title: Design of a slow-release capsule using laser drilling.
abstract: Conventional hard gelatin capsules were made GI-tract resistant by formalin vapor treatment. The residual formalin content was 80 micrograms/capsule 24 h after treatment, which decreased with increased storage time. An in vitro GI-tract resistance test was performed by exposing the capsules to simulated gastric fluid for 4 h and then to simulated intestinal fluid for 4 h at 37 degrees C. The resistance was further confirmed by in vivo X-ray studies in human volunteers. Minute pores were drilled on the hardened shells of the capsules with a carbon dioxide gas laser. This permitted the slow passage of the encapsulated tetracycline hydrochloride when subjected to 0.1 M HCl in in vitro dissolution studies. In vitro drug release from these capsules followed zero-order kinetics after an initial lag period of 30 min. The factors influencing the in vitro release rate of tetracycline hydrochloride from these capsules are discussed.
mesh_terms: D002214:Capsules; D002626:Chemistry, Pharmaceutical; D003692:Delayed-Action Preparations; D004064:Digestive System / Q000378:metabolism; D005557:Formaldehyde; D006801:Humans; D007700:Kinetics; D007834:Lasers; D010316:Particle Size; D012995:Solubility
chemical_list: D002214:Capsules; D003692:Delayed-Action Preparations; D005557:Formaldehyde