The metabolism of clomethiazole in gerbils and the neuroprotective and sedative activity of the metabolites

A single dose of clomethiazole (600 micromol kg(-1) i.p.) has previously been shown to be neuroprotective in the gerbil model of global ischaemia. In gerbils, clomethiazole (600 micromol kg(-1)) injection produced a rapid appearance (peak within 5 min) of drug in plasma and brain and similar clearance (plasma t(1/2): 40 min) from both tissues. The peak brain concentration (226+/-56 nmol g(-1)) was 40% higher than plasma. One major metabolite, 5-(1-hydroxyethyl-2-chloro)-4-methylthiazole (NLA-715) and two minor metabolites 5-(1-hydroxyethyl)-4-methylthiazole (NLA-272) and 5-acetyl-4-methylthiazole (NLA-511) were detected in plasma and brain. Evidence suggested that clomethiazole is metabolized directly to both NLA-715 and NLA-272. Injection of NLA-715, NLA-272 or NLA-511 (each at 600 micromol kg(-1)) produced brain concentrations respectively 2.2, 38 and 92 times greater than seen after clomethiazole (600 micromol kg(-1)). Clomethiazole (600 micromol kg(-1)) injected 60 min after a 5 min bilateral carotid artery occlusion in gerbils attenuated the ischaemia-induced degeneration of the hippocampus by approximately 70%. The metabolites were not neuroprotective at this dose. In mice, clomethiazole (600 micromol kg(-1)) produced peak plasma and brain concentrations approximately 100% higher than in gerbils, drug concentrations in several brain regions were similar but 35% higher than plasma. Clomethiazole (ED(50): 180 micromol kg(-1)) and NLA-715 (ED(50): 240 micromol kg(-1)) inhibited spontaneous locomotor activity. The other metabolites were not sedative (ED(50) >600 micromol kg(-1)). These data suggest that the neuroprotective action of clomethiazole results from an action of the parent compound and that NLA-715 contributes to the sedative activity of the drug. British Journal of Pharmacology (2000) 129, 95 - 100

The effects of ketoconazole on ziprasidone pharmacokinetics--a placebo-controlled crossover study in healthy volunteers

AIMS

To assess the effects of multiple oral doses of ketoconazole on the single-dose pharmacokinetics of oral ziprasidone HCl.

METHODS

This was a 14-day, open-label, randomized, crossover study in 14 healthy subjects aged 18-31 years. Group 1 received oral ketoconazole 400 mg once daily for 6 days, followed by a 2 day wash-out period and 6 days of placebo administration. Group 2 received placebo followed by ketoconazole. Single oral doses of ziprasidone HCl 40 mg were administered on days 5 and 13 in both groups. Ziprasidone pharmacokinetic parameters were compared between placebo and ketoconazole administration periods.

RESULTS

Co-administration of ziprasidone with ketoconazole was associated with a modest increase in ziprasidone exposure; mean ziprasidone AUC(0,infinity) increased by 33%, from 899 ng ml(-1) h with placebo to 1199 ng ml(-1) h with ketoconazole. Mean Cmax increased by 34%, from 89 ng ml(-1) to 119 ng ml(-1), respectively. The treatment effect on both of these parameters was statistically significant (P<0.02). Most adverse events were of mild intensity. There were no serious adverse events, laboratory abnormalities, abnormal ECGs, or clinically significant alterations in vital signs throughout the study.

CONCLUSIONS

The concurrent administration of ketoconazole and ziprasidone led to modest, statistically significant increases in ziprasidone exposure, although the changes seen were not considered clinically relevant. This suggests that other inhibitors of CYP3A4 are unlikely to significantly affect the pharmacokinetics of ziprasidone.

Single- and multiple-dose pharmacokinetics of ziprasidone in healthy young and elderly volunteers

AIMS

To compare the pharmacokinetics of ziprasidone in healthy young (18-45 years) men and women, and healthy elderly (> or = 65 years) men and women.

