Pharmaceutical Crystals

The crystalline state is the most commonly used essential solid active pharmaceutical ingredient (API). The characterization of pharmaceutical crystals encompasses many scientific disciplines, but the core is crystal structure analysis, which reveals the molecular structure of essential pharmaceutical compounds. Crystal structure analysis provides important structural information related to the API's wide range of physicochemical properties, such as solubility, stability, tablet performance, color, and hygroscopicity. This book entitled “Pharmaceutical Crystals"" focuses on the relationship between crystal structure and physicochemical properties. In particular, the new crystal structure of pharmaceutical compounds involving multi-component crystals, such as co-crystals, salts, and hydrates, and polymorph crystals are reported. Such crystal structures were investigated in the latest studies that combined morphology, spectroscopic, theoretical calculation, and thermal analysis with crystallographic study. This book highlights the importance of crystal structure information in many areas of pharmaceutical science and presents current trends in the structure–property study of pharmaceutical crystals. The Guest Editors of this book hope the readers enjoy a wide variety of recent studies on Pharmaceutical Crystals

Preface of the Special Issue “Pharmaceutical Crystals”

Dear Colleagues, [...

Physicochemical Properties and Transdermal Absorption of a Flurbiprofen and Lidocaine Complex in the Non-Crystalline Form

Amorphous drug formulations exploiting drug–drug interactions have been extensively studied. This study aims to develop a transdermal system containing an amorphous complex of the nonsteroidal anti-inflammatory drug (NSAID) flurbiprofen (FLU) and lidocaine (LDC) for alleviating chronic pain. The high-viscosity complex between FLU and LDC (Complex) was obtained by heating in ethanol. For the complex, attenuated total reflection-Fourier transform infrared spectroscopy showed a shift in the carboxy-group-derived peak of FLU, and differential scanning calorimetry indicated the endothermic peaks associated with the melting of FLU and LDC disappeared. 13C dipolar decoupling and 15N cross-polarization magic-angle spinning nuclear magnetic resonance measurement suggested the interaction between the carboxyl group of FLU and the secondary amine of LDC. The interaction between the aromatic rings of FLU and LDC contributed to the molecular complex formation. The solubility of FLU from the complex was about 100 times greater than FLU alone. The skin permeation flux of FLU from the complex through the hairless mouse skin was 3.8 times higher than FLU alone in hypromellose gel. Thus, adding LDC to the formulation can be an effective method for enhancing the skin permeation of NSAIDs, which can prove useful for treating chronic pain and inflammatory diseases