Serotonin reuptake inhibitors, selective dosage

St. John s wort also exhibits anti-inflammatory and antibacterial activity. Reports of antiviral activity arc unsubstantiated. The main adverse effect with St. John s wort is severe phototoxicity. A sunbum-like condition may occur at normal dosages. St. John s wort. should never be taken with MAOIs because of the risk of potentiation of the effects. Selective serotonin reuptake inhibitors (SSRIs) likewise should not be taken with St. John s wort because of the ri.sk of serotonergic syndrome. 

Serotonin-norepinephrine reuptake inhibitors (SNRIs) (e.g. duloxetine, venlafaxine and desvenlafax-ine) inhibit the reuptake of both serotonin and norepinephrine and are referred to as dual inhibitors or selective serotonin norepinephrine inhibitors . The SNRIs lack of anticholinergic side effects results in a distinct advantage over traditional TCAs [13,77,78]. For example, duloxetine is a potent, balanced inhibitor of serotonin and norepinephrine reuptake [79]. Venlafaxine inhibits serotonin reuptake at lower dosages and inhibits both serotonin and norepinephrine reuptake at higher dosages [70,80]. 

Another example of chiral switching is that of the selective serotonin reuptake inhibitor (SSRI) antidepressant Celexa, which was introduced to the market in 1998 by Forest Laboratories. Celexa is a racemic mixture of (i )-citalopram oxalate and (5)-citalopram oxalate. While orrly the (S) enantiomer has therapeutic antidepressant properties, both enantiomers contribute to the side effects of the drug and therefore limit effectiveness and patient tolerance. In 2002, the FDA approved Lexapro, a new antidepressant derived from Celexa but from which the therapeutically ineffective (R) enantiomer has been removed. The benefits of isolating the active isomer include smaller required dosages, reduced side effects, and a faster and better patient response to the drag. 

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