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Biomedical subjects

H Hakusui

Publications and source records attributed to H Hakusui.

At least 55 records · Page 3Linked to original sources
PubMed1992

Effects of antacids, ferrous sulfate, and ranitidine on absorption of DR-3355 in humans.

This study examined the effects of widely used antacids (aluminum hydroxide, magnesium oxide, and calcium carbonate), ferrous sulfate, and ranitidine on the absorption of a fluorinated quinolone, (-)-(S)-9-fluoro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-2,3-dihydro- 7H- pyrido-[1,2,3,-de][1,4]benzoxazine-6-carboxylic acid hemihydrate (DR-3355), in healthy male volunteers enrolled in three separate randomized crossover studies. Study 1 used 100-mg doses of DR-3355 and concurrent doses of aluminum hydroxide (1 g) or magnesium oxide (500 mg), while study 2 used DR-3355 (100 mg) and concurrent ferrous sulfate (160 mg) or calcium carbonate (1 g). Study 3 used DR-3355 (100 mg) and concurrent ranitidine (150 mg). Each study included control doses of DR-3355 (100 mg) alone. When aluminum hydroxide, ferrous sulfate, and magnesium oxide were coadministered with DR-3355, the relative bioavailability of DR-3355 was decreased to 56, 81, and 78%, respectively, of that for DR-3355 (100 mg) alone. Urinary excretion of DR-3355 was also significantly decreased by coadministration of these drugs. Thus, the magnitude of the decrease in the area under the concentration-time curve for DR-3355 varied among antacids, and the ranking of their inhibitory effects correlated with previously reported rankings of stability constants for chelate formation. DR-3355 bioavailability was not influenced by the concurrent administration of calcium carbonate and ranitidine, indicating that changes in gastric pH do not affect DR-3355 absorption.

Adult↗
PubMed1992

Species-related stereoselective disposition of ofloxacin in the rat, dog and monkey.

1. The stereoselective disposition of ofloxacin (OFLX) was studied in rats, dogs and monkeys after oral administration of racemic OFLX. 2. In rats serum concentrations of (R)-(+)-OFLX were much greater than those of (S)-(-)-OFLX, which is the active form of OFLX. In monkeys, by contrast, serum concentrations of (S)-(-)-OFLX predominated over (R)-(+)-OFLX levels. In dogs there were no differences in AUC or Cmax between the enantiomers. Thus, there exists a species-related difference in the stereoselective disposition of OFLX. 3. In rats the stereoselective differences were mainly due to stereoselective glucuronidation; OFLX is hardly metabolized in dogs, monkeys and humans. 4. In monkeys the AUC of (S)-(-)-OFLX was increased by co-administration of the (R)-(+)-form, indicating that the stereoselectivity of OFLX disposition in monkeys may be caused by competition between the enantiomers for renal excretion, especially for renal tubular secretion.

Administration, Oral↗
PubMed1991

Simple isocratic high-performance liquid chromatographic method for measurement of iodixanol in human plasma.

A simple isocratic high-performance liquid chromatographic method was developed for the determination of iodixanol in human plasma. Samples containing an internal standard were prepared for analysis using a simple clean-up procedure based on Sep-Pak C18 solid-phase extraction and chromatographed using a size-exclusion column with purified water as a mobile phase. The iodixanol peak was completely separated from the peaks of an internal standard and endogenous substances on this column. Three geometric isomers (exo-exo, endo-exo and endo-endo forms) of iodixanol could be eluted as a single peak. The method was found to be applicable to pharmacokinetic studies of iodixanol in human plasma.

Chromatography, High Pressure Liquid↗
PubMed1991

High-performance liquid chromatographic determination of (S)-(-)-ofloxacin and its metabolites in serum and urine using a solid-phase clean-up.

A sensitive and selective method for the simultaneous determination of (S)-(-)-ofloxacin [(S)-(-)-OFLX] and its metabolites in serum and urine was developed using isocratic high-performance liquid chromatography with a specific solid-phase extraction procedure. (S)-(-)-OFLX and its metabolites, desmethyl-(S)-(-)-OFLX and (S)-(-)-OFLX N-oxide, were eluted from a C8 solid-phase column with recoveries of more than 98%. These compounds were separated and determined by means of a reversed-phase column with fluorimetric detection. Validation studies showed that the results were linear for (S)-(-)-OFLX in serum over the range 10-1200 ng/ml and in urine over the range 1-200 micrograms/ml. Analysis for (S)-(-)-OFLX and its metabolites showed good precision and accuracy with a relative standard deviation of less than 6%.

