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Antidepressants: Can they lose effectiveness over time?

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Can antidepressants lose effectiveness over time? I've taken fluoxetine (Prozac) for several years. But recently, I've noticed the medication doesn't seem to be having the same effect, and I feel more depressed. Can you explain this?
- Mary / Minnesota

answered by...

Mayo Clinic psychiatrist Daniel Hall-Flavin, M.D., and colleagues answer select questions from readers.

Answer
You describe a phenomenon that affects approximately 20 percent of people who take antidepressants — the so-called "poop-out" effect. In such cases, the medications simply stop being effective. Doctors don't fully
understand what causes this. But factors that you and your doctor may want to consider include:

Relapse or worsening of depression. For most people, depression is a disease that will recur at least once — if not more frequently — after the first episode. Sometimes depression worsens for no apparent reason or due to added stress that overrides the effects of the medication.

Underlying medical condition. Some conditions, such as hypothyroidism, can cause depressive symptoms. It is important to rule out such conditions as a cause of worsening depression.

Aging. Sometimes depression can get worse as you get older.
A new medication. Some medications for unrelated conditions can interfere with the way your body metabolizes and uses antidepressants, decreasing their effectiveness.

Reassessment of original diagnosis. For example, it is possible that an illness previously diagnosed as depression may actually be bipolar disorder, in which depression is a prominent feature.

The good news is that adjusting the dosage, changing medications or adding other medications is usually effective in countering the poop-out effect. Psychotherapy also can help.

For all these reasons, it is important to have a psychiatrist trained in the use of antidepressant medications review all of the possible causes and interventions that may be helpful when an antidepressant seems to lose its effectiveness.



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