Validated stability-indicating HPLC method for the determination of dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate (DDB) and its degradation products

High-performance liquid chromatographic method was developed for the quantitative determination of dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate (DDB) and its degradation products. Forced degradation studies were performed on bulk sample of DDB using acid (1N hydrochloric acid), alkaline (0.1N sodium hydroxide), oxidation (0.33% hydrogen peroxide), heat (70 degrees C) and photolytic degradation. The chromatographic method was fine tuned using the samples generated from forced degradation studies. Good resolution between the peaks corresponds to degradation products and the analyte was achieved on 5 microm ODS column (Luna, Phenomenex, USA). The mobile phase consists of a mixture of acetonitrile and water (60:40, v/v). Quantitation was achieved with UV detection at 235 nm based on peak area. The proposed HPLC method was utilized to investigate the kinetics of acidic, alkaline and oxidative degradation processes of DDB at different temperatures and the apparent pseudo first-order rate constant, half-life and activation energy were calculated. The pH-rate profiles of degradation of DDB in Britton-Robinson buffer solutions within the pH range 2-11 were studied. The developed method was validated with respect to linearity, accuracy, precision, robustness and forced degradation studies prove the stability-indicating power of the method.     

The anti-fibrogenic effect of a pharmaceutical composition of [5-(2-pyrazinyl)-4-methyl-1,2-dithiol-3-thione] (oltipraz) and dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate (DDB)

Liver fibrosis is a prepathological state wherein damaged liver tissues in chronic liver diseases, such as hepatitis, are not repaired to normal tissues, but converted to fibrous tissue. 5-(2-Pyrazinyl)-4-methyl-1,2-dithiol-3-thione (oltipraz), a cancer chemopreventive agent, is effective against a wide variety of chemical carcinogens. Recently, we reported that oltipraz inhibits liver fibrogenesis (Kang et al., 2002). In the present study, the effects of oltipraz in combination with dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylene dioxybiphenyl-2,2'-dicarboxylate (DDB) on dimethylnitrosamine (DMN)-induced liver fibrogenesis were assessed in rats. Oltipraz (30 mg/kg body weight, p.o., 3 times per week for 4 weeks) was found to inhibit the increases in plasma ALT, AST and bilirubin by DMN, whereas DDB (30 mg/kg body weight, p.o., 3 times per week for 4 weeks) attenuated the increases in the plasma ALT and bilirubin. The lowered plasma protein and albumin contents in DMN-treated rats were completely restored by oltipraz, but not by DDB. DDB decreases liver cell injury and inflammation through inhibition of nuclear factor-kB. DMN increased the accumulation of liver collagen, as indicated by the increase in the 4-hydroxyproline content in liver homogenates, which was reduced by treatment with oltipraz, but not by DDB. Given the differential effect between oltipraz and DDB, the potential enhancement of antifibrotic efficacy by the drugs was assessed in the animal model. Despite the minimal effect of DDB on DMN-induced fibrogenesis, DDB (5-25 mg/kg), administered together with oltipraz (25-5 mg/kg), showed an additive protective effect against hepatotoxicity and fibrosis induced by DMN, which was shown by the blood chemistry parameters and histopathological analysis. The adequate composition ratio of oltipraz to DDB was 5:1. These results provide information on the pharmaceutical composition, comprising of oltipraz and DDB as the active components, for the treatment and/or prevention of liver fibrosis and cirrhosis.     

Antitumor agents. 293. Nontoxic dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylenedioxybiphenyl-2,2'-dicarboxylate (DDB) analogues chemosensitize multidrug-resistant cancer cells to clinical anticancer drugs