METHODS

Eight young men, 11 young women, 8 elderly men and 8 elderly women were given oral ziprasidone 40 mg day(-1), in two evenly divided daily doses, for 7 days, followed by a single 20 mg dose on day 8. Serum samples were collected immediately before the morning dose on days 1-8, for up to 12 h after dosing on day 1 and for up to 96 h after dosing on day 8. The resulting data were used to derive pharmacokinetic parameters of ziprasidone in each age and gender group.

RESULTS

Steady-state serum concentrations of ziprasidone were achieved within 2-3 days. The steady-state pharmacokinetics of ziprasidone, determined 8 days after the initiation of treatment, were similar in the young men, elderly men and young women. Assessment of gender effects by analysis of variance revealed statistically significant differences in Cmax (85 vs. 69 ng ml(-1) and tmax (3.19 vs. 4.81 h) but no differences in AUC(0,12 h) or lambda(z). Assessment of age effects by analysis of variance revealed statistically significant differences in AUC(0,12 h) (560 vs. 465 ng ml(-1) h), Cmax (85 vs. 69 ng ml(-1) and lambda(z) (0.126 vs. 0.197 l h(-1) but no difference in tmax. Assessment of age and gender effects by analysis of covariance, with body weight as the covariate, did not reveal any significant differences. The mean t(1/2), z in the young men, young women, elderly men and elderly women were 3.1, 4.1, 5.7 and 5.3 h, respectively. Standard deviations of the means for the pharmacokinetic parameters for the elderly women tended to be large.

CONCLUSIONS

The influence of age and gender on the pharmacokinetics of ziprasidone is not clinically significant.

Pharmacokinetics of orally administered desferrithiocin analogs in cebus apella primates

The pharmacokinetic behavior of three iron chelators based on the desferrithiocin (DFT) pharmacophore, (S)-4, 5-dihydro-2-(2-hydroxyphenyl)-4-thiazolecarboxylic acid (desmethyldesferrithiocin, DMDFT, 2); (S)-4,5-dihydro-2-(2, 4-dihydroxyphenyl)-4-thiazolecarboxylic acid [4-(S)-hydroxydesazaDMDFT, 3); and (R)-2-(2-hydroxyphenyl)-4-oxazolinecarboxylic acid, the oxazoline analog of desazaDMDFT, 4, is described. Although 2 and 3 are comparably effective in inducing iron excretion upon oral administration, they exhibit markedly different plasma pharmacokinetics. Ligand 2 achieves a substantially higher plasma concentration than does 3, yet the renal clearance of these compounds is similar. The oxazoline analog 4 shows poor iron clearance when administered orally, although it remains in the plasma for extended periods. Chelator 4 demonstrates a marked capacity to bind to human serum albumin compared with the thiazoline derivatives. The possible implications for designing ligands for the treatment of transfusional iron overload are discussed.

Binding study of semotiadil and levosemotiadil with alpha(1)-acid glycoprotein using high-performance frontal analysis

High-performance frontal analysis (HPFA) was used to investigate the binding properties of human alpha(1)-acid glycoprotein (AGP) with semotiadil ((R)-isomer, Ca-channel blocker) and its antipode levosemotiadil ((S)-isomer, Ca- and Na-channel blockers). An on-line HPLC system consisting of a HPFA column, an extraction column, and an analytical HPLC column was used to determine the unbound concentrations of these enantiomers, and the experimental data were subsequently subjected to the Scatchard analyses to estimate their binding parameters. The binding affinity of the (R)-isomer (K = 3.17 x 10(7) M, n = 0.74) is approximately 1.2 times stronger than that of (S)-isomer (K = 2.59 x 10(7) M, n = 0.74). An enantioselective competitive binding study indicated that both enantiomers are bound at the same site on AGP molecules.

