title: Promethazine-montmorillonite inclusion complex to enhance drug photostability.
abstract: The capability of montmorillonite as a matrix (MONT) to improve the photostability of photolabile drugs has been recently reported. Herein promethazine (PRO), which was chosen as a model drug because of its photodegradation mechanism, was intercalated into this inorganic matrix, and the effects on drug photoprotection were evaluated as well. The hybrid material (MONT-PRO) was successfully prepared with high drug loading and then was characterized by X-ray powder diffraction (XRPD), differential scanning calorimetry (DSC), and FTIR spectroscopy. The spectrophotometric measurements as a function of light exposure time showed that PRO intercalation into montmorillonite markedly improved the drug photostability because a 5-fold-slower degradation rate was determined compared to that measured for PRO in homogeneous solutions; nanosecond transient absorption measurements highlighted that the interaction with the inorganic matrix made negligible the photoionization process of the drug, and its efficiency in producing singlet oxygen was strongly reduced. The MONT-PRO intercalation compound could be easily formulated in gel or ointment media without losing its photostability.
authors.affiliation: Dipartimento di Scienze Farmaceutiche and ‡Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia , 06123 Perugia, Italy.
authors.forename: Valeria
authors.initials: V
authors.lastname: Ambrogi
authors.forename: Morena
authors.initials: M
authors.lastname: Nocchetti
authors.forename: Loredana
authors.initials: L
authors.lastname: Latterini
mesh_terms: D002152:Calorimetry, Differential Scanning; D004355:Drug Stability; D011398:Promethazine / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
chemical_list: D011398:Promethazine