顺铂在大鼠体内血药浓度测定方法学研究

目的 建立大鼠血浆中铂含量测定的方法学,探讨顺铂经静脉注射给药后在大鼠体内的药动学过程。方法 采用浓硝酸消解法,石墨炉原子吸收法GFAAS测定血浆中铂含量。结果 第一步干燥温度100 ℃,时间20 s,第二步干燥温度150 ℃,时间30 s;灰化温度1 500 ℃,时间30 s,升温速率150 ℃·s^-1;原子化温度为2 700 ℃,净化温度2 800 ℃下,此法测定铂标准曲线方程为：A=0.002 49C+0.007 2,相关系数为R²=0.999 7;检出限为1.93 ng·mL^-1。结论 石墨炉原子吸收法测定血浆中铂含量的方法准确可靠,简便易行。     

石墨炉原子吸收法测定异亮氨酸中的微量砷

目的建立石墨炉原子吸收法测定异亮氨酸中的微量砷。方法检测波长为193.7nm,灯电流为12.0mA,狭缝宽度为1.3nm。结果As在1.0000～50.0000μg.L-1范围内线性关系良好,相关系数为0.9994,平均加样回收率为97.01%(RSD=1.0%,n=9)。结论本文的研究有效控制了异亮氨酸的质量,方法简单、结果准确、灵敏度高。     

石墨炉原子吸收法测定苏氨酸中微量砷

目的采用石墨炉原子吸收法测定苏氨酸中微量砷。方法检测波长为193．7nm,灯电流为12．0mA,狭缝宽度为1．3nm。结果砷质量浓度在1．0000—50．0000μg／L范围内与吸光度线性关系良好,r=0．9994,平均加样回收率为98．31％,RSD=0．6％（n=9）。结论石墨炉原子吸收法能有效控制苏氨酸的质量,且简单、准确、灵敏。     

石墨炉原子吸收法用于硫酸铜中的铅盐检查

目的建立石墨炉原子吸收法检查硫酸铜中的铅盐。方法检测波长为283.3 nm,灯电流为9.0 mA,狭缝宽度为1.3 nm。结果Pb在10.0~100.0μg.L-1线性关系良好,相关系数为0.998 6,平均加样回收率为97.82%(RSD=0.8%,n=9)。结论方法简单、灵敏度高、结果准确,可用于检查硫酸铜中的铅。     

法莫替丁大鼠在体小肠吸收动力学研究

应用大鼠在体肠吸收实验方法研究了法莫替丁各肠段的吸收动力学特征。实验表明 :法莫替丁在肠道各部位的吸收速率按十二指肠、空肠、回肠、结肠顺序下降 ,吸收速率常数分别为0 0 5 0 8,0 0 44 6 ,0 0 415 ,0 0 2 87h-1。药物在肠道内的吸收呈现一级吸收动力学过程 ,其吸收机制为被动扩散     

大黄总蒽醌大鼠在体胃肠吸收

目的:研究大黄总蒽醌在大鼠胃、肠的吸收性质。方法:采用大鼠在体胃、肠吸收模型,以高效液相色谱法测定胃、肠灌注液中大黄总蒽醌的含量,并考察离子浓度增加对吸收的影响。结果:大黄总蒽醌在大鼠小肠2h累积吸收率为66.99%,在结肠中2h累积吸收率为23.54%,增加离子强度对吸收没有影响。结论:大黄总蒽醌在大肠吸收相对较少。提示根据其泻下作用机制,可以将大黄总蒽醌制备成口服结肠定位给药形式。     

在体单向灌流法研究加巴喷丁的大鼠肠吸收

采用在体单向灌流法考察加巴喷丁的大鼠肠吸收特性.结果表明,加巴喷丁在小肠各段(十二指肠段、空肠段和回肠段)和结肠均有吸收.低、中浓度(1和10 mmol/L)时药物在小肠各段的吸收速率常数(Ka)和有效渗透系数(Peff)显著大于结肠段(P＜0.05),高浓度(50 mmol/L)时十二指肠段的吸收显著大于结肠段(P＜0.05).加巴喷丁浓度对其在小肠各段的吸收有显著影响,低浓度组小肠各段药物的Ka和Peff显著大于高浓度组(P＜0.05),而药物浓度对结肠段的吸收无显著影响.     

石墨炉原子吸收法测定海藻酸中的微量砷

目的:建立石墨炉原子吸收法测定海藻酸中的微量砷。方法:检测波长为193.7nm,灯电流为12.0mA,狭缝宽度为1.3nm。结果:As在10.000 0~50.000 0μg.L-1范围内线性关系良好,相关系数为0.999 4,平均加样回收率为99.45%(RSD为0.2%,n=9)。结论:本方法有效控制了海藻酸的质量,方法简单、结果准确、灵敏度高。     

Pharmacokinetic study on gastrointestinal absorption of insulinomimetic vanadyl complexes in rats by ESR spectroscopy

Recently, we have shown that oral administrations of vanadyl (+4 oxidation state of vanadium) complexes normalize the blood glucose level of streptozotocin-induced diabetic rats (STZ-rats). To develop clinically useful insulin-mimetic vanadyl complexes, clarification of the pharmacokinetic features of vanadyl compounds is essential. First, we investigated the absorption processes of three compounds, an ionic form of vanadyl sulfate (VS) and the complex forms of bis(picolinato)oxovanadium(IV) (VO(pic)2) and bis(6-methylpicolinato)oxovanadium(IV) (VO(6mpa)2), from the gastrointestinal tract of healthy rats. The concentration curves of paramagnetic vanadyl species in the blood of rats after oral administration of these compounds, as monitored by X-band electron spin resonance (ESR) spectroscopy, exhibited biphasic increasing patterns, indicating that these compounds were absorbed from more than two sites in the gastrointestinal tract. The bioavailability of the compounds was enhanced in the following order on both oral and intraperitoneal administration: VO(6mpa)2 > VO(pic)2 > VS. In addition, bioavailability of the VO(6mpa)2 on ileal administration was enhanced compared with that using other administration sites such as the stomach and jejunum, and resulted in an enhancement about 1.8 fold that compared with oral administration. On the basis of these results, we concluded that the bioavailability of the complex is enhanced most effectively by delivery of the VO(6mpa)2 complex to the ileum.     