Analysis of 2-(3-methyl-4-aminophenyl)-benzothiazole (NSC 674495) in plasma by gas chromatography with mass-selective detection

Certain naturally occurring isoflavonoids have been shown to inhibit protein-tyrosine kinases, and this has led to investigations of ring-modified structural analogs. Most recently, 2-(3-methyl-4-aminophenyl)-benzothiazole (MAB: NSC 674495) was shown to possess significant activity against certain breast cell cancer lines in vitro and in vivo. Our efforts thus focussed on developing a simple and sensitive method for quantitating MAB in plasma using GC-MS. The GC-MS assay was found to be linear over the range of 0.050 to 5.0 microg/ml, and was applied to monitor the plasma concentration of MAB in a rat dosed with 25 mg/kg as a 1 min intravenous infusion. Plasma was collected at intervals from 3 through 180 min, and concentrations of MAB were determined. Non-linear regression analysis of the plasma concentration-time data revealed that levels declined from a maximum at 3 min of 18 microg/ml to 1 microg/ml at 3 h in a biphasic manner. In another investigation, significant plasma concentrations of a major metabolite was detected and determined to be mono-N-acetylated MAB.

Steady-state pharmacokinetics and dose proportionality of troglitazone and its metabolites

This study evaluated the steady-state pharmacokinetics and dose proportionality of troglitazone, metabolite 1 (sulfate conjugate), and metabolite 3 (quinone metabolite) following administration of daily oral doses of 200, 400, and 600 mg troglitazone for 7 days (per dosing period) to 21 subjects. During each dosing period, plasma samples were collected predose on days 1, 5, 6 and 7 and serially for 24 hours on day 7. Steady-state plasma concentrations for troglitazone, metabolite 1, and metabolite 3 were achieved by day 7. Troglitazone was rapidly absorbed with mean tmax values of 2.7 to 2.9 hours. Mean Cmax and AUC(0-24) values for troglitazone, metabolite 1, and metabolite 3 increased proportionally with increasing troglitazone doses over the clinical dose range of 200 mg to 600 mg administered once daily. Mean troglitazone CL/F, percent fluctuation, and AUC ratios of metabolite 1 and metabolite 3 to troglitazone were similar across dose groups. These data suggest that the pharmacokinetics and disposition of troglitazone and its metabolites are independent of dose over the dose range studied. Thus, troglitazone, metabolite 1, and metabolite 3 displayed linear pharmacokinetics at steady-state.

Dose-dependent inhibition of platelet cyclooxygenase-1 and monocyte cyclooxygenase-2 by meloxicam in healthy subjects

We evaluated whether therapeutic blood levels of meloxicam are associated with selective inhibition of monocyte cyclooxygenase (COX)-2 in vitro and ex vivo. Concentration-response curves for the inhibition of monocyte COX-2 and platelet COX-1 were obtained in vitro after the incubation of meloxicam with whole blood samples. Moreover, 11 healthy volunteers received placebo or 7.5 or 15 mg/day meloxicam, each treatment for 7 consecutive days, according to a randomized, double-blind, crossover design. Before dosing and 24 h after the seventh dose of each regimen, heparinized whole blood samples were incubated with lipopolysaccharide (10 microgram/ml) for 24 h at 37 degrees C, and prostaglandin E2 was measured in plasma as an index of monocyte COX-2 activity. The production of thromboxane B2 in whole blood allowed to clot at 37 degrees C for 60 min was assessed as an index of platelet COX-1 activity. The administration of placebo did not significantly affect plasma prostaglandin E2 (21. 3 +/- 7.5 versus 19.1 +/- 4 ng/ml, mean +/- S.D., n = 11) or serum thromboxane B2 (426 +/- 167 versus 425 +/- 150 ng/ml) levels. In contrast, the administration of 7.5 and 15 mg of meloxicam caused dose-dependent reductions in monocyte COX-2 activity by 51% and 70%, respectively, and in platelet COX-1 activity by 25% and 35%, respectively. Although the IC50 value of meloxicam for inhibition of COX-1 was 10-fold higher than the IC50 value of COX-2 in vitro, this biochemical selectivity was inadequate to clearly separate the effects of meloxicam on the two isozymes after oral dosing as a function of the daily dose and interindividual variation in steady-state plasma levels.

