The Cryopreservation of Liposomes. 1. A Differential Scanning Calorimetry Study of the Thermal Behavior of a Liposome Dispersion Containing Mannitol During Freezing/Thawing

The thermal behavior of water in liposome dispersions and in liposome dispersions containing mannitol at subzero temperatures was investigated with differential scanning calorimetry (DSC). The cooling curves from 20 down to - 60°C for a liposome dispersion (bilayer composition PL100H/DCP), monitored at cooling rates of 5 and 10°C/min, showed several heat flows related to water crystallization. All lipid-containing dispersions showed water crystallization at temperatures below –40°C. The magnitude of this heat flow strongly depended on the experimental variables. Cooling rate, particle size, lipid concentration, and location and nature of the cryoprotectant all influenced the water crystallization behavior as shown in the DSC cooling curve. Different fractions of water–presumably related to their location in the dispersion–could be distinguished. It is concluded that DSC provides a valuable tool for the detection of changes in the physical state of water in liposome dispersions during freezing/thawing. The insights gained from these DSC studies may make it possible to select–on the basis of rational considerations rather than by trial and error–optimum conditions for the cryopreservation of liposomes containing water-soluble drugs.     

Polymorphism of l,2-Dihydro-6-neopentyl-2-oxonicotinic Acid: Characterization,Interconversion, and Quantitation

Two polymorphs of l,2-dihydro-6-neopentyl-2-oxonicotinic acid have been characterized by X-ray diffraction (XRD), infrared spectroscopy (IR), differential scanning calorimetry (DSC), and thermal (hot-stage) microscopy (HSM). In batch-scale preparation, form I was crystallized in ethanol–water (3:1), while form II was obtained by recrystallization from acetone–water (2:1). The melting points for forms I and II are 193 and 196°C, respectively. Thermal studies (DSC and HSM) showed that form II melts at 196°C, while form I melts at 193°C, immediately followed by a resolidification and remelt at 196°C. The conversion of form II to form I was accomplished by recrystallization from ethanol or methanol, and the form I-to-form II transition was obtained by controlled heating of form I around 194°C. Quantitative XRD was used to determine the polymorphic composition, with a detection limit of less than 1% of the minor form and a linearity of 0–10% form I in form II (correlation coefficient of 0.999).     

Stabilization of Misoprostol with Hydroxypropyl Methylcellulose (HPMC) Against Degradation by Water

The stability of misoprostol oil is significantly improved in a hydroxypropyl methylcellulose (HPMC) dispersion (1:100). In order to assess the effect of water on misoprostol stability, the rate of misoprostol degradation was investigated in the misoprostol/HPMC dispersion at 55°C, along with the water sorption isotherm, under seven different relative humidity (RH) conditions ranging from 0 to 81%. The results indicated that the first-order rate constants of misoprostol degradation increased in a concave-up fashion as the water content of the dispersion increased. Below 30% relative humidity (2% water), the first-order rate constants of misoprostol degradation were found to be minimum. The results of the stability study were interpreted in terms of the changing structure of HPMC as it related to the mobility of water and misoprostol within the HPMC dispersion.     

Polymorph Control of Sulfathiazole in Supercritical CO2

Purpose. Sulfathiazole was used to investigate polymorph control in liquid and supercritical CO₂. Conventional techniques require a variety of solvents and techniques to produce different polymorphs. The present approach involves precipitation from an organic solution with liquid or supercritical CO₂ using the SEDS process. Methods. Sulfathiazole was precipitated from methanol or acetone solutions. Experiments were carried out within a temperature range of 0–120°C. Composition of the fluid phase was varied between x(CO₂) = 0.27–0.99. Pressure was constant at 200 bar. Samples obtained were analyzed using SEM, DSC, and XRPD. Results. Pure polymorphs were obtained at different temperatures and flow rate ratios of CO₂/solvent. With methanol Form I, III, and IV and their mixtures could be crystallized. With acetone Form I or a mixture of Form I and amorphous sulfathiazole was obtained. The fluid composition was used as a control parameter to define the process areas (T–x diagram) where the pure forms or mixtures of different forms could be obtained. Conclusions. The experiments enabled the relationship between flow and temperature for each polymorph to be determined. The crystallization method developed proved to be a simple and efficient technique for reproducible and consistent isolation of sulfathiazole polymorphs.     

