Pharmacokinetics of cefotiam after i.v. administration to healthy volunteers

The inability to calculate a definitive value for apparent volume of distribution at steady state is discussed and a method presented whereby the possible minimum and maximum values for V_ss may be determined for a drug obeying linear kinetics whose disposition may be characterized by means of a tri-exponential equation.     

The degradation of carboplatin in aqueous solutions containing chloride or other selected nucleophiles

The degradation kinetics of carboplatin in aqueous solution in the presence and absence of chloride ions were studied at elevated temperatures (43–70 °C) at pH 7.0 and at various pH values at 70 °C. Reaction rates were then extrapolated to temperatures of interest (infusion storage temperature, ‘in-use’ infusion temperature and body temperature) from Arrhenius plots. Additionally, the effects of pH and added chloride, thiosulphate, thiocyanate, azide and iodide on the rate of degradation of carboplatin were determined in an attempt to obtain a greater insight into the mechanism of nucleophilic substitution of carboplatin.     

Design of sterile muramyldipeptide-containing oligolamellar liposomes suitable for i.v. injection. Effect of liposome size and lipid composition on their ability to render peritoneal macrophages antitumoral

The water-soluble immunomodulator muramyldipeptide has been encapsulated in oligolamellar liposomes (mean diameter 200 nm) of various lipid compositions. These liposomes were sterilized by Millipore filtration without loss of entrapped solute and are therefore suitable for i.v. administration. The amount of encapsulated MDP increased when the volume of aqueous phase (containing a given MDP concentration) used for hydrating the phospholipid film increased and this did not vary for at least 15 days when the liposomes were kept at 4°C.The presence of cholesterol did not modify the encapsulation results but prevented the leakage of encapsulated water-soluble solute in serum-containing media.The internalization of various types of liposomes by murine peritoneal macrophages has been studied in order to define the best conditions for activating macrophages. For a given lipid composition, sterile oligolamellar vesicles (suitable for i.v. injection) were more efficient than multilamellar vesicles in rendering macrophages capable of inhibiting the growth of a syngeneic tumor, particularly when these vesicles contained muramyldipeptide in their aqueous space and cholesterol in their lipidic phase.     

Effect of pH on Sodium Usnate Thermostability in Dilute Aqueous Solutions

The objective of this study is the evaluation of sodium usnate thermostability. To this end, we used an isothermal method at four temperatures (40, 50, 60, and 70°C). The thermodegradation of dilute aqueous solutions of sodium usnate was studied at various pH values. This degradation appeared to follow first-order kinetics. Under the best stability conditions (pH = 8), the experiments gave a t_90% of 54.58 days, and a t_90% of 359.07 days at 20°C.     

Post-mortem degradation kinetics of brain norepinephrine

The post-mortem degradation kinetics of norepinephrine (NE) from brain stored at 25°, 15°, 0°, ?5° and ?10° have been determined. The first 20 per cent of NE was lost by zero-order kinetics, while degradation of the major part of the remaining NE followed two consecutive first-order processes. Both the zero- and first-order constants showed a temperature dependency and were used to construct Arrhenius temperature plots. The zero- and first-order rate constants yielded energies of activation of 17.2 and 16.3 $\text{kcal}\text{mole}$ respectively. When stored at 25°, approximately 25 per cent of total NE remained in mouse brain 144 hr after death. The amount of NE remaining 144 hr postmortem increased as the storage temperature decreased. Post-mortem NE degradation kinetics also were studied in rats. The NE degradation kinetics in rat brain were similar to those observed in mice. Although the zero-order degradation rate constant for rats was about one-third that found for mice, no difference was found in the first-order rate constants. Oxidative metabolism of NE in rat brain stopped shortly after death and metabolism proceeded non-oxidatively via normetanephrine. Monoamine oxidase (MAO) activity in mouse brain post-mortem also was found to be temperature dependent. Approximately 75 per cent of MAO activity remained in mouse brain when stored for 144 hr at 25°, while approximately 90 per cent remained when stored at ?10°.     

