Modelling of dissolving microneedles for transdermal drug delivery: theoretical and experimental aspects

A mathematical model was developed to predict the amount of drug delivered into the skin via the dissolution of a microneedle (MN). This approach differs markedly from previous research which focused on similar phenomena but failed to include a biological membrane. Dimensionless governing equations were derived to help predict the needle height and fate of the active ingredient in the skin layer after application of the device. Simulation studies with fentanyl revealed that the drug concentration was proportional to its mass fraction in the MN. The effect of the pitch on skin permeation was mildly nonlinear. A larger amount of fentanyl was delivered from microneedle arrays with smaller pitch size. The dissolution process was independent of changes in the elimination rate constant. An optimization algorithm was applied to show how to recover this parameter from needle height--time data.