Freeze-Drying From Organic Co-Solvent Systems,Part 2: Process Modifications to Reduce Residual Solvent Levels and Improve Product Quality Attributes

The use of co-solvent systems can benefit the freeze-drying process and product performance. In this study, cycle designs were applied based on existing recommendations for water-based formulations. Modifications thereof and the influence on the process (e.g., drying times) and product quality attributes (e.g., product appearance, residual solvent) were tested for various cosolvent systems. It was found that fast freezing was associated with the formation of large crystals for 50 mg/g polyvinylpyrrolidone in 40% 1,4-dioxane (w/w), resulting in a 7% reduction of primary drying. The application of high shelf temperatures during primary drying for 50 mg/g polyvinylpyrrolidone in 70% tert-butanol was feasible, resulting in shorter primary drying times but high residual solvent levels (7.7%). Most notable was that the inclusion of an evaporation step after freezing improved the product appearance for low-melting co-solvents (10% ethanol and 10% acetone). No ice or solvent nucleation occurred in the case of 50 mg/g mannitol in 50% N,N-dimethylacetamide during the normal freezing stage. Instead, the solution viscosity significantly increased after cooling to low shelf temperatures, followed by product evaporation (rather than sublimation) during the drying phase and failure to form a product cake after drying. The application of annealing enabled nucleation and sublimation.     

Physicochemical study of percutaneous absorption enhancement by dimethyl sulfoxide: kinetic and thermodynamic determinants of dimethyl sulfoxide mediated mass transfer of alkanols

By first determining the thermodynamic activities and activity coefficients of methanol, 1-butanol and 1-octanol in binary dimethyl sulfoxide:water media, it has been possible to separate solubilizing (thermodynamic) effects of dimethyl sulfoxide from its kinetic (diffusive) influence as they relate to the skin permeation of these small, nonelectrolyte alkanols. This was done by normalizing the experimental permeability coefficients found with full-thickness hairless mouse skin membranes to unit activity in the vehicle. When the dimethyl sulfoxide media were placed on both sides of the skin sections in a two compartment diffusion cell, activity-adjusted permeability coefficients of the permeants were invariant to dimethyl sulfoxide concentrations of 50% strength. Thus, up to this concentration and in the absence of net solvent crosscurrents, the permeabilities of methanol, 1-butanol, and 1-octanol appear to be strictly determined by partitioning into the stratum corneum. However, when the dimethyl sulfoxide percentage strength was raised to greater than or equal to 75%, activity-adjusted permeability increased systematically and profoundly, indicating severe barrier impairment with increased diffusion across the horny layer (kinetic effect). When neat dimethyl sulfoxide was placed on both sides of the skin, the experimental permeability coefficients of the three alcohols were maximal and equal in magnitude, suggesting total functional impairment of the stratum corneum. When the dimethyl sulfoxide media were placed in contact with the stratum corneum surface of the skin membranes only, accelerating effects were noted at dimethyl sulfoxide concentrations less than 50%, further supporting the idea that solvent cross flows themselves disrupt the horny structure. The degree of impairment was quantified under all experimental circumstances.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of fasting,diethyl maleate,and alcohols on carbon tetrachloride-induced hepatotoxicity

