What's in a Name, or the Curious Drug called Topiramate

Topiramate (Topamax): More Than What It's Called!

Patients frequently ask their psychiatrist: “Why are you prescribing me an antidepressant for anxiety when I’m not depressed?” or “Why are you prescribing me an antipsychotic for depression?”

Their puzzlement is caused by the categorization of medications with clear-cut labels. It originated from the initial decades of pharmacotherapy, when there were few medications and little was known about their actions. Imipramine was for depression, Thorazine was for psychosis. No questions needed to be asked.

With the advances in pharmacology, more useful categorizations, such as “SSRI”, “dopamine-blocker”, have become widespread in the profession but have not become widely known in the general public. It is the duty of the prescriber to explain to the patient that there is much more to a medication than the old style categorizations.

Which brings me to the curious molecule called Topiramate (brand name in the US: Topamax). 

What Is Topiramate (Topamax)? FDA Approvals and Mechanism of Action

Topiramate (brand name in the US: Topamax) was introduced in the late 1990s as a seizure medication (antiepileptic). Approximately a decade later it received a second FDA approval for migraine prevention. Scientifically, it is classified according to its primary mechanism: blocking sodium channels on nerve cells, which reduces abnormal electrical firing in the brain.

As several Several antiepileptic medications are also effective mood stabilizers (i.e. treat bipolar disorder), studies were conducted with Topiramate in that area as well. It has not been found to be as effective as others but can be used as a second-third line treatment. It has never obtained FDA-approval for that condition so "officially" it is not a mood stabilizer. "Unofficially" it is.

Topiramate and Weight Loss: When a Side Effect Becomes the Treatment

At this point I would like to introduce Sam (a fictionalized name, real person, case reported with permission).

I started seeing Sam in 2015 for a set of problems that included mood instability. He had gained a tremendous amount of weight on an "antipsychotic", aripiprazole (Abilify), which also works as a mood stabilizer. He weighed 370 pounds when I first saw him, and I suggested changing his mood stabilizer to Topiramate. Why Topiramate, if it is not a first line drug for that condition? Because in some people it leads to the loss of appetite, which is officially categorized as a side effect.

The loss of appetite is not complete, but it leads to  the person stopping eating before reaching the amount of calories needed to maintain weight. Sam was lucky, he was one of those people who developed this side effect. He kept losing weight - 5 pounds here, 10 pounds there – and at last checking, in 2020,  he was down to 238 pounds.

What Is a Medication, Really? Rethinking Drug Categories in Psychiatry

For Sam, Topiramate was an "appetite suppressant”, and we were using a side effect of the medication for treating a condition. 

I used an “antiepileptic” as a mood stabilizer (an unofficial main effect) and as an "appetite suppressant" (deliberately utilizing a known side effect). For Sam,  it was not an antiepileptic. 

So, what is a medication? Scientifically, drugs are categorized according to their mechanism of action — in topiramate’s case, sodium channel blockade. Clinically, however, a medication is what you use it for. The label on the bottle tells you what the drug was first approved for. It does not tell you what it can do for you specifically — and that is a conversation worth having with your prescriber.

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Alexander Papp, MD