Characterization of polymorphism of gepirone hydrochloride

Gepirone hydrochloride, an investigational anxiolytic drug, was found to have at least three polymorphic forms which melted at 180 degrees C (I), 212 degrees C (II), and 200 degrees C (III). Thermal analytical studies showed that forms I and II were an enantiotropic pair, as were forms I and III. Form III was monotropic with form II and there was no temperature at which III was the most stable polymorph. Solubility data from powder dissolution studies were used to estimate a transition temperature of 74 degrees C for the enantiotropic pair of I and II. The difference in enthalpy was 4.5 kcal/mol at 74 degrees C and 2.54 kcal/mol at 25 degrees C. Form I was the most physically stable below 74 degrees C, whereas form II was the most stable above 74 degrees C. Essentially pure samples of I and II could be obtained easily, but pure III could be developed only transiently on the differential scanning calorimeter heating block. Video taping of hot-stage microscopic observations for review was helpful for detecting seed crystals of II or III in samples of I. The information developed is presented in a hypothetical free energy-temperature diagram.     

Stability of polymorphic forms of ranitidine hydrochloride

Ranitidine-HCl can exist in two different polymorphic forms: form I (m.p. 134-140 degrees C) and form II (m.p. 140-144 degrees C). In the present study the stability of form I of ranitidine-HCl to a selection of powder pretreatments, to reflect conditions which might occur in manufacturing procedures, and also to a limited range of storage conditions was investigated. The original samples of form I and form II used were characterised by X-ray powder diffraction (XRPD), hot stage microscopy (HSM) and differential scanning calorimetry (DSC). A quantitative XRPD method for determining the fraction of form II in the presence of form I was used. XRPD data were analysed using regression techniques and artificial neural networks (ANN). The quantitative XRPD technique was then used to monitor the relative proportion of form II in each treated sample. Pretreatments of form I included (i) mixing with form II or with common excipients (ii) compression and grinding (iii) contact with solvents (followed by drying) before storage. Storage conditions involved three temperatures (20 degrees C, 30 degrees C, 42 degrees C) and three relative humidities (45% RH; 55% RH; 75% RH). Samples were stored for a period of 6 months. A limited factorial design was used. No increase in the form II:form I ratio was observed in the following pretreatment processes: introduction of form II nuclei into form I; introduction of excipients to form I; compression of form I powder at 5 and 15 tons; normal mixing and grinding processes; addition of isopropanol (IPA) or water/IPA mix followed by drying. In the pretreatment process where water was added to form I powder (with most or all of the powder dissolving), drying of the liquefied mass led to a mix of form I and form II. On storage at room temperature (20-30 degrees C), low relative humidity (45-55% RH), and in an air-tight container there was no increase in the form II:form I ratio. Storage of form I/form II mixes, particularly at high humidity, resulted in a preferential loss of form II (compared to form I). Loss was greater at 30 degrees C/75% RH than at 20 degrees C/75% RH. Form II was also preferentially lost under low humidity conditions created by a saturated solution of potassium carbonate (45% RH) at the elevated temperature of 42 degrees C. This environment was shown to be acidic.     

Solid-state studies on the hemihydrate and the anhydrous forms of flunisolide

Flunisolide exists in at least two different anhydrous crystalline forms (I and II) and in a hemihydrate form with distinctly different physico-chemical properties. Modification II and the hemihydrate form are the commercial products. Form I was obtained by heating all other forms above 230 degrees C. The different crystalline forms of flunisolide were investigated by FTIR spectroscopy, X-ray powder diffractometry, differential scanning calorimetry (DSC), thermogravimetric analysis and thermomicroscopy both coupled with FTIR spectroscopy (TG-FTIR and FTIR thermomicroscopy). The three forms were easily differentiated by their IR spectra, X-ray powder diffraction patterns and thermal behaviour. Their stability was investigated under different experimental conditions to verify the tendency to solid solid transition and to study the existence range of the three forms. The relationship among the two anhydrous polymorphs and the hemihydrate form and their equilibrium solubilities in water at 20 degrees C were also investigated.     