The binding of food dyes with human serum albumin

The binding interactions between human serum albumin (HSA) and the edible food dyes amaranth, tartrazine and sunset yellow have been studied. Intrinsic association constants and the free energy changes associated with dye-protein binding at physiological pH for amaranth and tartrazine, and at two different pH values for sunset yellow have been calculated from ultrafiltration data. The temperature dependence (20–40°C) of the intrinsic association constants at pH 7.4 for amaranth-HSA and tartrazine-HSA mixtures have been measured, from which a plot of the van't Hoff isochore exhibits a marked change in slope around 30°C indicating a possible change in protein conformation. The number of dye binding sites on HSA is reported for all the above conditions. HSA-ligand binding enthalpies have been used in conjunction with the N-B transitional binding enthalpy for HSA, to calculate the enthalpy for the N-B transition when ligands are bound with the protein.     

Advanced Kinetic Analysis as a Tool for Formulation Development and Prediction of Vaccine Stability

We have used a protein‐based vaccine, a live virus vaccine, and an experimental adjuvant to evaluate the utility of an advanced kinetic modeling approach for stability prediction. The modeling approach uses a systematic and simple procedure for the selection of the most appropriate kinetic equation to describe the degradation rate of compounds subjected to accelerated conditions. One‐step and two‐step reactions with unlimited combinations of kinetic models were screened for the three products under evaluation. The most appropriate mathematical model for a given product was chosen based on the values of residual sum of squares and the weight parameter w. A relatively simple n‐th order kinetic model best fitted the degradation of an adjuvanted protein vaccine with a prediction error lower than 10%. A more complex two‐step model was required to describe inactivation of a live virus vaccine under normal and elevated storage temperatures. Finally, an autocatalytic‐type kinetic model best fitted the degradation of an oil‐in‐water adjuvant formulation. The modeling approach described here could be used for vaccine stability prediction, expiry date estimation, and formulation selection. To the best of our knowledge, this is the first report describing a global kinetic analysis of degradation of vaccine components with high prediction accuracy.     

Monoamine oxidase in human platelets: Kinetics and methodological aspects

The kinetic properties of human platelet monoamine oxidase (MAO) were examined in 20 apparently healthy controls. The mean value (±S.D.) of the maximum velocity (V) was found to be 5.36 ± 1.97 pmoles of product formed/10° platelets/min and the Michaelis-Menten constants were for phenethylamine (K^PEA_m) 14.6 ± 8.20 μM and for oxygen (K_m^O₂)254 ± 125 μM, when assayed in 0.1 M phosphate buffer, pH 7.4. The relation between the value of the corresponding apparent constants was studied. Inhibition of the enzyme activity was seen at 20 μM of PEA and 180 μM of oxygen. The enzyme kinetics were also studied at different pH. Two pK values were found, pK₁ = 6.65 and pK₂ = 6.95. The influence of homogenization on the MAO activity was compared with the activity in the undisrupted platelet. At PEA concentrations below 10 μM higher MAO activities were found in the intact cell. A 15 per cent loss of activity was detected in platelet samples after storing at ?20° for three and a half years.     

Metabolism of aflatoxin B1 (AFB1), aflatoxin G1 (AFG1) and vitamin C intake by guinea pig liver preparation in vitro

Male and female guinea pigs weighing 150–200 g were divided into three groups, with equal number of males and females in each group. They were fed an experimental diet which varied as follows: group I, 0 mg vitamin C/g of diet; group II, 1.08 mg/g and group III, 5.4 mg/g, for 28 days. Twenty-four hours after the last feeding, liver slices and 9000 g supernatant were prepared from each group, according to sex, and used for enzyme assays. For the demethylation assay, enzyme activity expressed as amount of formaldehyde produced from AFB₁, or AFG₁/hr/g fresh liver was seen to increase with the two levels of ascorbic acid intake in females. Males showed an enhancement of activity only in group II and remained with the same production of formaldehyde as above in group III. Although in each dietary group, the activity was higher in males than in females the variation in the amount of formaldehyde produced from one group to another was higher with females than with male guinea pigs. However with both sexes, the production of formaldehyde from AFG₁, was greater than from AFB₁. For the hydroxylation assay, enzyme activity was expressed as amount of metabolites (a) and (b) produced. Compared to group II, which offered a control level of ascorbic acid, group I fed without vitamin C showed a decreased production of metabolite (a) and (b) with males and females. Moreover, high intake of ascorbic acid in group III decreased the production of metabolite (a) and (b) in males, while in female guinea pigs the reduction was observed only with (b).     

