The Prescription Cascade: Void Architecture in US Pharmaceutical Markets

Applies thermodynamic void framework to pharmaceutical market structure. N=33 drug categories scored on Opacity, Responsiveness, and Coupling. Spearman(V, HHI)=0.839, p<0.000001, LOO [0.823, 0.873]. International comparison: same drug (insulin glargine), same physiological coupling (α=3), radically different Pe based on regulatory architecture (US Pe=+43.9, Canada Pe=−4.2, Germany Pe=−25.9). Discriminant validity: Daraprim (highest HHI=10,000) Pe=12.9 vs OxyContin (α=3 coupling) Pe=43.9, 3.4× difference confirming α as harm multiplier over market concentration. Identifies PBM rebate layer as hidden systemic amplifier (Pe=25.2). Seven falsifiable predictions testable from public CMS, FDA, and IQVIA data 2025-2027.