Probing Beta Relaxation in Pharmaceutically Relevant Glasses by Using DSC

Purpose This study was conducted to demonstrate the use of differential scanning calorimetry (DSC) in detecting and measuring β-relaxation processes in amorphous pharmaceutical systems. Methods DSC was employed to study amorphous samples of poly(vinylpyrrolidone) (PVP), indomethacin (IM), and ursodeoxycholic acid (UDA) that were annealed at temperatures (T_a) around 0.8 of their glass transition temperatures (T_g). Dynamic mechanical analysis (DMA) was used to measure β-relaxation in PVP. Results Reheating the annealed samples gives rise to annealing peaks that occur below T_g. The peaks cannot be generated when annealing below the low temperature limit of β-relaxation. These limits are around 50°C for PVP, −20°C for IM, and 30°C for UDA. The effective activation energy (E) of the sub-T_g relaxation has been estimated for each T_a and found to increase with T_a, reflecting increasing contribution of the α-process. Estimates of E for β-relaxation have been obtained from the lowest T_a data, and are as follows: 68 (PVP), 56 (IM), 67 (UDA) kJ mol⁻¹. Conclusions DSC can be used for detecting β-relaxation processes and estimating its low temperature limit, i.e., the temperature below which amorphous drugs would remain stable. It can also provide comparative estimates of low temperature stability of amorphous drugs in terms of the activation energies of the β-relaxation.     

米非司酮阴道贴膜的研究

以羟丙基甲基纤维素（ＨＰＭＣ）为基质制备米非司酮（１）分散体的粘贴膜剂。其体外溶出及经粘膜渗透均比常规的１片剂快。月桂氮　酮能加速膜剂的渗透速率，但对片剂并无作用。差示热分析研究表明米非司酮／ＨＰＭＣ固态分散体中１以分子状态存在。     

Design and evaluation of gastroretentive levofloxacin floating mini-tablets-in-capsule system for eradication of Helicobacter pylori

Gastroretentive levofloxacin (LVF) floating mini-tablets for the eradication of Helicobacter pylori (H. pylori) were prepared using the matrix forming polymer hydroxypropyl methylcellulose (HPMC K100M), alone or with Carbopol 940P in different ratios by wet granulation technique. Buoyancy of mini-tablets was achieved by an addition of an effervescent mixture consisting of sodium bicarbonate and anhydrous citric acid to some formulations. The prepared mini-tablets were evaluated for weight variation, thickness, friability, hardness, drug content, in vitro buoyancy, water uptake and in vitro release. The optimized formula was subjected to further studies: FT-IR, DSC analysis and in vivo examination in healthy volunteers. The prepared mini-tablets exhibited satisfactory physicochemical characteristics. Incorporation of gas-generating agent improved the floating parameters. HPMC K100M mini-tablet formulation (F1) offered the best controlled drug release (>8 h) along with floating lag time <1 s and total floating time >24 h. The obtained DSC thermograms and FT-IR charts indicated that there is no positive evidence for the interaction between LVF and ingredients of the optimized formula. The in vivo test confirmed the success of the optimized formula F1 in being retained in the stomach of the volunteers for more than 4 h. LVF floating mini-tablets based on HPMC K100M is a promising formulation for eradication of H. pylori.Abbreviations: LVF, levofloxacin; H. pylori, Helicobacter pylori; HPMC, hydroxypropyl methylcellulose; FT-IR, Fourier transform infrared spectroscopy; DSC, differential scanning calorimetry; PVP, polyvinyl pyrrolidone; SI, swelling index     

Application of Calorimetry,Sub-Ambient Atomic Force Microscopy and Dynamic Mechanical Analysis to the Study of Frozen Aqueous Trehalose Solutions

Purpose Disaccharides such as trehalose are widely used as cryo-protectants to maintain the activity of proteinaceous drugs during freezing. One unresolved issue is the double transition that is observed very commonly in DSC experiments on disaccharide solutions in the frozen state; the assignment of these transitions remains disputed. Here we use calorimetry and two new techniques to shed light on the true nature of these transitions. Methods Modulated Temperature DSC (MTDSC), cryo atomic force microscopy (AFM) and a novel DMA technique were used to study these transitions. Results MTDSC identified the two transitions Tr₁ and Tr₂ at −35.4 and −27.9°C respectively in the reversing heat flow signal, an exotherm and endotherm were observed in the non-reversing signal at circa −32 and −29°C respectively. It is shown for the first time that AFM images can be obtained of a softening and melting sample without damaging it. A force modulation imaging technique showed a softening at Tr₁ and a loss of ice crystals at Tr₂. These observations were supported by the DMA results. Conclusions The results indicate Tr₁ is associated with a glass transition while Tr₂ is associated with the onset of loss of crystallinity.     

