Q. I am currently talking Remeron for depression. I am about 16 weeks pregnant and doing well. I recently started working with a new psychiatrist, and my new doctor suggested that I switch to Prozac because he thought it would be safer for the baby. I am a little worried about making a change; I have never tried Prozac before and had a bad reaction (horrible anxiety and insomnia) when I tried Lexapro.

A. While it is true that we have more information regarding the reproductive safety of Prozac (fluoxetine) than Remeron (mirtazapine), it does not necessarily mean that switching to Prozac is the best option at this point in your pregnancy.

During the earliest stages of pregnancy, formation of the major organ systems takes place and is complete within the first 12 weeks after conception. Exposure to certain agents, including medications, may interfere with this process and result in some type of organ malformation or dysfunction Thus, many women who are taking antidepressants for which there is less reproductive safety data elect to switch to an antidepressant that is better characterized (e.g., Prozac) to minimize the risk of any type of malformation.

This approach makes sense if it is done prior to conception or early in the first trimester, before organ formation is complete. However, later on in the pregnancy, after organogenesis is completed, there is little to suggest that one antidepressant is safer than another. The best treatment option at this stage is the one that is the most likely to keep you well. In other words, we would recommend that you remain on Remeron. Switching to another antidepressant may increase the risk of recurrent depression, and we do not know how you would tolerate or respond to the Prozac.

Ruta Nonacs, MD PhD

Djulus J, Koren G, Einarson TR, Wilton L, et al. Exposure to Mirtazapine During Pregnancy: A Prospective, Comparative Study of Birth Outcomes. J Clin Psychiatry 2006; 67(8):1280-1284.

*This post was originally published as an article in our March 2008 Newsletter.