Plasma Protein Binding Ratios Research Articles

Pharmacokinetics of Azalomycin F, a Natural Macrolide Produced by Streptomycete Strains, in Rats.

As antimicrobial resistance has been increasing, new antimicrobial agents are desperately needed. Azalomycin F, a natural polyhydroxy macrolide, presents remarkable antimicrobial activities. To investigate its pharmacokinetic characteristics in rats, the concentrations of azalomycin F contained in biological samples, in vitro, were determined using a validated high-performance liquid chromatography–ultraviolet (HPLC-UV) method, and, in vivo, samples were assayed by an ultra-high performance liquid chromatography–tandem mass spectrometric (UPLC–MS/MS) method. Based on these methods, the pharmacokinetics of azalomycin F were first investigated. Its plasma concentration-time courses and pharmacokinetic parameters in rats were obtained by a non-compartment model for oral (26.4 mg/kg) and intravenous (2.2 mg/kg) administrations. The results indicate that the oral absolute bioavailability of azalomycin F is very low (2.39 ± 1.28%). From combinational analyses of these pharmacokinetic parameters, and of the results of the in-vitro absorption and metabolism experiments, we conclude that azalomycin F is absorbed relatively slowly and with difficulty by the intestinal tract, and subsequently can be rapidly distributed into the tissues and/or intracellular f of rats. Azalomycin F is stable in plasma, whole blood, and the liver, and presents plasma protein binding ratios of more than 90%. Moreover, one of the major elimination routes of azalomycin F is its excretion through bile and feces. Together, the above indicate that azalomycin F is suitable for administration by intravenous injection when used for systemic diseases, while, by oral administration, it can be used in the treatment of diseases of the gastrointestinal tract.

Simultaneous determination of three iridoid glycosides of Rehmannia glutinosa in rat biological samples using a validated hydrophilic interaction-UHPLC-MS/MS method in pharmacokinetic and in vitro studies.

The purpose of this study was to develop a method for simultaneous analysis of aucubin, catalpol, and geniposide, which are representative iridoid glycoside constituents of Rehmannia glutinosa, in rat plasma, urine, and feces using hydrophilic interaction ultra high-performance liquid chromatography with tandem mass spectrometry. The three components were separated using 10mmol/L aqueous ammonium formate containing 0.01% (v/v) formic acid and acetonitrile as a mobile phase by gradient elution at a flow rate of 0.2mL/min, equipped with a Kinetex® HILIC column (50 × 2.1mm, 2.6 μm). Quantitation of this analysis was performed on a triple quadrupole mass spectrometer employing electrospray ionization and operated in multiple reaction monitoring mode. The chromatograms showed high resolution, sensitivity, and selectivity with no interference with plasma constituents. In all three iridoid glycosides, both the intra- and interbatch precisions (coefficient of variation %) were less than 4.81%. The accuracy was 96.56-103.55% for aucubin, 95.23-106.21% for catalpol, and 94.50-104.16% for geniposide. The developed analytical method satisfied the criteria of international guidance and was successfully applied to pharmacokinetic studies including oral bioavailability of aucubin, catalpol, and geniposide, and their urinary and fecal excretion ratios after oral or intravenous administration to rats. The new method was also applied to measure plasma protein binding ratios in vitro.

Pharmacokinetics of cisplatin in the absence or presence of Zengmian Yiliu granules (a traditional Chinese medicine compound) in rats determined via ICP-MS: An investigation on drug–herb interactions

Context: Cisplatin is a highly effective chemotherapeutic agent against many tumors; however, it has potent adverse effects. Zengmian Yiliu granule (ZMYL), a traditional Chinese medicine (TCM) compound, has been clinically used against platinum (Pt)-induced toxicity and to enhance the efficacy of cisplatin.Objective: The study was conducted to investigate the likelihood of potential pharmacokinetics drug–herbs interaction (DHI) between cisplatin and ZMYL.Materials and methods: An improved ICP-MS method combined with ultrafiltration and microwave-assisted digestion was performed to determine the total and free Pt concentrations in rat plasma after intraperitoneal administration of cisplatin (9 mg/kg) or a combined administration with ZMYL (1 g/kg) by gavage.Results: ZMYL produced a potential DHI on the pharmacokinetic parameters of cisplatin, calculated from the total Pt concentration. The clearance rate decreased from 110.52 to 66.12 mLh−1 kg−1, the mean residence time extended from 63.1 to 164.54 h, the area under the plasma concentration–time curve increased from 86.58 to 152.93 µg h mL−1, the elimination half-life extended from 48.38 to 126.4 h, and the elimination rate constant decreased from 0.017 to 0.006 h, in the ZMYL combination group (p < 0.05). In terms of free Pt concentration, the apparent volume of distribution and clearance rate was statistically different (p < 0.05). The Pt plasma protein binding ratios in the early dose stages were significantly boosted by the co-administration of ZMYL (p < 0.01).Discussion and conclusion: ZMYL is a potential complementary and alternative medicine for cisplatin chemotherapy. The therapeutic benefits of ZMYL–cisplatin chemotherapy derived from pharmacokinetic interaction needs further investigation.

