Convergent Modifiers of Exposure Variability in Approved Cannabinoid Medicines: Pharmacogenomics, Drug-Drug Interactions, and Parent-Metabolite Divergence.

Bagher A. · Pharmaceutics · 2026

**Background & Methods** This is a narrative, integrative review synthesizing evidence from bibliographic databases and regulatory documents on four approved cannabinoid medicines: cannabidiol, nabiximols, dronabinol, and nabilone. The review examines how pharmacogenomics, drug-drug interactions, and parent-metabolite divergence modify systemic exposure to these medications using a convergent exposure-modifier (CEM) framework that distinguishes victim pathways (where genotype and comedication modify cannabinoid exposure) from perpetrator pathways (where cannabinoids alter co-medication exposure). **Key Findings** - CYP2C19 and CYP2C9 represent the strongest evidence for exposure variability: cannabidiol increased N-desmethylclobazam (active metabolite) exposure 3.4-fold in healthy volunteers while parent clobazam remained unchanged, and CYP2C19 poor-metabolizer status independently increases baseline metabolite exposure. - Comedication may phenoconvert genotype-predicted enzyme activity, meaning drug-drug interactions can override genetic predictions of metabolic capacity and alter expected exposure patterns. - No approved-product study measured joint genotype-by-comedication effects, and evidence quality varies significantly across products: cannabidiol has the most robust data; nabiximols lacks genotype-stratified pharmacokinetics; and nabilone is excluded due to uncharacterized active-metabolite contributions. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Not reported. **Evidence Quality** This review has substantial limitations. The CEM framework is hypothesis-generating rather than validated, with three core predictions requiring prospective, falsifiable genotype-by-treatment testing. No prospective studies examining joint genotype-by-comedication interactions were identified in approved products. Evidence is unevenly distributed: strongest at specific CYP-substrate pairs (cannabidiol-clobazam, THC-containing medicines with CYP2C9), but weak or absent for nabiximols and nabilone. Notably, one prediction relies on oral Δ9-THC evidence of unspecified formulation. The authors explicitly conclude that label- and study-supported monitoring has independent evidentiary support, but the framework's predictions do not, and genotype-guided dosing of cannabinoids remains unvalidated. This is a narrative review without meta-analysis, limiting the strength of conclusions regarding clinical applicability.

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