With generics, some disorders require extra caution

Generic drugs are growing in popularity, enabling health care consumers to save money at a time when every dollar counts.

But consumers should take special care when considering the switch from brand name to generic drugs, a University of Cincinnati (UC) College of Medicine faculty member says – and some diseases and disorders require extra caution.

"People need to be careful and they need to talk with their doctor if a pharmacist suggests that they try a generic drug," says Michael Privitera, MD, a professor in the neurology department and director of the Epilepsy Center at the UC Neuroscience Institute at University Hospital. "There are many people who have medical disorders where drug failure is not an option."

For example, a patient with chronic pain whose pain gets worse after switching to a generic drug can simply have the dosage adjusted. But an epilepsy patient who has been seizure free with a certain medication can’t afford to switch that medication and take the risk of having a seizure while driving or working at a hazardous job, Privitera says.

According to an analysis by Wolters Kluwer Health, generic drugs accounted for more than 60 percent of all US prescriptions filled in 2008. The annual US growth rate for generic prescriptions since 2004 is 12 percent, according to the analysis.

"Many times insurance companies will call us and say, ‘You can put this person on a brand name drug, but he has to fail a generic first,’" says Privitera, a neurologist with UC Physicians. "And I say, ‘No, that’s not an option.’ It’s an option if you have a medical disorder where the clinician and patient are able to monitor and detect a small change in drug response, but not an all-or-none problem such as epilepsy, heart arrhythmia or many other conditions."

Privitera points out that while the US Food and Drug Administration (FDA) tests generic drugs for bioequivalence (within a certain range of the brand name drug’s potency as measured by single-dose blood tests in healthy volunteers), that does not guarantee therapeutic equivalence (the same clinical effectiveness and safety profile).

"They never really test the therapeutic equivalence," Privitera says. "They’re presuming therapeutic equivalence because the drugs fall within this bioequivalence range of 80 to 125 percent, but it’s possible that such a range is too broad and that on either end you might not get therapeutic equivalence."

Also, Privitera says, even though testing is confined to normal volunteers who have no other illnesses and are taking no other medications, the FDA presumes that the generic drugs will act exactly the same in a population that is likely to have other illnesses or disorders and be taking other drugs.

Privitera says further study is needed on generic drugs’ bioequivalence, using patient populations that have reported problems while taking such drugs as opposed to the normal populations the FDA uses for testing. Based on the results of such testing, the FDA could be persuaded to either tighten the range for bioequivalence or change the way in which bioequivalence is tested. Still ahead, Privitera says, would be a therapeutic equivalence study.

(Source: University of Cincinnati: June 2009)