## Anticholinergic Profile of Tricyclic Antidepressants **Key Point:** Nortriptyline is a secondary amine TCA with significantly lower anticholinergic activity compared to tertiary amine TCAs. ### TCA Classification by Amine Structure | TCA Type | Examples | Anticholinergic Activity | Sedation | |----------|----------|--------------------------|----------| | **Tertiary amines** | Amitriptyline, Imipramine, Doxepin, Trimipramine | High | High | | **Secondary amines** | Nortriptyline, Desipramine | Low | Low | **High-Yield:** Secondary amine TCAs (nortriptyline, desipramine) are metabolites of their parent tertiary amines (amitriptyline, imipramine) and retain antidepressant efficacy while having a much better tolerability profile. ### Why Nortriptyline Has Lower Anticholinergic Effects Nortriptyline is the N-demethylated metabolite of amitriptyline. The removal of the N-methyl group reduces: - Muscarinic receptor antagonism - Antihistamine effects - Alpha-adrenergic blockade **Clinical Pearl:** Nortriptyline is preferred in elderly patients, those with urinary retention, glaucoma, or cardiac conduction abnormalities because anticholinergic effects can worsen these conditions. **Mnemonic:** **SAND** = Secondary Amines (Nortriptyline, Desipramine) = Selective, Anticholine-sparing. Tertiary amines are "Total anticholinergic" (Amitriptyline, Imipramine, Doxepin, Trimipramine).
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