The thermal evolution of a crystalline organic-inorganic nanohybrid captopril intercalated Mg-Al layered double hydroxide (LDH) [Mg(0.68)Al(0.32)(OH)(2)] (C(9)H(13)NO(3)S)(0.130)(CO(3))(0.030)center dot 0.53H(2)O obtained by coprecipitation method is studied based upon in situ high-temperature X-ray diffraction, in Situ infrared and thermogravimetric analysis coupled with mass spectroscopy analysis. The results reveal that a metastable quasi-interstratified layered nanohybrid involving carbonate-LDH and reoriented less ordered captopril-LDH was firstly observed as captopril-LDH heat-treated between 140 and 230 degrees C. The major decomposition/combustion of interlayer organics occur between 270 and 550 degrees C. A schematic model on chemical and microstructural evolution of this particular drug-inorganic nanohybrid upon heating in air atmosphere is proposed. (C) 2008 Elsevier Ltd. All rights reserved.