Galanin: structure-dependent effect on pancreatic amylase secretion and jejunal strip contraction

Rat and porcine galanin and their fragments inhibited cholecystokinin-8 (CCK-8)-stimulated amylase secretion with the following activities: rat galanin-(1–29) = porcine galanin-(1–19) = galanin-(1–15) = rat galanin-(3–29) > rat galanin-(2–29) = porcine galanin-(2–29) > galanin-(1–10). Fragments of rat galanin-(9–29) and N^α-acetyl-galanin-(9–29) were able to inhibit CCK-8-stimulated pancreatic amylase secretion but only at higher dose levels. Porcine galanin-(15–29) and rat galanin-(21–29) were unable to produce significant inhibition. Rat and porcine galanin-(1–29), galanin-(1–15) and rat N^α-acetyl-galanin-(9–29) also inhibited basal pancreatic amylase secretion. In the rat jejunal strip contraction model, rat galanin-(1–29) and porcine galanin-(1–29) have similar potencies. Galanin-(1–15) and galanin-(1–10) stimulate rat jejunal strip contraction with decreasing potencies. Elimination of Gly¹ from the N-terminus of both rat and porcine galanin had no significant effect either on pancreatic amylase secretion or on jejunal strip contraction. The rat galanin-(3–29) and (9–29) are not active in the stimulation of rat jejunal strip contraction. Acetylation of porcine galanin-(9–29) created a peptide that was a powerful stimulator of rat jejunal strip contraction. The present data indicate that N-terminal rat galanin amino acid residues are crucial for rat jejunal strip contraction but are not required for inhibition of pancreatic amylase. These results suggest that the galanin amino acid sequence contains several specific domains, which can be recognized by specific galanin receptor subsets.     

Effect of casting solvent on crystallinity of ondansetron in transdermal films

The purpose of the present investigation is to assess the influence of casting solvent on crystallinity of ondansetron hydrochloride in transdermal polymeric matrix films fabricated using povidone and ethyl cellulose as matrix forming polymers. Various casting solvents like chloroform (CHL), dichloromethane (DCM), methanol (MET); and mixture of chloroform and ethanol (C-ETH) were used for fabrication of the transdermal films. Analytical tools like scanning electron microscopy (SEM), X-ray diffraction (XRD) studies, differential scanning calorimetry (DSC), etc. were utilized to characterize the crystalline state of ondansetron in the film. Recrystallisation was observed in all the transdermal films fabricated using the casting solvents other than chloroform. Long thin slab-looking, long wire-like or spherulite-looking crystals with beautiful impinged boundaries were observed in SEM. Moreover, XRD revealed no crystalline peaks of ondansetron hydrochloride in the transdermal films prepared using chloroform as casting solvent. The significantly decreased intensity and sharpness of the DSC endothermic peaks corresponding to the melting point of ondansetron in the formulation (specifically in CHL) indicated partial dissolution of ondansetron crystals in the polymeric films. The employed analytical tools suggested chloroform as a preferred casting solvent with minimum or practically absence of recrystallization indicating a relatively amorphous state of ondansetron in transdermal films.     