Novel dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylenedioxybiphenyl-2,2'-dicarboxylate (DDB) analogues were designed and synthesized to improve their chemosensitizing action on KBvin (vincristine-resistant nasopharyngeal carcinoma) cells, a multidrug resistant cell line overexpressing P-glycoprotein (P-gp). Structure-activity relationship analysis showed that aromatic and bulky aliphatic side chains at the 2,2'-positions effectively and significantly sensitized P-gp overexpressing multidrug resistant (MDR) cells to anticancer drugs, such as paclitaxel (TAX), vincristine (VCR), and doxorubicin (DOX). DDB derivatives 16 and 23 showed 5-10 times more effective reversal ability than verapamil (VRP) for TAX and VCR. Analogue 6 also exhibited five times greater chemosensitizing effect against DOX than VRP. Importantly, no cytotoxicity was observed by the active DDB analogues against both non-MDR and MDR cells, suggesting that DDB analogues serve as novel lead compounds for the development of chemosensitizers to overcome the MDR phenotype. The mechanism of action studies demonstrated that effective inhibition of P-glycoprotein by DDB analogues dramatically elevated the cellular concentration of anticancer drugs.     

Characterization of the selectivity and mechanism of cytochrome P450 inhibition by dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylenedioxybiphenyl-2,2'-dicarboxylate.

In vitro studies with human liver microsomes and cytochrome P450 (P450) prototype substrates were performed to characterize the selectivity and mechanism of inhibition of P450 by dimethyl-4,4'-dimethoxy-5,6,5',6'-dimethylenedioxybiphenyl-2,2'-dicarboxylate (DDB). DDB was found to be a strong inhibitor of testosterone 6beta-hydroxylation activity (CYP3A4) with a K(i) value of 0.27 +/- 0.21 microM. At higher concentrations, DDB marginally inhibited caffeine N(3)-demethylation (CYP1A2), diclofenac 4'-hydroxylation (CYP2C9), and dextromethorphan O-demethylation (CYP2D6) activities, but this compound had no effect on CYP2A6-, CYP2C19-, and CYP2E1-mediated reactions. Spectral analysis indicated that the formation of metabolite-P450 complex having absorbance at 456 nm was concentration-dependent; 5 to 33% of the total P450 was complexed in rat and human liver microsomes after a 5-min incubation with DDB. In addition, microsomal incubations with DDB in the presence of NADPH resulted in a loss of spectral P450 content, which was restored after adding K(3)Fe(CN)(6). This complex formation resulted in a time-dependent loss of CYP3A-catalyzed marker activity (testosterone 6beta-hydroxylation) in human liver microsomes. The inhibition was only partially restored upon dialysis. These results collectively suggest that formation of a metabolite-CYP3A complex with DDB was responsible for the CYP3A-selective time-dependent loss of catalytic function of CYP3A.     

Pharmacokinetic changes of oltipraz after intravenous and oral administration to rats with liver cirrhosis induced by dimethylnitrosamine

Pharmacokinetic changes of oltipraz were investigated after intravenous and oral administration at a dose of 30 mg/kg to control Sprague-Dawley rats and rats with liver cirrhosis induced by dimethylnitrosamine. After intravenous administration in rats with liver cirrhosis, the area under the plasma concentration-time curve from time zero to time infinity (AUC) was significantly greater (1490 microg min/ml versus 2840 microg min/ml) than that in control rats. This was due to significantly slower total body clearance (CL) (20.2 ml/(min kg) versus 10.6 ml/(min kg)) in the rats. The slower CL was due to significantly slower CL(NR) (20.1 ml/(min kg) versus 10.5 ml/(min kg)) in rats with liver cirrhosis. The significantly slow CL(NR) was due to slower hepatic blood flow rate and significantly slower in vitro intrinsic oltipraz disappearance clearance (CL(int), 77.2 ml/min per whole liver versus 11.5 ml/min per whole liver) because the free (unbound in serum proteins) fraction of oltipraz was significantly greater (15.1% versus 31.3%) in the rats. After oral administration in rats with liver cirrhosis, the AUC was also significantly greater (354 microg min/ml versus 812 microg min/ml) and this was not due to increased absorption in the rats. This also could be due to slower hepatic blood flow rate and significantly slower CL(int) in the rats.     

