons phenytoin is definitely not a good drug for me. I guess he thinks at least some of what I'm experiencing is due to the side effects. To think of doubling my current dosage would zombify me totally. I am pleased, because I didn't have bad side effects on neurontin in the past, and if it doesn't work out, I guess I can go back to the phenytoin but try a better brand as you suggested.

 

[Bernard]

Grapefruits have a chemical that interferes with liver metabolism of many drugs. Don't eat grapefruits while on AEDs (Keppra *might* be an exception as it's metabolized in the kidneys).

My wife has issues with her Dilantin levels around her menstruation period. Something about the hormone changes affects the protein binding* I guess.

* Most blood syrum tests are for total Dilantin, but apparently it's only the unbound Dilantin that is therapeutic. The Dilantin bound to proteins don't do the job.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1427743/

http://clincalc.com/Phenytoin/Correction.aspx

All that said, my wife had very bad experiences with generic forms of phenytoin. She could never keep a steady blood syrum with it. Switched back to brand name Dilantin and everything went back to normal.

 

[kirsten]

Thanks, Bernard. Fortunately, there's no risk of grapefruit ever entering my life. I hate it. But presumably the core issue is to keep away from an acidic diet.

 

[Nakamova]

Hey kirsten --

When I started on Dilantin, my dose was too high, and I experienced low appetite, balance problems and dizziness, fatigue etc. But unlike you, my seizures were controlled, even when I went to a lower dose, and even with the low blood serum levels that the lower dose produced.

I eventually switched because it was causing gum overgrowth, and because of the risk of bone loss. I hope you can switch as well.

 

[kirsten]

Nakamova, my epilepsy is usually really easy to treat, at least as far as getting rid of the tonic clonics. My issue is that I tend not to tolerate these medications. So if you had low levels but you also had control, I tend to think that the phenytoin has something to do with my current seizures.