Macromolecular absorption in the gastrointestinal tract

This article describes much of the information known on the ability of macromolecules to enter and penetrate the gastrointestinal mucosal epithelium of both neonates and adults. The study proposes that both types of epithelial cell are capable of transporting macromolecules from the intestinal lumen into the general circulation. The article discusses the implications that this can have for the transepithelial transport of macromolecules including drugs and delivery systems.     

Kinetics of piretanide absorption from the gastrointestinal tract

In a recent report, it was shown that the loop diuretic piretanide is rapidly absorbed after placement of a piretanide solution in the duodenum, while the rate of absorption is definitely slower when the drug is instilled into the ascending colon (5). When piretanide is instilled into the stomach, the absorption process does not differ significantly from that after placement in the duodenum, neither with respect to amount nor rate (5). However, it was not clear from this study whether piretanide is directly absorbed from the stomach or rapidly released into the duodenum. In a study with five volunteers piretanide was instilled into the stomach via a gastroscope. The volunteers took part in two trial phases in a randomized cross-over design: in one phase the administration of 6 mg piretanide was preceded by intravenous administration of 40 mg hyoscine-N-butylbromide (HNB) to immobilize the stomach while in the alternative phase this coadministration of HNB was omitted. Furthermore, the volunteers were lying on their left side to avoid the gastric fluid leaking out into the intestine by gravity. From the concentration-time-curves monitored it can be concluded that piretanide is absorbed directly from the stomach for almost all subjects but with different rates. The rate of absorption increases clearly when the immobilizing effect of HNB disappears. It is most probable that returning peristaltic waves and succeeding gastric emptying results in enhanced absorption from the upper intestinal tract. Furthermore, a pharmacokinetic model which takes into account the differences in the rate of absorption along the gastrointestinal tract was adjusted to the data.(ABSTRACT TRUNCATED AT 250 WORDS)     

Microemulsions for improved peptide absorption from the gastrointestinal tract

Results on gastrointestinal absorption of three peptides, insulin, cyclosporin from microemulsions, obtained from studies in our laboratories during the past years have been summarized. The routes of administration were period, intralumenal or rectal. The experiments were carried out in dogs, rabbits and rats. An absorption model for peptides using microemulsions as delivery systems is presented.     

Pharmacokinetics of diltiazem absorption in the rat gastrointestinal tract.

The absorption of diltiazem (CAS 42399-41-7) from the stomach, small intestine, and colon of the rat has been studied, using an in situ cannulation procedure. Diltiazem solutions (1 mg/ml) were prepared in isotonic buffers at pH 3.5 (stomach), 6.2 (small intestine), or 7.5 (colon). 10 ml of drug solution was used in the small intestine, 4 ml was used in the stomach and colon. Aliquot (100 microliters) of the solution was withdrawn at 5-min intervals for a period of 30 min, and assayed by HPLC. A semilog plot of percent remaining vs. time showed that absorption followed apparent first order kinetics with absorption rate constant, ka, equal 0.07 min-1, 0.02 min-1, and 0.01 min-1, in the small intestine, colon, and stomach, respectively.     

Allopurinol absorption from different sites of the rat gastrointestinal tract

Allopurinol exhibits good bioavailability (78-90%) after administration of oral dosage forms to humans and rabbits; however, it is not absorbed rectally from any of the dosage forms to any significant extent. Oral administration of allopurinol in a polyethylene glycol suspension, to which allopurinol may be reversibly complexed, to rabbits has been shown to produce erratic and poor absorption of allopurinol. This suggests the possibility of differential absorption of allopurinol from various sites of the GI tract. The mechanism of allopurinol absorption was investigated in rats using the in situ Levine technique. The allopurinol absorption rate was 0.56 +/- 0.10 microgram/min/cm from the upper portion of the small intestine and was 0.48 +/- 0.12 microgram/min/cm from the midgut. The absorption from the lower portion of the small intestine was 0.33 +/- 0.14 microgram/min/cm and from the upper and lower large intestine segments was negligible (0.04 +/- 0.06 microgram/min/cm). The normalization of these absorption rates for surface area yielded flux values (normalized absorption rate as microgram/min/cm2) with significant differences in permeability between small and large intestine for allopurinol. The allopurinol absorption rate increased with increases in the dose, and there was a linear relationship between dose and absorption rate. Thus, allopurinol absorption, although specific to particular sites, is not dose dependent in the dose range from 0.25 to 2.5 mg/mL. Differences in the rates of absorption may be due to anatomical differences of the various parts of the GI tract or due to physicochemical properties of the drug itself.     

The absorption site of cyclosporin in the human gastrointestinal tract.

1. An emulsion preparation of cyclosporin was administered locally to different parts of the small and large intestine by gavage: to the duodenum (opposite to the papilla of Vater), jejunum (150 cm distal to the teeth), ileum (300 cm distal to the teeth), and to the colon descendens (30 cm proximal to the anus). 2. The bioavailability of cyclosporin after these instillations was compared with that after oral administration of a hard gelatine capsule formulation. 3. Cyclosporin was found to be absorbed predominantly in the small intestine. This may have implications for dosage in patients with reduced absorptive surface area.