Color changing drug molecules as built in stability indicators

Antibiotic degradation compromises safety and efficacy but integrating chromogenic moieties into the drug structure allows built-in visual indicators. By coupling antibiotics with chromophores or pH-sensitive dyes that respond to triggers like hydrolysis, pH shifts, oxidation, or heat, the drug can remain one color when stable and change visibly upon degradation. This report explores the underlying mechanisms and design strategies for developing such colorimetric antibiotic indicators. We review common antibiotic degradation pathways and their triggers, discuss classes of chromogenic groups (e.g. pH indicators, spirolactams, leuco dyes), and outline synthetic approaches (e.g. cleavable linkers, prodrug conjugates, polymer encapsulation). Illustrative examples include natural cases (e.g. tetracycline darkens upon epimerization [1] cefotaxime turning yellow with hydrolytic impurity [2] and engineered indicators (e.g. a bromophenol/phenolphthalein time‐temperature indicator for amoxicillin syrup [3]. We highlight historical context and recent research (2018–2024) and discuss practical challenges.