The purpose of this study was to enhance the solubility and dissolution of a poorly water-soluble drug, tadalafil (TDF), by cocrystal formation with malonic acid (MOA), to characterize the cocrystal structure and to quantify the cocrystal solution behavior. The crystal structure revealed a 1:1 stoichiometry, wherein the TDF molecules form a double layered structure through N–H···OC interactions linked to a catemeric chain of MOA molecules via O–H···O hydrogen bonds. Cocrystal solubility advantage (SA defined as S cocrystal/S drug) or supersaturation index was determined from eutectic point measurements to be 102 to 129 in the pH range of 1 to 3. Cocrystal dissolution generated supersaturation levels (C max/S drug) of 30 in buffer and 120 in the presence of a nucleation inhibitor, HPMC. The amorphous form of TDF generated supersaturation three times lower than cocrystal in buffer, and not significantly different from cocrystal in the presence of HPMC. Thus, supersaturation index is a valuable metric for assessing the risk of cocrystal conversion during kinetic studies and for predicting conditions when the usage of a precipitation inhibitor may significantly increase cocrystal exposure levels.

The effects of different formulations and processes on inducing and maintaining the supersaturation of ternary solid dispersions of ezetimibe (EZ) in two biorelevant media fasted-state simulated intestinal fluid (FaSSIF) and fasted-state simulated gastric fluid (FaSSGF) at different temperatures (25 °C and 37 °C) were investigated in this work. Ternary solid dispersions of EZ were prepared by adding polymer PVP-K30 and surfactant poloxamer 188 using melt-quenching and spray-drying methods. The resulting solid dispersions were characterized using scanning electron microscopy, differential scanning calorimetry (DSC), modulated DSC, powder X-ray diffraction and Fourier transformation infrared spectroscopy. The dissolution of all the ternary solid dispersions was tested in vitro under non-sink conditions. All the prepared solid dispersions were amorphous in nature. In FaSSIF at 25 °C, the melt-quenched (MQ) solid dispersions of EZ were more soluble than the spray-dried (SD) solid dispersions and supersaturation was maintained. However, at 37 °C, rapid and variable precipitation behavior was observed for all the MQ and SD formulations. In FaSSGF, the melting method resulted in better solubility than the spray-drying method at both temperatures. Ternary solid dispersions show potential for improving solubility and supersaturation. However, powder dissolution experiments of these solid dispersions of EZ at 25 °C may not predict the supersaturation behavior at physiologically relevant temperatures.

Silodosin oral films: Development, physico-mechanical properties and in vitro dissolution studies in simulated saliva

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