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Investigate transdermal patch PK calculation: total dose vs. release rate relationship#23

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Investigate transdermal patch PK calculation: total dose vs. release rate relationship#23
NaiveTomcat with Copilot wants to merge 1 commit into
masterfrom
copilot/explain-transdermal-patch-calculation

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Copilot AI commented Mar 10, 2026

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The issue asked to clarify the relationship between total dose (doseMG) and release rate (RELEASE_RATE_UG_PER_DAY) in the transdermal patch pharmacokinetic model.

Findings

The codebase already implements two distinct, intentional modes in ParameterResolver.resolvePatchApply():

  • Rate mode (RELEASE_RATE_UG_PER_DAY present in extras): Zero-order kinetics. Unit conversion µg/day → mg/h via / 24_000, then applied as a constant infusion rate:
    A(τ ≤ T) = R/k₃ · (1 − e^(−k₃τ))
    A(τ > T) = A(T) · e^(−k₃(τ−T))
    
  • Dose mode (no release rate, legacy): First-order Bateman absorption with k₁ = GENERIC_K1 = 0.0075 h⁻¹. doseMG represents total reservoir content; rateMGh is unused.

The two modes are mutually exclusivedoseMG and RELEASE_RATE_UG_PER_DAY are not mathematically coupled in the current model. Dose mode does not derive a release rate; rate mode ignores doseMG entirely.

No code changes made

Per explicit direction, no modifications were applied. The existing implementation is consistent, tested, and intentional.


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Copilot AI changed the title [WIP] Explain logic for calculating transdermal patch dosage and release rate Investigate transdermal patch PK calculation: total dose vs. release rate relationship Mar 10, 2026
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