A new CYP2A6 gene deletion responsible for the in vivo polymorphic metabolism of (+)-cis-3,5-dimethyl-2-(3-pyridyl)thiazolidin-4-one hydrochloride in humans

(+)-Cis-3,5-dimethyl-2-(3-pyridyl)thiazolidin-4-one hydrochloride (SM-12502) is a newly developed drug as a platelet-activating factor receptor antagonist. The disposition of SM-12502 was investigated in plasma from 28 healthy Japanese volunteers after a single i.v. administration of SM-12502. Three of 28 subjects were phenotyped as poor metabolizers (PMs). Genomic DNAs from three extensive metabolizers or three PMs of SM-12502 were analyzed by Southern blot analysis with CYP2A6 cDNA as a probe. DNAs from three PMs digested with SacI and SphI showed novel restriction fragment length polymorphisms (RFLPs); one type without 4.5- and 2.6-kb fragments and a weak density of a 6.4-kb fragment (E-type), and the other type without 7.1- and 5.5-kb restriction fragments (C'-type) as compared with three extensive metabolizers, respectively. The deletional restriction fragments specific to three PMs in SacI- and SphI-RFLPs were identified as CYP2A6. Using polymerase chain reaction-RFLP analyses of the gene from the three PMs, we found that the exon 1, exon 8, and exon 9 in CYP2A6 were absent. A new RFLP characterized by SacI and SphI was found to be due to the entire gene deletion of the three exons and was associated with the decreased metabolism of SM-12502. This study demonstrates a new deletional allele in the human CYP2A6 gene responsible for the poor metabolic phenotype of SM-12502.

Pharmacokinetic analysis and antitumor efficacy of MKT-077, a novel antitumor agent

MKT-077 (1-ethyl-2-[[3-ethyl-5-(3-methylbenzothiazolin-2-yliden)]-4- oxothiazolidin-2-ylidenemethyl] pyridinium chloride), a novel rhodacyanine dye in phase I/II clinical trials, may provide a new approach to cancer therapy based on the accumulation in the mitochondria of the cells of certain carcinomas, for example, those of the colon, breast and pancreas. To support the development of MKT-077 for clinical application as an intravenous (i.v.) therapy, we investigated the metabolic fate of [14C]MKT-077 in BDF1 mice as well as the distribution of MKT-077 in experimental LS174T tumor-bearing mice using a high-performance liquid chromatography (HPLC) method. The plasma levels of 14C after i.v. administration of [14C]MKT-077 declined in a triphasic manner. In the first distribution phase, the levels of 14C decreased with a T1/2 of approximately 5 min. In the second and terminal phase, the T1/2 of 14C was 2.8-4.6 h and 16.2 h, respectively. Cmax (1 min after injection) increased from 0.3 to 1.5 microg/ml linearly, but less than proportionately between the doses. The AUC(0-infinity) at 0.3, 1 and 3 mg/kg were 0.030 +/- 0.002, 0.60 +/- 0.12 and 1.73 +/- 0.25 microg x h/ml, respectively. Plasma clearance was approximately 1.8 l/h per kg (at doses of 1 and 3 mg/kg). The steady state volume of distribution (6.8 and 25.1 l/kg) indicated that MKT-077 distributed as a lipid-soluble molecule. The mean residence time (MRT) was 4.1 (at a dose of 1 mg/kg) and 14.1 h (at a dose of 3 mg/kg). In the first rapid phase (5 min after dosing), 14C radioactivity was detected in most of the tissues and organs, most strongly in the kidney cortex, and not in the central nervous system and testes. In the terminal phase (24 h after dosing), 14C contents increased in the intestinal tract, and in the kidney and liver were nearly to the background level. After i.v. bolus administration at a dose of 3 mg/kg of [14C]MKT-077, the predominant route of elimination of the radioactivity was via the feces, and recoveries of total radioactivity in urine and feces corresponded to 33.5% and 61.1%, respectively. More than 60% was recovered within 24 h and 95% within 1 week. MKT-077 was primarily excreted in unmetabolized form with five unidentified metabolites found in the urine and plasma. Intact MKT-077 was retained in the tumor tissue longer than in plasma and kidney in LS174T tumor-bearing mice receiving MKT-077 at an i.v. therapeutic dose (10 mg/kg). This accumulation decreased very slowly, suggesting that the high membrane potentials of tumor cell mitochondria may help retain the drug in tumors.

