Influence of process variables on the properties of simvastatin self-emulsifying granules obtained through high shear wet granulation

Improvements of the oral bioavailability of lipophilic drugs can be obtained using lipidic formulations such as the self-emulsifying drug delivery systems. The high shear wet granulation (HSWG), using microemulsions as binder, is a viable process to produce self-emulsifying granules. However only few information are present in the literature on the effect of process variables on the properties of the granules obtained with these binders. Consequently, this article compares the effects of some relevant experimental variables (impeller speed and massing time) on thefinal technological and pharmaceutical properties of the granules produced using simple water, or alternatively, a microemulsion as binder and containing simvastatin (SV) as model drug. The effects of the variables were determined by evaluating the granule median diameter, their particle size distribution, roundness, disintegration time and dissolution rate of SV. Results clearly demonstrated that the microemulsion-based process was less sensitive tooperating conditions than the water-based process. With microemulsion the nucleation process and growth regimes were more difficult to control, resulting in products with broader PSDs. At the same operatingconditions microemulsion-based granules were more brittle but rounder and showed smaller median diameter compared to water-based granules. The dissolution rate of simvastatin was not significantly affected by the operating conditions

Mechanochemical reactivity inhibited, prohibited and reversed by liquid additives: examples from crystal-form screens

We demonstrate that liquid additives can exert inhibitive or prohibitive effects on the mechanochemical formation of multi-component molecular crystals, and report that certain additives unexpectedly prompt the dismantling of such solids into physical mixtures of their constituents. Computational methods were employed in an attempt to identify possible reasons for these previously unrecognised effects of liquid additives on mechanochemical transformations

Modulating Thermal Properties of Polymers through Crystal Engineering

Crystal engineering has exclusively focused on the development of advanced materials based on small organic molecules. We now demonstrate how the cocrystallization of a polymer yields a material with significantly enhanced thermal stability but equivalent mechanical flexibility. Isomorphous replacement of one of the cocrystal components enables the formation of solid solutions with melting points that can be readily fine-tuned over a usefully wide temperature range. The results of this study credibly extend the scope of crystal engineering and cocrystallization from small molecules to polymers

Drug Nanocrystals: Theoretical Background of Solubility Increase and Dissolution Rate Enhancement

The peculiar higher solubility of drug nanocrystals compared to macrocrystals appeals to the pharmaceutical field. Indeed, until now, about 70 % of the potential drug candidates are discarded due to low bioavailability related with poor solubility in water. Since a modern and efficient design strategy for nanocrystal-based delivery systems requires the knowledge of the theoretical relation between nanocrystal size and solubility, the aim of this paper is to build up a physically-oriented thermodynamic model relating to nanocrystal dimensions with their melting temperature, enthalpy, solubility and dissolution rate. In particular, the developed model will be applied to vinpocetine, a poorly soluble drug used in the treatment of various types of cerebrovascular circulatory disorders

Drug Nanocrystals: Theoretical Background of Solubility Increase and Dissolution Rate Enhancement

The peculiar higher solubility of drug nanocrystals compared to macrocrystals appeals to the pharmaceutical field. Indeed, until now, about 70 % of the potential drug candidates are discarded due to low bioavailability related with poor solubility in water. Since a modern and efficient design strategy for nanocrystal-based delivery systems requires the knowledge of the theoretical relation between nanocrystal size and solubility, the aim of this paper is to build up a physically-oriented thermodynamic model relating to nanocrystal dimensions with their melting temperature, enthalpy, solubility and dissolution rate. In particular, the developed model will be applied to vinpocetine, a poorly soluble drug used in the treatment of various types of cerebrovascular circulatory disorders

Selective Synthesis of a Salt and a Cocrystal of the Ethionamide-Salicylic Acid System

Herein is presented a rare example of salt/cocrystal polymorphism involving the adduct between ethionamide (ETH) and salicylic acid (SAL). Both the salt and cocrystal forms have the same stoichiometry and composition and are both stable at room temperature. The synthetic procedure was successfully optimized in order to selectively obtain both polymorphs. The two adducts' structures were thoroughly investigated by means of single-crystal X-ray diffraction, solid-state NMR spectroscopy, and density functional theory (DFT) calculations. From the solid-state NMR point of view, the combination of mono- and multinuclear experiments (1H MAS, 13C and 15N CPMAS, 1H-{14N} D-HMQC, 1H-14N PM-S-RESPDOR) provided undoubted spectroscopic evidence about the different positions of the hydrogen atom along the main N\ub7\ub7\ub7H\ub7\ub7\ub7O interaction. In particular, the 1H-14N PM-S-RESPDOR allowed N-H distance measurements through the 1H detected signal at a very high spinning speed (70 kHz), which remarkably agree with those derived by DFT optimized X-ray diffraction, even on a natural abundance real system. The thermodynamic relationship between the salt and the cocrystal was inquired from the experimental and computational points of view, enabling the characterization of the two polymorphs as enantiotropically related. The performances of the two forms in terms of dissolution rate are comparable to each other but significantly higher with respect to the pure ETH

Praziquantel meets Niclosamide: a dual-drug antiparasitic cocrystal

In this paper we report a successful example of combining drugs through cocrystallization. Specifically, the novel solid is formed by two anthelminthic drugs, namely praziquantel (PZQ) and niclosamide (NCM) in a 1:3 molar ratio, and it can be obtained through a sustainable one-step mechanochemical process in the presence of micromolar amounts of methanol. The novel solid phase crystallizes in the monoclinic space group of P2(1)/c, showing one PZQ and three NCM molecules linked through homo- and heteromolecular hydrogen bonds in the asymmetric unit, as also attested by SSNMR and FT-IR results. A plate-like habitus is evident from scanning electron microscopy analysis with a melting point of 202.89 °C, which is intermediate to those of the parent compounds. The supramolecular interactions confer favorable properties to the cocrystal, preventing NCM transformation into the insoluble monohydrate both in the solid state and in aqueous solution. Remarkably, the PZQ - NCM cocrystal exhibits higher anthelmintic activity against in vitro S. mansoni models than corresponding physical mixture of the APIs. Finally, due to in vitro promising results, in vivo preliminary tests on mice were also performed through the administration of minicapsules size M

Study on Polymer-Surfactant Interactions for the Improvement of Drug Delivery Systems Wettability

One of the possible causes of failure of the mechanochemical activation of poorly soluble drugs relies on the scarce drug wettability. Indeed, the mechanochemical process comports the disposition of drug nano-crystals and amorphous drug, generated by the destruction of original drug macro-crystals, on the surface of the carrier (acting as stabiliser), usually represented by crosslinked polymeric particles. Accordingly, the scarce drug wettability can reduce the beneficial action of mechanochemical activation (nano-crystals and amorphous drug are characterised by a higher solubility with respect to the original macro-crystals). In this light, this paper is focussed on the use of surfactants for the increase of delivery system (drug plus carrier) wettability. In particular, the surfactant-polymer systems are characterised for what concerns their bulk and surface properties. This allows to select the best surfactant and to experimentally verify its effect on the release kinetics of a poorly soluble and wettable drug