Tuesday, 1 October 2013

Preparation, Characterization, and Evaluation of Dipfluzine–Benzoic Acid Co-crystals with Improved Physicochemical Properties

Yulong Lin, Huan Yang, Caiqin Yang, Jing Wang

Pharmaceutical Research September 2013



To prepare and characterize the co-crystal of dipfluzine and benzoic acid. To investigate the feasibility of the co-crystal for improving solubility and a faster dissolution rate in vitro and evaluate the bioavailability and tissue distribution of co-crystal in vivo.


A novel dipfluzine–benzoic acid co-crystal prepared using the solvent-assisted co-grinding and the solvent ultrasonic methods were identified and characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), as well as Raman, solid-state nuclear magnetic resonance (ssNMR), and terahertz (THz) spectroscopy. Pharmacokinetics and tissue distribution were tested in vivo using murine models. Statistics analysis for dissolution data of co-crystal in vitro and animal experiment data in vivo were evaluated using t-test.


Results of PXRD and DSC identified the dipfluzine–benzoic acid co-crystals were formed with a molar ratio of 1:2. The IR, Raman, and ssNMR spectra verified the formation of O-H · · · O and O-H · · · F hydrogen bonds. The complex constant, K, was evaluated to be 109 orders of magnitude with ΔrG < 0. The co-crystal solubility, the rate of drug dissolution and the relative bioavailability were approximately 500 times, five times and double that of dipfluzine, respectively. Increased solubility of co-crystal did not reduce distribution in the brain; the mean concentrations in the brain increased, but the differences had no statistic significance (p > 0.05).


The co-crystal of dipfluzine–benzoic acid improved the physicochemical properties of dipfluzine, such as solubility and dissolution rate. Furthermore, the increased relative bioavailability of co-crystal indicated the potential use in further clinical study.

for full paper see http://link.springer.com/article/10.1007/s11095-013-1181-6#

... Nitrogen, at the flow rate of 20 mL/min, was used as the purging gas, at a flow rate of 20 mL/min. The THz spectra were acquired using a TPI ™ spectra 1,000 transmission spectrometer (TeraView Limited, Cambridge, UK). ...