Comparative protein binding of naringin and its aglycone naringenin in rat, dog and human plasma

Naringin and its aglycone naringenin, widely distributed in traditional Chinese medicines, had received extensive studies on their bioactivities. However, the plasma protein binding ratio, which played a very important role on pharmacokinetic and pharmacodynamic studies, remained unclear. In this present study, the protein binding of naringin and naringenin in rat, dog and human plasma was investigated using equilibrium dialysis and a liquid chromatography with electrospray ionization tandem mass/mass spectrometry (LC-ESI-MS/MS). The analytical time was less than 5 min without sacrificing resolution using ZORBAX Eclipse Plus-C18 (2.1 × 100 mm, 1.8 μm) column and MS/MS mode performed for multiple reaction monitoring. The plasma protein binding ratios of naringin were 83.30 to 84.56%, 72.14 to 74.06% and 48.17 to 51.33% in rat, human and dog plasma, respectively. No obvious concentration dependence was observed across the entire concentration range. On the other hand, the binding ratios for aglycone naringenin in three species plasma exceed 94% over all concentration studied, which suggested that naringenin existed predominantly in the bound form in the circulation blood at a wide range of naringenin concentration. The results may be speculated and make further impacts on their pharmacokinetic study. Key words: Plasma protein binding, naringin, naringenin.

Differences in the Pharmacokinetics of 4-Amino-3-Chlorophenyl Hydrogen Sulfate, a Metabolite of Resatorvid, in Rats and Dogs

The pharmacokinetics of 4-amino-3-chlorophenyl hydrogen sulfate, M-III of resatorvid, in rats and dogs were investigated using radiolabeled M-III ([(14)C]M-III). The elimination half-life of (14)C in the plasma of rats was approximately 1/30 of that of dogs after intravenous dosing of [(14)C]M-III at 0.5 mg/kg to rats and dogs. The in vitro and in vivo plasma protein binding ratios of M-III were relatively high and were the same in both species. The intrinsic clearance (CL(int)) of M-III in rats was much higher than the glomerular filtration rate in rats. Furthermore, the concentration of [(14)C]M-III in the kidney of rats was much higher than that in the plasma. On the contrary, in dogs, the concentration of [(14)C]M-III in the kidney was very much lower than that in the plasma. These results indicated that M-III was effectively taken up into the kidney and was excreted into the urine in rats; however, in dogs, ineffective renal uptake of M-III was presumed. When [(14)C]M-III and probenecid were simultaneously and continually infused intravenously to rats, the CL(int) of M-III decreased with increasing plasma concentrations of probenecid, indicating that kidney uptake of M-III in rats was inhibited by probenecid. It was also thought that uptake by the organic anion transport system(s) in the basolateral membrane is involved in the renal uptake of M-III in rats. The pharmacokinetic differences of M-III between rats and dogs are considered to be mainly caused by the difference in the urinary excretion via the renal distribution processes.

Evaluation of the protein binding ratio of drugs by a micro-scale ultracentrifugation method

Ultracentrifugation methods have been widely used for the determination of the free fraction of compounds in plasma, especially for lipophilic compounds. To estimate the effect of contaminated proteins in the “protein-free phase” fraction, 200μL of human plasma was separated into three layers by ultracentrifugation at 436 000g for 140min with a table-top ultracentrifuge. Twenty microliters of the middle layer was taken as the protein-free fraction. Major contaminated proteins were analyzed by liquid chromatography/electrospray ionization/tandem mass spectrometry (LC/ESI/MS/MS) and identified as albumin, α-1-antitrypsin, α-2-HS-glycoprotein, apolipoprotein E, and apolipoprotein A-1. α-1-acid glycoprotein was not detected. Contamination of albumin was 0.13% of that in plasma. Simulation analysis demonstrated that at an actual free fraction of 1% (protein binding ratio of 99%), the extent of overestimation of free fraction was just 13% and the apparent free fraction was 1.13%. Human plasma protein binding ratios of 10 drugs estimated by this method correlated well with reported values determined by other methods, such as ultrafiltration and equilibrium dialysis, with a correlation factor of 0.98 and a slope of 0.99. Collectively, our results indicate the reliability of this micro-scale ultracentrifugation technique for the evaluation of the protein binding of drugs despite a little contamination of albumin.

