Determination for Moisture Permeation in Film Coating

Moisture can affect product stability in several ways: (1) acceleration of the chemical degradation; (2) polymorphism of the API that can affect the dissolution /absorption rate; and (3) deformation of the solid dosage due to moisture absorption that is caused by volume expansion. Most of the moisture barrier film properties were tested by gravitational methodology which is the total moisture absorption of the entire tablet. This method does not account for the permeability of the film coating itself, but utilizes Water Vapor Transmission Rate (WVTR) analysis which is used to measure the permeation of water vapor normalized against surface area and thickness of the cast film which has a weak correlation with the actual moisture barrier property. This study evaluates permeability measurements of the film coating. This methodology also has a strong correlation with the total moisture uptake of the hygroscopic tablets.