联苯双酯（DDB）对Bel－7402人肝癌细胞株一些表型的作用及其机理

Ｂｅｌ－７４０２人肝癌细胞在ＤＤＢ（１０￣（－４）ｍｏｌ·Ｌ￣（－１））处理后，生长和克隆形成受到明显抑制，电子显微镜观察到ＤＤＢ作用过的细胞核仁减少或消失，核与胞浆比例缩小。Ｂｅｌ－７４０２细胞内环化腺苷酸（ｃＡＭＰ）和钙调蛋白（ＣａＭ）的含量，经ＤＤＢ处理不同时间后皆显示明显高于对照组。此外，ＤＤＢ还能降低从Ｂｅｌ－７４０２细胞内提取出的ＤＮＡ拓扑异构酶ＩＩ（ＴｏＰｏＩＩ）活力。说明ＤＤＢ对Ｂｅｌ－７４０２人肝癌细胞的作用机理与ｃＡＭＰ，ＣａＭ和ＴｏＰｏＩＩ有关。     

Effect of 2-methylaminoethyl-4,4'-dimethoxy-5,6,5',6'-dimethylenedioxybiphenyl-2-carboxylic acid-2'-carboxylate monohydrochloride (DDB-S) on indocyanine green (ICG) clearance in rats

The clearance of ICG, a known hepatic blood flow marker was investigated in rats in order to examine whether DDB-S influences hepatic blood flow. The effect of DDB-S on the protein binding and blood-to-plasma partition of ICG was measured. The steady-state plasma concentration of ICG was monitored before and after co-administration of various concentration of DDB-S, and ICG clearance was estimated from the steady-state concentration and the infusion rate of ICG. There was no significant difference in protein binding and blood-to-plasma partition of ICG with and without addition of DDB-S (10, 20, and 40 microg/mL). When ICG was infused into DDB-S pretreated rats, the steady-state concentrations of ICG decreased and the calculated ICG clearance increased. However, no dose-dependency of ICG Css on DDB-S Css was observed. Since DDB-S did not affect the protein binding and blood-to-plasma partition of ICG, the increased clearance of ICG with co-administration of DDB-S seems to be due to the increased hepatic blood flow by DDB-S.     

Metabolism and disposition of 2,2',4,4',5-pentabromodiphenyl ether (BDE99) following a single or repeated administration to rats or mice

The metabolism and disposition of 14C-labelled 2,2',4,4',5-pentabromodiphenyl ether (BDE99) were studied in F344 rats and B6C3F1 mice. Approximately 85% of a 1 micromol kg-1 oral dose was absorbed by male rats and mice. Within 24 h following oral doses ranging from 0.1 to 1000 micromol kg-1 to rats, 39-47% of the dose was excreted in the faeces (including 16% unabsorbed), up to 2% was excreted in the urine, and 34-38% remained in the tissues, mostly in adipose tissue. Mice excreted more in the urine and less in the faeces than rats. Tissue accumulation was observed following repeated dosing to rats. Two dihydrohydroxy-S-glutathionyl and two S-glutathionyl conjugates of BDE99, 2,4,5-tribromophenol glucuronide, two mono-hydroxylated BDE99 glucuronides, and three mono-hydroxylated tetrabromodiphenyl ether glucuronides were identified in male rat bile. 2,4,5-Tribromophenol and its glucuronide and sulfate conjugates, were identified in male rat urine. 2,4,5-Tribromophenol, one mono-hydroxylated tetrabromodiphenyl ether, and two mono-hydroxylated BDE99 were characterized in male rat faeces. BDE99 undergoes more extensive metabolism than does BDE47. Half of the absorbed oral dose in male rats was excreted in 10 days mostly as metabolites derived from arene oxide intermediates.     

Pharmacokinetic analysis of 6-monoamino-beta-cyclodextrin after intravenous or oral administration to rats using a specific enzyme immunoassay

