A New Version Of Dilantin Is Giving Pfizer Fits



One way that brand-name drugmakers fend off generic competition is to charge that a copycat version lacks bioequivalency, another way of saying the generic is absorbed differently in the body. Even though the FDA may have approved a generic as sufficiently similar to the brand-name med, slight differences can still cause some patients to experience problems if they switch drugs.

In an unusual twist, Pfizer seems to have created a switching problem for itself. Last fall, the drugmaker began marketing a new version of its age-old Dilantin med for treating epilepsy. Citing a need to upgrade manufacturing, Pfizer stopped selling Dilantin Kapseals and began selling Dilantin capsules. But some epileptics are complaining that the new product is causing seizures.

On one forum, for instance, Mike from Springfield, Illinois, writes: “Recently I was switched to the new dilantin. Not long after the switch I experienced a grand mal seizure. It is kind of wierd because my blood level was therapeutic. I had been stable and seizure free on dilantin kapseals for years. What is going on here? Any other folks experiencing problems?”

In effect, the world’s largest brand-name drugmaker is accused of causing some patients the kind of problems associated with a switch to a generic. Ironically, this occurs at the same time that the Epilepsy Foundation, which is supported by Pfizer and other drugmakers, has urged legislators in 18 states to introduce bills that would ban generic substitution for epilepsy drugs.

In fact, a foundation spokeswoman tells us any switching, in general, can be problematic. “Our anecdotal evidence shows there can be a difference and it could be fatal.” Although the new Dilantin isn’t considered a generic, the Abbreviated New Drug Application for the new version was approved by the FDA’s Office of Generic Drugs, not the neurology products division, an FDA spokeswoman tells us.

The new version “is not exactly the same, and that’s where the problem lies,” says Ilo Leppik, a physician, University of Minnesota pharmacology professor and director of research at Mincep, a Minneapolis clinic for epileptics that has issued a warning about the new Dilantin. “When it comes to switching drugs, epileptics are a special case. Even small changes can make a fairly large difference in blood levels.”


For its part, a Pfizer spokesman denies the drugmaker claimed there was no difference between the two versions. To know the extent, you must read the fine print in a letter sent to healthcare professionals last fall, where Pfizer disclosed that bioequivalence studies were conducted. But the new capsule failed to meet acceptance criteria for something called AUC, which is an index of drug absorption among patients who ate before taking the med. (There were also studies on patients who fasted before taking the capsule).

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However, the criteria Pfizer used was not requested by the FDA to show bioequivalence and was different from the FDA criteria, according to an FDA spokeswoman. She adds that the FDA was unable to review the study protocols before Pfizer proceeded and the agency doesn’t know why Pfizer chose different acceptance criteria. Nonetheless, the agency did approve the new Dilantin.

To some experts, the FDA approval is sympomatic of a wider problem involving the approval of generics and bioequivalency. Leppik, for instance, says “their standards are too loose. It may be okay for approving painkillers, but with epilepsy, it’s a fine line.”

To Joe Graedon, a pharmacologist, author and talk-show host who runs The People’s Pharmacy web site devoted to issues with meds, the Dilantin episode is reminiscent of the recent flap over generic Wellbutrin, which caused patient side-effect complaints but was cleared by an FDA probe. “We could have a somewhat similar situation,” he says.

Michael Privitera, a University of Cincinnati neurology professor, who also is also a speaker for Pfizer and other drugmakers, says that, “You have to ask whether the new and old versions are truly bioequivalent…In general, we’ve seen that there’s a subgroup of patients that clearly have some kind of problem with generics.”

Of course, Pfizer isn’t marketing its new Dilantin as a generic which, as Privitera notes, makes the situation both a “little unusual and, yes, ironic.”

Hi Birbomb,
Thank you very much for sharing this info. I have found that some generic AED's are not as strong as the brand name AED's and when it comes to the drugmaker Pfizer I don't trust them at all!! After they did off market labeling with the drug neurontin and have had over $240 million in lawsuits do to what neurontin has done to many people causing status sz. and 72 suicides I don't trust them at all especially when it was one of their own employees who turned them in. Here's wishing you well and May God Bless You!

Sue

I want to agree with Sue (as usual ) - Our insurance company decided it would not pay for any brand name AEDs if generics were available.

My prescription for Trileptal called for no generics but the pharmacy could not fill it after the generic became available. I had to buy two months supply at full price. My epileptologist wrote a letter for me to send to the insurance company with my appeal but I was still refused. So she wrote a letter with a second demand/appeal and I was finally given approval to keep taking the brand name Trileptal.

I was amazed that she worked so long and hard insisting that I do not take generics EVER.