Advantage of Extracellular Water Volume for the Relation between Serum Carbamazepine Concentration and Transformed Daily Dose.

We conducted a study to clarify the most suitable factors related to the carbamazepine daily dose (D) with the serum concentration (Ct).Therapeutic drug monitoring data obtained from epileptic patients who were chronically treated with single and repetitive oral administrations of carbamazepine (CBZ). The 119 steadystate data were used.First, when the extracellular water volume (VECW) was employed as a transforming factor, Ct/(D/VECW) ratio was found to be independent of the patient's age. In addition, a multiple regression analysis revealed that Ct was dependent on only D/VECW. From these findings, we concluded that Ct could only be related with D/VECW.Next, a l -compartment model including two assumptions that CBZ binds to plasma protein and the distribution volume of free-CBZ is proportional to VECW, was postulated for our analysis. At steady-state, Ct was expressed as follows:C1=αX (1+KaCbs+αKaX)/(1+αKaX) (X=D/VECW.α, Ka, Cbs: parameter)The parameter values were estimated by the nonlinear least squares method as α, Ka and Cbs were 0.013, 1.6 and 12.8, respectively.The plasma protein binding ratios were 92.3, 90.2 and 87.1 (%) when the serum CBZ concentrations were 6, 8 and 10 [μg/mL], respectively. These values closely corrected with those reported previously.As a result, VECW is considered to be a suitable transforming factor for the relation between Ct and D, and our model seems to be approriate.

DRUG INTERACTION WORKING GROUP: HAB DATABASE

The Drug Interaction Working Group consisting of 31 Japanese pharmaceutical companies was organized to generate a drug interaction database by the Human and Animal Bridge Discussion Group. Protocols for the assay methods of 10 isoforms of human liver cytochrome P450 (CYP1A1 & 2, CYP2A6, CYP2B6, CYP2C8 & 9, CYP2C19, CYP2D6, CYP2E1 and CYP3A4) were provided, and the collection of the data on inhibition of these isoforms (Ki) by drugs already on the market has been started. A common, human liver microsome pool, which was prepared from 10 liver samples supplied by the National Disease Research Interchange in the USA, is being used for this measurement. In the case of no inhibition, the highest concentration of the test article examined is to be reported. As well, information on plasma concentration, plasma protein binding ratios in humans, the main metabolic pathway and the drug-metabolizing enzymes for the drug in question are being collected. As a result, the database will be able to automatically calculate, using the above-described parameters, a theoretical estimate of the magnitude of the drug interaction caused by the enzyme inhibition.

Factors Influencing the Serum Concentration of Antiepileptic Drugs-Relationship between the Serum Valproic Acid Concentration and Daily Dose in Epileptic Patients.

The relation between the serum valproic acid (VPA) concentration and the daily dose was studied using the therapeutic drug monitoring data obtained from epileptic patients who were treated with the oral administration of the sustained-release preparations of VPA. The 233 data at steady-state after repetitive dosing were used.A multiple regression analysis revealed the serum VPA concentration to be dependent on only one variable regarding the daily dose per ideal body weight.An 1-compartment model including two assumptions that VPA binds to plasma protein and the distribution volume of VPA is proportional to the ideal body weight, was postulated for this analysis. The plasma protein binding ratios were calculated based on the values estimated by the nonlinear least squares method and they were found to be 96.0, 94.7, 92.6 (%) when the serum VPA concentrations were 40, 70, 100 (μg/mL), respectively. These values showed a good correlation with those reported by previous investigators and this model also seemed to demonstrate good confidence level.

