Tricyclic antidepressants agitation from

The CNS manifestations of tricyclic antidepressant overdose may vary from mild agitation or drowsiness to delirium, coma, respiratory depression, or seizures. These manifestations are thought to result in part from central anticholinergic and antfliistaminic actions of these drugs. 

Another risk of antidepressants in vulnerable patients (particularly those with unrecognized bipolar depression) is switching, sometimes suddenly, from depression to hypomanic or manic excitement, or mixed, dysphoric-agitated, manic-depressive states. To some extent this effect is dose-related and is somewhat more likely in adults treated with tricyclic antidepressants than with serotonin reuptake inhibitors, bupropion, and perhaps with MAO inhibitors. Risk of mania with newer sedating antidepressants, including nefazodone and mirtazapine, also may be relatively low, but some risk of inducing mania can be expected with any treatment that elevates mood, including in children with unsuspected bipolar disorder. 

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