The effect of fasting, diethyl maleate treatment, and methanol, ethanol, iso-propanol, or tert-butanol treatment on carbon tetrachloride (CCl₄)-induced hepatotoxicity in male Sprague-Dawley rats was studied. A 24-hr fast and the administration of diethyl maleate were found to be equipotent and not additive in potentiating CCl₄-induced hepatotoxicity; this potentiation appeared to be due to a depletion of hepatic glutathione (GSH) levels. Concomitant diurnal variations in hepatic GSH content and in CCl₄-induced hepatotoxicity also suggested hepatic GSH involvement in CCl₄-induced hepatic damage. Whereas ethanol has been reported to potentiate CCl₄-induced hepatotoxicity and to lower hepatic GSH levels, the present study suggested that these effects are due to an ethanol-induced loss of body weight. Methanol, iso-propanol, and tert-butanol, on the other hand, show the same maximal potentiation of CCl₄-induced hepatotoxicity and do so without inducing a depletion of hepatic GSH content or producing a loss of body weight. In contrast to a previous report, however, methanol was found to be markedly less effective on an equimolar basis than either iso-propanol or tert-butanol in potentiating CCl₄-induced hepatotoxicity. The study suggests that GSH is an important modulator of CCl₄-induced hepatotoxicity and also suggests that methanol, iso-propanol, and tert-butanol, but not ethanol, potentiate CCl₄-induced hepatotoxicity by a mechanism that does not involve altered hepatic GSH levels.     

Sarin trasport across excised human skin III. The effect on solvant pretreatment on adsorption and desorption by keratin

Keratin powder was pretreated with either methyl o-formate, p-dioxane, or dimethyl sulfoxide in order to determine the effect on the adsorption and desorption of sarin. Heats of adsorption and heats of activation for adsorption and desorption were determined. A rank order correlation was observed between the heat of activation for desorption and previously reported activation energies for transport through callous membranes.     

Stimulation of tolbutamide hydroxylation by acetone and acetonitrile in human liver microsomes and in a cytochrome P-450 2C9-reconstituted system.

Organic solvents are often used to solubilize lipophilic new chemical entities before their addition to in vitro test systems such as microsomal stability or cytochrome P-450 (CYP) inhibition. However, the effect of these organic solvents on the test systems is not usually characterized. This study was initiated to evaluate the effect of acetonitrile and acetone, in addition to other organic solvents, on the tolbutamide hydroxylation activity of CYP2C9 in both human liver microsomes and a CYP2C9-reconstituted system. Both acetonitrile and acetone significantly stimulated the NADPH-dependent tolbutamide hydroxylation by nearly 2- to 3-fold in human liver microsomes and CYP2C9-reconstituted system when incubated at 2 and 4% final solvent concentrations. When cumene hydroperoxide was used instead of NADPH, both acetone and acetonitrile significantly inhibited tolbutamide hydroxylation. This NADPH-dependent stimulatory effect was further evaluated by examining the effect of a series of other organic solvents with different carbon chain lengths and various functional groups, including hydroxyl, ketone, and aldehyde. Unlike acetone, two other ketone-containing solvents, methyl ethyl ketone (2-butanone) and diethyl ketone (3-pentanone) failed to significantly enhance tolbutamide hydroxylation. Other solvents tested, including methanol, ethanol, propanol, 1-butanol, 2-butanol, 1-pentanol, 2-pentanol, acetaldehyde, and dimethyl sulfoxide significantly inhibited NADPH-dependent tolbutamide hydroxylation. Overall, the stimulatory effect of both acetonitrile and acetone on tolbutamide hydroxylation was found to be primarily due to a consistent increase in V(max), whereas K(m) was unchanged in both human liver microsomes and the reconstituted CYP2C9 system. These data suggest that acetone and acetonitrile stimulate NADPH-mediated tolbutamide hydroxylation via the CYP reductase and not by modifying the affinity of tolbutamide for the CYP2C9 enzyme.     

Preparation of a solid dispersion of felodipine using a solvent wetting method.

A straightforward solvent wetting method was used to prepare felodipine solid dispersions in the presence of various carriers. Dichloromethane is not needed when HPMC solid dispersions were produced using the solvent wetting method. The amount of ethanol used to prepare solid dispersions did not have a significant effect on the dissolution rate of felodipine. The results of X-ray diffraction and thermal analysis indicated that the drug was in the amorphous state when PVP, HPMC, and poloxamer were used as carriers. The dissolution rates of felodipine in PVP, HPMC, or poloxamer solid dispersions were much faster than those for the corresponding physical mixtures. However, dissolution profiles were found to depend on the carrier used; the dissolution rate of felodipine increased slowly for solid dispersions prepared using HPMC, whereas rapid initial dissolution rates were observed for solid dispersions prepared using PVP or poloxamer. Increases in dissolution rates were partly dependent on the ratios of felodipine to carrier. No significant changes in crystal form were observed by X-ray diffraction or thermal analysis, and no significant changes in dissolution rate were observed when sorbitol and mannitol were used as carriers.     

