Measurement of film-coating adhesiveness

A modified balance was used to measure the adhesive force between the film coating and the tablet surface of 10 commercial film-coated tablets. The adhesiveness or force required to remove the film coating from a unit area of tablet surface ranged from 1.06 to 4.67 x 10(4) Nm-2. Measurement of at least eight film coatings from the sides of four tablets was calculated to be required to obtain a result with 95% confidence. The method also was useful in studying the influence of solvents and humidity on bonding of the film coating to the tablet.