Venlafaxine. Pharmacology and therapeutic potential in the treatment of depression

Venlafaxine is the first available antidepressant of the structurally novel SNRI (serotonin noradrenaline-reuptake inhibitor) class of drugs. It resembles the tricyclics in its ability to inhibit presynaptic reuptake of both serotonin and noradrenaline to a clinically significant degree. However, it does not cause appreciable effects at other receptor sites, including cholinergic, adrenergic and histaminergic, which are responsible for most of the unwanted side effects and toxicity associated with antidepressant treatment. It has the unusual ability to reduce β-noradrenergic responsiveness after a single dose, which has led to the suggestion that it may have an earlier onset of therapeutic effect than traditional antidepressants. Clinical trials provide evidence that venlafaxine is of comparable efficacy to reference antidepressants, but may have a faster onset of antidepressant effect when given in high dosage.