We have developed a highly sensitive enzyme immunoassay for 6-monoamino-beta-CD (mono(6-amino-6-deoxy)cyclomaltoheptaose) and its parent compound (beta-CD) with a detection limit in the 100 pg/mL range. The polyclonal antibodies obtained are highly specific for the beta-cyclodextrin core and do not recognize other cyclic cyclodextrins (i.e., alpha- and gamma-CD) or linear analogues. This enzyme immunoassay can be used to quantify 6-monoamino-beta-CD in rat urine and plasma. Using this immunoassay, we have evaluated the main pharmacokinetic parameters of 6-monoamino-beta-CD after iv administration to the rat of a 25 mg/kg dose. Since this method is strictly specific to the native beta-CD form, we have demonstrated that the molecule rapidly disappeared from plasma but is probably distributed in the tissues. The urinary route appears as the predominant way of elimination since almost all the administered drug is recovered in urine. Finally, analysis of the same molecule after oral administration to the rat (25 mg/kg) demonstrates low plasma levels and that about 1% of the administered dose is excreted in urine. These experiments demonstrate the high stability of the beta-CD core irrespective of the method of administration. This immunological method could provide relevant information on the fate of beta-CD and some derivatives for drug delivery using different modes of administration (oral, parenteral, transmucosal, or dermal).     

Pharmacokinetics of oltipraz after intravenous and oral administration in rats with dehydration for 72 hours

Pharmacokinetic parameters of oltipraz were compared after intravenous and oral administration at a dose of 30 mg/kg to control rats and rats with water deprivation for 72 h (rats with dehydration). The plasma protein binding of oltipraz was measured in both groups of rats using an equilibrium dialysis technique. The concentrations of oltipraz were measured by the reported HPLC analysis. After intravenous administration, the total area under the plasma concentration-time curve from time zero to time infinity (AUC), terminal half-life, time-averaged total body and nonrenal clearances, and apparent volume of distribution at steady state were not significantly different between the two groups of rats. However, after oral administration to rats with dehydration, the AUC was significantly smaller than that in control rats (180 versus 316 microg min/ml) mainly due to decrease in absorption. In rats with dehydration, plasma protein binding was significantly greater than that in control rats (91.5 +/- 0.309 versus 81.3 +/- 2.79%).     

Pharmacokinetic interaction between tanshinones and polyphenolic extracts of salvia miltinorrhiza BUNGE after intravenous administration in rats

The objective of this study was to investigate the interaction between tanshinones and polyphenolic extracts of Salvia miltiorrhiza BUNGE in rats. The rats in the medium dose groups were given an intravenous administration of 10 mg/kg tanshinones extract-loaded emulsion (equivalent to 4.0 mg/kg tanshinone IIA (TSIIA)), 100 mg/kg polyphenolic extract solution (equivalent to 61.2 mg/kg salvianolic acid B (Sal B)) or mixed extracts-loaded emulsion (equivalent to 4.0 mg/kg TSIIA and 61.2 mg/kg Sal B). The dosage given to the low dose groups was half that of the medium dose groups, while the high dose groups received twice the dosage of the medium dose groups. The areas under the plasma concentration-time curve (AUC) of TSIIA and Sal B were considerably increased (about 2-14 fold) after intravenous administration of mixed extracts-loaded emulsion in comparison with the equivalent dose of the corresponding extract administration. An increase of about 2-fold was observed in both the low and medium dose groups for TSIIA and Sal B, while there was at least a 14- and 5-fold significant increase (p<0.01) for TSIIA and Sal B in the high dose groups, respectively which was due to a significant (p<0.01) reduction in total plasma clearance (CL(t)). The peak plasma concentrations (C(0.083 h)) of TSIIA and Sal B were also both significantly increased (p<0.01). However, no significant differences in the terminal elimination half-life (t(1/2)) of TSIIA and Sal B in the mixed extracts-loaded emulsion groups were found compared with that of the corresponding extract groups except for the high dose groups of TSIIA (p<0.05). Therefore, a pharmacokinetic interaction occurs between tanshinones and polyphenolic extracts of Salvia miltinorrhiza BUNGE after intravenous administration in rats, which affects the pharmacokinetic process of TSIIA and Sal B in vivo.     

Pharmacokinetic profiles in rats after intravenous, oral, or dermal administration of dapsone.

