Olanzapine solvates

Cocrystals, Salts, and Salt-Solvates of olanzapine; selection of coformers and improved solubility

Pharmaceutical cocrystals and salts are extensively researched in recent years due to their ability to tune the physicochemical properties of active pharmaceutical ingredients (APIs). A model API, olanzapine, an atypical antipsychotic drug classified as Biopharmaceutical Classification System class II, is used in this study. Cocrystals and salts of olanzapine are discovered using solvent drop grinding and ball milling. Appropriate coformers were selected based on a combination of hydrogen-bond propensity (HBP) and hydrogen-bond coordination (HBC) calculations. Eight new multicomponent phases of olanzapine, including one cocrystal hydrate with phenol; four anhydrous salts with salicylic acid, terephthalic acid, anthranilic acid, 3-hydroxybenzoic acid, and 2-aminoterephthalic acid; one salt dihydrate with terephthalic acid; and one salt solvate with 3-hydroxybenzoic acid and acetonitrile, have been discovered and characterized by PXRD and DSC. One reported cocrystal (olanzapine-resorcinol) has also been considered for the dissolution test. All these newly formed solid phases followed the "ΔpK_a rule of 3". The crystal structures of cocrystal/salts were determined by single-crystal X-ray (sc-XRD) diffraction. With the collected single-crystal data, the crystal packings were found to be primarily stabilized via strong hydrogen bonds between carboxyl, phenolic hydroxyl of co-formers/salt-formers with the piperazine and diazepine nitrogen of olanzapine, which confirmed the predicted result from the HBP and HBC calculations. HPLC coupled with UV-vis detector was used in the solubility and dissolution test instead of UV-vis spectroscopy, to avoid the peak overlap between olanzapine and co-formers/salt-formers. A threefold increase in the solubility was observed in olanzapinium 3-hydroxybenzoate and olanzapinium anthranilate, and an almost fivefold increase in solubility of olanzapinium 2-aminoterephthalate.

Crystal forms in pharmaceutical applications: olanzapine, a gift to crystal chemistry that keeps on giving

This contribution reviews the efforts of many scientists around the world to discover and structurally characterize olanzapine crystal forms, clearing up inconsistencies in the scientific and patent literature and highlighting the challenges in identifying new forms amidst 60+ known polymorphs and solvates. Owing to its remarkable solid-state chemistry, olanzapine has emerged over the last three decades as a popular tool compound for developing new experimental and computational methods for enhanced molecular level understanding of solid-state structure, form diversity and crystallization outcomes. This article highlights the role of olanzapine in advancing the fundamental understanding of crystal forms, interactions within crystal structures, and growth units in molecular crystallization, as well as influencing the way in which drugs are developed today.

On the entropy cost of making solvates

We present a simple way of estimating the entropy cost of solvate formation in crystals. The entropy penalty of making solvates can be as low as <1 kJ mol^-1 or as high as >9 kJ mol^-1 and is entirely dependent on the nature of the liquid component and the temperature of solvate formation. A link is found between a low entropy cost and a higher likelihood for a solvent to make solvates.

Polymorphs of DP-VPA Solid Solutions and Their Physicochemical Properties

Different solid forms possess various physicochemical properties, which can significantly affect the stability, bioavailability, and manufacturability of the final product. DP-VPA, a complex of 1-stearoyl-2-valproyl-sn-glycero-3-phosphatidylcholine (DP-VPA-C₁₈) and 1-palmitoyl-2-valproyl-sn-glycero-3-phosphatidylcholine (DP-VPA-C₁₆), is currently under development as an antiepileptic drug. DP-VPA-C₁₆ and DP-VPA-C₁₈ crystallize together in solid solution forms. The solid forms of DP-VPA solid solution were studied herein. Powder X-ray diffraction (PXRD), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), dynamic vapor sorption (DVS) and optical microscopy were used to characterize the different crystalline forms, known as polymorphs. The physicochemical properties, including hygroscopicity, thermodynamic behavior, and relative stability, of each form were investigated. DVS analysis showed that DP-VPA solid solution reduced the hygroscopicity of DP-VPA-C₁₆. The relative humidity stability study revealed that Forms A and B are relatively stable, while Forms A-1, B-1, C and D are highly unstable under natural humidity. Further analysis revealed that Form A transforms into Form B through milling. Given the physicochemical properties of the available physical forms, Form B may be the optimal form for the formulation and development of antiepileptic drugs.

