Side Effects of Serotonin-Blocking Medications

When we talk about serotonin-blocking medications, a point of clarification must be made. In most cases, medications do not block overall serotonin activity but instead block the activity at one of the many serotonin receptor types. For example, the antidepressants trazodone, nefazodone, and mirtazapine increase total serotonin activity yet they block certain of the serotonin receptors. Mirtazapine increases both serotonin and norepinephrine activity by interfering with the alpha-2 receptor. By also blocking the serotonin-2 and serotonin-3 receptors, mirtazapine avoids the sexual dysfunction and GI side effects commonly experienced with other serotoninboosting medications. We cannot truly call these serotonin-blocking medications, because they are serotonin-boosting medications that selectively block certain serotonin receptors. 

As noted in the previous section, buspirone produces both serotonin-boosting and serotonin-blocking effects by stimulating the serotonin-lA receptor. These mixed effects produce an overall milder serotonin-boosting effect that limits it potential side effects but also results in a more limited range of clinical uses than is available to other serotonin-boosting medications. Clearly, we cannot really say that buspirone blocks serotonin activity in the same way that antipsychotics block dopamine activity. 

Finally, many of the atypical antipsychotics act, at least in part, by blocking activity at the serotonin-2 receptor. This may lessen the potential for extrapyramidal side effects and contribute to reducing psychotic symptoms. Atypical antipsychotics 

The closest things to true antiserotonin medications used by psychiatrists are those used to treat serotonin-induced side effects. In particular, cyproheptadine has an overall serotonin-blocking effect. With repeated use, this medication can theoretically cause depression and anxiety, and there are case reports of recurrence of depressive symptoms following frequent administration of cyproheptadine. 

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