Antidepressants classification

Table 70-3 shows the commonly accepted classification of available antidepressants. 

The traditional scheme is complicated by the fact that some antidepressants exhibit characteristics of more than one class. For example, clomipramine, a tricyclic antidepressant (TCA) with side effects and toxicity similar to other TCAs, works more like the selective serotonin reuptake inhibitors (SSRls). Similarly, venlafaxine and duloxetine, which are usually grouped with the atypical antidepressants, have a side effect and safety profile comparable to the SSRls. Although a classihcation system based on mechanism of action offers some advantage (see Table 3.7), even this scheme is limited by the fact that antidepressants that work in the same way may have widely divergent side effect and safety profiles. In the following discussion, the traditional classification system is adopted. Although fraught with problems and inconsistencies. 

TABLE 7-16. Classification of antidepressants by chemical structure and mechanisms of action... 

We do not currently have a complete and adequate explanation of how antidepressant drugs work. What we do know is that all effective antidepressants have identifiable immediate interactions with one or more monoamine neurotransmitter receptor or enzyme. These immediate actions provide the pharmacological foundation for the current classification of the different antidepressants. 

Original drug classifications in the 1960s emphasized that there were important distinctions between the antidepressants (e.g., tricyclic antidepressants) versus the anxiolytics (e.g., benzodiazepines) available at that time. This reflected the diagnostic notions then prevalent, which tended to dichotomize major depressive disorder and... 

FIGURE 8—10. In the late 1990s the antidepressants venlafaxine XR and others have become first-line treatments for generalized anxiety disorder. Thus, antidepressants are now first-line treatments for both depression and anxiety disorders, rendering the classification of antidepressant versus anxiolytic inappropriate for many antidepressants. 

Scientists were looking for drugs to treat different medical problems when their observations almost accidentally led them to the study of depression and its treatment. Many scientists continued in this new direction to the discovery of the current three classifications of antidepressant drugs used today monamine oxidase... 

The antidepressants available in the United States are classified by either their chemical structure (e.g., the tricyclics, TCAs) or their actions on neurotransmitters (e.g., SSRIs and MAOIs) or simply as other (e.g., Wellbutrin). In the future, the classification of the antidepressants may become more confusing as new drugs are developed that are neither TCAs, SSRIs, or MAOIs. 

Krijzer FNCM, van der Molen R (1987) Classification of psychotropic drugs by rat EEG analysis the anxiolytic profile in comparison to the antidepressant and neuroleptic profile. Neuropsychobiology 18 51-56 Krijzer F, Koopman P, Olivier B (1993) Classification of psychotropic drugs based on pharmaco-electrocorticographic studies in vigilance-controlled rats. Neuropsychobiology 28 122-137... 

TABLE 3.5. Classification of Antidepressants According to Their Presumed Mechanism of Action ... 

---