Polymorphism of Alprazolam (Xanax): a review of its crystalline phases and identification, crystallographic characterization, and crystal structure of a new polymorph (form III)

A new polymorphic form of Alprazolam (Xanax), 8-chloro-1-methyl-6-phenyl-4H-[1,2,4]triazolo-[4,3-alpha][1,4]benzodiazepine, C(17)H(13)ClN(4), has been investigated by means of X-ray powder diffraction (XRPD), single crystal X-ray diffraction, and differential scanning calorimetry (DSC). This polymorphic form (form III) was obtained during DSC experiments after the exothermic recrystallization of the melt of form I. The crystal unit cell dimensions for form III were determined from diffractometer methods. The monoclinic unit cell found for this polymorph using XRPD after indexing the powder diffractogram was confirmed by the cell parameters obtained from single crystal X-ray diffractometry on a crystal isolated from the DSC pans. The single crystal unit cell parameters are: a = 28.929(9), b = 13.844(8), c = 7.361(3) angstroms, beta = 92.82(3) degrees , V = 2944(2) angstroms(3), Z = 8, space group P2(1) (No.4), Dx = 1.393 Mg/m(3). The structure obtained from single crystal X-ray diffraction was used as initial model for Rietveld refinement on the powder diffraction data of form III. The temperature phase transformations of alprazolam were also studied using high temperature XRPD. A review of the different phases available in the Powder Diffraction File (PDF) database for this drug is described bringing some clarification and corrections.     

Recrystallization of fluconazole using the supercritical antisolvent (SAS) process

The supercritical antisolvent (SAS) process was used to modify solid state characteristics of fluconazole. Fluconazole was recrystallized at various temperatures (60-80 degrees C) and pressures (8-16MPa) using dichloromethane (DCM) as a solvent. Acetone and ethanol were also employed as solvents. The fluconazole polymorphs prepared by the SAS process were characterized by differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Furthermore, the equilibrium solubility of the samples in aqueous solution was determined. Fluconazole anhydrate form I was obtained at low temperature (40 degrees C) and anhydrate form II was obtained at high temperature (80 degrees C). The variation of pressure during the SAS process may influence the preferred orientation. Anhydrate forms I and II were also obtained using various solvents. Therefore, it was shown that solid state characteristics of fluconazole, including the polymorphic form and preferred orientation, can be controlled by changing operating conditions of the SAS process such as temperature, pressure, and solvent.     

The thermodynamic dissociation constants of four non-steroidal anti-inflammatory drugs by the least-squares nonlinear regression of multiwavelength spectrophotometric pH-titration data

The mixed dissociation constants of four non-steroidal anti-inflammatory drugs (NSAIDs) ibuprofen, diclofenac sodium, flurbiprofen and ketoprofen at various ionic strengths I of range 0.003-0.155, and at temperatures of 25 degrees C and 37 degrees C, were determined with the use of two different multiwavelength and multivariate treatments of spectral data, SPECFIT/32 and SQUAD(84) nonlinear regression analyses and INDICES factor analysis. The factor analysis in the INDICES program predicts the correct number of components, and even the presence of minor ones, when the data quality is high and the instrumental error is known. The thermodynamic dissociation constant pK(a)(T) was estimated by nonlinear regression of (pK(a), I) data at 25 degrees C and 37 degrees C. Goodness-of-fit tests for various regression diagnostics enabled the reliability of the parameter estimates found to be proven. PALLAS, MARVIN, SPARC, ACD/pK(a) and Pharma Algorithms predict pK(a) being based on the structural formulae of drug compounds in agreement with the experimental value. The best agreement seems to be between the ACD/pK(a) program and experimentally found values and with SPARC. PALLAS and MARVIN predicted pK(a,pred) values with larger bias errors in comparison with the experimental value for all four drugs.     

