About 175 people taking Eprex between 1998 and this April contracted a disease called pure red cell aplasia, according to a paper being published in The New England Journal of Medicine today. Their bodies mounted an immune response to the drug, and this response also attacked their own EPO. Unable to make enough red blood cells, these patients often became dependent on blood transfusions to survive.

But the cause of the side effect, which had rarely been seen in the years before 1998, was a mystery. And why were virtually identical versions of EPO sold in the United States – Amgen’s Epogen and Johnson & Johnson’s Procrit – associated with far fewer cases?

Scientists evaluated this phenomenon and apparently have solved the mystery – Trouble With Anemia Drug Is Reduced, but Issues Remain

Epidemiologic investigation discovered differences in how the drug was packaged and used!

Dr. Charles L. Bennett, a professor of medicine at Northwestern University and lead author of the New England Journal paper, said two changes seemed to spur the problem.

One was that Johnson & Johnson stopped using human serum albumin, a blood protein, as a stabilizer in vials of the drug because European regulators were concerned about the risk of mad cow disease. Another is that more kidney disease patients began getting the drug by injection under the skin rather than intravenously because studies showed less of the expensive drug would be needed that way.

Now subcutaneous injection of Eprex for kidney patients is essentially prohibited in Europe. Since that change and others in the packaging and handling of the drug, the incidence of aplasia has decreased by 83 percent and is now back to nearly where it was before 1998.

“The problem is probably over,” Dr. Bennett said.

Patients unfortunately suffered. This investigation does reveal many important lessons:

• Drugs can act differently when we vary the route of administration
• Additives can make a difference, thus evaluation of generics must include formulation issues
• Sometimes an effort to save a few dollars is dangerous
• Post-marketing surveillance is crucial for new drugs

This is a most interesting and unfortunate story. Erythropoeitin provides great benefits for chronic kidney disease patients who have anemia. Determining the best and most cost-effective means for delivering erythropoietin should have a high health services research priority. Unfortunately, most studies which we read are drug company sponsored. We need an agency to sponsor these studies for the common good.

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