An in vitro assessment of liquid-filled Capill® potato starch capsules with biphasic release characteristics

This paper describes the first use of liquid-filled Capill® potato starch capsules formulated for biphasic release and reports the development of dissolution methods suitable for assessment of drug release from this type of dosage vehicle. The liquid filling of Capill® capsules was made possible by overcoming the problem of incomplete sealing of the Capill® cap and body which initially resulted in leakage of liquid capsule contents. This was achieved by modification of the formulation to incorporate a thermosoftening agent which remained solid below 30°C, but melted at 37°C. The use of enteric-coated liquid-filled Capill® capsules formulated for biphasic release required further development of the dissolution method to incorporate a dissolution medium containing bile acids at a concentration of 14 mM to produce a similar release profile to that seen from enteric-coated hard gelatin capsules containing the same formulation. The concentration of bile salts used is in agreement with the acceptable range previously validated for use with enteric-coated hard gelatin capsules whilst also remaining within the physiological levels of bile acids found in vivo.