Species-dependent plasma metabolism of the ester compound daidzein 7,4'di-succinic acid mon-ester-O-ethoxy (DZ5).

Daidzein 7,4'di-succinic acid mon-ester-O-ethoxy (DZ5) is an ester-containing compound, which was recently synthesized. The objective of this study was to determine the hydrolysis rate of DZ5 in blood from the rat and the dog. The data showed that the hydrolysis rate of DZ5 in plasma was much more rapid in rats than in dogs following intravenous administration. Moreover, similar results were observed after in vitro incubation of DZ5 in the rat or dog plasma. The findings suggested that plasma esterases in the rat plasma have higher activity than in the dog and plasma metabolism of DZ5 is species-dependent.

Pharmacodynamics and potential toxicity of intranasally administered dipyrone.

Dipyrone is a non-narcotic analgesic and antipyretic drug used in both pediatric and adult patients. Dipyrone solution can be used intranasally as an antipyretic agent for infants. However, dipyrone is not stable in liquid state. Therefore, a stable dipyrone formulation was developed and the antipyretic effect of the formulation was studied after intranasal administration in rabbits and rats, respectively. To guarantee dose accuracy in animal studies, effect of dose volume on the distribution of dipyrone solution in rabbit nasal cavities were studied, using gentian violet as an indicator. Animal fever model and intranasal administration methods were established. In addition, the potential toxicity of the dipyrone formulation was studied. It was shown that the nasal volume of rabbits is large enough to hold 100 microl solution. After intranasal administration, improved pharmacodynamics was obtained with the new developed dipyrone formulation compared to the normal dipyrone solution, and significantly decreased body temperature was observed 10 min after dosing. The toxicity was negligible. In conclusion, the dipyrone formulation is effective and safe for clinical medication.

A novel method to prepare highly encapsulated interferon-alpha-2b containing liposomes for intramuscular sustained release.

A novel modified film-hydration-dilution method was employed to prepare highly encapsulated interferon-alpha-2b containing liposomes for intramuscular sustained release. The liposomes produced by this technique were a mixture of mainly unilamellar vesicles and a small number of multilamellar vesicles. The trapping efficiency was above 80%. With at least 60-fold dilution, Triton X-100 at the concentration of 0.3% (w/v) in phosphate buffered saline (PBS) was able to solubilize phospholipids without denaturing the protein and/or interfering with the enzyme-linked immunoassay (ELISA). After three homogenization cycles under a pressure of 70 MPa the size of liposomes was reduced from 978 to 101 nm while the activity of interferon-alpha-2b decreased by 9.9% compared to the control. Although liposomes were physically stable for 22 months at 4 degrees C the mean size of the liposomes increased slightly from 101 to 122 nm. The levels of free interferon-alpha-2b at the site of intramuscular injection decreased rapidly with only 4.15% of initial dose retained at the injection site after 0.33 h following injection of an interferon-alpha-2b solution (nonencapsulated). In contrast, interferon-alpha-2b encapsulated in liposomes was retained at the site of intramuscular injection at higher levels than free interferon-alpha-2b (p < 0.05). Larger liposomes containing interferon-alpha-2b (978 nm) were the most effective for local retention because 27.8% of interferon-alpha-2b was retained after 24 h. These liposomes have the potential to be topically injected for treating genital herpes with prolonged interferon levels at the local injection site. Since the smaller liposomes (75.8 and 101 nm) retained interferon-alpha-2b at the injection site for shorter times while enhancing the blood circulation of the drug, they are potentially good carriers for systemic therapy with higher bioavailability and liver targeting.

Validation of an HPLC method for the simultaneous determination of DZ5 and its active metabolite in dog plasma and its pharmacokinetics.

A validated HPLC method is described for the simultaneous determination of daidzein 7,4'-di-succinic acid mon-ester-O-ethoxy (DZ5) and its active metabolite daidzein 7,4'-dioxy-ethoxy (DZ4) in dog plasma. DZ5 and DZ4 were determined by reversed-phase HPLC (column: Hypersil C18 5 microm silica, 200 mm x 4.6 mm i.d.; eluent: 400 ml water, 500 microl 85% phosphoric acid, 600 ml methanol) and photometric detection (250 nm), with Kaempferol as the internal standard. The calibration curve was linear over the range 0.1-50.0 microg/ml in dog plasma. The average extraction recoveries were 84.6% (DZ5), 82.7% (DZ4) and the within-day and between-day precisions were less than 10.93%. The assay was applied to the analysis of samples from a pharmacokinetic study. Following the oral administration and intravenous administration of DZ5, DZ5 was eliminated rapidly from the plasma and DZ4 was found in plasma. The absolute bioavailability of total DZ5 and DZ4 was 41.5%. The method was demonstrated to be feasible for pharmacokinetic studies of DZ5 in dogs.