Dapsone is a potent anti-inflammatory and antibacterial agent that has been used extensively in the oral treatment of leprosy and dermatitis herpetiformis. This study compared the pharmacokinetic profile of dapsone in rats given a single oral or i.v. 12 mg/kg dose (n = 8/group) or a single dermal application of 12 or 60 mg/kg (n = 12/group) in an aqueous gel application medium containing 10 or 25% diethylene glycol monoethyl ether (DGME). Blood samples (200 microl) were collected via tail vein from each rat and pooled at intervals up to the 24-h period. A terminal blood sample was collected by cardiac puncture from each animal. Plasma concentrations of dapsone were determined by liquid chromatography atmospheric pressure ionization tandem mass spectroscopy. There was no treatment-related overt toxicity observed in any of the animals. Peak levels were reached 1 h after oral dosing (4890 ng/ml), and 6 to 8 h after dermal application, with Cmax values of 1.62, 5.56, and 12.8 ng/ml, for 12 mg/kg at 10 or 25% DGME, and for 60 mg/kg at 25% DGME, respectively. Bioavailability was calculated at 78% after oral dosing and <1% after dermal application. Apparent elimination half-lives (t(1/2))s were similar after i.v. and oral dosing. Both the calculated area under the plasma concentration versus time curve up to 24 h and Cmax values were 3- to 4-fold higher in the dermal application group administered 12 mg/kg dapsone in 25 versus 10% DGME gel, whereas the calculated area under the plasma concentration versus time curve up to 24 h and Cmax values for the 60 mg/kg group were only 3.3- and 2.3-fold greater than those obtained after application of 12 mg/kg in 25% DGME. These results show that both systemic exposure and peak plasma concentrations of dapsone are minimized by dermal versus oral administration of the compound.     

Pharmacokinetic study of salvianolic acid D after oral and intravenous administration in rats

A sensitive, specific and rapid LC-MS method was developed and validated for the determination of salvianolic acid D (SalD) in rat plasma. This method used a single quadrupole mass spectrometer with an electrospray ionization (ESI) source. A single ion monitoring scanning (SIM) mode was employed. It showed good linearity over the concentration range from 3.3 to 666.7 ng/mL for the determination of SalD. The R.S.D.% of intra-day and inter-day precision values were no more than 7.69%, and the accuracy was within 91%−104% at all quality control levels. This LC-MS method was applied to the pharmacokinetic study of SalD in rats. A two-compartmental model analysis was employed. The plasma concentrations at 2 min (C_2min) were 5756.06±719.61, 11,073.01±1783.46 and 21,077.58±5581.97 μg/L for 0.25, 0.5 and 1 mg/kg intravenous injection, respectively. The peak plasma concentration (C_max) was 333.08±61.21 μg/L for 4 mg/kg oral administration. The area under curve (AUC_0−t) was 14,384.379±8443.184, 22,813.369±11,860.823, 46,406.122±27,592.645 and 8201.740±4711.961 μg/L·h for intravenous injection (0.25, 0.5 and 1 mg/kg) and oral administration (4 mg/kg), respectively. The bioavailability of SalD was calculated to be 4.159%±0.517%.Abbreviations: AUC, the area under curve; CI, confidence interval; CL, clearance; C_max, peak plasma concentration; ECE-1, endothelin converting enzyme 1; ESI, electrospray ionization; IS, internal standard; LLOQ, lower limit of quantification; QC, quality control; R.E., relative error; R.S.D., relative standard deviation; SalB, salvianolic acid B; SalD, salvianolic acid D; SIM, single ion monitoring; TCM, traditional Chinese medicine; ULOQ, upper limit of quantificationKEY WORDS: Salvianolic acid D, LC-MS, Pharmacokinetics, Bioavailability, Dose proportionality, Salvia miltiorrhiza, Danshen, Analysis method     

红外分光光度法测定联苯双酯同质异晶体的研究

本文报道了用红外分光光度法检测治疗慢性、迁延性肝炎新药联苯双酯的２种同质异晶体在原料药中的相对含量。产品的溴化钾压片在７３８ｃｍ￣（－１）处的吸收带为低熔点片状晶体的特征峰。高熔点棱柱状晶体在此处无吸收干扰，故可用其测定前者的百分量。平均回收率为９７．０６％，相对标准偏差为３．８６％，本法简便快速。     

