Physical-mechanical properties of film-coated soft gelatin capsules

Soft gelatin capsules containing ibuprofen dissolved in either PEG 400 or Miglyol(R) 812 were coated with an aqueous dispersion of Eudragit(R) L 30 D-55 using a Mini I-Ii-Coater. The physical-mechanical properties of the coated capsules, including tensile strength, Young's modulus and tensile toughness, were determined using a Chatillon DFGS50 force gauge attached to a Chatillon TCD-200 motorized test stand. The diametral compression tests were conducted at a rate of 12.7 mm/minute. Force-deflection curves were obtained and mathematically manipulated to yield stress-strain diagrams. The influence of two plasticizing agents, triethyl citrate (TEC) and tributyl citrate (TBC), on the physical-mechanical properties was determined. The hydrophilic plasticizer TEC was found to be the best plasticizer for the acrylic films, regardless of the fill liquid. The physical-mechanical properties of the coated and uncoated soft gelatin capsules were a function of the fill liquid. Temperature and humidity were found to influence the physical-mechanical properties of the coated capsules. The adhesion between the gelatin capsule and the acrylic polymer was found to be dependent on both the fill liquid and plasticizer in the coating formulation. Coating dispersions plasticized with TEC exhibited good adhesion with both the PEG 400 and the Miglyol(R) 812, whereas the TBC plasticized film coating showed good adhesion with the Miglyol(R) 812 fill liquid. The acrylic film coatings for the PEG-containing capsules and plasticized with TBC exhibited an increased adhesion of the polymer to substrate over time when stored at both high temperature and high humidity.