Types segmentation distinguishes molecules by side-chain chemistry, determining pharmacokinetics and market share. Tertiary aminesโamitriptyline, clomipramine, imipramine, trimipramineโcollectively held 64 % of 2023 revenue, favoured for broader receptor activity but burdened by higher anticholinergic liabilities. Secondary aminesโnortriptyline, desipramine, protriptylineโaccount for the remaining 36 %, offering reduced sedation and comparatively safer cardiovascular risk profiles, a decisive factor in geriatric prescribing. Within tertiary amines, amitriptyline alone generated 38 % of class sales, underpinned by multi-indication approvals and low generic pricing that keeps patient access high. Market taxonomy analysis shows that the average ex-factory price differential between tertiary and secondary amines is only 4 %, but adherence-adjusted revenue per patient favours secondary amines by 11 % because of better tolerability and longer persistence, subtly reshaping competitive dynamics despite smaller unit volumes.