Solid-state properties and crystallization behavior of PHA-739521 polymorphs

PHA-739521 is an experimental compound that exhibits polymorphism. The two anhydrous crystal forms, I and II, are characterized using powder X-ray diffractometry, thermal analyses, moisture sorption gravimetry. Both Forms I and II are non-hygroscopic and are stable to compaction pressure. The melting temperature is about 152 degrees C for Form I and 168 degrees C for Form II. Forms I and II are enantiotropically related where Form I is more stable below a transition temperature of approximately 70 degrees C. Crystallization behavior of this compound from solutions and during heating is also studied. Information obtained is used to design an appropriate crystallization process to successfully manufacture desired polymorph at large scale.     

Physicochemical and crystallographic evidence for polymorphism of the racemic ethyl (2-chloromethyl-2,3-dihydro-5H-oxazolo [3, 2-a]pyrimidin-5-one)-6-carboxylate

The various crystalline forms of an original bicyclic compound [ethyl (2-chloromethyl-2,3-dihydro-5H-oxazolo[3, 2-a]pyrimidin-5-one)-6-carboxylate); EOC] have been obtained and characterized by powder and single-crystal X-ray diffraction, differential scanning calorimetry (DSC), and infrared (IR) and Raman spectroscopy. At 4 degrees C in methanol, a monoclinic racemate (form II) crystallized from the racemic mixture, whereas at 20 degrees C, an orthorhombic racemate (form I) was isolated in trichloroethylene. By increasing the temperature, a solid-solid transition from the stable form II to the stable form I was observed with a Guinier-Simon camera. A I --> II transformation was observed at ambient temperature by DSC.     

Formation of physically stable amorphous drugs by milling with Neusilin

Each of four drugs (ketoprofen, indomethacin, naproxen, and progesterone) was milled with Neusilin (amorphous magnesium aluminosilicate) to effect conversion from crystalline to amorphous states, and the physical stability of the resultant drugs was investigated. Ball milling the drugs alone for 48 h resulted in no amorphization. X-ray powder diffractometry (XPD), birefringence, and differential scanning calorimetry (DSC) data indicated amorphization of all the four drugs on ball milling with Neusilin. Fourier transform infrared spectroscopy (FTIR) data showed a reduction in the absorbance of the free and the hydrogen-bonded acid carbonyl peaks accompanied by a corresponding increase in the absorbance of the carboxylate peak, indicating an acid-base reaction between the carboxylic acid-containing drugs and Neusilin on milling. On storage of milled powders (at 40 degrees C and 75% RH for 4 weeks), XPD, birefringence, and DSC data showed the absence of reversion to the crystalline state, and FTIR data revealed continued absence of the carbonyl peaks. Whereas the carboxylic acid-containing drugs convert from their crystalline acid form to amorphous salt form on milling with Neusilin, progesterone seems to interact with Neusilin via hydrogen bonding. The amorphous Neusilin-bound states of all four drugs were physically stable during storage. The water of adsorption seems to mediate the conversion of the crystalline state to an amorphous Neusilin-bound state.     

金钱白花蛇及其伪品的Cyt b基因片段序列分析和PCR鉴别研究

对金钱白花蛇及其伪、混品药材和原动物的Cyt b基因片段的序列分析发现,该基因片段在金钱白花蛇及其伪品间的差异远远大于金钱白花蛇种内个体间的差异,是理想的用于鉴别金钱白花蛇及其伪混品的分子遗传标记。在对Cyt b基因片段序列分析的基础上,设计了金钱白花蛇PCR鉴别的一对高度特异性引物BuL-1和BuH-1。结果表明,该对引物在对金钱白花蛇的PCR鉴别中,用60℃～65℃的复性温度,可以100%检出金钱白花蛇,误检率和漏检率为0,并能在混合的药材粉末中检测出被检样品中是否含有金钱白花蛇组份。本研究还表明PCR鉴别将有可能成为中成药复方组分鉴别的一种新手段。     

Crystal forms of ketorolac

Four crystal forms of ketorolac have been obtained by recrystallization in organic solvents under variable conditions. Different ketorolac polymorphs and pseudopolymorph were characterized by X-ray powder diffraction crystallography (XRD), Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). In the dissolution studies in water at 37 +/- 0.5 degrees C, four crystal forms showed different patterns. The solubility of Form I were the highest. The solubility decreased in rank order: Form I > Form II > Form III > Form IV. Form land Form III were shown to have a good physical stability at room temperature for 60 days. However, Form II is converted to Form III and Form IV is converted to Form I after 60 days storage. Therefore, these observations indicate that crystalline polymorphism for ketorolac is readily inter-convertible and the relationship may have to taken into consideration in the formulation of the drug.     

