Absorption of iothalamate after oral administration and absorption enhancement by amino acids in dogs and rats

The oral absorption of iothalamate and the effect of amino acids on its absorption were studied in 6 dogs and 6 rats using a simple HPLC assay. The results showed that iothalamate was absorbed in dogs, averaging 9.9, 8.5, and 10.0 per cent following the administration of 40 and 100 mg kg-1 of iothalamic acid capsules and 50 mg kg-1 of sodium iothalamate solution, respectively. The absorption from the capsule was slower and more sustained than that from the solution. In rats, the absorption appeared to be dose-independent (averaging about 4.2 per cent) in the dose range of 20-800 mg kg-1. The low bioavailability obtained was mainly due to the high polarity of iothalamate molecules as suggested by the GI recovery and in vitro partition studies. Among several amino acids tested as possible ion-pair formers, only homoarginine hydrochloride increased the partition of iothalamate into chloroform layer. However, both homoarginine hydrochloride and arginine hydrochloride at the amino acid/iothalamate molar ratio of 25 were found to significantly enhance (about 70 per cent) the iothalamate absorption in dogs. The in situ rat small intestinal loop study indicated that the absorption-enhancing effect of arginine was sodium dependent. At the sodium chloride concentration of 0.09 M, no significant increase in the absorption was observed, while at the concentration of 0.3 M or higher, a marked increase (about twofold) was obtained in both upper and lower intestine. Thus, the mechanism of the amino acids in facilitating the iothalamate absorption may be more closely related to the active amino acid transport system rather than the possible increase in lipophilicity of the ion-pair formed. The potential use of such naturally occurring, relatively non-toxic amino acids for increasing the GI absorption of water-soluble weak acids or bases through ion-pair formation remains to be fully investigated.     

Mechanisms for absorption enhancement of inhaled insulin by sodium taurocholate.

The effects of sodium taurocholate (NaTC) on the absorption of inhaled insulin was investigated using both in vivo and in vitro experiments. The absolute bioavailability of insulin when given as a nebulized solution (0.6 mM) to anesthetized intubated beagle dogs was low (2.6+/-0.3%). However, when NaTC at different concentrations (2-32 mM) were included in the formulations the bioavailability increased and at 32 mM it was about nine times higher (23.2+/-4.4%) than for pure insulin. In a similar concentration interval (20-25 mM) NaTC decreased the transepithelial electrical resistance (TEER) across Caco-2 cell monolayers leading to an increased permeability of insulin. At higher concentrations (above 30 mM) the viability of the Caco-2 cells decreased and the insulin permeability increased dramatically. Furthermore, we show that NaTC in the concentration range 2-15 mM gradually decreases the aggregation state of insulin, i.e., produces mono- or dimeric insulin from hexameric insulin. In conclusion, NaTC increases the bioavailability of nebulized insulin, increases the permeability of insulin across Caco-2 cell monolayers, and decreases the aggregation state of insulin at similar concentrations. We suggest that the main mechanisms behind the absorption enhancement of inhaled insulin by NaTC are the production of insulin monomers and an opening of tight junctions between adjacent airway epithelial cells.     

Increased oral absorption enhancement of insulin by medium viscosity hydroxypropyl cellulose

The hypoglycemic effect of orally given insulin was studied on rabbits, using two different absorption promoters, and two different carriers. The effects of hydroxypropyl cellulose (HPC) of different degrees of substitutions (Klucel® GF, MF, and HF), and consequently of different viscosities, on the oral bioavailability of insulin have been studied. The fatty acid-Brij® system was not affected by the HPC studied, while the salicylate-cellulose system resulted in a significantly better absorption of insulin in the presence of the medium viscosity Klucel®. More than 70% reduction in blood glucose levels was achieved for rabbits, treated with the salicylic acid-Klucel MF-Avicel® system containing 5 units of insulin per kg of animal weight.     

