## Anticholinergic Profile of TCAs **Key Point:** Nortriptyline is a secondary amine TCA with significantly lower anticholinergic activity compared to tertiary amine TCAs (amitriptyline, imipramine, doxepin). ### TCA Classification by Amine Structure | TCA Type | Examples | Anticholinergic Activity | Sedation | |----------|----------|--------------------------|----------| | **Tertiary amines** | Amitriptyline, Imipramine, Doxepin, Trimipramine | High | High | | **Secondary amines** | Nortriptyline, Desipramine, Protriptyline | Low | Low–Moderate | **High-Yield:** Secondary amine TCAs (metabolites of tertiary amines) have fewer side effects and are preferred in elderly patients, those with cardiac conduction abnormalities, or those at risk of anticholinergic toxicity (urinary retention, constipation, dry mouth, blurred vision, tachycardia). **Clinical Pearl:** Nortriptyline is the N-demethylated metabolite of amitriptyline and has a narrower therapeutic window (50–150 ng/mL), making plasma level monitoring useful in clinical practice. **Mnemonic:** **SAND** = Secondary Amine = Nortriptyline, Desipramine (fewer side effects; safer in elderly).
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