‹ AED Page List/Topic Index | Common uses of AEDs/ACs ›

Like antidepressants anticonvulsants (ACs), or antiepileptic drugs (AEDs) - the terms are nearly interchangeable¹ - are broken up into different classes based upon things like how your liver deals with them, chemical structure, and even how they work in your brain. Unlike antidepressants there is overlapping membership, classes that consist of a single drug, or a drug and subsequent drugs derived from it, and existing anticonvulsants will be added or removed from categories as the understanding of their pharmacodynamics and/or pharmacokinetics improved. Thus the taxonomy of AEDs is as complex and fungible as that of mushrooms.

The primary classifications of anticonvulsants are if they are benzodiazepines or non-benzodiazepine anticonvulsants. While some are used as AEDs, most benzos are prescribed only for anxiety and other conditions these days, so they get their own pages. Some, like Xanax (alprazolam), are not even approved by the FDA to treat epilepsy or any kind of seizure disorder. Unless otherwise specified the terms “antiepileptic drug” and “anticonvulsant” will refer to non-benzodiazepine anticonvulsants.

The next classifications are based on pharmacokinetics.

1.  Enzyme-inducing AEDs

The first is which AEDs induce CYP450 and/or UGT enzymes. Enzyme-inducing AEDs (EIAEDs) can have numerous drug-drug interactions, as well as deplete your body of vitamin D₃. EIAEDs include:

• Tegretol (carbamazapine)
• Dilantin (phenytoin)
• phenobarbital
• primidone
• Trileptal (oxacarbazepine)
• Topamax (topiramate)
• Sabril (vigabatrin)

Most of the time EIAEDs refers only to Tegretol, Dilantin, and phenobarbital, because:

• primidone is converted to phenobarbital.
• Trileptal’s induction of UGT enzymes is only moderate and it doesn’t do much in the way of CYP3A4/5 induction like Tegretol does.
• Topamax induces some enzymes, but only at higher dosages.
• Lamictal barely induces UGT enzymes, so it rarely makes a difference.
• Why Sabril speeds up the clearance of some meds hasn’t been identified. Enzyme induction is assumed.
• Anything else that may induce CYP or UGT enzymes is so rarely prescribed these days that any doctor who prescribes it had better know everything there is about that med.

Lots of other medications, both crazy and non-crazy meds, induce CYP450 and UGT enzymes. AEDs are singled out because epileptics have been given more than one med to control their seizures for over 150 years;² so neurologists as a group are more aware of drug-drug interactions and how the slightest change in dosage can affect their patients’ symptoms than most other doctors.

2.  Enzyme-inhibiting AEDs

Some doctors, researchers, et al. lump remaining AEDs into a category called non-EIAED, but the true flipside of enzyme induction is enzyme inhibition or suppression. There is only one group of commonly-prescribed AEDs that inhibits UGT and CYP450 enzymes involved in the metabolism of any medications to any meaningful extent, and that’s the valproates:

• Depakote (divalproex sodium)
• Depakene (valproic acid)
• Stavzor (delayed-release valproic acid)
• Depacon³ (valproate sodium or sodium valproate)⁴

---

---

3.  Aromatic Anticonvulsants

The next group is the aromatic anticonvulsants. These meds don’t help you smell purty. Aromatic refers to aromatic hydroxylation, which is part of the process when these drugs are metabolized. With a very small percentage of people (somewhere between 1 in 1,500 to 1 in 10,000) the metabolism isn’t done correctly and a toxic substance (arene oxides) is left over instead of getting cleaned up. The leftover triggers anticonvulsant hypersensitivity syndrome, and that sucks donkey dong. Anticonvulsants with a particular chemical structure (similar to TCAs, and TCAs may trigger a similar reaction) are going to be converted into the problem toxin, but there’s no way (yet) of telling if someone won’t be able to properly metabolize the toxin once it is created. While the odds are a bad reaction of one of these drugs means a bad reaction to one or more, if not all of the others, someone may have a problem with just one of them.⁵ Or there may be one of them they can take.

• Lamictal (lamotrigine)
• Trileptal (oxcarbazepine)
• Zonegran (zonisamide)
• Tegretol (carbamazepine)
• Dilantin (phenytoin)
• phenobarbital (the data are mixed regarding primidone)
• Felbatol (felbamate)

Stevens-Johnson Syndrome (SJS), a.k.a. The Lamictal Rash, is thought to be a component of anticonvulsant hypersensitivity syndrome. So if you got SJS, or any rash scary enough that you and/or your doctor thought it best to discontinue one or more of the above meds, the odds are you’ll get a rash from one or more of the others.

4.  All other AED classes

Finally we come to classifications of AEDs that are chemically related and/or work in similar ways. There may be only one drug per class because it is unique, or it is the only still on the market, or that ever made it to the market in the first place.
The classes Carbonic Anhydrase Inhibitors (CAI) and GABA Reuptake Inhibitors contain drugs that do only that, otherwise most AEDs would be classified as a GABA reuptake inhibitor, and Topamax and Zonegran would also be CAIs.

