Three years ago, Pfizer made a seemingly curious move. The drugmaker began marketing a new version of its venerable Dilantin drug for treating epilepsy, and stopped selling Dilantin Kapseals in favor of new Dilantin capsules. The explanation? Manufacturing needed to be upgraded. But in doing so, the drugmaker upset some epileptics, who began reporting seizures after switching meds.

There was unfortunate irony in the move. You may recall brand-name drugmakers often carp that generics lack bioequivalency, which refers to how a generic is absorbed differently in the body. Slight differences can cause some patients to experience problems after making a switch. Yet Pfizer placed itself on both sides of the argument. And at the same time, the Epilepsy Foundation, which the drugmaker has supported, was warning that generic substitution is not a good thing.

Although Pfizer denied there was any difference between the two versions, the drugmaker handled the changeover in a way that caused confusion to those paying attention. Bioequivalency studies were conducted, but not with the criteria normally used by the agency, which was unable to review the study protocols before Pfizer proceeded. Meanwhile, the newer Dilantin was not considered to be a generic, but the Abbreviated New Drug Application was approved by the FDA’s Office of Generic Drugs (background).

The issue, though, largely disappeared from most radar screens - until now. A Maryland couple has filed what is believed to be the first wrongful death lawsuit against Pfizer for switching its products. Their 32-year-old son, Jeremy Jackson, began taking the newer Dilantin in October 2007 after being on the older version for three years. Within a month, he died in his sleep of a grand mal seizure.

The lawsuit, which was filed last year in state court in Arizona because Jackson resided there at the time, charges Pfizer knew changes in bioequivalency could adversely affect some patients, but failed to sufficiently warn doctors and consumers, given that its own bioequivalency study failed to rely on the usual protocols, among other things. [We only learned of the lawsuit recently, and since we were the first to report the controversy, we thought an update was in order. We should also add that the doctor is being dropped as a defendant in the lawsuit].

“The prior published studies on Dilantin’s active ingredient, phenytoin, collectively state that any change to the dissolution characteristics of a drug with a narrow therapeutic index or high biokinetic volatility like phenytoin will present serious problems to a sizable percentage of consumers, such as suffering unexpected seizures,” Max Maccoby, a Washington, DC-based attorney who represents the Jackson, writes us. “That is exactly what happened in our case, where Jeremy, a young man in otherwise perfect health with normal levels of phenytoin in his system, was unable to absorb phenytoin from the new Dilantin.”

He goes on to say that the FDA recently provided him with more than 1,500 complaints filed to its Medwatch system for capturing adverse events by consumers who claim they suffered injuries due to the change in Dilantin between late 2007 and the end of 2008. Not surprisingly, he is now considering expanding the lawsuit to seek class action status with additional plantiffs. Whether he can succeed with such a move may depend on resolving any issues surrounding statutes of limitations.