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Antidepressant medications are notorious for causing weight gain, sometimes to significant degrees. This effect is fairly common, and finding an antidepressant that doesn't cause weight gain may prove to be a real challenge.

Generally speaking, antidepressants may be classified in 4 large groups:

  1. Tricyclic Antidepressants (TCA) - the older type of antidepressant drugs - including agents such as Amitryptilline (Elavil), Imipramine (Tofranil), Desipramine (Norepramine) and Doxepin (Sinequan). These agents work by increasing the amount of Norepinephrine and Serotonin in the brain. Unfortunately, they are often associated with significant side effects, including weight gain, constipation, drowsiness, dizziness, sexual dysfunction, etc.

  2. Monoamine Oxidase Inhibitors (MAOI) - including agents such as Isocarboxazid (Marplan), Phenelzine (Nardil) and Tranylcipromine (Parnate) - which work by increasing the amount of monoamines (epinephrine, norepinephrine and dopamine) available in the brain. Similar to the tricyclic antidepressants, these agents are often associated with weight gain. They may also cause dangerous cardiovascular side effects, such as extreme hypertension and cardiac arrhythmias, which limit their clinical use.

  3. Selective Serotonin Reuptake Inhibitors (SSRIs) - the newer type of antidepressant drugs - including agents such as Zoloft (Sertraline), Prozac (Fluoxetine), Paxil (Paroxetine), Luvox (Fluvoxamine), Celexa (Citalopram) and Lexapro (Escitalopram). These agents work by selectively inhibiting the reuptake of Serotonin in the brain synapses, thereby increasing the amount of Serotonin available to the brain neurons. Overall, SSRIs have a much safer side effect profile as compared to tricyclic agents and MAOI.

  4. Other Antidepressant Agents - which cannot be classified strictly under one of the categories above - such as Remeron (Mitrazapine), Wellbutrine (Buproprion HCL), Nefazodone (Serzone), Trazadone (Desyrel), and Venlafaxine (Effexor).

Most antidepressant agents have been found to be associated with weight gain, although this may vary on an individual basis. As far as the mechanism of weight gain, it is believed to be due to increased appetite leading to increased food intake.

Below is a review of the most commonly used antidepressants and their relationship with weight gain:

  • Amitryptilline, Imipramine, Desipramine and Doxepin (the tricyclic agents) may cause weight gain quite frequently and to a significant degree. Weight gain appears to be dependent on the dose and length of therapy.
  • Phenelzine, Isocarboxazid and Tranylcipromine (from the MAOI class) - may also cause significant weight gain, although some authors feel this happens to a lesser degree than with tricyclic agents.
  • Zoloft, Paxil and Prozac (from the SSRI class) - can all cause weight gain to varying degrees, especially with long-term usage. Some studies have shown an average weight gain of 15-20 lbs over time. The magnitude of the effects varies on an individual basis, ranging from no weight gain at all to moderate or even severe weight gain.
  • Celexa and Lexapro appear to cause less weight gain than other SSRIs, although some studies indicated increased carbohydrate cravings with Celexa. Lexapro has been reported to cause weight gain in up to 5% of people taking it.
  • Trazodone, which is not a classical SSRI, causes weight gain uncommonly. However, Trazodone is sometimes used in association with one of the agents above (the classical SSRIs), so weight gain may actually occur due to this fact.
  • Wellbutrine has not been shown to cause increased appetite or weight gain.
  • Similarly, Nefazodone (Serzone) doesn't appear to be linked to weight gain.
  • Remeron, an antidepressant with sedative action, has been associated to significant weight gain.
  • Effexor has been shown to cause weight gain, but less pronounced than Prozac, Zoloft or Paxil.

In conclusion, here's a list of antidepressants believed to cause little or no weight gain:

  • Wellbutrine (Buproprion HCl) - has not been shown to cause increased appetite or weight gain.
  • Nefazodone (Serzone) - has not been shown to cause increased appetite or weight gain.
  • Trazodone (Desyrel) - associated with weight gain uncommonly.
  • Effexor (Venlafaxine) - associated with weight gain, but less than other SSRIs
  • Lexapro (Escitalopram) - associated with weight gain in up to 5% of people taking it.



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