Fate of Erythritol after Single Oral Administration to Rats and Dogs

The absorption and distribution of radiolabeled erythritol were studied in Wistar rats and beagle dogs after a single oral administration in doses ranging from 0.125 to 2.0 g erythritol/kg body wt. Erythritol concentrations in blood and plasma of rats reached their maxima 1 hr after administration and then declined biexponentially. In the blood and plasma of dogs, the highest concentrations occurred after 1/2 hr followed by a similar decline. Blood plasma distribution ratios and plasma protein binding ratios increased as blood plasma levels declined. At 120 hr after administration, 95.68 ± 2.25% of the radioactivity had been excreted in the urine of dogs and 92.70 ± 0.44% in the urine of rats; 0.33 ± 0.05% had been excreted in the feces of dogs and 1.19 ± 0.09% in the feces of rats; 1.17 ± 0.04% had been excreted in expired air from dogs and 4.80 ± 0.32% in expired air from rats. The results demonstrate that erythritol is rapidly absorbed and excreted, principally through the urinary pathway.

Placental transfer, lacteal transfer and plasma protein binding of gemcitabine.

1. The placental transfer, lacteal transfer and plasma protein binding of gemcitabine have been studied in rat and dog after single intravenous administration of 10 mg/kg 14C-gemcitabine. 2. Radioactivity was distributed to the foetuses at 5 min after administration to rat on days 12 and 18 of gestation. The concentrations of radioactivity in the foetal liver, lung and kidney on day 18 of gestation were 4.0-6.4 times higher than in the maternal blood at 4 h after administration. Relatively high levels of radioactivity were noted in foetal tissues 24 h after administration, indicating slow elimination from the foetus. 3. The concentration of radioactivity in milk reached a maximum at 15 min after administration to the lactating rat on day 10 after delivery, then declined in a biphasic manner, and was below the detection limit at 48 h. The concentrations of radioactivity in milk were lower than plasma concentrations of radioactivity. 4. Plasma protein binding ratios were 10-16 and 1-7% between 5 min and 8 h after administration to the male rat and dog respectively. When fresh plasma from male rat, dog and adult man was spiked with 14C-gemcitabine at concentrations of 0.1-25 micrograms/ml, the plasma protein binding ratios were about 7% in both rat and dog, and 10% in man.

Studies on the metabolic fate of angiotensin II. (I): Changes of plasma concentration after administration of angiotensin II.

Plasma angiotensin II levels were examined in rats, rabbits and dogs after single i.v. administration or i.v. infusion. The plasma concentrations were determined by radioimmunoassay.1. After single i.v. administration of 0.1, 1.0 and 10.Oμg/kg to male and female rats, the plasma concentrations declined rapidly with half-lives (T1/2) of 11.9-19.1sec.2. After single i.v. administration of 1μg/kg to rabbits and dogs, their profiles of plasma concentration-time curve were similar to that of rats, and declined with T1/2 of 23.4 and 26.8 sec, respectively.3. After i.v. infusion of 1μg/kg/min for 15min in rats and dogs, the plasma concentrations declined in similar manner as after single i.v. administration. The T1/2 were regarded to be equal after both administration methods.4. After consecutive administrations to rats and dogs for 7 days, no significant accumulation occurred in the plasma concentrations. A similar concentration-time curves were obtained between lth and 7th day.5. After single i.v. administration to nephrectomized rats, the plasma concentration was not different from that of normal rats.6. In vitro plasma protein binding ratios of angiotensin II in rats, dogs and human were 42.9, 58.3 and 57.9%, respectively. In vivo plasma protein binding ratios were 48.0% in rats at 15sec after single i.v. administration and 60.0% in dogs at 15min after beginning of i.v. infusion.

Studies on the Metabolic Fate of Betamethasone Butyrate Propionate. (V). Metabolism and protein binding in rats and rabbits.

