Generic Epilepsy Drugs Not the Same
Patients Warned Switching Between Dilantin and Generic Brands Can Cause Relapses
Oct. 25, 2004 -- Don't switch from brand-name Dilantin to a generic version of the antiseizure drug -- or from generic to brand name, epilepsy specialists warn.
The warning comes after epilepsy patients at MINCEP Epilepsy Care, in Minneapolis, Minn., suddenly began having severe seizures. The patients' seizures previously had been kept under control with Dilantin treatment.
What happened? An investigation by Ilo E. Leppik, MD, MINCEP research director and professor of pharmacy at the University of Minnesota, found a clue. A change in State of Minnesota health plans required the use of generic drugs instead of brand-name drugs. Without notifying their doctors, the health plans switched the patients from brand-name Dilantin to a generic version.
"We didn't even know they had done this until we saw these developmentally delayed kids and adults coming into the clinic or emergency room with seizures," Leppik tells WebMD. "It turned out all these kids had been switched from brand-name Dilantin to generic."
Because they had a carefully kept record of the patient's Dilantin blood levels, the researchers were able to compare the effects of the switch. Sure enough, the patients had much lower blood levels of the drug after switching to the generic version. Once they switched back, drug levels increased into a range that controls seizures.
The findings appear in the October issue of Neurology.
Dilantin: A Tricky Epilepsy Drug
Dilantin, made by Parke-Davis, is the brand name for phenytoin (FEN-ih-toyn). For more than 50 years, it's helped people with epilepsy keep their seizures under control. Doctors use it often -- but it's one of the trickiest drugs around, says Gregory L. Barkley, MD, chair of the Epilepsy Foundation's professional advisory board and clinical vice chair of neurology at Detroit's Henry Ford Hospital.
"The issue with phenytoin is it is the single most difficult anticonvulsant drug to use because it has very different metabolism than most medicines," Barkley tells WebMD. "Small changes in dose result in wild swings in metabolism."
The small differences between Dilantin and generic phenytoin can have big clinical effects.
"Given the nature of the thin margin between too much and too little phenytoin, I am not surprised switching from one brand to the other makes problems," Barkley says.