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The development of efficient strategies for drug delivery is considerably desired. Indeed, often several issues such as the drug solubility, the control of the drug release rate, the targeted delivery of drugs, the drug bioavailability, and the minimization of secondary effects still present great obstacles. Different methodologies have been proposed, but the use of nano-hybrids compounds that combine organic and inorganic substances seems particularly promising. An interesting inorganic host is the layered double hydroxide (LDH) with a sheets structure and formula [M 2+ M 1-x M 3+ x (OH) 2 ](A n- O (M x/n  = Zn, Mg; M 2 O (M 2+  = Zn, Mg; M 3+  = Al; A n-  = nitrates, carbonates, chlorides). The possibility to exchange these counterions with drug molecules makes these systems ideal candidates for the drug delivery. In this article, we synthesize by co-precipitation method the hybrid compound Carprofen-Zn 2 Al-LDH. Carprofen, a poorly soluble anti-inflammatory drug, could also benefit of the association with a natural antacid such as LDH, to reduce the gastric irritation after its administration. Through X-ray diffraction and Fourier-transformed infrared spectroscopy (FT-IR), we could verify the effective drug intercalation into LDH. The dissolution tests clearly demonstrate a significant improvement of the drug release rate when carprofen is in the form of hybrid compound., (Copyright © 2018 American Pharmacists Association®. Published by Elsevier Inc. All rights reserved.)

Nicergoline (NIC), a poorly water-soluble semisynthetic ergot derivative, was crystallized from several organic solvents, obtaining two different polymorphic forms, the triclinic form I and the orthorhombic form II. NIC samples were then characterized by several techniques such as (13)C cross-polarization magic angle spinning solid-state spectroscopy, room-temperature and high-temperature X-ray powder diffraction, differential scanning calorimetry, and by analysis of weight loss, solvent content, powder density, morphology, and particle size. Solubility and intrinsic dissolution rates determined for the two polymorphic forms in water and hydrochloride solutions (HCl 0.1 N) were always higher for form II than for form I, which is actually the form used for the industrial preparation of NIC medicinal products. Preformulation studies might encourage industry for the evaluation of polymorph II, as it is more suitable for pharmaceutical applications. Results in drug delivery, as well as those obtained by the above-mentioned techniques, and the application of Burger-Ramberger's rules make it possible to conclude that there is a thermodynamic relation of monotropy between the two polymorphs. This last assumption may help formulators in predicting the relative stability of the two forms., (Copyright © 2011 Wiley-Liss, Inc. and the American Pharmacists Association)

Commercial and recrystallized polycrystalline samples of carprofen, a nonsteroidal anti-inflammatory drug, were studied by thermal, spectroscopic, and structural techniques. Our investigations demonstrated that recrystallized sample, stable at room temperature (RT), is a single polymorphic form of carprofen (polymorph I) that undergoes an isostructural polymorphic transformation by heating (polymorph II). Polymorph II remains then metastable at ambient conditions. Commercial sample is instead a mixture of polymorphs I and II. The thermodynamic relationships between the two polymorphs were determined through the construction of an energy/temperature diagram. The ab initio structural determination performed on synchrotron X-Ray powder diffraction patterns recorded at RT on both polymorphs allowed us to elucidate, for the first time, their crystal structure. Both crystallize in the monoclinic space group type P2(1) /c, and the unit cell similarity index and the volumetric isostructurality index indicate that the temperature-induced polymorphic transformation I → II is isostructural. Polymorphs I and II are conformational polymorphs, sharing a very similar hydrogen bond network, but with different conformation of the propanoic skeleton, which produces two different packing. The small conformational change agrees with the low value of transition enthalpy obtained by differential scanning calorimetry measurements and the small internal energy computed with density functional methods., (Copyright © 2011 Wiley-Liss, Inc.)

The anhydrous sodium naproxen (ASN) can form several hydrated phases if maintained at different relative humidities (RH). The water uptake can promote crystallographic modifications, according to the amount of water. In a previous work, the authors showed that a dihydrated form could be obtained either by crystallization in water or by exposure of the anhydrous form to a RH of 55%. In the present work, the authors report about the formation and characterization of a new tetrahydrated form, obtained by exposing the ASN to RH >or= 75%. All the hydrated compounds were characterized by the combined use of several spectroscopic, thermal, and crystallographic techniques. The thermal stability of both the dihydrated and tetrahydrated compounds was also tested., ((c) 2006 Wiley-Liss, Inc. and the American Pharmacists Association.)

The polymorphism of rac-5,6-diisobutyryloxy-2-methylamino-1,2,3,4-tetrahydro-naphthalene hydrochloride (CHF 1035) was investigated. Three different crystal forms (Form I, Form II, and Form III) were obtained by recrystallization procedures from common organic solvents. The polymorphs were characterized by Raman and carbon-13 nuclear magnetic resonance ((13)C NMR) spectroscopy, in solution and in solid state (cross polarization-magic angle spinning), powder X-ray diffractometry, and thermal methods (differential scanning calorimetry, hot stage microscopy, and thermogravimetry). Moreover, the diffraction patterns of Form I, collected at controlled temperatures, gave evidence of the presence of two reversible structural rearrangements at approximately 60 and approximately 75 degrees C. These structural variations were confirmed by the results obtained by differential scanning calorimetry and hot stage microscopy techniques. The analysis of the Raman spectra allowed the identification of peculiar absorption bands for each polymorph. Form III was the stable crystal form at room temperature as determined by the basis of slurry conversion method., (Copyright 2001 Wiley-Liss, Inc.)