联苯双酯(DDB)对Bel-7402人肝癌细胞株一些表型的作用及其机理

Bel-7402人肝癌细胞在DDB(10^-4mol·L^-1)处理后,生长和克隆形成受到明显抑制,电子显微镜观察到DDB作用过的细胞核仁减少或消失,核与胞浆比例缩小。Bel-7402细胞内环化腺苷酸(cAMP)和钙调蛋白(CaM)的含量,经DDB处理不同时间后皆显示明显高于对照组。此外,DDB还能降低从Bel-7402细胞内提取出的DNA拓扑异构酶II(ToPoII)活力。说明DDB对Bel-7402人肝癌细胞的作用机理与cAMP,CaM和ToPoII有关。     

Metabolism and disposition of 2,2',4,4'- tetrabromodiphenyl ether following administration of single or multiple doses to rats and mice

The metabolism and disposition of (14)C-labelled 2,2',4,4'-tetrabromodiphenyl ether (BDE47) were investigated in F344 rats and B6C3F1 mice. Approximately 75-85% of 1 micromol BDE47 kg(-1) was absorbed following oral administration to either rats or mice. Sex and species differences were observed in tissue distribution and excretion of BDE47-derived radioactivity. Absorption and distribution of (14)C to major tissues were dose-proportional in male rats from 0.1 to 1,000 micromol kg(-1). BDE47-derived radioactivity increased in all rat and mouse tissues examined following repeated daily doses of 1 micromol kg(-1). Accumulation of (14)C in tissues of mice was less than in corresponding rat tissues. Glutathione conjugates of BDE47 were excreted in rat bile. A glucuronide and a sulfate conjugate of 2,4-dibromophenol were detected in the urine of BDE47-treated rats. BDE47 appears to induce its own metabolism. Increased formation of reactive metabolites over time may correlate with toxicological effects in BDE47-treated rodents.     

Pharmacokinetic study of all-trans-retinoyl-beta-D-glucuronide in Sprague-Dawley rats after single and multiple intravenous administration(s).

All-trans-retinoyl-beta-D-glucuronide (RAG) is an endogenous active metabolite of all-trans-retinoic acid (ATRA). In the present study, the pharmacokinetics of RAG was examined after the administration of a single intravenous does (5, 10, or 15 micromol/kg) and of multiple daily intravenous doses (5 micromol/kg) to rats for 8 days. The plasma concentrations of RAG and ATRA were measured by a reverse-phase HPLC method. A rapid distribution phase of approximately 1 h was observed in all of the rats after single or multiple doses. Thereafter, RAG was eliminated through a first-order process, in accord with a typical two-compartment first order pharmacokinetic profile. After single intravenous doses, the AUC of RAG increased proportionally with the dose and the clearance remained unchanged within the tested doses. There was no statistical significant difference in distribution rate constants from central compartment to peripheral compartment (K(12)) and from peripheral compartment to central compartment (K(21)) between different doses. However, as the dose increased from 5 micromol/kg to 10 micromol/kg, the volume of distribution at the steady state (V(ss)) and the volume of peripheral compartment (V(p)) decreased significantly (p < 0.05) from 1.290 +/- 0.269, 0.928 +/- 0.232. L/kg to 0.961 +/- 0.149, 0.647 +/- 0.107 L/kg, respectively. V(ss) and V(p) at a dose of 15 micromol/kg (0.924 +/- 0.187, 0.698 +/- 0.165 L/kg) were not significantly different from that at 10 micromol/kg. Thus, RAG might saturate the tissue-binding sites at higher doses. ATRA was detected as a metabolite of RAG at low levels (usually < 0.05 microM) only in the first 2 h after intravenous administration. RAG clearly was not extensively hydrolyzed to ATRA in our study. After multiple daily intravenous administration of RAG, the clearance (Cl) and the elimination rate constant (K(10)) remained unchanged (p > 0.05), indicating that long-term daily administration of RAG did not induce its accelerated metabolism. However, K(12), V(p), and V(ss) declined significantly (p < 0.05) from 1.67 +/- 0.54 h(-1), 0.928 +/- 0.232 L/kg, and 1.290 +/- 0.269 L/kg to 0.96 +/- 0.48 h(-1), 0.494 +/- 0.147 L/kg, and 0.818 +/- 0.187 L/kg, respectively. Therefore, long-term daily dosing of RAG seemed to decrease its distribution profile. Although the AUC of RAG did not change significantly after multiple dosing, the AUC of ATRA after RAG dosing significantly declined (p < 0.05) from 0.032 +/- 0.019 microM x h to 0.010 +/- 0.006 microM x h. The decline in the AUC of ATRA might reflect an increase in its uptake by tissue and/or in its metabolism. Because enhanced clearance is not associated with RAG after multiple administrations, RAG could be considered as an alternate to ATRA in appropriate clinical applications.     