Correlationship of Drug-Polymer Miscibility,Molecular Relaxation and Phase Behavior of Dipyridamole Amorphous Solid Dispersions

In present work, a correlationship among quantitative drug-polymer miscibility, molecular relaxation and phase behavior of the dipyridamole (DPD) amorphous solid dispersions (ASDs), prepared with co-povidone (CP), hydroxypropyl methylcellulose phthalate (HPMC P) and hydroxypropyl methylcellulose acetate succinate (HPMC AS) has been investigated. Miscibility predicted using melting point depression approach for DPD with CP, HPMC P and HPMC AS at 25 °C was 0.93% w/w, 0.55% w/w and 0.40% w/w, respectively. Stretched relaxation time (τ^β) for DPD ASDs, measured using modulated differential scanning calorimetry (MDSC) at common degree of undercooling, was in the order of DPD- CP > DPD-HPMC P > DPD-HPMC AS ASDs. Phase behavior of 12 months aged (25 ± 5 °C and 0% RH) spray dried 60% w/w ASDs was tracked using MDSC. Initial ASD samples had homogeneous phase revealed by single glass transition temperature (T_g) in the MDSC. MDSC study of aged ASDs revealed single-phase DPD-CP ASD, amorphous-amorphous and amorphous-crystalline phase separated DPD-HPMC P and DPD-HPMC AS ASDs, respectively. The results were supported by X-ray micro computed tomography and confocal laser scanning microscopy studies. This study demonstrated a profound influence of drug-polymer miscibility on molecular mobility and phase behavior of ASDs. This knowledge can help in designing “physical stable” ASDs.     

Interaction Phenomena in some Aqueous-Based Tablet Coating Polymer Systems

Molecular interactions in aqueous-based tabletfilm coating systems consisting of hydroxypropyl methylcellulose (HPMC) in combination with either polyvinyl alcohol (PVA), polyethylene glycol (PEG) 400 or PEG 1000 have been investigated by viscometry and thermal analysis. The viscosity results indicate that the solvent (water) inhibited polymer-polymer interaction and this inhibitory effect was directly related to the solvent affinity of the polymer additive. The presence of crystallinity in the films was examined using a differential scanning calorimeter (DSC). HPMC/PVA blends were partially crystalline but the plasticized HPMC films showed no signs of crystallinity. Glass transition data were also obtained with the DSC. The plasticizer effects of PEG 400 and PEG 1000, respectively, in HPMC were confirmed by the fall in the glass transition temperature (Tg) of HPMC. On the other hand, incorporation of PVA increased the Tg of HPMC, and this was attributed to the presence of a crystalline phase in the blend. Maximum compatibility levels of PVA, PEG 400 and PEG 1000 in the polymer blends were found to be 40, 20 and 15 wt %, respectively, based on glass transition data.     

Evaluation of injection moulding as a pharmaceutical technology to produce matrix tablets

The aim of this study was to develop sustained-release matrix tablets by means of injection moulding and to evaluate the influence of process temperature, matrix composition (EC and HPMC concentration) and viscosity grade of ethylcellulose (EC) and hydroxypropylmethylcellulose (HPMC) on processability and drug release. The drug release data were analyzed to get insight in the release kinetics and mechanism. Formulations containing metoprolol tartrate (30%, model drug), EC with dibutyl sebacate (matrix former and plasticizer) and hydrophilic polymer HPMC were extruded and subsequently injection moulded into tablets (375 mg, 10 mm diameter, convex-shaped) at temperatures ranging from 110 to 140 °C. Tablets containing 30% metoprolol and 70% ethylcellulose (EC 4 mPa s) showed an incomplete drug release within 24 h (<50%). Increasing production temperatures resulted in a lower drug release rate. Substituting part of the EC fraction by HPMC (HPMC/EC-ratio: 20/50 and 35/35) resulted in faster and constant drug release rates. Formulations containing 50% HPMC had a complete and first-order drug release profile with drug release controlled via the combination of diffusion and swelling/erosion. Faster drug release rates were observed for higher viscosity grades of EC (Mw > 20 mPa s) and HPMC (4000 and 10,000 mPa s). Tablet porosity was low (<4%). Differential scanning calorimetry (DSC) and X-ray powder diffraction studies (X-RD) showed that solid dispersions were formed during processing. Using thermogravimetrical analysis (TGA) and gel-permeation chromatography no degradation of drug and matrix polymer was observed. The surface morphology was investigated with the aid of scanning electron microscopy (SEM) showing an influence of the process temperature. Raman spectroscopy demonstrated that the drug is distributed in the entire matrix, however, some drug clusters were identified.     