PREPARATION AND PROPERTIES OF HORSERADISH PEROXIDASE CROSS-LINKED IN NONAQUEOUS MEDIA

Horseradish peroxidase (hydrogen peroxide oxidoreductase [1.11.1.7]) has been cross-linked in methylene chloride using N,N'-carbonyldiimidazole to produce a water insoluble preparation which retains enzymatic activity. Relative to native enzyme, which was treated with methylene chloride but not N,N'-carbonyldiimidazole, the cross-linked product displayed significant stability toward denaturation in aqueous mixtures of ethanol, methanol, and 1,4-dioxane. The cross-linked product showed a a marked stability toward thermal denaturation relative to the native protein. Applications of the catalyst in chemical reactors for the preparation of synthetic quinones are discussed.     

顶空气相色谱法测定盐酸溴己新原料药中4种有机溶剂的残留量

目的:建立测定盐酸溴己新原料药中4种有机溶剂(丙酮、乙醇、甲苯和乙酸)残留量的方法。方法:采用顶空气相色谱法分别测定。色谱柱均为HP-FFAP柱,检测器均为氢火焰离子化检测器,温度均为250℃;丙酮、乙醇、甲苯检测进样口温度为200℃,程序升温,顶空瓶平衡温度80℃,时间30 min,以二甲基亚砜为溶解介质;乙酸检测进样口温度为150℃,柱温60℃,顶空瓶平衡温度60℃,时间20 min,以甲醇为溶解介质,衍生化法检测。结果:在2种色谱条件下,各被测溶剂峰均分离良好,线性相关系数均大于0.999;丙酮、乙醇、甲苯和乙酸的平均回收率分别为104.4%、98.7%、105.7%、100.8%,RSD分别为2.3%、2.6%、2.7%、2.1%(n=3);检测限分别为0.25、1.21、0.18、0.32μg/ml。样品中只检出乙醇。结论:建立的方法准确、迅速,可用于检测盐酸溴己新原料药中残留的丙酮、乙醇、甲苯和乙酸。     

Solubility prediction of clonazepam in aqueous mixtures of ethanol,polyethylene glycol 200 and propylene glycol at 30 °C

Solubility of clonazepam in aqueous binary mixtures of ethanol, polyethylene glycol 200 and propylene glycol was determined at 30 °C using the shake flask method. The maximum solubility of clonazepam was observed at volume fraction of 0.90 of ethanol, whereas for aqueous mixtures of polyethylene glycol 200 and propylene glycol, the maximum values were observed in the neat cosolvents. The generated data was fitted to the Jouyban-Acree model and its constants were computed, then the back-calculated solubilities were compared with the corresponding experimental values by calculating the mean percentage deviation (MPD) in which the overall MPD for three cosolvent systems was 7.0 %. The solubility data in cosolvent + water mixtures was predicted using previously trained versions of the Jouyban-Acree model and the prediction MPDs were 13.4, 54.2 and 24.9 %, respectively for ethanol, polyethylene glycol 200 and propylene glycol mixtures and the overall MPD was 30.8 %.     

