title: Study of the recrystallization in coated pellets - effect of coating on API crystallinity.
abstract: Coated diltiazem hydrochloride-containing pellets were prepared using the solution layering technique. Unusual thermal behavior was detected with differential scanning calorimetry (DSC) and its source was determined using thermogravimetry (TG), X-ray powder diffraction (XRPD) and hot-stage microscopy. The coated pellets contained diltiazem hydrochloride both in crystalline and amorphous form. Crystallization occurs on heat treatment causing an exothermic peak on the DSC curves that only appears in pellets containing both diltiazem hydrochloride and the coating. Results indicate that the amorphous fraction is situated in the coating layer. The migration of drugs into the coating layer can cause changes in its degree of crystallinity. Polymeric coating materials should therefore be investigated as possible crystallization inhibitors.
authors.affiliation: Department of Pharmaceutical Technology, University of Szeged, H-6720 Szeged, Eötvös utca 6, Hungary.
authors.forename: Krisztina
authors.initials: K
authors.lastname: Nikowitz
authors.affiliation: Department of Pharmaceutical Technology, University of Szeged, H-6720 Szeged, Eötvös utca 6, Hungary.
authors.forename: Klára
authors.initials: K
authors.lastname: Pintye-Hódi
authors.affiliation: Department of Pharmaceutical Technology, University of Szeged, H-6720 Szeged, Eötvös utca 6, Hungary. Electronic address: geza.regdon@pharm.u-szeged.hu.
authors.forename: Géza
authors.initials: G
authors.lastname: Regdon
mesh_terms: D065966:Absorption, Physicochemical; D000180:Acrylic Resins / Q000737:chemistry; D000959:Antihypertensive Agents / Q000737:chemistry*; D002152:Calorimetry, Differential Scanning; D002626:Chemistry, Pharmaceutical; D004110:Diltiazem / Q000737:chemistry*; D004355:Drug Stability; D006358:Hot Temperature; D065347:Hypromellose Derivatives / Q000737:chemistry; D008956:Models, Chemical; D008968:Molecular Conformation; D010592:Pharmaceutic Aids / Q000737:chemistry*; D011205:Povidone / Q000737:chemistry; D033362:Powder Diffraction; D017693:Sodium Bicarbonate / Q000737:chemistry; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013608:Tablets, Enteric-Coated; D013818:Thermogravimetry
chemical_list: D000180:Acrylic Resins; D000959:Antihypertensive Agents; D010592:Pharmaceutic Aids; D013608:Tablets, Enteric-Coated; D065347:Hypromellose Derivatives; D017693:Sodium Bicarbonate; D004110:Diltiazem; D011205:Povidone