The metabolism of 3H-betamethasone butyrate propionate (BBP) in male rats and rabbits was studied after dermal application. Plasma protein binding was also investigated.Except in epidermis and dermis, the unchanged BBP was not detected in any of studied specimen.1. Dermal metabolites High ratios of unchanged BBP as 70 ?? 80% of radioactivity were observed in both epidermis and dermis of the topical skin of rats at 24hr after the application. The major metabolites were BM-17•B in both tissues and BM-21•B in epidermis.2. Plasma metabolites The main metabolites in plasma were BM-17•B and BM-21•B, and the ratio of those decreased with time. On the other hand, the ratio of BM increased with time and it reached the highest 6hr after the application. After the repeated dosing, the main metabolite in plasma was BM, and the composition of the metabolites was similar to that after single dosing. In rabbits, the main metabolite in plasma was BM-17•B, and the ratio of BM-21•B was lower than that in rats.3. Metabolites in liver and kidney The major metabolites in rat liver and kidney were BM-17•B-6-OH, BM-17•B and BM. Many kinds of minor unknown metabolites were also detected in both organs.4. Urinary metabolies In rat urine, unknown metabolites U7, U8, U9, U11 and many minor metabolites including BM-17•B-6•OH, BM-6•OH, BM were detected. The similar composition was observed after the repeated dosing. In rabbit urine, unknown metabolites RU5, RU2 and many minor metabolites including BM-6•OH and BM were detected. After enzymatic hydrolysis of rabbit urine, increase of BM ratio was observed.5. Fecal metabolites In rabbit feces, BM-6•OH and BM were observed as the major metabolites.6. Plasma protein binding The in vivo plasma protein binding ratios of BBP after subcutaneous administration to rats were 86.4, 86.7and 59.7% at 1, 4 and 24hr, respectively. Those in vitro were as high as more than 97% both in case of rat and human plasma. Both ketotifen fumalate and chlorpheniramine maleate did not affect the in vitro bindings of BBP to rat and human plasma.

Relation between renal and hepatic excretion of drugs: XIII. Pharmacokinetics of new antiarrhythmic drug Bonnecor® in rats with normal and impaired excretory functions

The clearance of 14C-Bonnecor, a weak organic cation, was measured in anaesthetized rats during 6 h after administration. The drug and its labelled metabolites are excreted both via kidney and liver. The renal excretion dominates especially following high doses. After bile duct ligation the renal excretion of Bonnecor increases significantly whereas in nephrectomized rats the biliary excretion of this substance is distinctly reduced. Plasma protein binding ratios amount to 60-70%. Renal removal of Bonnecor and the formed metabolites is in part a result of glomerular filtration. Increased urinary excretion of 14C-Bonnecor-activity under conditions of forced diuresis indicates the involvement of tubular reabsorption in renal handling of the drug and its metabolites. These in vivo results could be confirmed in experiments on renal cortical slices indicating a distinct tubular transport of the drug and its metabolites. In the kidney the aerobic accumulation of Bonnecor is very effective. Surprisingly, under anaerobic incubation conditions, uptake of Bonnecor into renal tissue remains relatively high indicating a distinct binding of Bonnecor within the tubular cells. In the liver the accumulation of Bonnecor is lower compared to the kidney. Furthermore, enterohepatic circulation of Bonnecor and its metabolites was checked. In animals with intact biliary tract, renal removal of 14C-Bonnecor-activity from the organism is significantly higher than in rats with bile duct cannulation. Reinfusion of bile increased renal excretion of 14C-Bonnecor-activity additionally. Both results indicate an effective intestinal reabsorption and enterohepatic circulation of this drug.

新しい睡眠薬４５０１９１‐Ｓの健常成人における薬物速度論的研究

A new hypnotic, 450191-S, is a ring-opened benzodiazepine derivative. It is knownthat the unchanged drug is not detected in plasma and urine after oral administration ofthis drug to humans, and that the metabolites of 450191-S, M-1, M-2, M-A, M-3, and M-4are found in plasma and mainly M-4 is excreted in urine. Some papers have shown thatthe main active metabolites of 450191-S are M-1, M-2, M-A, and M-3.This paper deals with the pharmacokinetics of 450191-S in healthy volunteers . Plasmahalf-lives of metabolites of 450191-S were M-1, 1.2±0.5hr;M-2, 3.2±0.8hr;M-A, 5.0±1.2hr;M-3, 8.5±1.Ohr;and M-4, 1.7±0.1hr (mean±SD).The half-life of total activemetabolites (the sum of the plasma concentration of M-1, M-2, M-A, and M-3) was 10.5±2.6hr.Plasma concentration of each metabolite after administration of 0.5, 1, 2, 4mgof 450191-S was approximately proportional to the dose. Mean urinary excretion ratio of M-4 was 62. 3% of the dose. Effect of food on the pharmacokinetic parameters was notfound. Plasma concentration of each metabolite after multiple administration showed asimilar time course to the simulation curve calculated using pharmacokinetic parametersestimated from observed plasma concentrations after the first dose. Plasma protein binding ratios measured by ultrafiltration at 37° were M-1, 79.3%;M-2, 81.2-87.5%;M-A, 76.8-78.7%;M-3, 80.8-81.4%;and M-4, 88.9-89.7%.