Precision Cannabis Medicine: Genetics and Cannabinoid Response

Pharmacogenomics and Cannabis Metabolism

• CYP2C9 and CYP3A4 enzymes are primarily responsible for metabolising THC in the liver
• Genetic variants in these enzymes can significantly alter cannabis pharmacokinetics
• CYP2C9 poor metabolisers may experience elevated THC levels and stronger effects at standard doses
• Pharmacogenomic testing can identify patients who may require dose adjustments based on metaboliser status

Precision medicine approaches to cannabis therapeutics are grounded in the recognition that individual variation in cannabinoid response is substantially influenced by genetics. The enzymes responsible for metabolising THC and other cannabinoids are encoded by genes that exist in multiple variants across the population. Understanding a patient’s metaboliser status can provide clinically actionable information that improves the safety and efficacy of the titration process.

Endocannabinoid System Genetics

• CNR1 and CNR2 genes encode the CB1 and CB2 cannabinoid receptors respectively
• Variants in these genes have been associated with differences in cannabis sensitivity and response
• FAAH gene variants affect the breakdown of anandamide, influencing endocannabinoid tone
• Research is ongoing into how endocannabinoid system genetics predict therapeutic response

Genetic variation in the endocannabinoid system itself — not just in the enzymes that metabolise cannabinoids — may influence therapeutic response. Variants in the genes encoding CB1 and CB2 receptors, and in the enzymes that regulate endocannabinoid levels, could potentially predict which patients are most likely to benefit from cannabinoid therapies and which preparations are most likely to be effective. This area of research is developing but has not yet reached clinical application.

The Entourage Effect and Product Selection

• The entourage effect describes the potential interaction between cannabinoids and terpenes
• Different strains and preparations have distinct cannabinoid and terpene profiles
• Individual genetics may influence how patients respond to different cannabinoid combinations
• Genetically-informed product selection remains largely theoretical but is an active research direction

The entourage effect — the hypothesis that cannabinoids and terpenes interact synergistically rather than acting independently — has significant implications for personalised product selection. If confirmed, it would suggest that matching specific product profiles to individual patient genetics and pharmacology could substantially improve outcomes compared to a generic prescribing approach. Whilst the evidence base for the entourage effect is still developing, it provides a conceptual framework for thinking about precision cannabis medicine.

Clinical Application: Where Pharmacogenomics is Already Useful

• Identifying CYP2C9 poor metabolisers before initiating THC-containing prescriptions is clinically feasible
• Drug interaction prediction is enhanced by pharmacogenomic knowledge
• Patients with unusual or unexpected responses to standard doses may warrant pharmacogenomic investigation
• Several commercial pharmacogenomic testing services can provide relevant metaboliser status information

Whilst whole-genome precision medicine for cannabis therapeutics remains largely in research settings, some pharmacogenomic applications are already clinically relevant. CYP2C9 and CYP3A4 metaboliser status testing is available and can inform cannabis prescribing decisions, particularly for patients who experience unexpected potency at standard doses or who have significant drug interactions to manage. Proactive integration of pharmacogenomic thinking into medical cannabis practice is a marker of clinical sophistication.