Dual Agents
The "newer" antidepressants were originally developed to be selective, with singular mechanisms of action so as to be more tolerable than medications such as the tricyclic antidepressants. However, it was discovered that medications with more mechanisms, such as the so called "dual agents" sometimes had greater efficacy. Increasingly, psychiatrists are using antidepressants with multiple mechanisms for patients with difficult to treat, chronic, or recurrent depression.
On the flip side, more mechanisms can mean more side effects. The side effects seen with noradrenergic antidepressants can include motor activation, tremor, agitation, increased blood pressure, and increased heart rate. Moreover, noradrenergic receptors in the SNS can cause a net reduction of parasympathetic cholinergic tone, leading to dry mouth, constipation, and urinary retention.
The SNRIs (Serotonin/Norepinephrine Reuptake Inhibitors)
There are currently three medications in this class. These medications are both serotonin reuptake inhibitors (SERTs) and Norepinephrine Reuptake Inhibitors (NETs) They also have some net augmentation of dopamine in the prefrontal cortex (since the norepinephrine reuptake pump also takes up dopamine)