Imaging and behaviour of solid oral dosage forms in vivo

The kinetics of the hydrolysis of methyl, ethyl and n-propyl 4-hydroxybenzoate esters and a subsequent decarboxylation of 4-hydroxybenzoic acid have been studied at pH 1.26–10.59 and the sterilizing temperature of 130.5°C. Enthalpies (ΔH1) and entropies (ΔS1) of activation are reported for k_obs and the derived rate constants. The decarboxylation reaction showed a maximum rate near the mid-pH region where the esters were more susceptible to hydrolysis. The overall pathway for the degradation of the esters was accounted for by a consecutive reaction sequence:

where A represents ester, B, 4-hydroxybenzoic acid and C, phenol. Interference with the spectrophotometric assay by the subsequent oxidation of phenol, made necessary the exhaustive de-oxygenation of solutions for the kinetic runs where phenol was formed. The esters were found to be sufficiently stable to withstand a heat sterilization process within the pH range 3–6. The rate of phenol formation by decarboxylation of the acid was greater in the pH range where the esters are frequently used commercially, as preservatives.     

硫酸链霉素水溶液化学稳定性的研究

本实验在广泛pH范围内对硫酸链霉素的化学稳定性进行研究,测定不同温度下不同pH时的速度常数,得到不同pH时的分解活化能及不同温度下的最稳定pH值。活化能数值在pH4～5及pH6～7出现极大值,而不同温度下的两个最稳定pH[(pH)_m]恰落在这两个pH范围内。分别用经典恒温法及单测点法进行实验,所得结果无显著性差异。     

A Systematic Degradation Kinetics Study of Dalbavancin Hydrochloride Injection Solutions

The degradation kinetics of the glycopeptide antibiotic dalbavancin in solution are systematically evaluated over the pH range 1–12 at 70°C. The decomposition rate of dalbavancin was measured as a function of pH, buffer composition, temperature, ionic strength, and drug concentration. A pH-rate profile was constructed using pseudo first-order kinetics at 70°C after correcting for buffer effects; the observed pH-rate profile could be fitted with standard pseudo first order rate laws. The degradation reactions of dalbavancin were found to be strongly dependent on pH and were catalyzed by protons or hydroxyl groups at extreme pH values. Dalbavancin shows maximum stability in the pH region 4–5. Based on the Arrhenius equation, dalbavancin solution at pH 4.5 is predicted to have a maximum stability of thirteen years under refrigerated conditions, eight months at room temperature and one month at 40°C. Mannosyl Aglycone (MAG), the major thermal and acid degradation product, and DB-R6, an additional acid degradation product, were formed in dalbavancin solutions at 70°C due to hydrolytic cleavage at the anomeric carbons of the sugars. Through deamination and hydrolytic cleavage of dalbavancin, a small amount of DB-Iso-DP2 (RRT-1.22) degradation product was also formed under thermal stress at 70°C. A greater amount of the base degradation product DB-R2 forms under basic conditions at 70°C due to epimerization of the alpha carbon of phenylglycine residue 3.     

Enhanced ultrasound-assisted enzymatic hydrolysis extraction of quinolizidine alkaloids from <Emphasis Type="Italic">Sophora alopecuroides</Emphasis> L. seeds