Chromatography, High Pressure Liquid↗
PubMed1991

Enantioselective disposition of ofloxacin in humans.

The enantioselective disposition of ofloxacin (OFLX) was studied in healthy subjects after oral administration of (+/-)-OFLX at a dose of 200 mg. S-(-)-OFLX and R-(+)-OFLX concentrations in serum and urine were measured separately by high-performance liquid chromatography, and various pharmacokinetic parameters were calculated from the data. The ratio of S-(-) to R-(+) enantiomer concentrations in serum showed a increase with time, with S/R ratios of 1.01 at 2 h and 1.31 at 24 h. The terminal elimination half-life of S-(-)-OFLX was 6.9 h, which was significantly greater (P less than 0.05) than that of the R-(+) enantiomer (6.3 h). S-(-)-OFLX also revealed a significantly greater area under the concentration-time curve in serum, mean residence time, and total body clearance than the R-(+) enantiomer did. The renal clearance of S-(-)-OFLX (7.14 liters/h/1.73 m2) was significantly lower than that of the R-(+) enantiomer (7.53 liters/h/1.73 m2). Although the difference in the pharmacokinetic parameters of the enantiomers was small, their disposition in humans was found to be stereoselective. The difference between the enantiomers may be explained by the difference in their renal excretion.

Administration, Oral↗
PubMed1991

Identification of the metabolites of irinotecan, a new derivative of camptothecin, in rat bile and its biliary excretion.

1. To investigate the metabolites and biliary excretion of new camptothecin analogue, irinotecan, the drug was administered i.v. to rats (10 mg/kg) and bile, urine and faeces were collected. 2. In rat bile, unchanged irinotecan, the metabolite 7-ethyl-10-hydroxycamptothecin (EHCPT) and unknown metabolite M-1 were found by t.l.c. and h.p.l.c. From beta-glucuronidase hydrolysis, n.m.r. spectrometry and mass spectrometry, M-1 was identified as EHCPT-glucuronide (EHCPT Glu). Other metabolites in the bile were negligible. 3. The cumulative biliary and urinary excretion of radioactivity after dosage of rats with irinotecan were 62.2% and 33.3% dose, respectively, and 9.0% of the radioactivity was excreted in the faeces. 4. Approx. 55% of the biliary radioactivity excreted in 24 h was unchanged irinotecan, 22% was EHCPT Glu, and 9% was EHCPT. 5. Approx. 18% of the biliary radioactivity was reabsorbed from the intestine.

Animals↗
PubMed1990

Pharmacokinetics of midaglizole, a new hypoglycaemic agent, in healthy subjects.

The objective of this study was to evaluate the pharmacokinetics of midaglizole, a new orally effective hypoglycaemic agent, in healthy male subjects. In Study I, volunteers were given single oral doses of 150, 200, 300, and 500 mg of midaglizole 20 min before breakfast. In Study II, 200 mg of midaglizole was given 30 min after breakfast. In Study III, multiple oral administration study was carried out at a dose of 200 mg t.i.d. 20 min before meals for 7 days. The disposition of midaglizole was adequately described by a one-compartment open model with first order absorption. It was essentially dose-dependent up to 500 mg given orally. The pharmacokinetic parameters calculated by employing this model indicated that the disposition of this drug was characterized by good absorption from the intestine, a wide distribution in the body, and a rapid excretion via the kidneys. The absorption rate of midaglizole from the intestine was definitely slowed by the presence of food, probably due to a decrease in the rate of gastric emptying. No clinical significant accumulation of midaglizole in the body was observed during or after multiple doses. A linear correlation was found between the area under the curve of plasma concentration of midaglizole versus time and the area calculated from the curve of change in blood glucose level versus time after oral administration of midaglizole.

Adult↗
PubMed1990

Assay and disposition of carvedilol enantiomers in humans and monkeys: evidence of stereoselective presystemic metabolism.