甲基斑蝥胺在大鼠胃肠道的吸收动力学

目的研究甲基斑蝥胺(MCD)在大鼠胃及肠道的吸收动力学特征。方法采用封闭灌注技术进行原位胃灌注吸收研究,在体循环法考察小肠全肠段吸收,采用单向肠灌流技术进行不同肠段吸收研究,建立HPLC法测定MCD的浓度,考察MCD大鼠胃肠吸收特征及吸收机制。结果 116.34mg·L~(-1)MCD在十二指肠、空肠、回肠、结肠及胃中的吸收速率常数(K_a)分别为(0.0635±0.0091)、(0.0687±0.0008)、(0.0315±0.0009)、(0.0399±0.0009)和(0.0033±0.0001)min~(-1),不同药物浓度59.55、116.34、204.15mg·L~(-1)时胃及空肠中的K_a分别为(0.0031±0.0001)、(0.0033±0.0001)、(0.0031±0.0001)min~(-1)及(0.0667±0.0010)、(0.0687±0.0008)、(0.0705±0.0011)min~(-1);在空肠不同pH值(5.0,6.2,7.4)时K_a分别为(0.0801±0.000 9)、(0.0783±0.0009)、(0.0758±0.0009)min~(-1)。MCD在胃中吸收很弱;在空肠、十二指肠、结肠和回肠中均有一定吸收,在空肠吸收最好,在肠中吸收呈一级动力学过程,吸收机制为被动扩散。MCD溶液浓度及pH值对其肠吸收速率无显著影响(P>0.05)。结论 MCD属于生物药剂学分类系统Ⅰ类药物。     

Thymosin-loaded enteric microspheres for oral administration: preparation and in vitro release studies

Thymosin, a water-soluble polypeptide compound, was encapsulated within enteric microspheres of acrylic acid resin II by modified oil in oil (o/o) emulsion solvent evaporation method. The mixture emulsifier composed of lecithin and Span 80 was critical to the formation of sphere-shaped thymosin microparticles. Optimizing process parameters, such as the volume ratio of organic solvent to water, initial drug feed and polymer concentration, resulted in high drug encapsulation efficiency of 89.7% (6% polymer concentration and 0.5% initial drug feed). In vitro release studies suggested that thymosin release from microspheres exhibited pH dependent profiles. For formulation with 6% polymer concentration and 0.5% initial drug feed, 68.7% thymosin was released within 4h in pH 6.8 PBS buffer, while only 6.5% was observed in acid medium.     

Mechanisms for the enhancement of the nasal absorption of insulin by surfactants

The mechanisms of the promoting effect of surfactants on the nasal absorption of insulin was investigated in rats. The promoting effect of several non-ionic surfactants, sodium lauryl sulfate and saponin, were paralleled by their abilities to lyze the rabbit erythrocyte and to release protein from the nasal mucosa, whereas the promoting effect of bile acid salts was attributed not only to their direct effect on the nasal mucosa, but also to their inhibitory effect on proteolytic enzymes. Mucosal alterations, observed by scanning electron microscopy, were reversible and the membrane was relatively rapidly restored. Bile acid salts were found to be less irritative to the nasal mucosa than non-ionic ether type surfactants.     

脱氧胆酸钠—环糊精联用促进鼻对胰岛素的吸收

目的:评价β-环糊精(β-CD)或二甲基-β-环糊精与脱氧胆酸钠(SDC)联用对胰岛素的吸收促进作用。方法:通过胰岛素降血糖作用来反映其吸收效果;用扫描电镜观察单次给药后的鼻纤毛毒性;测定亮氨酰氨肽酶的活性。结果:0.75％ SDC/β-CD(1:2)联用时,鼻腔给予胰岛素产生的降血糖作用相对缓慢而持久,血糖最低值为初始的(72.6±2.1)％,血糖-时间曲线在1至4h内较平稳。虽然与0.75％ SDC组比较,两组的最低血糖水平有显著性差异,但血糖-时间曲线上面积AOC_(0-t)值无显著性差异(P>0.05)。扫描电镜结果显示大鼠鼻腔给药4h后粘膜纤毛无明显改变。0.01％ SDC促吸收能力很弱,但仍有纤毛毒性。SDC与β-环糊精或二甲基-β-环糊精联用后,亮氨酰氨肽酶的活性抑制率由89.2％下降至60％-70％。结论:β-环糊精与SDC联用后,降低了SDC的纤毛毒性,但仍保留了较强的胰岛素吸收促进作用。这种促进作用并不是由于SDC浓度的降低,而是与亮氨酰氨肽酶的活性被抑制有关。     

