Mathematical modeling of drug delivery from monolayer intravaginal ring

IGNACIO M. HELBLING; DRA. MARÍA I. CABRERA; DR. JULIO A. LUNA

Congreso; 1st Annual Symposium of Drug Delivery Systems; 2011

The vagina has some advantages over oral administration that make it as a good alternative route for drug delivery. Intravaginal rings are elastomeric, torus-shaped devices designed to release drug to the vagina for local or systemic treatments. Several designs of ring have been developed, including matrix, reservoir and shell-type variants, each providing very different drug release profiles. The prediction of these profiles is a goal of crucial interest in the Pharmaceutical Industry and encourages the development of mathematical models. Following this, a mathematical modelling of controlled release of drug from torus-shaped single-layer devices was derived. Analytical solutions based on the pseudo-steady state approximation were obtained for both the position of the “dissolution–diffusion moving front” and the cumulative amount of drug released. The obtained equations were incorporated into a programming routine and simulations were performed in the software MATLAB®. The validity and usefulness of the model was ascertained by comparison of the simulation results with matrix-type vaginal rings experimental release data reported in the literature. The values used for the model parameters were taken from the respective bibliographical studies consulted. In order to measures quantitatively the fit of the theoretical model to the experimental data, the pair-wise procedure was used. A good agreement between the model prediction and the experimental data was observed. In all cases f1 was less than 4 and f2 was greater than 98, indicating the ability of the model to predict the experimental drug release profiles. An analysis of the effect of the variation in torus design parameters (outer radius of the ring, cross sectional area, etc) on the solute release was also presented. The results showed that the drug release rate is strongly influenced by the design parameters of the device. In conclusion, a mathematical model that successfully predicts the drug release from ring-shaped devices was derived. The equations are of practical usefulness and relatively simple to use with the help of an adequate computational software.