Polymorphism of racemic felodipine and the unusual series of solid solutions in the binary system of its enantiomers.

The aim of this study was to investigate the binary phase diagram and the polymorphism and pseudopolymorphism of racemic and enantiomeric felodipine, including their spectroscopic and thermodynamic properties. Different crystal forms were obtained by crystallization from solvents or from the annealed melt and investigated by thermal analysis (hot stage microscopy, differential scanning calorimetry, thermogravimetric analysis), spectroscopic methods (Fourier transform infrared-and Fourier transform-Raman spectroscopy), and X-ray powder diffractometry. The binary melting phase diagram was constructed based on thermoanalytical investigations of quantitative mixtures of (+)- and (+/-)-felodipine. Two polymorphic forms of racemic felodipine, mod. I (mp, approximately 145 degrees C) and mod. II (mp, approximately 135 degrees C), as well as an acetone solvate (S(Ac )) were characterized. Melting equilibria of felodipine crystal forms decrease due to thermal decomposition. Enantiomeric felodipine was found to be dimorphic (En-mod. I: mp, approximately 144 degrees C; En-mod. II: mp, approximately 133 degrees C). Evaluation of the binary system of (+)- and (-)-felodipine results in the formation of a continuous series of mixed crystals between the thermodynamically stable and higher melting modifications, mod. I and En-mod. I. Their unusual curve course, termed as Roozeboom Type 2 b, passes through a maximum in the racemic mixture and is flanked by a minimum at 20% and at 80% (+)-felodipine. From the thermodynamic parameters, racemic mod. I and II are monotropically related. In contrast to S(Ac), the thermodynamically unstable mod. II shows a considerable kinetic stability. Because its crystallization is badly reproducible, the use of mod. II is not advisable for processing. However, desolvation of S(Ac) leads to a profitable crystal shape of mod. I, representing a pseudoracemate by definition.     

Quality of herbal remedies from Allium sativum: differences between alliinase from garlic powder and fresh garlic

Alliinase (EC 4.4.1.4) has been isolated from commercially available garlic (Allium sativum L., Alliaceae) powder and was investigated with respect to its use as ingredient of herbal remedies. The enzyme was purified to apparent homogeneity and results were compared with those obtained from a sample of fresh A. sativum var. pekinense. The purification of the enzyme involved a gel filtration step as well as affinity chromatography on concanavalin-A agarose. Vmax using L-(+)-alliin as substrate (252 mumol min-1 mg-1) was at the lower range of data given in the literature (214-390 mumol min-1 mg-1). L-(-)-Alliin was also accepted as substrate (54 mumol min-1 mg-1). Vmax for alliinase from A. sativum var. pekinense was at 332 mumol min-1 mg-1 and 90 mumol min-1 mg-1 for L-(+)- and L-(-)-alliin, respectively. The Km values for alliinase from garlic powder were estimated to be 1.6 mM for L-(+)-alliin and 2.8 mM for L-(-)-alliin. In contrast to literature values, both temperature and pH optima were somewhat higher (36 degrees C and pH 7.0 versus 33 degrees C and pH 6.5, respectively). The enzyme was found to be active in a range from pH 5 to pH 10. Gel electrophoresis gave evidence that the alliinase obtained from garlic powder consisted of two slightly different subunits with molecular weights of 53 and 54 kDa whereas alliinase obtained from fresh garlic consists of two identical subunits. It is assumed that the alliinase gets significantly altered during the drying process of garlic powder but is still capable to convert alliin to allicin.     

