<p>Desipramine hydrochloride is a dibenzazepine-derivative tricyclic antidepressant (TCA). TCAs are structurally similar to phenothiazines. They contain a tricyclic ring system with an alkyl amine substituent on the central ring. In non-depressed individuals, desipramine does not affect mood or arousal, but may cause sedation. In depressed individuals, desipramine exerts a positive effect on mood. TCAs are potent inhibitors of serotonin and norepinephrine reuptake. Secondary amine TCAs, such as desipramine and nortriptyline, are more potent inhibitors of norepinephrine reuptake than tertiary amine TCAs, such as amitriptyline and doxepine. TCAs also down-regulate cerebral cortical β-adrenergic receptors and sensitize post-synaptic serotonergic receptors with chronic use. The antidepressant effects of TCAs are thought to be due to an overall increase in serotonergic neurotransmission. TCAs also block histamine-H<sub>1</sub> receptors, α<sub>1</sub>-adrenergic receptors and muscarinic receptors, which accounts for their sedative, hypotensive and anticholinergic effects (e.g. blurred vision, dry mouth, constipation, urinary retention), respectively. See toxicity section below for a complete listing of side effects. Desipramine exerts less anticholinergic and sedative side effects compared to tertiary amine TCAs, such as amitriptyline and clomipramine. Desipramine may be used to treat depression, neuropathic pain (unlabeled use), agitation and insomnia (unlabeled use) and attention-deficit hyperactivity disorder (unlabeled use).</p>