Quinolizidine alkaloids are the main bioactive components in Sophora alopecuroides L. This study reports a novel ultrasound-assisted enzymatic hydrolysis method for the extraction of these important alkaloids. Box–Behnken design, a widely used response surface methodology, was used to investigate the effects of process variables on ultrasound bath-assisted enzymatic hydrolysis (UAEH) extraction. Four independent variables, pH, extraction temperature (°C), extraction time (min) and solvent-to-material ratio (mL/g), were studied. For the extraction of sophocarpine, oxysophocarpine, oxymatrine, matrine, sophoramine, sophoridine and cytisine, the optimal UAEH condition was found to be a pH of 5, extraction temperature of 54 °C, extraction time of 60 min and solvent-to-material ratio of 112 mL/g. The experimental values obtained under optimal conditions were fairly consistent with the predicted values. UAEH extraction was then compared with reflux heating, enzymatic extraction and ultrasound-assisted extraction. Of these extraction methods, UAEH extraction under optimal conditions produced the highest yield for seven types of alkaloids. In addition, UAEH extraction resulted in lower ingredient degradation than reflux heating extraction.     

Aqueous stability of leuprolide acetate: effect of temperature,dissolved oxygen,pH and complexation with β-cyclodextrin

In the present research, the aqueous stability of leuprolide acetate (LA) in phosphate buffered saline (PBS) medium was studied (pH?=?2.0–7.4). For this purpose, the effect of temperature, dissolved oxygen and pH on the stability of LA during 35 days was investigated. Results showed that the aqueous stability of LA was higher at low temperatures. Degassing of the PBS medium partially increased the stability of LA at 4?°C, while did not change at 37?°C. The degradation of LA was accelerated at lower pH values. In addition, complexes of LA with different portions of β-cyclodextrin (β-CD) were prepared through freeze-drying procedure and characterized by Fourier transform infrared (FTIR) and differential scanning calorimetry (DSC) analyses. Studying their aqueous stability at various pH values (2.0–7.4) showed LA/β-CD complexes exhibited higher stability when compared with LA at all pH values. The stability of complexes was also improved by increasing the portion of LA/β-CD up to 1/10.     

The Role of Covalent Dimerization on the Physical and Chemical Stability of the EC1 Domain of Human E-Cadherin

The objective of this work was to evaluate the solution stability of the EC1 domain of E-cadherin under various conditions. The EC1 domain was incubated at various temperatures (4, 37, and 70°C) and pH values (3.0, 7.0, and 9.0). At pH 9.0 and 37 or 70°C, a significant loss of EC1 was observed due to precipitation and a hydrolysis reaction. The degradation was suppressed upon addition of dithiothreitol (DTT), suggesting that the formation of EC1 dimer facilitated the EC1 degradation. At 4°C and various pH values, the EC1 secondary and tertiary showed changes upon incubation up to 28 days, and DTT prevented any structural changes upon 28 days of incubation. Molecular dynamics simulations indicated that the dimer of EC1 has higher mobility than does the monomer; this higher mobility of the EC1 dimer may contribute to instability of the EC1 domain. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3562–3574, 2009     

HPLC determination of chloramphenicol degradation in eye drops

Anhplc-method is described for the simultaneous determination of chloramphenicol and its most important degradation products. A 15 cm long C-18 reversed phase column was used with a mobile phase consisting of boric acid solution-acetonitrile (60+45) adjusted to a pH of 3. The amount of degradation of chloramphenicol eye drop solutions containing boric acid and borax, at pH 4.7 and 7.2 respectively, is determined at 4, 21, 100 and 120°C. The solution of pH 7.2 is more stable than that of pH 4.7 at 4 and 21°C, but is less stable at 100 and 120°C. Preparation has to be accomplished in subdued light. The solutions have to be protected from light during storage.     

STUDIES OF EVOLUTIONARY TEMPERATURE ADAPTATION: MUSCLE FUNCTION AND LOCOMOTOR PERFORMANCE IN ANTARCTIC FISH

1. Studies of evolutionary temperature adaptation of muscle and locomotor performance in fish are reviewed with a focus on the Antarctic fauna living at subzero temperatures. 2. Only limited data are available to compare the sustained and burst swimming kinematics and performance of Antarctic, temperate and tropical species. Available data indicate that low temperatures limit maximum swimming performance and this is especially evident in fish larvae. 3. In a recent study, muscle performance in the Antarctic rock cod Notothenia coriiceps at 0°C was found to be sufficient to produce maximum velocities during burst swimming that were similar to those seen in the sculpin Myoxocephalus scorpius at 10°C, indicating temperature compensation of muscle and locomotor performance in the Antarctic fish. However, at 15°C, sculpin produce maximum swimming velocities greater than N. coriiceps at 0°C. 4. It is recommended that strict hypothesis-driven investigations using ecologically relevant measures of performance are undertaken to study temperature adaptation in Antarctic fish. Recent detailed phylogenetic analyses of the Antarctic fish fauna and their temperate relatives will allow a stronger experimental approach by helping to separate what is due to adaptation to the cold and what is due to phytogeny alone.     

