Browsing by Author "Qiao, Ning"

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    Insight into Flufenamic Acid Cocrystal Dissolution in the Presence of a Polymer in Solution: from Single Crystal to Powder Dissolution
    (ACS American Chemical Society, 2017-11-01) Guo, Minshan; Wang, Ke; Qiao, Ning; Fabian, Laszlo; Sadiq, Ghazala; Li, M.
    Effects of three polymers, polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), and copolymer of vinylpyrrolidone/vinyl acetate (PVP-VA), on the dissolution behavior of the cocrystals of flufenamic acid with theophylline (FFA-TP CO) and nicotinamide (FFA-NIC CO) were investigated at multiple length scales. At the molecular level, the interactions of crystal surfaces with a polymer were analyzed by observing etching pattern changes using atomic force microscopy. At the macroscopic scale, dissolution rates of particular faces of a single crystal were determined by measurement of the physical retreat velocities of the faces using optical light microscopy. In the bulk experiments, the FFA concentration in a dissolution medium in the absence or presence of a polymer was measured under both sink and nonsink conditions. It has been found that the dissolution mechanisms of FFA-TP CO are controlled by the defect sites of the crystal surface and by precipitation of the parent drug FFA as individual crystals in the bulk fluid. In contrast, the dissolution mechanisms of FFA-NIC CO are controlled by surface layer removal and by a surface precipitation mechanism, where the parent drug FFA precipitates directly onto the surface of the dissolving cocrystals. Through controlling the dissolution environment by predissolving a polymer, PVP or PVP-VA, which can interact with the crystal surface to alter its dissolution properties, improved solubility, and dissolution rates of FFA-TP CO and FFA-NIC CO have been demonstrated.
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    Investigating Permeation Behavior of Flufenamic Acid Cocrystals Using a Dissolution and Permeation System
    (ACS Publications, 2018-08-06) Guo, Minshan; Wang, Ke; Qiao, Ning; Yardley, Vanessa; Li, M.
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    Investigation of Carbamazepine-Nicotinamide cocrystal solubility and dissolution by a UV imaging system
    (De Montfort University, 2014-04) Qiao, Ning
    In this study, the ability of pharmaceutical cocrystals on improving solubility and dissolution behaviour of poorly water soluble drug has been studied by a novel technique SDI300 UV imaging surface dissolution system. Pharmaceutical cocrystals of poorly water soluble drug carbamazepine (CBZ) were synthesized, which are 1: 1 carbamazepine - nicotinamide (CBZ-NIC) cocrystal, and 2:1 carbamazepine - succinic acid (CBZ-SUC) cocrystal. Firstly, dissolution and solution mediated phase transformation behaviour (SMPT) of CBZ-NIC cocrystal was studied by in situ techniques of UV imaging and Raman spectroscopy. This study has shown that in situ UV imaging and Raman spectroscopy with a complementary technique of SEM can provide an in depth understanding of cocrystal dissolution processes. It has been found that CBZ-NIC cocrystal including other polymorphs of CBZ III and I and mixture are converting to CBZ DH during dissolution. The influence of surfactants, SLS and Tween 80, on the solubility and dissolution behavior of the CBZ-NIC cocrystal has been studied. Results show that the SMPT of CBZ III and CBZ-NIC cocrystal can be altered by inclusion of a surfactant in dissolution medium. However, CBZ III and CBZ-NIC cocrystal have shown different transformation behavior with different surfactants. The solubility and dissolution behaviour of CBZ-NIC cocrystal, CBZ-SUC cocrystal in four biomedia (simulated gastric fluid, pH1.2 HCl buffer, simulated intestinal fluid, and pH 6.8 PBS buffer) were studied. Results have shown that equilibrium solubility of CBZ samples varied in different media. The two cocrystals dissolution rates show different trends as that of parent drug CBZ III. This can be explained by that the formation of cocrystal change the dissolution ability of CBZ III