Systemic exposure to rosiglitazone is unaltered by food

OBJECTIVE

To evaluate the effect of food on the bioavailability and pharmacokinetics of the insulin sensitizer rosiglitazone.

METHODS

In a randomized, open-label, period-balanced, single-dose, crossover study, rosiglitazone 2 mg was administered to 12 healthy male volunteers either in the fasting state or following a standard high-fat breakfast. The primary end points of the study were AUC(0-inf) and Cmax.

RESULTS

Single oral doses of rosiglitazone were safe and well tolerated. Overall exposure to rosiglitazone was unaffected by food. The geometric mean ratio of AUC(0-inf) in the fed:fasted regimens was 0.94 (95% CI: 0.82, 1.06); t1/2 was unaffected. Absorption of rosiglitazone in the fed state was more gradual and sustained than in the fasted state. Cmax was reduced by approximately 20% (point estimate 0.80; 95% CI 0.65 to 0.97) and tmax was modestly delayed in the fed state.

CONCLUSION

These data support dosing guidelines that will permit the administration of rosiglitazone without regard to meals for treatment of type 2 diabetes mellitus.

Determination of MKT-077, a novel antineoplastic agent, in plasma samples by high-performance liquid chromatography and its application to pharmacokinetics in rats

A simple high-performance liquid chromatographic method was developed for determination of a novel antineoplastic agent MKT-077 in plasma. MKT-077 was extracted from 50 microl of plasma with acetonitrile containing 1 ml trifluoroacetic acid per liter. Chromatographic separation was achieved within 13.5 min using a reverse-phase Puresil C18 analytical column. A visible detector operated at 490 nm was used. The linearity of the calibration curve was obtained (r2 = 0.99986) over the analytical range of 10-500 ng/ml(-1). The intra- and inter-assay precision was in the range of 0.9-11.1 and 0.3-4.4%, respectively. The intra- and inter-assay bias ranged from -7.3 to 11.1% and from 0.4 to 11.6%, respectively. The utility of this assay was demonstrated after the administration of a single dose of MKT-077 to rats. The plasma elimination half-life of MKT-077 was 1.8-4 h.

[Pharmacodynamic and pharmacokinetic aspects of the non-inflammatory non-steroidal agent meloxicam in dogs]

The pharmacodynamics of non-steroidal anti-inflammatory drugs (NSAIDs) are for the most part well-understood. All NSAIDs inhibit the enzyme cyclooxygenase (COX), and for this reason prostaglandin synthesis. Two isoforms of COX could be isolated. COX-1 is detectable in most tissues on a constant level and is responsible for the synthesis of prostaglandins with cytoprotective effects. COX-2 is induced through inflammation and supports the inflammatory process by producing pro-inflammatory prostaglandins. The desired effects of NSAIDs are related to inhibition of COX-2, whereas inhibition of COX-1 has been linked to the typical side-effects of NSAIDs, especially in the stomach and kidney. The great differences between effects and side-effects in the numerous substances can be explained because of different interactions of the NSAIDs on COX-1 and COX-2. In various test systems meloxicam has been shown to be a preferential inhibitor of COX-2. There are also large differences between the individual NSAIDs with regard to pharmacokinetics. Meloxicam is completely absorbed from the gastrointestinal tract and has an elimination half-life of 24 hours in the dog. It is excreted in faeces and urine. The metabolites, detectable in urine are biologically inactive and do not influence the prostaglandin synthesis in the kidney. In the underlying study, plasma concentration of meloxicam was determined after a subcutaneous injection of 0.2 mg/kg b. w. (day 1) followed by oral treatment of 0.1 mg/kg b. w. (days 2-14). The results confirm the recommended dosage regime of meloxicam with its initial loading dose and the subsequent maintenance dose. This dosing regime results in a very favourable curve of concentrations with a very rapidly attained steady state after roughly two days, without accumulation even in long-term treatment.

