Four out of every five prescriptions in the United States are filled with the generic version of a drug. The use of generics has saved over $700 billion during the past decade. However, generic drugs can deviate in strength and ingredients from the name brand medication. With certain conditions it is important to be quite precise. So, how and when should we use generics?

Consider a study out of the University of Cincinnati. Subjects with Parkinson’s disease were given one of two injections. They were told that one drug was more expensive, and that the other was similar in effectiveness but was, due to manufacturing differences, much cheaper. Patients who received the “more expensive” drug showed 28% more improvement in motor skills. One might assume that one injection was with a name brand medication, and the second was a generic…but actually, both injections were placebos, made up of a saline (salt) solution! Our beliefs certainly do indeed affect our outcomes. Keep this study in mind as you read on.

In today’s regulatory environment, developing an original medication is extremely complex and enormously expensive. A new drug undergoes research, trial and error, animal studies and human studies, FDA regulations, and marketing. After spending an average of some $2.6 billion on every new drug that actually makes it to market, a pharmaceutical company retains the exclusive right to it for approximately seven years. After that, the FDA allows one company to make a generic copy. That company will then have about six months of exclusivity before other companies are allowed to make their own generic versions.

It is clear that a major reason generic drugs are so much cheaper is that, although they do incur manufacturing and marketing costs, they bypass most of the expenses for research and development.

The FDA requires that copies of a drug result in blood concentrations that are within a specified range of the original drug. It is important to know that the FDA does not require that a generic drug contain the same inactiveingredients as the brand name product, as these inactive ingredients don’t contribute to a drug’s therapeutic action. These include binding materials, dyes, preservatives, and flavoring agents. A generic drug often looks nothing like the original product. These differences often explain why patients’ reactions may vary among different generics as well as with the original drug.

Note that this applies to over-the-counter medications as well. For example, the binding materials, dyes, preservatives, and flavoring agents used in the CVS brand of acetaminophen are not the same as those used in the Walgreens version, and these generic versions of acetaminophen each vary from the original Tylenol.

The FDA permits certain specified variations (most typically around plus or minus 3-4%) of the active ingredients for most generic drugs. Usually, that small difference will not matter. However, our bodies are unique - we have different metabolisms, shorter or longer colons, different reactions to filler chemicals, etc. Some of us may be extra sensitive to small changes in blood concentrations of a drug. In addition, what matters may not be the dose of the medication, but how much of it the body can actually utilize. Some disease treatments have a narrow therapeutic index, where the blood concentrations must stay within a very limited range, and a small difference can have serious consequences. These medications include those used for seizures, heart arrhythmias, thyroid disorders, as well as blood thinners and lithium. It’s possible that a name brand drug may indeed be better.

We do live in the real world. Price differences between brand names and generics can be enormous. Many people avoid a generic due to a preconception that it is inferior to the name product. When you consider that University of Cincinnati study mentioned above, together with stringent FDA criteria, the generic is often worth considering. And, when one generic drug fails, it may well be a good idea to try a second generic before emptying the piggy bank and going straight to that name brand.

When switching from a name brand to a generic product, or from one generic product to another, always pay attention to how you feel, and inform your doctor of any changes immediately. Always feel free to have a discussion about how generic alternatives to name brand medications may relate to your own particular needs.

Dr. Alan Frischer is former chief of staff and former chief of medicine at Downey Regional Medical Center. Write to him in care of this newspaper at 8301 E. Florence Ave., Suite 100, Downey, CA 90240.