Fractional Compartment Pharmacokinetics — Exact Cp5 Engine
| Param | Observed | Predicted | PE% | OK |
|---|
| Param | Observed | Predicted | PE% | ≤20% |
|---|
| Drug | Dose | Model | N | AAFE | CCC | R² | %2-fold | MPE% | Verdict |
|---|
| Subject | n_frac | R² Classical | R² Fractional | ΔOFV |
|---|---|---|---|---|
| 1 | 1.000 | 0.995 | 0.994 | -1.1 |
| 2 * | 0.865 | 0.960 | 0.958 | -0.4 |
| 3 | 0.947 | 0.944 | 0.957 | +2.9 |
| 4 | 1.000 | 0.995 | 0.995 | -0.5 |
| 5 | 1.000 | 0.991 | 0.965 | -14.6 |
| 6 * | 0.870 | 0.977 | 0.989 | +7.6 |
| Feature | FractaLPK | Classical Model | Simcyp |
|---|---|---|---|
| Fractional Compartments (n ∈ ℝ) | ✅ Cp5 exact | ❌ integer only | ❌ integer only |
| Solution for n ∈ ℝ | Analytic (Cp5) | N/A | N/A |
| ↑ FractaLPK supports fractional compartments (n ∈ ℝ) with exact analytical evaluation. Standard tools round to the nearest integer (up to 34% error). | |||
| TCM 1D (oral transit, n ∈ ℝ) | ✅ exact | ⚠️ chain n∈ℤ | ⚠️ chain n∈ℤ |
| Mammillary 2D (n ∈ ℝ) | ✅ exact | ❌ | ❌ |
| Numerical Precision (n ∈ ℝ models) | ~10⁻¹⁰ (analytic) | ~10⁻⁶ (RK45) | ~10⁻⁶ (ODE) |
| * For integer-compartment models, all solvers achieve adequate clinical precision. FractaLPK advantage is specific to fractional n ∈ ℝ. | |||
| SAEM Estimation | ✅ (OFV=263.4*) | ✅ | ❌ |
| FOCE-I (Cp5 gradients) | ✅ OFV=252.2* | ✅ (gold std) | ❌ |
| * Validated on 2 real datasets: Theophylline (12 subjects, Boeckmann 1994) + Indomethacin IV (6 subjects, Kwan 1976). FOCE-I converges in 17 iter with analytical Cp5 Mittag-Leffler gradients. Cp5 auto-detects subdiffusion (n_frac<0.90) in 2/6 Indomethacin subjects. | |||
| MCMC Bayesian (NUTS) | ✅ | ✅ | ❌ |
| Parallel Computing | ✅ | ✅ | ⚠️ |
| GOF Diagnostics | ✅ | ✅ | ⚠️ |
| VPC / Covariate SCM | ✅ | ✅ (PsN) | ❌ |
| Drug Library Fitting | ✅ (8 ref drugs) | ✅ (gold standard) | ⚠️ |
| Interactive Dashboard | ✅ | ❌ (CLI) | ⚠️ |
| AI Assistant | ✅ (prototype) | ❌ | ❌ |
| Regulatory Acceptance | Pending | ✅ FDA/EMA | ✅ FDA |
| Price (target) | TBD | $5-20K/yr | $50-150K/yr |
| Drug | Route | Tissue | α clinical | d* | α_fit | Error | Status |
|---|
Fixed d* per tissue (from Step 3). Varying tissue thickness R₂ across the biologically plausible range. Shows that variability in α between patients comes from variability in tissue geometry.
| Drug | d* | α range (predicted from R₂) | α range (clinical IIV) | dα/dR₂ | Coverage |
|---|
Validates the full mechanistic chain: patient weight → allometric R₂ → PDE-predicted α. Uses Abacavir pediatric data (169 children, Zhao 2012).
The fractional order α estimated by FractaLPK from clinical PK data is not empirical — it corresponds to the fractional order d of the diffusion PDE governing drug transport in tissue. PDE: ∂ᵈT/∂tᵈ = (1/r)∂T/∂r + ∂²T/∂r² (Caputo, cylindrical coords) BC: T(R₁,t) = 1 (drug source) | ∂T/∂r(R₂,t) = 0 (impermeable boundary) Collapsing: C(t) = 2/(R₂²-R₁²) ∫ T(t,r)·r dr Fitting: C(t) = A · [1 - Eα(-(k·t)α)] Result: α_fit ≈ d with error < 5%. This validates that FractaLPK recovers the true tissue geometry parameter from observational C(t) data alone.
C(t) = Σ (F·D/V) · E_α(-(CL/V)·(t-t_n)^α)
Simulates C(t) for multiple patients using their individual α (from weight via allometric model). Compares fractional vs classical model. Shows Time In Range (TIR) for each regimen.
| Patient | α | WT (kg) | Best regimen | QD frac TIR% | BID frac TIR% | TID frac TIR% | BID classic TIR% |
|---|
Find optimal dose + interval for a specific patient (α, weight). Maximizes Time In Range using differential evolution.
Haffajee et al. 1983 / Dokoumetzidis 2009 — 3-model comparison
Amiodarone IV (400 mg bolus) exhibits heavy power-law tails that classical mono-exponential models cannot capture. This demo compares three models: mono-exponential (2 params), bicompartimental (4 params), and FractaLPK fractional (3 params, Mittag-Leffler). The fractional model captures the anomalous tail with fewer parameters.
| Model | Params | R² | RMSE | AIC | Key Parameters |
|---|
| t (h) | Cp5 (FractaLPK) | Std Interp | Diferencia | Err FractaLPK | Err Std Interp |
|---|
C(t) = Σ_{k=0}^{n} (kₐt)ᵏ / Γ(k+1) · e^{-kₐt}
FractaLPK evaluates fractional transit compartments (n ∈ ℝ) exactly.
Standard tools round to the nearest integer (up to 34% error).
F(n₁,n₂) = Σ_{j=0}^{n₁} Σ_{k=0}^{n₂} c₁ʲ·c₂ᵏ·t^{α₁j+α₂k} / [Γ(α₁j+1)·Γ(α₂k+1)]
Blood (α₁) + tissue (α₂) compartments with anomalous kinetics.
Both compartment orders can be fractional simultaneously (n₁,n₂ ∈ ℝ).
Standard tools have no 2D fractional evaluator — they approximate using bilinear log interpolation.
Published datasets · FractaLPK vs NONMEM/Classical comparison
CSV → Diagnostics → Model Selection → Fractional ODE → Fit → Validation