Barbiturates

• mephobarbital
• Nembutal (pentobarbital sodium)
• phenobarbital

Bromides

• potassium bromide

Carbamates

• Felbatol (felbamate)

Carbonic Anhydrase Inhibitors (CAIs)

• Diamox (acetazolamide)
• sultiame

Dibenzapine derivities (carboxamides)

• Tegretol (carbamazapine)
• Trileptal (oxacarbazepine)
• Banzel (rufinamide)
• eslicarbazepine

Fatty acid derivities

• valproates:
  • Depakote (divalproex sodium)
  • Depakene? (valproic acid)
  • Depacon? (valproate sodium or sodium valproate)
• Gabatril (tiagabine)
• Gabrene (progabide)
• Sabril (vigabatrin)

GABA analogues

• Gabrene (progabide)
• Sabril (vigabatrin)
• Neurontin (gabapentin) and Lyrica (pregablain) were once considered GABA analogues.

GABA reuptake inhibitors

• Gabatril (tiagabine)
• Neurontin (gabapentin)
• Lyrica (pregablain) - although not everyone agrees on just how Neurontin and Lyrica work…

alpha 2 delta ligands

• Neurontin (gabapentin) - because they’re also categorized as this
• Lyrica (pregablain)

Hydantoins

• Peganone (ethotoin)
• Mesantoin (fosphentyoin)
• Dilantin (phenytoin)

Oxazolidinediones

• trimethadione

Phenyltriazines / Triazines

• Lamictal (lamotrigine)

Pyrrolidines

• Keppra (levetiracetam)
• Keppra derivatives (e.g. brivaracetam) that UCB is working on.

Succinimides

• ethosuximide
• methsuximide
• phensuximide

Sulfamate-substituted monosaccharides / Fructose derivatives

• Topamax (topiramate)

Sulfonamides

• Diamox (acetazolamide)
• sulthiame
• Zonegran (zonisamide)

---

---

5.  AED equivalences

Given how there are so few AEDs in each class it’s little wonder few of them work the same way. Many people ask about AEDs/ACs that are equivalent, the way SSRIs are. Very few AEDs are:

• The valproates are essentially interchangeable, there are some dosage adjustments required, as well as getting used to different side effects.
• Trileptal is a derivative of Tegretol. They aren’t exactly alike, but they are close enough that switching from one to the other can be done without titration if absolutely necessary. 300mg of Trileptal (oxcarbazepine) = 200mg of Tegretol (carbamazepine USP). The US PI sheets (Trileptal’s prescribing information Tegretol’s prescribing information) are full of information about switching between the two.
• Lyrica isn’t derived from Neurontin, but they probably mechanisms of action, whatever they may be, that are similar.
• Diamox and sultiame
• Zonegran and Topamax have a vaguely similar chemical structure and a very similar mechanism of action.

‹ AED Page List/Topic Index | Common uses of AEDs/ACs ›

Page design and explanatory material copyright © 2004 - 2012 Jerod Poore. All rights reserved.

Almost all of the material on this site is copyright © 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, and 2012 Jerod Poore. Except, of course, the PI sheets - those are the property of the drug companies who developed the drugs the sheets are about - and any documents that are written by other people which may be posted to this site will remain the property of the original authors. You cannot reproduce this page or any other material on this site outside of the boundaries of fair use copying without the express permission of the copyright holder. That’s usually me, so just ask first. That means if want to print out a few pages to take to your doctor, therapist, counselor, support group, non-understanding family members or something like that - then that’s OK to just do. Go for it! Please. As long as you include this copyright notice and the following disclaimer, I’m usually cool with it.