在体法研究二氢杨梅素的吸收特性

目的:研究二氢杨梅素(dihydromyricetin,DMY)在大鼠胃和肠道中的吸收行为,为DMY新制剂的研究与开发提供依据。方法:运用在体胃研究模型和在体肠单向灌流模型,采用高效液相色谱法研究DMY在大鼠胃和不同肠段的吸收情况,并考察药物浓度(20,40,80 μg·mL^-1)对DMY肠吸收的影响。结果:DMY的胃吸收百分率为(2.3±0.9)%。在各肠段的吸收中,DMY的P_eff＜5.0×10^-5cm·s^-1,其中在空肠和结肠中的K_a和P_eff大于十二指肠和回肠(P＜0.05)。以空肠为吸收肠段,与低、中浓度组相比,高浓度组中DMY的K_a和P_eff明显降低(P＜0.05)。结论:胃部不是DMY的主要吸收和代谢部位。DMY为低渗透性药物,其在空肠和结肠部位的吸收较好。另外,DMY在吸收过程中存在高浓度饱和现象,表明DMY在肠道的转运可能有载体参与。     

Bioavailability enhancement of ondansetron after nasal administration of Caesalpinia pulcherrima-based microspheres

Abstract

Context: Natural polymers have attracted a great deal of attention for use as potential carriers in site-specific delivery over past decades. Mucoadhesive microspheres are useful tools for nasal drug delivery.

Objectives: To prepare and evaluate mucoadhesive microspheres as mode for nasal delivery of ondansetron using Caesalpinia pulcherrima galactomannan (CPG).

Materials and methods: Conventional spray-dried CPG nasal microspheres loaded with ondansetron for intranasal drug delivery in order to avoid the first pass metabolism with improved therapeutic efficiency in treatment of nausea and vomiting as an alternative therapy to parenterals. Developed microspheres were evaluated for characteristics like particle size, entrapment efficiency, zeta potential, swelling ability, in-vitro mucoadhesion, in-vitro drug release, DSC, XRD study and histopathological evaluation of tissue. CPG-based ondansetron microspheres were studied in rabbits for screening nasal absorption potential of nasal formulation.

Results: Developed nasal microspheres possess entrapment efficiency of 80–89%, higher mucoadhesion of 72–84% across goat nasal mucosa. In-vivo study showed that microspheres based on mucoadhesive polymer were able to promote quick drug absorption as well as enhanced bioavailability of drug.

Discussion: Histopathological studies evaluated biocompatible and nontoxic nature of CPG in nasal cavity. Developed mucoadhesive microspheres by nasal route showed enhancement of bioavailability as compared to oral route in rabbits.

Conclusion: CPG-based mucoadhesive microspheres can successfully deliver ondansetron intranasally, sustain its effect, avoid first pass effect, an alternative route of administration to injection and thus enhance systemic bioavailability of ondansetron hydrochloride.     

糖苷PAL在大鼠胃肠道吸收动力学研究

目的探索糖苷PAL在大鼠胃、肠以及各肠段的吸收动力学特征及吸收部位。方法采用大鼠在体肠灌流吸收实验,以高效液相色谱法测定循环液中药物的浓度。结果同一药物浓度糖苷PAL在全肠段每小时吸收百分率为26．68％,在各肠段即在十二指肠、空肠、结肠和回肠的每小时吸收百分率依次为37．97％、36．10％、25．02％、11．23％,不同的药物浓度：0．80、0．40、0．16mg·mL^-1,在全肠段每小时吸收百分率依次为26．68％、26．12％、25．65％。结论糖苷PAL在胃中不太稳定,在肠道中稳定,吸收也较好,且吸收窗口较长,提示可制成肠溶制剂以供口服吸收。     

Gastrointestinal absorption and metabolism of capsaicin and dihydrocapsaicin in rats