Solvent Interaction with Polydimethylsiloxane Membranes and Its Effects on Benzocaine Solubility and Diffusion

The effect of polar solvents and polar cosolvent mixtures on the transport properties of benzocaine in polydimethylsiloxane (PDMS) was studied. Methanol, ethanol, n-propanol, and n-butanol, as well as aqueous cosolvent mixtures of each n-alkanol, were used as vehicles for benzocaine. A constant activity gradient was maintained in all diffusion studies, with the membrane exposed to saturated donor suspensions of drug, and sink conditions maintained in the receiver. In spite of the constant activity gradient, steady-state benzocaine flux was substantially enhanced with increasing n-alkanol volume fraction and reached a maximum for the pure n-alkanol in each case. At any given composition, the degree of benzocaine flux enhancement generally increased with n-alkanol carbon number. In terms of the appropriate Fick's first law expression for this system, these observations were attributed to simultaneous changes in benzocaine concentration within the PDMS membrane, the diffusion coefficient of benzocaine in PDMS, fillerless membrane volume fraction, tortuosity, and the membrane thickness. These parameters were in turn correlated with the cosolvent composition in contact with the membrane. Both membrane solubility and diffusion coefficient were found to increase substantially, but decreases in tortuosity and increases in fillerless membrane volume fraction and membrane thickness were minor.     

气相色谱法测定阿奇霉素原料药中残留的6种有机溶剂的含量

目的建立气相色谱法分离并测定阿奇霉素原料药中甲醇、乙醇、丙酮、乙酸乙酯、二氯甲烷、氯仿6种残留溶剂的含量。方法以OV-1701弹性石英毛细管柱为色谱柱(30 m×0.32 mm,0.5μm),载气为氮气,采用氢火焰离子化检测器,进样口温度为200℃,检测器温度为240℃,柱温采用程序升温(30℃、保持4 min,以25℃.min-1升至120℃、保持5 min),以二甲亚砜为溶剂,进样量1μL。结果甲醇、乙醇、丙酮、乙酸乙酯、二氯甲烷、氯仿在各自的浓度范围内,其峰面积与内标的峰面积比值与浓度呈良好的线性关系,r为0.999 1~0.999 6,平均加样回收率为94.9%~99.6%(n=9)。结论该法分离完全,操作简便快速,灵敏度高,精密度良好,是一种较好的测定原料药中残留溶剂含量的方法。     

Development and validation of a stability-indicating RP-HPLC method for assay of betamethasone and estimation of its related compounds

Betamethasone (9α-fluoro-16β-methylprednisolone) is one of the members of the corticosteriod family of active pharmaceutical ingredient (API), which is widely used as an anti-inflammatory agent and also as a starting material to manufacture various esters of betamethasone. A stability-indicating reverse-phase high performance liquid chromatography (RP-HPLC) method has been developed and validated which can separate and accurately quantitate low levels of 26 betamethasone related compounds. The stability-indicating capability of the method was demonstrated through adequate separation of all potential betamethasone related compounds from betamethasone and also from each other that are present in aged and stress degraded betamethasone stability samples. Chromatographic separation of betamethasone and its related compounds was achieved by using a gradient elution at a flow rate of 1.0 mL/min on a ACE 3 C18 column (150 mm × 4.6 mm, 3 μm particle size, 100 Å pore size) at 40 °C. Mobile phase A of the gradient was 0.1% methanesulfonic acid in aqueous solution and mobile phase B was a mixture of tert-butanol and 1,4-dioxane (7:93, v/v). UV detection at 254 nm was employed to monitor the analytes. For betamethasone 21-aldehyde, the QL and DL were 0.02% and 0.01% respectively. For betamethasone and the rest of the betamethasone related compounds, the QL and DL were 0.05% and 0.02%. The precision of betamethasone assay is 0.6% and the accuracy of betamethasone assay ranged from 98.1% to 99.9%.     

Influence of Solvent Composition on the Miscibility and Physical Stability of Naproxen/PVP K 25 Solid Dispersions Prepared by Cosolvent Spray-Drying

Purpose  

To investigate the influence of solvent properties on the phase behavior and physical stability of spray-dried solid dispersions containing naproxen and PVP K 25 prepared from binary cosolvent systems containing methanol, acetone and dichloromethane.     

