Tricyclic antidepressants classification

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. 

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... 

A. Classification and Pharmacokinetics The major classes of antidepressant drugs are shown in Figure 30-1 tricyclic antidepressants, heterocyclic antidepressants, selective serotonin reuptake inhibitors, and monoamine oxidase inhibitors. 

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. 

MAO inhibitors are another group of antidepressant medications that have historically been used to treat major depressive disorders. Currently, this classification of medications is considered a second-line or third-line treatment of depression (Brophy, 1991 Tierney et al., 1997). There are times however, that this group of drugs can be utilized as the first line of treatment for depression of an atypical nature (Tierney et al., 1997). Generally, these medications with their dangerous treatment-effect profiles should only be considered after the tricyclic or the newer classifications of antidepressants have been tried (Tierney et al., 1997). 

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