Could switching from Zoloft to generic sertraline explain weight gain?
Ask the expert
Q. Is there a difference between prescription Zoloft and the generic version? I took Zoloft for almost one year more than 20 years ago. My doctor recently prescribed it again, but this time the pharmacy filled a generic version of sertraline. I think I've gained weight since I started this one, which didn't happen before. Is it possible that the generic version causes me to gain weight when Zoloft didn't?
A. I can't imagine that the change from Zoloft to the generic form of sertraline has caused your weight gain, especially if it is a similar dose as before.
The FDA requires that a generic drug contain exactly the amount of active ingredient as the brand-name drug. For example, a 50-milligram generic sertraline tablet must contain the same amount of the active ingredient in a 50-milligram Zoloft tablet.
The generic sertraline probably has a different appearance than the original Zoloft tablets. It may be a different color or shape. Or instead of a tablet, you might be taking a capsule. These differences are related to the inactive ingredients that are used to hold a tablet together and give a tablet its color.
These inactive ingredients can affect the way the active ingredient is absorbed from the intestine into the bloodstream. But the FDA requires that any variation in the amount and rate of absorption between a generic and its brand-name counterpart be minimal. So for most medications, including sertraline, these small variations shouldn't change how you respond to the generic product.
However, for some medications it is important that your doctor knows if you have changed to a generic. Even small differences in how much certain medications get absorbed can be important. If you notice a change in how the pills or tablets look on a refill, ask the pharmacist if your doctor also needs to know. You may need a blood test to make sure you don't need an adjustment in dose.
Now, to get back to the weight gain. This probably would have happened even if you were still on the original Zoloft. As we age, our bodies handle drugs differently and you may need to change the dose of sertraline (just as you would have needed to change the dose of Zoloft, had you stayed on the brand-name product). Or perhaps there is another reason for the weight gain, not related to this medication.
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About the Author
Howard E. LeWine, MD, Chief Medical Editor, Harvard Health Publishing; Editorial Advisory Board Member, Harvard Health Publishing
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