The Vehicle Modulates Cellular and Humoral Responses in Contact Hypersensitivity to Oxazolone

The development of contact hypersensitivity (CHS) greatly dependson the allergenicity of the inducing agent. However, variouscofactors are known to influence the outcome of the responseas well. From this perspective, we have compared the effectsof Eve different vehicles: acetone, ethanol, dimethyl formamide(DMF), dimethyl sulfoxide (DMSO), and a 4 to 1 mixture of acetoneand olive oil (AOO) on the cellular and humoral immune responsesto epicutaneously applied oxazolone in female BALB/c mice. Asingle application of 0.2% oxazolone dissolved in acetone orethanol induced stronger proliferative responses and higherlymph node cell numbers than the other three vehicles. Moreover,both vehicles led to higher numbers of oxazolone-specific Abforming cells in the draining lymph nodes of sensitized animals.When the IgG2a/IgG1 ratios were determined to indicate the typeof T helper cell involved, the highest values were obtainedwith AOO and lowest with DMF and DMSO, while acetone and ethanolwere in between. Moreover, no correlation was found betweenoxazolone-specific antibody production and cellular responses,measured as [³H]thymidine incorporation of draining lymph nodecells after sensitization and increased ear thickness afterchallenge. From this study it can be concluded that cellularand humoral responses in CHS to oxazolone are dissimilarly affectedby the vehicles used.     

非那雄胺中有机溶剂残留量的顶空毛细管GC测定

非那雄胺（finasteride，1）是一种甾体激素类化合物，为5α-还原酶特异性抑制剂，用于治疗良性前列腺增生。1在生产过程中使用的有机溶剂有：甲醇、二嗯烷、二氯甲烷、甲苯、乙酸乙酯、丙酮。本研究采用毛细管顶空进样的气相色谱法测定1原药中上述6种溶剂的残留量。     

Formation of 8-hydroxydeoxyguanosine in calf thymus DNA treated with tert-butylhydroquinone,a major metabolite of butylated hydroxyanisole

Oxidative DNA damage caused by butylated hydroxyanisole (BHA), 2-tert-butyl(1,4)hydroquinone (TBHQ, a metabolite of BHA) and 2,5-di-tert-butyl(1,4)hydroquinone (DTBHQ), as well as 2,6-di-tert-butyl(1,4)benzoquinone (BHTQ, a metabolite of butylated hydroxytoluene), was evaluated by measuring the formation of 8-hydroxy-deoxyguanosine (80HdG) in calf thymus DNA. 80HdG formation was greatly increased by TBHQ in a concentration-dependent manner. This effect was strongly enhanced by CuCl₂ and suppressed by EDTA, bathocuproinedisulfonic acid disodium salt, methionine, glutathione reduced form or catalase, but was not affected by mannitol, sodium benzoate or sodium azide. Thus, TBHQ-induced 80HdG formation may be mediated by copper. DTBHQ also induced the formation of 80HdG, though to a much lesser extent than TBHQ, and its effect was stimulated by CuCl₂. BHA had a small enhancing effect at high concentration, only in the presence of CuCl₂, whereas in the case of BHTQ, it occurred both in the presence of CuCl₂ and FeCl₂.     

Solubility studies on valdecoxib in the presence of carriers,cosolvents, and surfactants

Enhancement of the solubility of valdecoxib was examined using a series of hydrophilic carriers (mannitol, polyethylene glycol (PEG) 4000, PEG 6000, PEG 8000, and urea), surfactants (Tween‐20, Tween‐80, and sodium lauryl sulfate [SLS]) and cosolvents (ethanol, methanol, and glycerol) at 37°C. The solubility of valdecoxib could be enhanced significantly using PEG 4000 as a carrier, ethanol as cosolvent, and SLS as a surfactant. Because the solubility of valdecoxib increased dramatically in the presence of polyethylene glycols, these are suitable dispersing agents for preparing solid dispersions containing valdecoxib. Gibbs free energy (ΔG) values were all negative for all hydrophilic carriers tested, indicating the spontaneous nature of valdecoxib solubilisation. Among the cosolvents, ethanol exhibited higher solubilization potential than methanol and glycerol. As the dielectric constant of the cosolvent–water mixtures decreased, the solubility of valdecoxib increased. Finally, SLS exerted maximum solubilization of valdecoxib when compared to Tween‐20 or Tween‐80. The crystallinity of valdecoxib was explored by X‐ray diffraction study and showed numerous crystalline peaks. Examination of surface morphology by scanning electron microscopy depicted a near spherical shape of valdecoxib with irregular surface characteristics. Drug Dev. Res. 62:41–48, 2004. © 2004 Wiley‐Liss, Inc.     

