Authored by the Simon group - Providing more effective and affordable health care

Laboratory Online is a series of educational and interactive modules offered by the Simon group. The purpose of the project is to enhance knowledge in drug-delivery technologies and underlying engineering principles. Within this user-friendly environment, practitioners and researchers can enter their own process parameter values in corresponding boxes (or use the default quantities provided). The findings of the simulation study are monitored in real-time by pressing the red-shaded button near the bottom of the page.

Two-pathway transdermal drug-delivery model

This program simulates drug transport through a two-pathway transdermal drug-delivery system. The model includes drug metabolism and allows for molecule transfer between the intercellular and transcellular phases (Fig. 1). An infinite reservoir, sink condition and mass flux continuity at the interface between the stratum corneum and viable epidermis are assumed. Simulation results are scaled based on the concentration in the donor cell and the total area. The parameters of the model are [1, 2]:

hs	stratum corneum thickness
hv	viable epidermis thickness
DT,s	drug diffusivity in the transcellular phase of the stratum corneum
DI,s	drug diffusivity in the intercellular phase of the stratum corneum
DT,v	drug diffusivity in the transcellular phase of the viable epidermis
DI,v	drug diffusivity in the intercellular phase of the viable epidermis
Kf,s	rate constant of the forward reaction in the stratum corneum
Kf,v	rate constant of the forward reaction in the viable epidermis
Kb,s	rate constant of the reverse reaction in the stratum corneum
Kb,v	rate constant of the reverse reaction in the viable epidermis
KT,s	metabolic rate constant of the drug in the transcellular phase of the stratum corneum
KT,v	metabolic rate constant of the drug in the transcellular phase of the viable epidermis
KI,s	metabolic rate constant of the drug in the intercellular phase of the in stratum corneum
KI,v	metabolic rate constant of the drug in the intercellular phase of the viable epidermis
δT	drug partition coefficient from a patch (or reservoir) into the transcellular phase
δI	drug partition from a patch (or reservoir) into the intercellular phase
γT	drug partition coefficient between the stratum corneum and the viable epidermis in the transcellular domain
γI	drug partition coefficient between the stratum corneum and the viable epidermis in the intercellular domain

Fig. 1. Drug transport across the stratum corneum and the viable epidermis.

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ENTER DATA HERE

D_T,s : m²/s     D_I,s : m²/s     D_T,v : m²/s     D_I,v : m²/s

K_T,s : s^-1     K_I,s : s^-1     K_T,v : s^-1     K_I,v : s^-1

K_f,s : s^-1     K_b,s : s^-1     K_f,v : s^-1     K_b,v : s^-1

γ_T :           γ_I :           δ_T :           δ_I :

h_s : m           h_v : m

Cumulative amount of drug released



Diffusion flux into the receiver compartment (s^-1)

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References

[1] Lee, A. J., King, R. J. and Rogers, T. G. (1996), A multiple-pathway model for the diffusion of drugs in skin, Journal of Mathematics Applied in Medicine & Biology, 13, 127–150.

[2] Goyal, A. Mandapuram, S., Michniak, B. and Simon, L. (2007), Application of orthogonal collocation and regression techniques for recovering parameters of a two-pathway transdermal drug-delivery model, Computers & Chemical Engineering, 31, 107-120.

Released 11/05/08. Recently modified 11/05/08.
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