Characterization and body distribution of beta-elemene solid lipid nanoparticles (SLN).

Solid lipid nanoparticles (SLN) containing beta-elemene, a volatile oil used for the treatment of cancer, were prepared by the method combining probe sonication and membrane extrusion. Effects of the formulations and procedures on the characteristics of SLN were investigated. Body distribution of beta-elemene SLN in rats after intravenous administration was compared with that of the commercial emulsion. The results showed that dispersing the surfactant in the melted lipid matrix could obtain smaller particles than that dispersing in the water phase. Increasing the ratio of monostearin in the lipid matrix or the concentration of surfactant reduced the mean volume size of the SLN. Optimized formulation was composed of monostearin and precirol ATO 5 at a mass ratio of 3:7, which was quite stable for 8 months at room temperature. In vitro release of beta-elemene from the SLN was slow and stable without obvious burst release and was found to follow the Higuich equation. After intravenous administration, the beta-elemene levels after 5 min injection of SLN formulation were 1.5, 2.9, and 1.4 times higher than those of beta-elemene emulsion in liver, spleen, and kidney, respectively, while the concentrations of beta-elemene were decreased 30% in heart and lung. Therefore, the SLN containing beta-elemene might be an attractive candidate for the treatment of liver cancer.

Investigations on 5-fluorouracil solid lipid nanoparticles (SLN) prepared by hot homogenization.

The purpose of this study was to investigate the effect of different formulation factors on the properties of solid lipid nanoparticles (SLN) prepared by a hot homogenization method. Using the particle size, physical stability constant (K(e)) and zeta-potential as standards, the stability of SLNs was investigated as a function of phospholipid and poloxamer contents. It was demonstrated that the content of phospholipid had a significant influence on the zeta-potential, which increased considerably with increasing phospholipid content. However, the particle size increased remarkably when the phospholipid content was as high as 1.5% due to the increased viscosity. Poloxamer 188 exhibited no remarkable influence on particle size when the concentration was as low as 1.0%. The influence of the phospholipid and poloxamer content on the embedding ratios of drug substances was further studied using 5-fluorouracil (5-Fu) as a model drug. It was shown that the embedding ratio increased considerably with phospholipid content and independent of poloxamer content, implying that 5-Fu was incorporated into the phospholipid bilayer membrane.

[Preparation of ondansetron hydrochloride osmotic pump tablets and their in vitro drug release].

AIM: To prepare ondansetron hydrochloride osmotic pump tablets (OND-OPT) and investigate their in vitro drug release behavior. METHODS: OND-OPT were prepared with a single punch press and pan coating technique. Osmotic active agents and plasticizer of coating film were chosen by drug release tests. The effects of the number, position and direction of drug release orifice on release behavior were investigated. The relation between drug release duration and thickness of coating film, PEG content of coating film and size of drug release orifice was established by uniform design experiment. The surface morphological change of coating film before and after drug release test was observed by scanning electron microscopy. The osmotic pumping release mechanism of OND-OPT was confirmed by drug release test with high osmotic pressure medium. RESULTS: Lactose-mannitol (1:2) was chosen as osmotic active agents and PEG400 as plasticizer of coating film. The direction of drug release orifice had great effect on the drug release of OND-OPT without HPMC, and had no effect on the drug release of OND-OPT with HPMC. The OND-OPT with one drug release orifice at the centre of the coating film on one surface of tablet released their drug with little fluctuation. The drug release duration of OND-OPT correlated with thickness of coating film and PEG content of coating film, and didn't correlate significantly with the size of drug release orifice. OND-OPT released their drug with osmotic pumping mechanism predominantly. CONCLUSION: OND-OPT are able to realize ideal controlled drug release.

The depolymerization of chitosan: effects on physicochemical and biological properties.

