Americans spent more than $235 billion on prescription drugs in 2004 to treat everything from heart disease to teenage acne. For years, public health experts have been saying that we could cut those costs if people would substitute generic equivalents of brand-name drugs when they are available. Now, a group of researchers from the Brigham and Women's Hospital in Boston and the University of California–San Francisco have figured out just how much we could be saving.

What the researchers wanted to know: How much would people save if generic drugs were always substituted for brand names when possible?

What they did: The researchers cross-checked survey findings from more than 18,000 people about the prescription medications they took with pharmacy records showing how much the patients paid, what drugs they got, and the strength of the medication. Then, they used a database filled with information on drug prices and brand/generic equivalents to estimate how much the people who got brand-name drugs would have saved if they had gotten a generic instead.

What they found: More than half of the drugs prescribed in this study had both brand-name and generic forms, and 39 percent of those prescriptions were dispensed as the brand-name version. Had people taken the generic forms of these drugs, the overall spending on drugs would have been reduced by $5.9 billion in 2000, an average of $46 per person. People over the age of 65, who take a greater number of prescriptions, would be expected to save an average of $78 per year by switching to generics when possible.

What it means to you: Americans could be spending more money than they need to on brand-name drugs. The FDA certifies that generics are the equivalent of their brand-name counterparts, and pharmacists are often allowed, or sometimes even mandated, to substitute generics when they're available. Talking to your doctor and your pharmacist about how to lower your prescription costs is always a good idea, and, depending on what you're taking, switching to generic drugs could be a big part of that savings plan.

Caveats: The individual savings calculated by these researchers is a very broad average. Drug prices are influenced by many things, including where you live, which pharmacy you visit, and how much your insurance will pay, so it's impossible to say how much any one individual could save by switching to generic drugs.

Find out more: The Federal Trade Commission has a page explaining what generic drugs are, how they differ from brand-name drugs, and when you could use them.

Premera, a division of the Blue Cross insurance company, has a website that allows you to see how much you would save per year by switching from a brand name to its generic equivalent:

Read the article: Hass, J.S. et al. "Potential Savings From Substituting Generic Drugs for Brand-Name Drugs: Medical Expenditure Panel Survey, 1997–2000." Annals of Internal Medicine. June 7, 2005, Vol. 142, No. 11, pp. 891-897.

Abstract online: http://www.annals.org