Relationship between initial sensitivity,acute tolerance and chronic tolerance to ethanol in a heterogeneous population of Swiss mice

Acute and chronic tolerance to ethanol hypothermia as a function of the initial sensitivity were examined in a heterogeneous population of Swiss mice. Based on their day 1 hypothermic response to a challenge dose of ethanol (4 g/kg, IP), 60 mice were divided into three groups: high responders (HR: T _max 6.5–9° C,n=14); medium responders MR: T _max 4.75–6.25° C,n=31); and low responders sponders (LR: T _max 3–4.5° C,n=15). Animals were injected once daily (between 9 and 11 A.M.) with 4 g/kg ethanol (20% w/v) for a period of 7 days. Testing was repeated on days 3 and 7 after the administration of the same dose of ethanol. The HR group showed the highest degree of chronic tolerance to ethanol hypothermia, followed by the MR group, while the LR group developed no chronic tolerance. Acute tolerance was considered to be present when T was lower at the same blood alcohol concentration (BAC), or BAC was higher at the same T, at later times in the same mouse. On days 3 and 7, the HR and MR showed acute tolerance, while the LR did not. Although metabolic tolerance to ethanol was detected in all three groups, ethanol metabolism played a minor role in initial sensitivity and acute and chronic ethanol tolerance.     

Development of Press-Coated,Floating-Pulsatile Drug Delivery of Lisinopril

Lisinopril is an angiotensin-converting enzyme (ACE) inhibitor, primarily used for the treatment of hypertension, congestive heart failure, and heart attack. It belongs to BCS class III having a half-life of 12 hrs and 25% bioavailability. The purpose of the present work was to develop a press-coated, floating-pulsatile drug delivery system. The core tablet was formulated using the super-disintegrants crosprovidone and croscarmellose sodium. A press-coated tablet (barrier layer) contained the polymer carrageenan, xanthan gum, HPMC K4M, and HPMC K15M. The buoyant layer was optimized with HPMC K100M, sodium bicarbonate, and citric acid. The tablets were evaluated for physical characteristics, floating lag time, swelling index, FTIR, DSC, and in vitro and in vivo behavior. The 5% superdisintgrant showed good results. The FTIR and DSC study predicted no chemical interactions between the drug and excipients. The formulation containing xanthan gum showed drug retaining abilities, but failed to float. The tablet containing HPMC K15M showed a high swelling index. The lag time for the tablet coated with 200 mg carrageenan was 3±0.1 hrs with 99.99±1.5% drug release; with 140 mg HPMC K4M, the lag time was 3±0.1 hrs with 99.71±1.2% drug release; and with 120 mg HPMC K15M, the lag time was 3±0.2 hrs with 99.98±1.7% drug release. The release mechanism of the tablet followed the Korsmeyer-Peppas equation and a first-order release pattern. Floating and lag time behavior have shown good in vitro and in vivo correlations.     

Stability of the New Anticancer Platinum Analogue 1,2-Diaminomethyl-Cyclobutane-Platinum(II)-Lactate (Lobaplatin; D19466) in Intravenous Solutions

The chemical stability of the new anticancer platinum analogue 1,2-diaminomethyl-cyclobutane-platinum(II)-lactate (D19466) in infusion media was studied in an accelerated stability testing experiment with a selective HPLC-UV method. Variables were time, temperature, light, concentration, and infusion mixture. Mean reaction rate constants of decomposition were, respectively, 0.9555 *10^–2, 2.127 *10^–2, and 4.221 *10^–2 hr^–1 at 37, 56, and 66°C at a concentration of 200 mg/L in normal saline. From the Arrhenius equation, shelf lives (5% loss) at 4, 22, 37, and 121°C were, respectively, calculated to be 41.6, 13.2, 5.7, and 0.15 hr. Mean reaction rate constant in 5% dextrose was 3.106 * 10^–2 hr^–1 (200 mg/L; 56°C) and differed from that in normal saline (P < 0.005). Mean reaction rate constant in Ringer lactate was 2.084 *10^–2 hr^–1 (200 mg/L; 56°C) (P > 0.05). There was no influence of normal daylight on the rate of decomposition. It is recommended to prepare D19466 infusions in normal saline. Chemical stability is then maximal 12 hr at room temperature or 24 hr at 4°C. No protection against normal daylight is required. Sterilization by heat is not possible.     

