THE DIFFUSION MODEL AND OTHER TRANSPORT MECHANISMS
IN THE DESIGN OF A TRANSDERMAL DRUG DELIVERY SYSTEM
Click here to view full manuscript

Sanjiv D. Parikh

Abstract

The delivery of medication across skin tissue with a transdermal drug delivery(TDD) system is dependent on the transport mechanism called diffusion. Diffusion is influenced by the following important local variables: 1) Scale of the species; 2) Convection conditions; 3) Environmental conditions; 4) Time scale; and 5) other Material Properties (mechanical, electrical, chemical, biological). The goal of this research is to model and study the mechanisms of transport of medication from a foreign source to a target site within the human body. This project focuses on bio-mechanics aspects of diffusion.

An approximation of the second order non-homogeneous equation for diffusion in two-dimension is made numerically through the use of a finite-difference method (Crank-Nicolson). A FORTRAN program is developed to generate concentration data for a grid area over time. Visualization of the output resulting from this program is used to help understand the intricacies of the diffusion model. The diffusion model is representative of the transport of medication from the TDD system to the first metabolically active site within the tissue. Metabolic processes add nonlinear and unquantifiable phenomena to the diffusion model of drug transport. In conclusion the medication transport model will be improved when the effects of metabolic processes are included in the diffusion model.

OUTLINE

							       Page
Section 1.   Introduction				
	-Introduction						1
	-Current drug delivery systems				2
	-Problem definition					3

Section 2.   The Analytical Transdermal Drug Deliver Model
	-Formation of a diffusion model				5
	-Transport parameters					7
	-Main variables						9
		Scale and geometry							
		Heat dissipation								
		Competing mechanisms						

Section 3.   The Numerical Diffusion Model
	-Program information					14
	-Defining input variables				15
	-Visualizing the output					16

Section 4.   Conclusion
	-Conclusions						20
	-Recommendations and future work			21

Acknowledgments							23

References							24

Appendices
	I Numerical Implementation of Finite Difference Theory
	II Finite Difference Model Theory			25

	III Download FORTRAN program and data files 					34