Tricyclic antidepressants (TCAs) are drugs used to treat depression, bipolar disorder, and other conditions such as chronic pain and insomnia. They primarily work by blocking norepinephrine and serotonin (5HT2) reuptake. They also block acetylcholine and histamine receptors which contribute to their side effect profile.⁠ ⁠ 👉🏻 Muscarinic M1 block: anticholinergic side effects including dry mouth, blurry vision, constipation, and urinary retention⁠ ⁠ 👉🏻 Histamine 1 receptor block: sedation and weight gain⁠ ⁠ 👉🏻 Adrenergic alpha block: postural hypotension, tachycardia, and erectile disfunction ⁠ ⁠ 👉🏻 Sodium channel block: QTc prolongation, arrhythmias ⁠ ⁠ 👉🏻 Serotonin uptake block: weight gain⁠