All rights reserved. No warranty is expressed or implied in this information. Consult one or more doctors and/or pharmacists before taking, or changing how you take any neurological and/or psychiatric medication. Your mileage may vary. What happened to us won’t necessarily happen to you.
The information on Crazy Meds pertains to and is intended for adults. While some information about children and adolescents is occasionally presented (e.g. US FDA approvals), pediatric-specific data such as dosages, side effects, off-label applications, etc. are rarely included in the articles on drugs or discussed on the forum. If you are looking for information regarding meds for children you’ll have to go somewhere else.
Know your sources!
Nobody on this site is a doctor, therapist, or a pharmacist. We don’t portray them either here or on TV. Only doctors can diagnose and treat an illness. Some doctors tend to get pissed off by patients who know too much about medications, so tread lightly when and where appropriate. Diagnosing yourself from a website is like defending yourself in court, you suddenly have a fool for a doctor. Don’t be a cyberchondriac, thinking you have every disease you see a website about, or that you’ll get every side effect from every medication¹. Self-prescribing is as dangerous as buying meds from fraudulent online pharmacies that promise you medications without prescriptions.
All information on this site has been obtained through our personal experience and the experiences family, friends, what people have reported on various reputable sites all over teh intergoogles, the medications’ product information / summary of product characteristic (PI/SPC) sheets, and from sources that are referenced throughout the site. As such the information presented here is not intended as a substitute for real medical advice from your real doctor, just a compliment to it. You should never, ever, replace what a real doctor tells you with something from a website on the Internet. The farthest you should ever take it is getting a second opinion from another real doctor. Educate yourself - always read the PI/SPC sheet or patient information leaflet (PIL) that comes with your medications and never ever throw them away.
Crazy Meds is not responsible for the content of sites we provide links to. We like them, or they’re paid advertisements, or they’re something else we think you should read to help you make an informed decision about a particular med. Sometimes they’re more than one of those things. But what’s on those sites is their business, not ours.
Very little information about visitors to this site is collected or saved. From time to time I look at search terms used and which pages they bring up in an effort to make the information I present more relevant. And the country of origin, just because I’m geeky like that. That’s about it. Depending on how you feel about Schrodinger, our privacy policy should either assuage or exacerbate your paranoia.
All brand names of the drugs listed in this site are the trademarks of the companies named on the PI/SPC sheet associated with the medication, sometimes on the pages about the drugs, even though those companies may have been acquired by other companies who may or may not be listed in this site by the time you read this. Or the rights to the drug were sold to another company. And any or all of the companies involved may have changed their names.
Crazy Meds is optimized for the browser you’re not using on the platform you wish you had. Between you and me, it all looks a lot cleaner using Firefox or Safari, which is what a plurality of visitors use. And I’m running Windows XP3. On a computer that sits on top of my desk. With a 23 inch monitor. Hey, at least you can make the text larger or smaller by clicking on the + or - buttons in the upper right hand corner. If you have Java enabled. Like 99% of the websites on the planet, Crazy Meds is hosted on domain running an open source operating system with a variety of open source applications, including the software used to display what you’ve been reading. As such Crazy Meds is not responsible for whatever weird shit your browser does or does not do when you read this site².
No neurologists, psychiatrists, therapists or pharmacists were harmed in the production of this website. Use only as directed. Void where prohibited. Contains nuts. Certain restrictions may apply. All data are subject to availability. Not available on all mobile devices or in all dimensions of reality.

‘Everything is true, nothing is permitted.’ - Jerod Poore

¹ While there are plenty of books to help you with hypochondria, for some reason there’s not much in the way of websites. Then again, staying off of the Internet is a large part of curing/managing the disorder.

² Have I mentioned how open source operating systems for commercial applications is one of the dumbest ideas in the history of dumb ideas?
[begin rant] I rent a dedicated server for Crazy Meds. It’s sitting on a rack somewhere in Southern California along with a bunch of other servers that other people have rented. The hardware is identical, but no two machines have exactly the same operating systems. I don’t even need to see what is on any of the others to know this. If somebody got their server at the exact same time, with the exact same features as I did, I’m confident that there would be noticeable differences in some aspects of the operating systems. So what does this mean? For one thing it means that no two computers in the same office of a single company have the same operating system, and the techs can spend hours figuring out what the fuck the problem could be based on that alone. It also means that application software like IP board that runs the forum here has to have so many fucking user-configurable bells and whistles that even when I read the manual I can’t find every setting, or every location that every flag needs to be set in order for a feature to run the way I want it to run. And in the real world it means you can get an MBA not only with an emphasis on resource planning, but with an emphasis on using SAP - a piece of software so complex there are now college programs on how to use it. You might think, “But don’t people learn how to use Photoshop or Adobe Illustrator in college?” Sure, in order to create stuff. And in a way you’re creating stuff with SAP. But do you get a Bachelor of Fine Arts degree with an emphasis on Photoshop?
Back in the Big Iron Age the operating systems were proprietary, and every computer that took up an entire room with a raised floor and HVAC system, and had less storage and processing power than an iPhone, had the same operating system as every other one, give or take a release level. But when a company bought application software like SAP, they also got the source code, which was usually documented and written in a way to make it easy to modify the hell out of it. Why? Because accounting principles may be the same the world over, and tax laws the same across each country and state, but no two companies have the same format for their reports, invoices, purchase orders and so forth. Standards existed and were universally ignored. If something went wrong it went wrong the same way for everyone, and was easy to track down. People didn’t need to take a college course to learn how to use a piece of software.
I’m not against the open source concept entirely. Back then all the programmers read the same magazines, so we all had the same homebrew utilities. We even had the forerunner to QR Code to scan the longer source code. Software vendors and computer manufacturers sponsored conventions so we could, among other things, swap recipes for such add-ons and utilities. While those things would make our lives easier, they had nothing to do with critical functions of the operating system. Unless badly implemented they would rarely cause key application software to crash and burn. Whereas today, with open source everything, who the hell knows what could be responsible some part of a system failing. [/end rant]