Polymorphism of tedisamil dihydrochloride

The results of studies on tedisamil dihydrochloride in the solid state demonstrate that the compound occurs in three polymorphic forms. The three modifications have been characterized by thermomicroscopy, differential scanning calorimetry (DSC), vibrational spectroscopy, solid-state nuclear magnetic resonance (NMR), and X-ray powder diffractometry (XRPD). The thermodynamic relationships are illustrated in a semischematic energy/temperature diagram that gives information about the relative stability and physical properties of the three modifications between 0 K and the melting temperatures. The three modifications are enantiotropically related. Modification II, the material obtained during manufacturing, is the thermodynamically stable crystal form at 20 degrees C. The thermodynamic transition point of mod II with I (instant melting point: 248-250 degrees C) is between 100 and approximately 140 degrees C (DeltaH(t,II/I) = 4.4+/-0.8 kJ/mol (95% CI)). A phase transition of mod II (probably into mod III) was detected thermomicroscopically at about -180 degrees C. The thermodynamic transition point of mod III with I was determined to be at -9 to -6 degrees C. Because mods I and III are thermodynamically and kinetically unstable at ambient conditions, these crystal forms are of analytical interest.     

野木瓜甙YM10和YM12的结构

从野木瓜(Stauntonia chinensis DC.)中分离得到二个去甲五环三萜皂甙化合物,经化学和光谱分析,分别鉴定为3-O-α-L-吡喃鼠李糖-(1→2)-α-L-吡喃阿拉伯糖-30去甲齐墩果-12,20(29)-二烯-28-羧酸-28-O-α-L-呲喃鼠李糖-(1→4-β-D-吡喃葡萄糖-(1→6)-β-D-吡喃葡萄糖酯,命名为野术瓜甙YM10(Ⅰ)和3-O-α-L-呲喃鼠李糖-(1→2)-α-L-吡喃阿拉伯糖-30-去甲齐墩果-12,20(29)-二烯-28-羧酸-28-O-β-D-吡喃葡萄糖-(1→6)-β-D-吡喃葡萄糖酯,命名为野木瓜甙YM₁₂(Ⅱ)。Ⅰ和Ⅱ均系首次从植物中得到的新化合物。     

Stability-indicating methods for the determination of doxazosin mezylate and celecoxib

Two stability-indicating methods were developed for the determination of doxazosin mesylate (I) and celecoxib (II) in the presence of their degradation products. The first method depends on the use of first derivative spectrophotometry (D(1)) at 256, 269 nm for (I) and (II), respectively. This method determines (I) and (II) in concentration ranges of 0.8-12 and 1-20 microg ml(-1) with mean percentage accuracies of 99.21+/-0.88 and 99.59+/-1.67% for (I) and (II), respectively. The second method depends on the quantitative densitometric evaluation of thin-layer chromatography of (I) and (II) in the presence of their degradation products without any interference. Methylisobutyl ketone-glacial acetic acid-water (20:10:10) was used as a mobile phase for (I) and cyclohexane-dichloromethane-diethyleamine (50:40:10) for (II). The chromatograms were scanned at 248 and 253 nm for (I) and (II), respectively. This method determines (I) and (II) in concentration ranges of l-4 microg per spot for both drugs with mean percentage accuracies of 100.19+/-0.95 and 99.91+/-1.95% for (I) and (II), respectively. The suggested methods were used to determine doxazosin mesylate and celecoxib in bulk powder, laboratory-prepared mixtures and pharmaceutical dosage forms (cardura tablet and celebrex capsule). The results obtained by applying the proposed methods were statistically analysed and compared with those obtained by the reported methods.     

Dissolution systems for chloramphenicol tablet bioavailability.

The relationship between chloramphenicol (I) tablet bioavailability and in vitro dissolution rates was examined. The effect of solid food on the I tablet and powder bioavailability was also studied. Five tablets of I were selected for bioavailability testing on the basis of the dissolution rates of 18 I tablets (250 mg) determined by several methods. Compound I, 500 mg, was administered orally to five subjects, following overnight fasting, according to a crossover design. The bioavailability parameters were obtained from urinary I excretion. Among the five formulations studied, only one tablet (F) showed significantly poorer bioavailability. The dissolution rates at pH 1.2 did not give the same rank order as the bioavailability. The dissolution rate of Tablet F showed remarkable pH dependency. The dissolution rates at pH 4 showed good correlation with in vivo bioavailability data. The bioavailability of I powder was not affected by solid food. Tablet F, which had poor bioavailability in the fasting state, showed good bioavailability when administered just after the standard breakfast.     