Data Analysis of Kinetic Modelling Used in Drug Stability Studies: Isothermal Versus Nonisothermal Assays

Purpose Kinetic modelling was applied to predict the stability of cholecystokinin fragment CCK-4 in aqueous solution, which was analyzed by isothermal and nonisothermal methods using a validated stability indicating HPLC method.Methods The isothermal studies were performed in the temperature range 40 to 80°C at pH 12 and ionic strength 0.01 M as constants, whereas nonisothermal stability studies were performed using a linear increasing temperature program, heating rate 0.25°C/h and a temperature interval 40–82°C. The isothermal studies require two-step linear regression to estimate the parameters, resulting in a well-defined confidence interval. Nonisothermal kinetic studies require nonlinear or linear regression by previous transformation of data to estimate the parameters. In this case, the two most popular approaches, derivative and integral, were used and compared.Results Under isothermal conditions, an apparent first-order degradation process was observed at all temperatures. The linear Arrhenius plot suggested that the CCK-4 degradation mechanism was the same within the studied temperature range, with quite large uncertainties due to the small number of degrees of freedom based only on the scatter in the plot, and giving an estimated shelf life at 25°C of 35.2 days. The derivative approach yields high variability in the Arrhenius parameters, since they are dependent on the number of polynomial terms chosen, so several statistical criteria were applied to select the best model. The integral approach allows activation parameters to be calculated directly from experimental data, and provides results in good agreement with those of the traditional method, but have the advantage that the uncertainty in the final result directly reflects the goodness of fit of the experimental data to the chosen kinetic model. The application of the bootstrap technique to estimating confidence limits for the Arrhenius parameters and shelf life is also illustrated, and shows there is no difference between the asymptotic and bootstrap confidence intervals.Conclusions Nonisothermal studies give us fast and valuable information about drug stability, although their potential for predicting isothermal behaviour is conditioned by the data analysis method applied.     

三磷酸腺苷二钠水溶液化学稳定性研究

本实验在广泛pH范围对三磷酸腺苷二钠化学稳定性进行了研究。测定了不同温度、不同pH的速度常数,按Arrhenius方程测得不同pH的分解活化能及不同温度下最稳定的pH。并证明柠檬酸根离子对三磷酸腺苷二钠水解反应有催化作用。     

Analysis of the aryl hydrocarbon hydroxylase assay

The assay method and the properties of aryl hydrocarbon hydroxylase were studied with rat liver microsomes. The assay could be carried out by two methods: (1) the microsomes (initially at 15–20°) were pre-incubated at 37° and then benzo[a]pyrene and NADPH were added to initiate the assay; and (2) benzo[a]pyrene was added to microsomes at 15–20°, pre-incubated at 37°, and then NADPH was added to initiate the reaction. The aryl hydrocarbon hydroxylase activity obtained by method 1 was usually 60–120 per cent higher than that obtained by method 2. Several lines of study suggested that the microsomes can exist in two states. Binding of benzo[a]pyrene at temperatures lower than 20° would limit the microsomes to a low activity state whereas binding at temperatures above 25° would enable the microsomes to exist in a high activity state. The molecular basis of these activity states remains to be investigated. The effects of acetone and methanol, both having been widely used as the solvents for benzo[a]pyrene, on aryl hydrocarbon hydroxylase have also been studied. The aryl hydrocarbon hydroxylase activities of control and phenobarbital-induced microsomes were higher with acetone as the solvent for benzo[a]pyrene as compared with methanol. The hydroxylase activity of 3-methylcholanthrene-induced microsomes, however, was slightly higher with methanol.