Influence of crystal packing on the thermal properties of cocrystals and cocrystal solvates of olanzapine: insights from computations

A multicomponent supramolecular host with adaptive guest accommodation abilities is observed in the cocrystal solvates of the olanzapine–hydroquinone system.

Mechanochemical synthesis of drug–drug and drug–nutraceutical multicomponent solids of olanzapine

Drug–drug and drug–nutraceutical multicomponent solids of an antipsychotic drug olanzapine (OLN) are prepared using mechanochemistry.

First-line antituberculosis drug, pyrazinamide, its pharmaceutically relevant cocrystals and a salt

A few pyrazinamide (Pyz) cocrystals involving hydroxybenzoic/cinnamic acid derivatives [2,4-dihydroxybenzoic acid (24DHBA); 2,6-dihydroxybenzoic acid (26DHBA); 3,5-dihydroxybenzoic acid (35DHBA) and nutraceutical molecule ferulic acid (FRA)] and the first example of a molecular salt with p-toluenesulfonic acid (pTSA) have been prepared and characterized using various solid-state techniques. A high-temperature cocrystal polymorph of Pyz·FRA has been characterized from the endothermic peaks observed using differential scanning calorimetry. The presence of substituent groups carrying hydrogen bond donors or acceptors and their influence on supramolecular synthon formation has been investigated using a Cambridge Structural Database search. Equilibrium solubility of all the binary complexes of Pyz follows the order of their coformer solubility, i.e. Pyz+·pTSA− > Pyz·35DHBA > Pyz > Pyz·26DHBA > Pyz·24DHBA > Pyz·FRA. A twofold enhancement in solubility of Pyz+·pTSA− molecular salt compared with the parent drug suggests a potential drug formulation for the treatment of tuberculosis.

Formation of new polymorphs without any nucleation step. Desolvation of the rimonabant monohydrate: directional crystallisation concomitant to smooth dehydration

Rimonabant monohydrate can be dehydrated at 100 °C or above with complete loss of structural information; in this case the amorphous material can lead to nucleation and crystal growth. The water molecules can also be removed by a smooth process below T_g (78 °C) of the anhydrous phase. In that latter process there is a structural filiation between the mother phase and the daughter phase. The solvent molecules escape from the mother structure by using a network of specific channels; the new non-solvated material undergoes a relaxation process similar to a directional crystallization. By this soft mode of desolvation inside a material which has a very limited mobility, the nucleation of a non-solvated material can be avoided. The structural information contained in the mother phase is not used as a template for crystal growth but it is more a progressive rearrangement of the new desolvated material towards the nearest well in energy. Thus, a metastable new polymorph of a non-solvated component can be obtained by: (i) the crystallization of the component as a solvate and (ii) a smooth desolvation at T < T_g. Other parameters liable to interfere with that transmission of structural information are discussed.

Design of olanzapine/lutrol solid dispersions of improved stability and performances

Eleven solid dispersions containing olanzapine, with carriers of different composition (Lutrol^® F68, Lutrol^® F127, Gelucire^® 44/14), were prepared and examined by thermal (differential scanning calorimetry (DSC); thermomicroscopy (HSM)) and X-ray diffraction (XRD) analysis, both as fresh or aged (one year) samples. Drug and carriers were preliminarily selected in order to avoid problems related to the aging of the formulation, according to the solubility parameters of carriers and drug. These parameters make it possible to predict the low solubility of olanzapine in the carriers (alone or in mixtures). Systems containing only Lutrol (also in the presence of Transcutol^®) contain the drug in the form of particles of reduced size and in a crystalline form. Gelucire^® 44/14 apparently increases the amount of olanzapine dissolved in the solid carrier, but this is presumed to be a metastable state, probably related to the heterogeneous nature of the carrier that delays crystallization of the drug. The high hydrophilicity of the carriers proves suitable to an accelerated and quick release of the drug regardless of aging. Differences in the release profiles between Lutrol- and Gelucire-containing systems were interpreted in terms of the formation of polymer micelles by the Lutrols when in aqueous solution.