Energy/temperature diagram and compression behavior of the polymorphs of D-mannitol

Three modifications of D-mannitol were produced and investigated: mod. I (mp 166.5 degrees C, heat of fusion 53.5 kJ mol(-1)), mod. II (mp 166 degrees C, heat of fusion 52.1 kJ mol(-1)), and mod. III (mp incongruent 150-158 degrees C, heat of transition, III to I 0.2 kJ mol(-1)). The measured densities are 1.490 +/- 0.000 g cm(-3) [95% confidence interval (CI)] for mod. I, 1.468 +/- 0.002 g cm(-3) (95% CI) for mod. II, and 1.499 +/- 0.004 g cm(-3) (95% CI) for mod. III. It was possible to relate the different modifications given in the literature to one of the three pure crystal forms or to mixtures of two or all three modifications. The thermodynamic relationship among the crystal forms is represented in a semi-schematic energy/temperature diagram. From these data we can conclude that mod. III is thermodynamically stable at absolute zero. It is enantiotropically related to mod. I and mod. II. FTIR and Raman spectra, differential scanning calorimetry curves, and X-ray powder patterns of these crystal forms are depicted for doubtless assignment in the future. The water uptake of the three modifications at 92% relative humidity and 25 degrees C is less than 1%. The differences of the heat capacities and the heats of solution between mod. II and III are not significant, whereas mod. I shows small significant differences compared with the other modifications. In addition, compaction studies of these crystal forms were performed by means of an instrumented hydraulic press. The results show that mod. III should have the best tableting behavior under these conditions.     

Evaluation of reversible polymorphic phase transitions by thermal analysis

Crystalline states of 1,2-dihydro-6-neopentyl-2-oxonicotinic acid, an investigational antidiabetic drug, were evaluated by thermal analyses. Two polymorphs were detected for the drug, Form I (m.p. 193 degrees C) and Form II (m.p. 196 degrees C). Interconversion of the polymorphs upon cyclic solid-melt transitions provided confirmation of the crystal forms. Solidification of the melt was observed to occur either at 162 or 182 degrees C with the formation of Form I or Form II crystals, respectively. Form I underwent partial conversion to Form II upon heating at 10 degrees C min-1 when nucleating crystals of Form II were present in the sample. Differential scanning calorimetry (DSC) thermograms were recorded for different lots of the drug, solvent-recrystallized samples, and a series of known mixtures of Form I and II polymorphs. The study illustrates the usefulness of cyclic heat-cool studies to characterize polymorphic crystal forms of drugs.     

Effect of surface characteristics of theophylline anhydrate powder on hygroscopic stability

The hygroscopicity of theophylline anhydrate has been investigated by gas adsorption and hydration kinetic methods. Type 1 theophylline anhydrate was obtained by recystallization from distilled water at 95 degrees C, and type II was obtained by dehydration of theophylline monohydrate. The X-ray diffraction pattern of types I and II agreed with the data of theophylline anhydrate. However, the diffraction peaks of the (200) and (400) planes of type I were much stronger than those of type II. The particles of type I were clear crystalline-like single crystals. However, the particles of type II had many cracks. The gas affinity balance (H/N) of type II, measured by gas adsorption, was about 7 times that of type I. After the hygroscopicity of types I and II had been tested at various levels of relative humidity (RH) at 35 degrees C, type I was stable at less than 82% RH, but transformed into the monohydrate at more than 88% RH. Type II was stable at less than 66% RH and transformed into the monohydrate at less than 75% RH. The hydration data of type I at 88% RH and type II at 75% RH were calculated for hydration kinetics using various solid-state kinetic models, but no particular model could be preferred from these data.