Mass transfer analysis of transdermal drug delivery using microneedles

Microneedle is a promising technique for delivering high molecular weight drugs across skin. The microneedles can offer a number of benefits over other drug delivery methods. For example, the drugs only diffuse over a short distance before reaching the blood circulation which enhances the absorption of drugs by the tissue. However, the drug transport behaviour in skin is affected by a complex interplay of many parameters (e.g., microneedle geometries, permeability across skin, etc).In this thesis, many aspects of the microneedle field were examined. A mathematical model for drug transport from microneedle systems into skin was developed. Issues such as microneedle penetration, surface area of the microneedle arrays, etc. were investigated. This work helped us to focus into optimizing the design of microneedles by developing an in-house algorithm to enhance the performance of transdermal drug delivery using microneedles. Following the development of this algorithm, the influence of skin thickness with its classification (i.e., age group, race, etc.) on drug permeability across skin was studied. Attention was then given to determine the effective permeability (Peff) and the effective skin thickness (Heff) for various solid microneedle models. The outcome of this research allowed us to study the influence of microneedle dimensions on the drug concentration in blood (Cb). Furthermore, the 'pattern' (shape) of the microneedles array (i.e., square or rectangular) and the 'distribution' (arrangement) of the microneedles inside an array (i.e., triangular or diamond) were investigated to identify the optimum microneedle models. Finally, the effect of skin metabolism on both the patch (without microneedles) and the microneedle arrays on drug intake were examined.