We struck a nerve yesterday. Our post about a study on consumer perceptions and use of generic drugs ignited a firestorm of comments.

That firestorm came from all directions. Some readers attacked Big Pharma. Others blasted the generic manufacturers. Some commenters hit both.

Dan from Hiram, Maine said, “After drug companies obscenely cranked up drug prices over the past 5 years, a generic drug at 30-50% price reduction is still vastly overpriced.”

Jeff from Mystic, Connecticut wrote: “Just remember that generic drug makers spend more on lawyers than anything else. They are parasites.”

Tim from Houston, Texas basically defended the major drug companies: “Remove enough of Big Pharma’s revenue stream, and someday in the distant future, there might not be any new drugs to copy.”

But here’s how we really stirred up controversy yesterday: By claiming that generics are identical to brand-name drugs.

Frank from Oregon wrote: “The web is full of stories about people suffering major health problems after switching to generics…They contain the same active chemical. That does not mean the work the same way.”

Ryan from San Diego, California told me to “do my homework…the FDA allows for a 20%-25% Variance in bioavailablity.”

Well, today we went back to Jackie Kosecoff, CEO of Prescription Solutions, the in-house Prescription Benefits Manager (PBM) for UnitedHealth Group , whose visit sparked yesterday’s Postcard on this very subject. She responds to the debate: “Generics are identical–or bioequivalent–to a brand-name drug in dosage form, safety, strength, route of administration, quality, performance characteristics and intended use. ”

The FDA website echoes Kosecoff’s statement: “A generic drug is the same as a brand-name drug in dosage, safety, strength, quality, the way it works, the way it is taken and the way it should be used. FDA requires generic drugs have the same high quality, strength, purity and stability as brand-name drugs.”

So, in fact, we did our homework (and Ryan, re your point about the variance in bioavailability, this is commonly misunderstood. According to 2004 letter from Dr. Steven Galson, then director of the Center for Drug Evaluation and Research at the FDA and now U.S. Surgeon General, that -20/+25%, “actually represents the acceptable bounds on the 90% confidence intervals around the ratio of the mean result for each of the two products.” He also writes that the average difference in absorption was 3.3% for 127 bioequivalence studies of generic drugs approved in 1997. And a study published in JAMA in December, 2008 found “no evidence of superiority of brand-name drugs to generic drugs.”)

I’m more convinced than ever that confusion about generics — the very point of yesterday’s Postcard — isn’t going away.