Transdermal drug delivery by coated microneedles: geometry effects on drug concentration in blood

Abstract

Drug administration through transdermal delivery is restricted by the top layer of skin, the stratum corneum. One possible solution to overcome the barrier function of the stratum corneum is to employ microneedle arrays. However, detailed theoretical models relating drug‐coated microneedles and their geometry to the drug concentration in the blood are limited. This article aims to address this issue by examining the blood concentration profiles for a model drug, insulin, that has been administered via coated microneedles. A mathematical model is introduced and applied to predict theoretical blood concentrations. Furthermore, the insulin concentration in blood is calculated for a range of different microneedle shapes and dimensions to identify the most effective geometry. The results indicate that the optimum microneedle geometry in terms of maximizing insulin concentration was a rocket‐shaped needle with a constant tip angle of 90°. Also, it has been found that the number of microneedles in an array is the most significant factor in determining maximum insulin concentration in the blood (Cb, max). Penetration depth of the microneedle, centre‐to‐centre spacing and microneedle thickness had a less significant effect on the maximum insulin concentration in the blood. It is envisaged that the current study will help in designing microneedles of optimum size and shape for transdermal drug delivery. Copyright © 2009 Curtin University of Technology and John Wiley & Sons, Ltd.

A New Paradigm for Numerical Simulation of Microneedle-Based Drug Delivery Aided by Histology of Microneedle-Pierced Skin

“…MNs treated skin and the thickness of the skin change, so the effective thickness of the skin is 362 introduced in consistent with our previous studies [32,33]. Therefore, we deduce the diffusion 363 coefficient from the experiment data of passive diffusion and the effective thickness in this studycan be simply considered as reduction of the real skin thickness.…”

“…As discussed earlier in our papers, an effective skin thickness can be defined for MN treated skin 355 which represents the average path length for drug diffusion through the skin [32,33]. Using the 356 same concept, we calculate the effective thickness in this work using the images that we have 357 collected.…”

“…The real skin thickness is 1.6 365 mm which is the average over 20 randomly selected samples. An effective thickness of the MNs 366 treated skin is then calculated using equations (2) and (3) as discussed earlier [33]. 367…”

Transdermal Drug Delivery by Microneedles: Does Skin Metabolism Matter?

“…During the injection of microneedles, the drug molecules are assumed to move through an isotropic media which is consistent with many previous works (e.g., Davis, 2003). The detailed explanation of FEMLAB has been avoided in this paper due to brevity of the paper and since they were explained in our other work (Davidson et al, 2008;Al-Qallaf et al, 2009). Fig.9.…”

A theoretical compartment model for antigen kinetics in the skin

“…Both models have been developed on the macroscopic (tissue) and microscopic (cell) levels, where aspects such as metabolic activity, binding to skin components, diffusion and partitioning are considered. In addition, some models focused on the transport through the skin after drug administration with microneedles (Al-Qallaf et al, 2009;Kim et al, 2015;Lv et al, 2006;Zhang et al, 2009). Most of these models focus on transport to the systemic circulation, as opposed to kinetics within the skin.…”