Antiischemic effects of CP-060S, an inhibitor of pathologically modified sodium channels, assessed in the canine experimental model of angina pectoris

CP-060S is a novel compound that can inhibit the slow inward calcium current as well as the veratridine-induced, noninactivating sodium current. Antiischemic and cardiovascular effects of CP-060S were assessed by using halothane-anesthetized beagle dogs and compared with the effects of semotiadil, a benzothiazine calcium antagonist. The first or second diagonal branch was narrowed. ECG, unipolar electrograms from both ischemic and nonischemic regions, and systemic and left ventricular pressure were monitored. The left ventricle was electrically driven at 190-240 beats/min for 3 min to induce reversible myocardial ischemia. The severity of ischemia was judged by the magnitude of ST-segment depression. CP-060S (0.1 mg/kg, i.v.) significantly attenuated the pacing-induced ST-segment depression in the ischemic region >2 h, whereas during the sinus rhythm, it showed reversible negative chronotropic, inotropic, and dromotropic effects and induced transient depressor response, which would not necessarily be considered favorable (n = 8). A smaller dose of CP-060S (0.03 mg/kg, i.v.) showed a similar antiischemic and cardiovascular profile, but each effect was less potent than that of the higher dose (n = 7). Semotiadil (0.1 and 0.3 mg/kg, i.v.) also showed cardiovascular suppression similar to that of CP-060S; however, the antiischemic effect was not detected during the whole experimental period (n = 6). Thus the inhibition of the noninactivating sodium current may be the primary reason for the antiischemic effect of CP-060S and could become a new cytoprotective principle in the treatment of patients with ischemic heart disease.

Investigation of serum minimal inhibitory concentrations of some benzimidazole, imidazole and benzothiazole derivatives and their effects on liver and renal functions

In previous studies many benzimidazole, imidazole and benzothiazole derivatives had been synthesized and their antimicrobial activities were tested in vitro conditions. Four of these compounds showed minimal inhibitory concentrations (MIC) of 5-25 micrograms/ml against standard strains and clinical isolates. In order to determine whether these four compounds can be used for therapeutic purpose, their serum MIC values and side effects on hepatic and renal functions were determined. Different concentrations of the compounds were tested on Wistar rats. Compound 1 was administered orally, intramuscularly and intravenously; compounds 2, 3 and 4 were given orally and intramuscularly. Blood samples were taken 4 and 24 h after administration of the compounds. Serum MIC values were investigated by bioassay and serum levels of biochemical parameters by autoanalyzer. None of the tested compounds showed antimicrobial activity at their serum concentrations. Although creatinine activity was found at normal levels in all experiments, compounds 1 and 2 caused a significant increase in blood urea nitrogen (BUN) level. The values of aspartate aminotransferase and/or alanine aminotransferase and/or alkaline phosphatase which are characteristic for liver function were generally found at high levels. According to these results, it can be concluded that the tested compounds caused damage in liver and biliary tracts without antimicrobial activity by their serum concentrations.

Bioavailability, multiple-dose pharmacokinetics, and biotransformation of the aldose reductase inhibitor zopolrestat in dogs

Zopolrestat (Alond) is a new drug that is being evaluated as an aldose reductase inhibitor for the treatment of diabetic complications. The bioavailability in dogs of a 2 mg/kg oral dose of zopolrestat was 97.2%. In a 1-year, multiple-dose, pharmacokinetic study, systemic exposure increased with increasing dose (50, 100, and 200 mg/kg/day), and there were no consistent changes in exposure with multiple dosing. Renal clearance at 1 year appeared to be higher in males. The magnitude of the potential gender difference in exposure was relatively small and was unlikely to have had a meaningful impact on the pharmacokinetics of zopolrestat in dogs. In studies with bile duct-cannulated dogs, radioactivity from [14C]zopolrestat was primarily eliminated as unchanged drug and acyl glucuronide in the bile and feces (77.3% of the dose) and in urine (18.3% of the dose). The concentrations of acyl glucuronide in urine and feces were approximately 50% of the zopolrestat concentrations. Minor metabolites (each accounting for <1% of the dose) included those resulting from hydroxylation of the phthalazinone ring and glutathione conjugation of the benzothiazole ring.

