Phenoconversion is when a drug or illness makes a patient behave as a different metaboliser from their genotype. Inhibitors push towards poor-metaboliser behaviour and inducers towards rapid or ultrarapid behaviour.
Before interpreting a pharmacogenetic result or a drug level, list everything the patient takes, including over-the-counter products, and check for inhibitors or inducers of the enzyme concerned.
- Take a full medicine list, including over-the-counter drugs and herbal products.
- Ask which enzyme handles the drug and which co-medications inhibit or induce it.
- Interpret genotype together with co-medication, not on its own.
- Consider a drug level when the clinical response does not match expectation.
- Document the interaction in the record so it travels with the patient.
Why it matters
A correct genotype can still predict the wrong phenotype when the patient also takes an enzyme inhibitor or inducer.
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