Venlafaxine characteristics

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. 

RBD is characterized by a relative absence of the atonia characteristic of REM sleep. This lack of atonia permits the physical acting out of dream mentation, particularly dreams involving confrontation, aggression and violence. RBD is seen most frequently in older men. RBD occurs in both acute and chronic forms. Acute RBD can occur during withdrawal from alcohol or sedative-hypnotics. RBD has also been induced by the tricyclics, SSRIs and venlafaxine. The chronic form of RBD may occur as part of an identifiable underlying neurological disorder, but typically is idiopathic. RBD may also be an initial manifestation of parkinsonism. RBD is very responsive to clonazepam, although this use has not been FDA approved. 

Like venlafaxine and the SSRIs, acute withdrawal of duloxetine causes a characteristic abstinence syndrome, with tachycardia, dizziness, insomnia, headache, and anxiety. 

Horst WD, Preskorn SH. Mechanisms of action and clinical characteristics of three atypical antidepressants venlafaxine, nefazodone, bupropion. Journal of Affective Disorders 1998 51 237-254. 

Efexor (Venlafaxine hydrochloride). Wyeth Pharmaceuticals. UK Summary of product characteristics, May 2006. 

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