Let me offer up a scenario: A man named Richard had epilepsy, but he hadn't had a seizure in over a year since he began taking the anticonvulsive medication Keppra. He was beginning to wonder if he could stop taking medications altogether. About a month after taking a new job, however, he had a seizure while walking his dog, causing him to lose consciousness. Some passers-by were able to call for help, and he was taken to the emergency room. Why had Richard seized now? His new job didn't expose him to any new toxins. His work hours were actually better, and he was getting plenty of sleep. After some thought, he remembered that when he took his new job, his insurance company also changed. This insurance company had requested that the more expensive brand name Keppra be replaced with a generic medication. He hadn't thought much about it at the time. Wasn't a generic medication basically the same thing as a brand name drug?
There's been a lot of controversy over whether generic and brand name anti-epileptic medications are what is called "therapeutically equivalent." In other words, there's some question whether or not generic medications work as well as the often much more expensive brand name counterparts. If you're thinking of switching from a brand name drug to a generic anticonvulsive medication, or even if you're considering switching from one generic medication to another, you need to be well versed on this issue in order to make an informed decision. You'll also want to discuss your decision with your physician.
The FDA deems a generic drug to be "therapeutically equivalent" to a brand-name drug if it has the same amount of the active ingredient, and meets standards for strength, quality, purity and identity. Two measures are particularly scrutinized: the area-under-the-curve (AUC) and maximum plasma concentration (Cmax). These measure how much medication gets absorbed into the blood stream. The FDA requires that the AUC and Cmax of a generic substitute need to be within 80% to 125% of the brand-name measures with 90% confidence. That seems like a pretty wide margin, especially if the drug in question has a small "therapeutic window" -- the difference between a dose that's effective and a dose that causes unacceptable side effects. Tests to establish that generic drugs meet this standard are usually done on about 35 people. This is a very different standard than the often hundreds of people tested for a brand-name drug.
... For example, if one generic medication has 125% the effective dose found in a brand name anti-epileptic, and you switch to a medication that has 80% that dose, your true medication dose has fallen considerably.
The risks of switching from brand name to generic or between generics will partially depend on which medications are being taken. Patients using Keppra, Lamictal or divalproex are most likely to switch back from generic to brand name products, often for increased seizures or a change in adverse medication reactions.
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