Carvedilol is a new beta-blocking agent with vasodilating activities, which is a racemic mixture of R(+)- and S(-)-enantiomers. Since the two enantiomers differ in pharmacological properties, it is necessary to individually measure their plasma concentrations in order to evaluate the pharmacological effects of racemic carvedilol after oral administration. In this study, a sensitive, stereospecific high-performance liquid chromatographic assay was used to determine the plasma concentration of each enantiomer. The assay involves the diastereomeric derivatization of racemic carvedilol with 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate as a chiral reagent. After oral administration of racemic carvedilol to humans, the mean Cmax and AUC infinity values for R(+)-enantiomer were 2.6 and 2.8 times greater, respectively, than those for the more active S(-)-enantiomer. Similarly, in monkeys, the respective R:S enantiomer ratios for Cmax and AUC infinity were 1.5 and 1.2. The difference in AUCoral between these enantiomers is ascribed to the greater intrinsic clearance of S(-)-enantiomer than that of the R(+)-enantiomer in the liver, and to a lower plasma protein binding of the S(-)-enantiomer.

Adrenergic beta-Antagonists↗
PubMed1990

The pharmacokinetics and pharmacodynamics of a new thromboxane synthetase inhibitor, 6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid (DP-1904) in man after repeated oral doses.

The pharmacokinetics of DP-1904, a new potent and selective thromboxane synthetase inhibitor, and its effects on ex-vivo prostanoid formation have been studied in groups of Japanese normal male volunteers, who received repeated oral doses of 200 mg every 12 h for 4 doses, or 400 mg every 24 h for 2 doses, or 200 mg every 12 h for 14 doses. The drug was well tolerated by all subjects without evidence of adverse reactions. Repeated administration showed no significant changes in half-lives, tmax values, cmax values and AUC values. DP-1904 did not exhibit time-dependent kinetics. Its plasma levels were lower than the quantifiable level (50 ng mL-1) at 12 h after each dose. These data suggest no significant accumulation of DP-1904 in normal volunteers. DP-1904 reduced the serum thromboxane B2 by about 80% during the medication, the serum concentrations returning to about 44, 75 and 20% of the predrug control values at 36 h after the last 200 mg doses and 48 h after the last 400 mg dose.

Administration, Oral↗
PubMed1990

Identification of a dithiol intermediate metabolite of malotilate in rats.

1. A chemically unstable dithiol intermediate metabolite of malotilate was identified by g.l.c.-mass spectrometry after conversion of the dithiol to a stable derivative by a cyclization reaction with 1,3-dichloroacetone. The dithiol, namely, 2,2-di(isopropoxycarbonyl)ethylene-1,1-dithiol, was present in rat liver at low concentrations. 2. A study of glucuronidation in vitro indicated that the dithiol was converted to the corresponding thio-glucuronide by rat hepatic microsomal enzymes. 3. It was thus confirmed that metabolism of malotilate proceeds via the dithiol intermediate to form the thio-glucuronide, which is a major metabolic pathway.

Animals↗
PubMed1990

Identification of two major biliary metabolites of carvedilol in rats.

1. After separate administration of R(+)-carvedilol, S(-)-carvedilol and (+/-)-14C-carvedilol to rats at an oral dose of 10 mg/kg, the metabolic pattern in the bile was studied using h.p.l.c. with radioactivity and u.v. monitoring. 2. Two major metabolites, M-1 and M-2, present in the bile, accounted for 39% and 22% dose, respectively. 3. M-1 and M-2 were characterized as 1-hydroxycarvedilol O-glucuronide and 8-hydroxycarvedilol O-glucuronide, respectively, from FAB-mass spectrometry, 1H-n.m.r. and enzymic hydrolysis. 4. Oral administration of R(+)-carvedilol led to highly selective excretion of M-1 in bile whereas S(-)-carvedilol resulted predominantly in excretion of M-2 rather than M-1.

Administration, Oral↗
PubMed1990

Disposition and effect of the new thromboxane synthetase inhibitor 6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid in man.