顶空气相色谱法测定托拉塞米中7种有机溶剂残留量

目的建立托拉塞米中9种有机溶剂残留量的测定方法。方法采用顶空毛细管气相色谱法,以二甲基亚砜为溶剂,DB-624色谱柱（30m×0.32mm×0.250μm）,FID检测器。结果 7种残留有机溶剂甲醇、乙醇、丙酮、二氯甲烷、正丙醇、二氧六环、甲苯均达到了完全分离。结论该方法灵敏度、准确度均达到有机溶剂残留量的检测要求,可用于托拉塞米中7种残留溶剂的同时检测。     

Crystal modifications and dissolution rate of piroxicam

Piroxicam is a nonsteroidal anti-inflammatory drug with low aqueous solubility which exhibits polymorphism. The present study was carried out to develop polymorphs of piroxicam with enhanced solubility and dissolution rate by the crystal modification technique using different solvent mixtures prepared with PEG 4000 and PVP K30. Physicochemical characteristics of the modified crystal forms of piroxicam were investigated by X-ray powder diffractometry, FT-IR spectrophotometry and differential scanning calorimetry. Dissolution and solubility profiles of each modified crystal form were studied and compared with pure piroxicam. Solvent evaporation method (method I) produced both needle and cubic shaped crystals. Slow crystallization from ethanol with addition of PEG 4000 or PVP K30 at room temperature (method II) produced cubic crystal forms. Needle forms produced by method I improved dissolution but not solubility. Cubic crystals produced by method I had a dissolution profile similar to that of untreated piroxicam but showed better solubility than untreated piroxicam. Cubic shaped crystals produced by method II showed improved dissolution, without a significant change in solubility. Based on the XRPD results, modified piroxicam crystals obtained by method I from acetone/benzene were cube shaped, which correlates well with the FTIR spectrum; modified needle forms obtained from ethanol/methanol and ethanol/acetone showed a slight shift of FTIR peak that may be attributed to differences in the internal structure or conformation.     

Systematic study of the flow behaviour and mechanical properties of Carbopol Ultrez 10 hydroalcoholic gels.

Flow behaviour and mechanical properties of 0:100, 15:85, and 30:70 v/v gelled ethanol:water mixtures are studied as a function of pH (4.0-7.0) and Carbopol Ultrez 10 concentration (0.1-0.5%). As previously reported individually for 30% v/v alcoholic Ultrez 10 gels, flow curves were adjusted to the Ostwald's model, and similar sigmoidal dose response functions were obtained to describe the pH dependence of consistency index and mechanical properties of the systems. The concentration dependence of flow indexes was also best adjusted to one-phase exponential decay functions. As a result, the influence of ethanol content on polymer network is meaningfully assessed by means of the obtained empirical parameters: bottom value of each variable (Y(max)), pH value required for a 50% polymer network development (pH(50)), and asymptotic flow index value for the fully structured gels (n(min)). Also, it is assessed the influence of cosolvent on the above-mentioned empirical variables, by studying pH-dependence of gelation in methanol:water, 1-propanol:water and 1-butanol:water 15:85% v/v mixtures. As a result, the alcohol induced variations in consistency and mechanical properties of hydroalcoholic gels were well correlated to modifications in the solubility parameter (delta(T)).