Switching From One Generic Seizure Medication To Another

The brand vs generic issue is a hot-topic in the epilepsy community. Patients with epilepsy may take generic antiepileptic drugs (AEDs) as a way to avoid the potentially high cost of brand AEDs. For some patients, paying for brand AEDs is not a realistic option—the cost can be several hundred dollars per month (or higher!). Although the FDA mandates that the brand and generic seizure medications be very close in terms of function and metabolism, there can be some differences between brand and generic AEDs.

AED levels are the level of the AED found in a patient’s blood—for example, a person can get their blood drawn and be found to have a keppra level of 38. If a patient’s levels are drawn while taking brand keppra, it is expected that there would be very little change in the blood level, if the patient was switched to generic keppra (=levetiracetam). However, there can be some variability in some individuals. The concern, of course, is what happens if levels change when switched from brand to generic? If the levels drop too low, then the patient could have a seizure. If the levels go too high, the patient may become dizzy or have other side effects.

or most patients, changing from brand to generic AEDs does not cause problems. This is because, again, the FDA mandates that the brand and generic AED be very close, in terms of their function and metabolism. The way the studies are usually done are to compare the generics to the brand. To clarify: assume we have generic medication A, generic medication B and generic medication C. Currently, each of these medications are compared to the brand seizure medication- to make sure the metabolism of the drugs are very similar.

Illustration 1

To illustrate how studies are usually done (FDA required):




A recent article (Krauss 2011) was published that compared the metabolism of different generic AEDs. Thus, they compared blood levels of generic medication A to generic medication B to generic medication C.

Illustration 2

GENERIC A compared to GENERIC B compared to GENERIC C

Remember, usually the generic medications are compared to the brand, as required by the FDA (see Illustration 1, above). This study did something that the FDA does not require—it compared the metabolism of the different generic AEDs to one another (see Illustration 2, above). What they found was that for some patients, the differences between the various generic formulations was significant.

This study did not determine if the variability in blood levels caused problems- such as seizures. That will be left to another study. What the study suggests is that switching from one generic AED to another generic AED may result in significant increases or decreases in AED levels- for a small percentage of patients. It is thought that some patients may have seizure activity due to this fluctuation, although the percentage of patients is likely not high.

As our readers may well know, a pharmacy can switch from one generic AED to another. There can be more than 10 different generic AED manufacturers for a given seizure medication. A patient may be getting a peach colored pill that is shaped like a diamond one month, then the patient is switched to a white round pill. This may be due to changing the manufacturer. Thus, the study I describe in this article is important—it demonstrates that levels can fluctuate significantly in a small percentage of patients- when patients are switched from one generic AED to another.

The message of this article is NOT- stop taking generic seizure meds. Rather, the message is – understand that there may be some risk in changing from one generic AED to another. This is a risk that can be discussed between a patient and their clinician. It is important and complex!

For more information on the brand vs generic seizure medication debate, see our article on this website:

What to take: Brand vs generic seizure medications?



The reference for the above described study:

Krauss GL, Caffo B, Chang YT, Hendrix CW, Chuang K. Assessing bioequivalence of generic antiepilepsy drugs. Ann Neurol 2011;70:221-228.

The article is reviewed in Epilepsy Currents.

Gidal BE. Generic antiepileptic drugs: How good is good enough? Epilepsy Currents 2012;12:32-34.

You can review the Epilepsy Currents article at:


James White, MD

Dr. White has been practicing as a full-time epileptologist since 1999. His practice focuses on optimizing the diagnosis and treatment of patients with seizure disorders. Dr. White’s special interests include patient education, improving the side-effect profile of seizure medications, and epilepsy surgery.

2 Responses to “Switching From One Generic Seizure Medication To Another”

Pat Hopkins June 29, 2015 at 6:03 pm

Is it possible that a blood level would be -0- due to switching from one generic to another generic?

Steven Naimon November 27, 2018 at 5:37 am

Will continually taking the new generic medication eventually make any new seizures subside?