Gastrointestinal absorption of capsaicin and dihydrocapsaicin was studied in rats in vivo and in situ. Rapid absorption of capsaicin or dihydrocapsaicin from stomach and small intestine occurred in vivo. About 85% of the dose was absorbed in the gastrointestinal tract within 3 hr. In situ, within 60 min after the administration of capsaicin and dihydrocapsaicin into stomach, jejunum, and ileum, about 50, 80, and 70% of the respective dose had disappeared from the lumen. When 2,4-dinitrophenol or NaCN was added, no significant reduction in uptake of [3H]dihydrocapsaicin was observed in the jejunum. These results suggested that capsaicin and its analogs were absorbed by a nonactive process in jejunum. [3H]Dihydrocapsaicin was mainly absorbed via the portal system but not a mesenteric lymphangial one. The radioactivity in the portal blood was composed of 85% of [3H]dihydrocapsaicin and 15% of its metabolite (8-methyl nonanoic acid) bound to the albumin fraction. Dihydrocapsaicin-hydrolyzing enzyme activity was found in jejunal tissue. These results suggest that capsaicin and its analogs partly received a first-pass effect, i.e., metabolism of a compound following first absorption in the gastrointestinal tract. It is concluded that capsaicin and its analogs are readily transported to the portal vein through the gastrointestinal tract by a nonactive process and partly metabolized during absorption.     

高效液相色谱法测定吲达帕胺肠溶微球的含量

目的采用反相高效液相色谱法测定吲达帕胺肠溶微球中的含量。方法采用Agilent Eclipse XDB-C18色谱柱(150mm×4.6mm,5μm),以甲醇-水-冰乙酸(45∶55∶0.1)为流动相,检测波长为240nm。结果吲达帕胺在8～48μg/ml与峰面积呈良好的线性关系(r=0.9999),低、中、高浓度的回收率分别为99.55%、98.95%、100.63%,RSD分别为1.15%、0.57%、1.05%。结论所用方法结果准确,专属性强,灵敏度高,重复性好。     

The uptake and translocation of latex nanospheres and microspheres after oral administration to rats

Non-ionic and carboxylated fluorescent polystyrene microspheres (100, 500 nm, 1 and 3 microns in diameter), were fed by gavage (2.5% w/v; 1.25 mg kg-1) daily for 10 days to female Sprague Dawley rats. Peyer's patches, villi, liver, lymph nodes and spleen of animals fed the non-ionic microspheres from 100 nm to 1 micron showed unequivocal evidence of uptake and translocation of the particles. Heart, kidney and lung showed no evidence of the presence of microspheres. Carboxylated microspheres were taken up to a lesser degree than the non-ionised particles. Experiments with 125I radiolabelled 100 nm and 1 micron particles showed a higher uptake of the smaller particles, which were concentrated in GI tissue and liver. Particles were not distributed randomly in the tissues, but were concentrated at the serosal side of the Peyer's patches and could be seen traversing the mesentery lymph vessels towards the lymph nodes. The results demonstrate a need to re-examine the possibilities of particulate oral delivery, as well as the potential toxicity of ingested particulates.     

Nasal absorption enhancement of insulin using PEG-grafted chitosan nanoparticles.

The objective of this work was to explore the potential of polyethylene glycol-grafted chitosan (PEG-g-chitosan) nanoparticles as a system for improving the systemic absorption of insulin following nasal administration. Insulin-loaded PEG-g-chitosan nanoparticles were prepared by the ionotropic gelation of PEG-g-chitosan solution using tripolyphosphate ions as the crosslinking agent. The nanoparticles were in the size range 150-300 nm, had a positive electrical charge (+16 to +30 mV) and were associated with insulin (loading efficiency 20-39%). The physicochemical properties of nanoparticles were affected by the composition of the copolymer. In vitro insulin release studies showed an initial burst followed by a slow release of insulin. Intranasal administration of PEG-g-chitosan nanoparticles in rabbits enhanced the absorption of insulin by the nasal mucosa to a greater extent than a suspension of insulin-PEG-g-chitosan and control insulin solution. PEG-g-chitosan nanoparticles are promising vehicles for insulin transport through the nasal mucosa.     

