Coencapsulation of therapeutic agents within targeted nanocarriers can coordinate their biodistribution and improve combination-treatment outcomes. However, the drug ratio established during formulation may change during circulation, tissue accumulation, cellular uptake, intracellular processing, and pharmacological target engagement. This article develops a mechanism-based theoretical account of how these transitions affect the relationship between pharmaceutical drug-ratio preservation and combination pharmacology. Drawing on published experimental, clinical, analytical, and mechanistic research, the analysis distinguishes initial coencapsulation ratios, compartment-specific intact-carrier ratios, released-drug proportions, intracellularly available concentrations, and pharmacologically effective exposure relationships. The central proposition is that coencapsulation creates an opportunity for coordinated delivery, while the preservation of therapeutically relevant ratios remains conditional on drug-specific transport, release, metabolism, sequestration, and temporal exposure. A further distinction separates ratio-dependent synergy from benefits attributable to greater total delivery, improved tolerability, or independent drug actions. The resulting account identifies measurable transitions, competing mechanisms, and discriminating experiments for evaluating combination nanocarriers. It accommodates circumstances in which synchronized exposure is beneficial and situations requiring sequential or spatially differentiated drug action. Therapeutic ratio preservation should therefore be evaluated as a compartment-specific, time-dependent pharmaceutical mechanism whose pharmacological significance requires direct evidence.
IJPRAS
