CYP450 Constraints in Infants: A Multidomain Convergence Framework for Investigating Mechanistic Vulnerability

Aim and background: Cytochrome P450 (CYP450) enzymes are the primary hepatic Phase I oxidative biotransformation system for many drugs and xenobiotics; variability in CYP capacity is therefore a key determinant of metabolic reserve.Reserve varies with developmental ontogeny, genotype, and acquired suppression (e.g., cytokine-mediated phenoconversion).Early infancy represents a developmental window in which clearance capacity and redox/energetic buffering may be comparatively constrained.We introduce a hypothesis-generating Three-Axis Convergence Framework (TCF) modeling interacting effects of (i) developmental/genetic reserve limits, (ii) immune-cytokine modulation of metabolism, and (iii) exposure/disposition context, and translate this synthesis into a structured postmortem interpretive tool integrated into the primary medicolegal autopsy, using an enhanced analytic panel applied selectively based on case context and specimen validity/QC to support mechanistic characterization of infant deaths remaining unexplained (often SUID/SIDS).Methods: A structured narrative synthesis was conducted spanning developmental pharmacology, pharmacogenetics, immunology, redox biology, neuropathology, and toxicology.Routine medicolegal postmortem practices used in SUID investigations were reviewed to identify measurement gaps that may limit mechanistic resolution in unexplained cases.The synthesis was formalized into five analytic domains: CYP450 capacity, immune/cytokine load, redox balance/energetics, neurochemical integrity, and xenobiotic/metal burden.Results: The Metabolic Vulnerability Index (MVI) operationalizes the TCF as a five-domain ordinal scoring system (0-15).Domain 1 is anchored by hepatic CYP protein abundance (a more postmortem-stable proxy than CYP activity assays, which are generally constrained by rapid functional decay and QC limitations), normalized to adult reference and interpreted against age-matched developmental expectations.Domain-combination lookup tables route users to 14 mechanistically defined archetypes and specify modifier/exposure-context documentation.Appendices define an operational postmortem workflow, specimen validity rules, analytic QC constraints, detection limits, and a worked example.A Cytokine-Metabolic Suppression Profile (CMSP) is presented as an interpretive coherence summary and does not modify MVI scoring or certification. Conclusion:The MVI provides a structured framework for describing multidomain physiologic constraints in unexplained infant deaths alongside standard forensic practice.In this way, the TCF, MVI, and CMSP together offer a disciplined response to long-standing mechanistic uncertainty in early life-by enabling systematic measurement, coherent interpretation, and transparent identification of evidence gaps, rather than asserting new causes.