The disposition of a new thromboxane synthetase inhibitor, 6-(1-imidazolylmethyl)-5,6,7,8-tetrahydronaphthalene-2-carboxylic acid (DP-1904) upon administration of a single 200-mg oral dose to normal Japanese volunteers was studied. DP-1904 proved to be rapidly absorbed from the gastrointestinal tract and converted to its ester glucuronide, which appeared in plasma within 30 min after dosing. The AUCs of DP-1904 and its ester glucuronide were 7.23 +/- 0.54 and 7.93 +/- 0.86 micrograms.h/ml (mean +/- S.E., n = 5), respectively. Both compounds were also eliminated very rapidly from the body (half-lives greater than 60 min). The primary route of elimination was renal, with 52.1 +/- 2.2 and 37.6 +/- 1.6% of the dose being excreted in the urine as the unchanged form and the glucuronide conjugate within 48 h, respectively. The cumulative fecal excretion rates of DP-1904 up to 48 h after dosing were approximately 0.5%. The main metabolite of DP-1904 in humans was DP-1904 glucuronide. Serum thromboxane (TX) B2 levels were reduced more than 98% within 1 h after dosing. There was still more than 75% suppression of serum TXB2 levels at 12 h after dosing. At 72 h TXB2 concentrations returned to control levels. These data indicate that DP-1904 is a potent and long-acting thromboxane synthetase inhibitor.

Adult↗
PubMed1989

Isolation and characterization of a new thio-glucuronide, a biliary metabolite of malotilate in rats.

1. The metabolism of malotilate, possessing a 1,3-dithiole ring, was studied in rats. A major biliary metabolite of malotilate was isolated and determined to be a thio-glucuronide of the dithiol formed by ring-opening, namely, 1-mercapto-2,2-di(isopropoxycarbonyl)-ethenyl 1-thio-beta-D-glucosiduronic acid. The structure was elucidated by proton-n.m.r., 13C-n.m.r. and high-resolution mass spectrometry. 2. The thio-glucuronide was completely hydrolysed by beta-glucuronidase. This enzymic reaction was inhibited by saccharo-1,4-lactone.

Animals↗
PubMed1989

Metabolic fate of the oral hypoglycaemic agent, midaglizole, in rats.

1. The metabolic fate of midaglizole, 2-[2-(4,5-dihydro-1H-imidazole-2-yl)-1-phenylethyl]pyridine dihydrochloride sesquihydrate, was studied in rats after a single oral dose of 10 mg/kg. 2. After oral administration of 14C-midaglizole to rats, 63% of the dose was excreted in the urine and 41% in the faeces within 72 h. The major radioactive compound in the urine was unchanged midaglizole and accounted for 38.1% of the dose. In the faeces, two major radioactive compounds, M-VII and unchanged midaglizole, were present. These accounted for 17.2 and 14.1% of the dose, respectively. M-VII is a new metabolite, identified as 2-[2-(4,5-dihydro-1H-imidazole-2-yl)-1-(4-hydroxyphenyl)ethyl]pyridine by n.m.r. and mass spectrometry. 3. The biliary excretion of the radioactivity after oral administration of 14C-midaglizole to bile-duct cannulated rats amounted to 53% of the dose. Of the total amount of radioactivity excreted in the bile, 48% was calculated to be subject to enterohepatic recycling. 4. Four biliary metabolites were new metabolites and were identified by n.m.r., mass spectrometry and enzymic hydrolysis. These compounds are 2-[2-(4,5-dihydro-1H-imidazole-2-yl)-1-(4-hydroxyphenyl)-ethyl]pyridine O-glucuronide (M-XI), 2-[2-(4-hydroxyphenyl)-2-(2-pyridyl)]ethyl-2-imidazole O-glucuronide (M-XII),3-(4-hydroxyphenyl)-3-(2-pyridyl)propioimidamide O-glucuronide (M-XIII) and 2-[2-(4,5-dihydro-1H-imidazole-2-yl)-1-(4-hydroxy- 3-methoxyphenyl)ethyl]pyridine O-glucuronide (M-XIV). These glucuronides accounted for 35.4% of the dose. 5. Midaglizole was metabolized in rats mainly via phenyl ring para-hydroxylation followed by glucuronidation, with or without the biotransformation of the imidazoline ring moiety.

Animals↗
PubMed1987

Identification of the metabolites of a new hypoglycaemic agent, midaglizole, in dogs.

1. The metabolism of a new hypoglycaemic agent, midaglizole, was studied. Six major metabolites were isolated from the urine of dogs dosed with 14C-midaglizole. The structures of these metabolites were elucidated by n.m.r., i.r., u.v. and mass spectrometry, and confirmed by comparison with synthesized authentic samples. 2. For midaglizole, oxidation on the imidazoline ring and subsequent ring-opening were the major metabolic pathways in dogs. 3. Two metabolites, namely, the imidazole analogue (M-I) and amidine analogue (M-III), had hypoglycaemic activity.

Animals↗