Development of a Deterministic Web Tool for Evaluation of Fixed-Dose Combinations

Fixed-dose combinations (FDCs) are widely utilised pharmaceutical products combining two or more active ingredients in a fixed ratio, developed with the aim of improving therapeutic convenience and patient adherence. However, deviations from established pharmacological principles during FDC development have resulted in formulations that lack clear evidence of benefit or introduce unnecessary safety risks. In India and other low- and middle-income countries, the prevalence of non-recommended and irrational FDCs remains substantial despite large-scale regulatory bans, reflecting gaps between policy interventions and enforcement effectiveness. Current identification of irrational FDCs is predominantly retrospective, occurring through post-marketing regulatory reviews and policy-based restrictions rather than through prospective screening at the formulation stage. This work operationalises a previously described, deterministic, rule-based pharmacological framework into an interactive web-based tool—the Predictive FDC Risk Analyzer v3.1—that provides transparent, narrative-based appraisal of mechanistic compatibility, pharmacokinetic alignment and safety overlap for two-drug combinations. The tool executes entirely within the user's browser, does not access patient-level data and explicitly restricts its intended use to educational and conceptual screening contexts without clinical validation or regulatory authority. Illustrative case examples demonstrate that the tool generates consistent, qualitative verdicts for rational, high-risk and policy-restricted combinations, reflecting the underlying rule-based logic in a transparent manner. The Analyzer serves as a structured, reproducible framework for teaching and early-stage reasoning around fixed-dose combination pharmacology, but does not provide empirical risk prediction and must not be used for clinical decision-making or regulatory submission.