Opioid-Induced Respiratory Depression and Analgesia May Be Mediated by Different Subreceptors

Use of selective delta opioid antagonists provide evidence that the delta receptor within the brain seems an integrated part in the mediation of respiratory depression induced by a potent analgesic like fentanyl. Low doses of the delta antagonists RX-8008M (3–6 µg/kg) as well as ICI 174,864 (3–6 µg/kg) reversed fentanyl-related respiratory depression (arterial blood gases) in the unanesthetized canine. Opioid-induced blockade of afferent sensory nerve volleys (amplitude height of the somatosensory-evoked potential) could be reversed only by a high dose (9 µg/kg) of RX-8008M. Depression of amplitude height of the SEP could not be reversed by ICI 174,864 over the whole dose range (3–6–9 µg/kg). In comparison, naloxone (1–5–10 µg/kg) not only reversed depression of P _aO₂, it also reversed the blockade of afferent sensory nerve impulses in the low (5-µg/kg)-dose range. A highly selective delta antagonist may have a therapeutic value in reversing opioid-related respiratory depression, resulting in little or no attenuation of analgesia.     

Characterization of cellulosic hot-melt extruded films containing lidocaine.

Hot-melt extrusion technology was used to produce thin films containing a model drug, lidocaine, and the cellulosic polymers hydroxypropyl cellulose (HPC) and hydroxypropyl methyl cellulose (HPMC). Two film formulations were extruded and compared, one containing only HPC and the other containing HPC:HPMC (80:20). Thermal analysis of the films using differential scanning calorimetry (DSC) suggested that the drug existed in the amorphous condition, which was confirmed by wide angle X-ray diffractometry. Sustained release of the drug was observed from both of the polymer matrices. Dissolution profiles suggested that HPMC retarded the drug release from HPC:HPMC (80:20) films. However, the mechanism of drug release from both of the films was predominantly diffusion of the drug through the polymer matrices. Incorporation of HPMC also increased both adhesive strength and work of adhesion as compared to the HPC-only films.     

Novel Film Modifiers to Alter the Physical Properties of Composite Ethylcellulose Films

No HeadingPurpose. Polyvinylpyrrolidone (PVP), molecular-composite PVP, and Plasdone S-630 copolyvidonum are potential polymeric film modifiers for achieving improved drug release. The aim of this study was to investigate how these polymeric additives would affect the physicomechanical properties of composite ethylcellulose films.Methods. The miscibility of these polymeric additives with ethylcellulose was determined from the differential scanning calorimetry (DSC) thermograms of various polymer blends formed from organic solvents. It was found that ethylcellulose (EC) was miscible with the polymeric additives up to a concentration of 50%. Ten percent to 30% w/w polymeric additives were then added to aqueous ethylcellulose dispersion to form composite films. The morphology, film transparency, dynamic mechanical analysis (DMA) thermograms, and mechanical properties of the composite ethylcellulose films were studied. In addition, puncture strength and % elongation of the dry and wet films were also compared from indentation test.Results. Significant reduction and change in film transparency and morphology was obtained for EC films blended with PVP of higher molecular weight (MW). The composite EC films also showed higher T_g, greater elastic modulus, tensile and puncture strength depending on the concentration and type of additives present.Conclusions. The interaction between ethylcellulose and the polymeric additives is dependent on the MW and concentration of additives. The composite films offer new opportunities for the use of ethylcellulose as modified release coatings for dosage forms.     

Silymarin-solid dispersions: characterization and influence of preparation methods on dissolution

The influence of preparation methodology of silymarin solid dispersions using a hydrophilic polymer on the dissolution performance of silymarin was investigated. Silymarin solid dispersions were prepared using HPMC E 15LV by kneading, spray drying and co-precipitation methods and characterized by FTIR, DSC, XRPD and SEM. Dissolution profiles were compared by statistical and model independent methods. The FTIR and DSC studies revealed weak hydrogen bond formation between the drug and polymer, while XRPD and SEM confirmed the amorphous nature of the drug in co-precipitated solid dispersion. Enhanced dissolution compared to pure drug was found in the following order: co-precipitation > spray drying > kneading methodology (p < 0.05). All preparation methods enhanced silymarin dissolution from solid dispersions of different characteristics. The co-precipitation method proved to be best and provided a stable amorphous solid dispersion with 2.5 improved dissolution compared to the pure drug.