Chitosan has been extensively used as an absorption enhancer for macromolecules and as gene delivery vehicle. Both properties are molecular weight (MW) dependent. Here, we investigate factors affecting the oxidative depolymerization of chitosan and physicochemical properties of the resulting polymer fractions including their cytotoxicity. The molecular weight of the depolymerized chitosan was influenced by the initial concentration and the source of chitosan. At constant initial concentrations, the molecular weight decreased linearly with the chitosan/NaNO2 ratio and was a function of logarithm of the reaction time. Chitosan with larger molecular weight was more sensitive to depolymerization. No structural change was observed during the depolymerization process by infrared and proton nuclear magnetic resonance spectroscopy. In addition, thermal properties of chitosan fragments were studied by thermal gravimetric analysis and it was found that the decomposition temperature was molecular weight dependent. Furthermore, the solubility of different molecular weight chitosan was assayed as a function of pH and it increased with decreasing molecular weight. The cytotoxicity of chitosan was concentration dependent but almost molecular weight independent according to MTT assay using L929 cell line recommended by USP26. In summary, low molecular weight fractions of chitosan may potentially useful for the design of drug delivery systems due to the improved solubility properties.

Intranasal administration of melatonin starch microspheres.

Using melatonin as model drug, starch microspheres for intranasal administration were prepared by an emulsification-crosslinking technique using a uniform design to optimize preparation conditions. The entrapment ratio of melatonin in the microspheres was 11.0% and particle sizes ranged from 30 to 60 microm. Melatonin was released from the microspheres in a sustained manner in vitro. Nasal clearance of 99mTC labeled starch microspheres was investigated using gamma scintigraphy. It was revealed that >80% of the starch microspheres could be detected in the nasal tissue 2h after administration, compared to 30% for a solution. The pharmacokinetics of melatonin starch microspheres was investigated after intranasal administration. The absorption rate was rapid (T(max) min), and the absolute bioavailability was high, 84.07%. A good correlation was found between in vitro release and in vivo absorption data.

[Preparation of solid lipid nanoparticles by microemulsion technique].

AIM: To prepare solid lipid nanoparticles by microemulsion technique. METHODS: Stearic acid was used as the oil phase, lecithin as surfactant, alcohol as cosurfactant and distilled water as the aqueous phase. Microemulsion was prepared by mixing the above component in proper ratio. The corresponding pseudoternary phase diagram monitored Microemulsion formation field of different lecithin/alcohol. Solid lipid nanoparticles (SLN) were prepared by dispersing warm microemulsion in cold water under magnetic stirring. Then appropriate microemulsions that can contain more water phase and suitable oil phase were selected to prepare SLN. The influence of formulation, process variables on the preparation and quality of SLN were studied. Based on the investigation of single factors, orthogonal design was used to optimize SLN formulation and preparation process, and more, the reproducibility of the optimized results were studied. RESULTS: The results showed that the device temperature (Ti), water temperature (Tw), and delivery rate (Rd) were the key factors that influence the preparation process of SLN, and Tw was extremely important. The ratio of microemulsion formulation, the ratio of microemulsion and distilled water had also influence on its quality. CONCLUSION: Microemulsion technique can be used to prepare solid lipid nanoparticles.

Aminated gelatin as a nasal absorption enhancer for peptide drugs: evaluation of absorption enhancing effect and nasal mucosa perturbation in rats.

This study was carried out to evaluate the potential of aminated gelatin as a nasal absorption enhancer for peptide drugs. The absorption-enhancing effect was investigated in rats using insulin and fluorescein isothiocyanate-dextran with a molecular weight of 4.4 kDa (FD-4) as model drugs. The absorption of insulin was estimated by measuring the changes in plasma glucose levels following intranasal administration, and that of FD-4 was determined by measuring its plasma concentration after dosing. The hypoglycaemic effect after intranasal administration of insulin with aminated gelatin significantly increased compared with that after intranasal administration of insulin in phosphate buffered saline, indicating that aminated gelatin effectively enhanced the nasal absorption of insulin. In contrast, neither kind of native gelatin (isoelectric point = 5.0 and 9.0) showed any absorption-enhancing effect. The pH of the formulations and the concentration of aminated gelatin were found to affect the hypoglycaemic effect. In addition, aminated gelatin at a concentration of 0.2% significantly enhanced the absorption and the efflux of FD-4 through the rat nasal mucosa. The possible perturbation of aminated gelatin to nasal mucosa was evaluated by measuring the leaching of lactate dehydrogenase (LDH) using an in-situ perfusion rat model. Aminated gelatin presented a concentration-dependent (0.1-0.4%) but relatively small effect on the LDH leaching from the rat nasal epithelial membrane. These results suggest that positively charged aminated gelatin could be a new absorption enhancer for nasal delivery of peptide drugs.