Pharmacokinetics of 3H-pipethiaden after single oral and intravenous administration in rats

Tritium labelled anti-migraine drug 4-(1-methyl-4-piperidyliden)-4,9-dihydrothieno[2,3-c]-2-b enzothiepine (pipethiaden) was prepared. After oral and intravenous administration to rats not only the courses of total radioactivity in plasma and various organs were determined, but by means of TLC-radiometry also the levels of pipethiaden itself. After the oral dose 1.35 mg/kg the plasma levels of pipethiaden did not exceed 3.5 ng/ml. Some pharmacokinetic parameters (e.g. t1/2 el-4 h) were calculated by compartmental analysis of plasma levels.     

Pharmacokinetic and pharmacodynamic changes of furosemide after intravenous and oral administration to rats with alloxan-induced diabetes mellitus

Because some physiological changes occurring in diabetes mellitus patients could alter the pharmacokinetics and pharmacodynamics of the drugs to treat the disease, the pharmacokinetics and pharmacodynamics of furosemide were investigated after intravenous (i.v.) and oral administration of the drug (6 mg per whole body weight) to control rats and alloxan-induced diabetes mellitus rats (AIDRs). After i.v. administration, the total body clearance (5.47 versus 7.05 mL min⁻¹ kg⁻¹) was significantly slower in AIDRs and this was due to significantly slower renal clearance (2.35 versus 4.33 mL min⁻¹ kg⁻¹) because the nonrenal clearance was comparable between two groups of rats. The 8 h urinary excretion of furosemide after i.v. administration decreased significantly (2280 versus 3760 μg) in AIDRs due to impaired kidney function; the glomerular filtration rate measured by creatinine clearance was significantly slower (2.86 versus 4.33 mL min⁻¹ kg⁻¹) and both the plasma urea nitrogen (43.5 versus 17.3 mg dL⁻¹) and kidney weight (0.953 versus 0.749% of body weight) increased significantly in AIDRs. This resulted in a significant decrease in the 8 h urine output per g kidney (17.8 versus 43.6 mL) in AIDRs. However, the 8 h diuretic efficiency was not significantly different between two groups of rats. After oral administration, the area under the plasma concentration–time curve from time 0 to 8 h decreased significantly in AIDRs (1200 versus 1910 μg·min mL⁻¹) due to considerably decreased absorption of furosemide from gastrointestinal tract of AIDRs. After oral administration, the 8 h urine output per g kidney (18.6 versus 36.4 mL) also decreased significantly in the AIDRs due to significantly decreased 8 h urinary excretion of furosemide (405 versus 2210 μg), however, the 8 h diuretic efficiency increased significantly (127 versus 35.2 mL mg⁻¹) in AIDRs. © 1998 John Wiley & Sons, Ltd.     

Pharmacokinetic changes of cyclosporine after intravenous and oral administration to rats with uranyl nitrate-induced acute renal failure

The effects of renal failure on the pharmacokinetics of cyclosporine were investigated after intravenous, 30 mg/kg, and oral, 100 mg/kg, administration of the drug using a rat model of uranyl nitrate-induced acute renal failure (U-ARF). After intravenous administration to rats with U-ARF, the volume of distribution at steady state (1.97 vs. 2.56 l/kg) was significantly smaller, and the area under the blood concentration-time curve (348 vs. 296 microg h/ml) tended to be greater and total body clearance (0.0851 vs. 0. 102 l/h per kg) tended to be slower than those in control rats. After oral administration, the pharmacokinetic parameters were not significantly different between the control rats and rats with U-ARF, suggesting that U-ARF did not considerably affect the pharmacokinetics of cyclosporine after oral administration.