Characterization of human insulin microcrystals and their absorption enhancement by protease inhibitors in rat lungs

Pulmonary route appears to be an attractive alternative as a non-invasive systemic delivery for peptide and protein drugs. An appropriate formulation, however, is important for increasing their bioavailability in lung. In this study, the human insulin microcrystals were produced. The particle size analysis and scanning electron microscopy (SEM) showed that the microcrystals were uniform and had a monodispersed size distribution (mean diameter = 0.95 microm) for pulmonary delivery. The physicochemical properties of the microcrystals developed were similar to those of the commercial crystalline powder in powder X-ray diffraction (XRD) and differential scanning calorimetry (DSC) analyses. The percentage of high molecular weight proteins (%HMWP), the percentage of other insulin related compounds (%OIRC) and the percentage of A-21 desamido insulin (%D) of the microcrystals were very low. In addition, the cytotoxicity of microcrystals developed and protease inhibitors (aprotinin, bacitracin and soybean-trypsin inhibitor) was investigated, and the enhancement of insulin absorption in the presence of these protease inhibitors at various concentrations was studied. The cell viability of A549 was over 80% at various concentrations of aprotinin and soybean-trypsin inhibitor, except for bacitracin (below 60%). The percent of decrease in blood glucose (D%) was 42.68+/-1.62% after intratracheal instillation of insulin microcrystals (5 U/kg). An enhancement of hypoglycemic effect with protease inhibitors was also found. Soybean-trypsin inhibitor (48.86+/-3.24% at 10 mg/ml; 55.78+/-0.71% at 5 mg/ml; 51.49+/-5.27% at 1 mg/ml) and aprotinin (52.57+/-8.78% at 10 mg/ml; 51.97+/-1.98% at 5 mg/ml; 56.90+/-3.42% at 1 mg/ml) were effective for absorption enhancement. These findings suggest that the use of insulin microcrystals and protease inhibitors would be useful to improve the hypoglycemic effect in pulmonary route.     

Use of enteric polymers for production of microspheres by extrusion-spheronization

To simplify the manufacture of enteric dosage forms, incorporation of enteric polymers into the matrix of phenylbutazone microspheres produced by extrusion-spheronization was compared to the coating of cores. The effect of different polymers, cellulose acetate phthalate (CAP), hydroxypropylmethyl cellulose phthalate (HPMCP) and Eudragit L100-55 and the amount of granulating liquid were evaluated for the effect of selected physical properties and drug release behavior. Using the enteric polymers in the microsphere cores showed a similar pattern of release to the coated spheres with no notable difference in drug release behavior being observed between the dosage forms. The microspheres with Eudragit L100-55 in the matrix were less friable and disintegration times were much closer to the coated microspheres than formulations including the other polymers. Variation of the amount of Eudragit L100-55 in the cores allowed optimization of disintegration and drug release profiles.     

肠溶性瑞巴派特壳聚糖胶囊的制备及大鼠口服给药吸收评价

目的评价肠溶性瑞巴派特壳聚糖胶囊的释药作用,考察其结肠定位效果。方法将瑞巴派特1 mg装入壳聚糖胶囊中,并用羟丙基甲基纤维素邻苯二甲酸酯(HPMCP)包裹胶囊,观察胶囊的体外释药性能。在乙醚麻醉下通过聚乙烯管大鼠口服给予瑞巴派特壳聚糖胶囊4 mg,对照组口服同剂量的明胶胶囊和羧甲基纤维素溶液。于给定的时间间隔取血,取出结肠组织,分离提取药物,用HPLC法测定大鼠血液及结肠中药物浓度。结果在6 h体外溶出试验中,即人工胃液2 h和人工肠液4 h中,瑞巴派特从壳聚糖胶囊中的释药量的质量分数小于10%。大鼠口服瑞巴派特壳聚糖胶囊时,在结肠黏膜中的药物含量-时间曲线下面积(AUCLI0-9,16.01 mg.h.L-1)分别是明胶胶囊和羧甲基纤维素溶液的2.5倍和4.4倍。口服瑞巴派特壳聚糖胶囊,大鼠血浆药物含量-时间曲线下面积(AUCPL0-9)为1.02 mg.h.L-1,同剂量的明胶胶囊和羧甲基纤维素溶液分别是2.16 mg.h.L-1和1.89 mg.h.L-1,表明在壳聚糖的作用下,与明胶胶囊或羧甲基纤维素溶液比较,瑞巴派特从胃肠道吸收进入血液循环的量较少。结论在HPMCP的保护下,壳聚糖是瑞巴派特在结肠释药的一种有效的载体。     

低分子肝素在麻醉大鼠胃肠道的吸收

以血浆抗Ｘａ活性及体内抗静脉血栓形成为指标，考察了低分子肝素溶液及乳剂在麻醉大鼠胃肠道的吸收情况。