An endogenous metabolism marker may change far less than the drug exposure it is intended to represent.
What the paper found
A pharmacometric model used clinical ketoconazole, rifampin and midazolam data to evaluate 4-beta-hydroxycholesterol as a CYP3A4 marker. Simulations showed a narrower response range for the marker than for midazolam exposure, particularly during inhibition.
What the evidence cannot establish
The numerical predictions depend on model assumptions, sampling duration and the underlying clinical data. Biomarker performance in a modeled population is not a reconstruction of one patient’s clearance.
Implications for forensic review
A modest marker change should not automatically exclude a substantial interaction. Identify oral versus intravenous administration and the duration of the interacting treatment. Where available, direct drug measurements and an actual medication timeline are more informative than assuming equal sensitivity of the two measures.
Source and related reading
Source: PMC4076805, supplied full-text paper. Findings are paraphrased; case-review implications are an interpretation.
Related: Unchanged Midazolam Exposure Does Not Establish Absence of Every Lemborexant Interaction.
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