Q: I’ve been taking Zoloft. Recently, my pharmacist filled my prescription with a generic form of the drug. Does the brand name matter?
A: The patent expired on Zoloft, one of the popular selective serotonin reuptake inhibitor (SSRI) antidepressants, in June 2006. Now, many patients are switching to, or starting with, a less expensive form of the drug that bears its generic (chemical) name, sertraline.
A few years ago, a patient of mine noticed some changes when he exchanged his brand-name antidepressant Celexa for the generic form, citalopram. For the next month or two, he felt slightly apathetic and made some mistakes that caused him mild embarrassment. That can happen when the dose of an antidepressant is too high. But he feared that he would relapse if he reduced the dose, so instead he decided to return to the brand-name drug.
Why was the dose too high if he was still taking the same drug? The answer requires a closer look at the differences between brand-name and generic psychiatric medications.
The generic is not a “knockoff” of the original, like a fake Rolex watch. The FDA requires that a generic drug be essentially similar to the brand-name version. It should contain the same amount of active drug. It must be taken by the same route (for example, by mouth). And at a given dose, it should deliver about the same amount of active ingredient into the bloodstream – anywhere from 20 percent less to 25 percent more than the brand-name drug.
It doesn’t always deliver exactly the same amount because generic pills contain inactive substances that distinguish them from the original. In fact, the U.S. government actually requires this, to prevent fraudulent marketing. The otherwise inactive substances in a pill can affect how the active chemical is absorbed by the bloodstream, delivered to its target, and eliminated; for example, it may break up faster or more slowly in the gastrointestinal tract.
The healthy volunteers who act as subjects in tests of generic drugs usually receive relatively small doses. In real patients taking higher doses, the difference between the amount of active ingredient in the bloodstream in the brand-name and generic forms may exceed the FDA-approved 25 percent.
My patient and I were satisfied with his decision to go back to the brand-name drug.
– Michael Craig Miller, M.D., Editor in Chief, Harvard Mental Health Letter