Pharmacokinetics of 2-oxothiazolidine-4-carboxylate, a cysteine prodrug, and cysteine

The pharmacokinetics of both 2-oxothiazolidine-4-carboxylate (OTZ), a prodrug of cysteine, and total blood cysteine (cysteine plus cystine) were investigated in 18 healthy volunteers. OTZ was given either as a single, 2-hour intravenous infusion (56-66 mg/kg) or similarly infused (70-100 mg/kg) every 8 hours for four doses. Blood was assayed for OTZ, total blood cysteine, and glutathione. The pharmacokinetics of OTZ were analyzed alone and simultaneously with total cysteine using the NONMEM software package (University of California at San Francisco. The pharmacokinetics of OTZ were best described by Michaelis-Menten kinetics with parallel first-order elimination. OTZ was efficiently removed from the plasma. The Michaelis-Menten route of elimination was attributed to conversion of OTZ to total cysteine. At plasma OTZ concentrations equal to the Michaelis constant Km, 84% of OTZ was converted to total cysteine. These findings suggest that OTZ administered intravenously is an efficient means of increasing total blood cysteine.

Pharmacokinetics of lubeluzole (Prosynap) after single intravenous doses in healthy subjects

The single-dose pharmacokinetics of lubeluzole were investigated in 2 single-blind, placebo-controlled, dose-escalation studies in healthy male subjects. In the first study, 6 subjects received an intravenous infusion of 2.5, 5, and 10 mg lubeluzole. In the second study, a 15 mg dose of lubeluzole was administered to 6 subjects, of whom 5 also received 20 mg and 2 also 25 mg lubeluzole. Following the infusion, plasma lubeluzole concentrations decayed biphasically, with a mean distribution half-life (t1/2alpha) of 30 to 65 minutes and a mean terminal half-life (t1/2beta) of 15 to 24 hours. The results of the 2 studies indicate that lubeluzole exhibits linear kinetics over the dose range tested in healthy male subjects.

Pharmacokinetics of troglitazone, a PPAR-gamma agonist, in patients with hepatic insufficiency

OBJECTIVE

Troglitazone is an agonist of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma), which has been shown to improve the metabolic control of type 2 diabetes. Troglitazone undergoes hepatic metabolism to an inactive sulphate conjugate and an oxidative quinone metabolite with minor activity. The objective of this study was to compare the pharmacokinetics of troglitazone in patients with hepatic insufficiency and normal subjects.

METHODS

Three groups of eight subjects with normal liver function and moderate or severe hepatic impairment (Pugh-Child classification) completed this open study. Subjects received a single 400-mg dose of troglitazone 30 min after breakfast. Plasma concentrations of troglitazone and its metabolites were measured and standard pharmacokinetic parameters derived.

RESULTS

A 46% increase in area under the plasma concentration-time curve (AUClast) was observed for troglitazone, together with a 154% increase for the quinone metabolite in the patients with moderate hepatic impairment compared with normal subjects, but these did not reach statistical significance. Corresponding increases of 18% and 53% in the severe group also failed to reach statistical significance. For the sulphate conjugate, the AUClast values for both moderate and severe hepatic impairment were in the order of fourfold higher than those in the normal group. There were reductions in the maximum observed plasma concentration (Cmax) of troglitazone to 61% of the normal group in the severe group for troglitazone, and twofold increases in sulphate metabolite Cmax in the moderate and severe groups. There was an approximately threefold increase in the half-life of the sulphate conjugate in subjects with both moderate and severe impairment of liver function compared with normal individuals. First times to maximum concentrations of troglitazone, its sulphate conjugate and the quinone metabolite were significantly longer in all severely impaired subjects compared with those with normal hepatic function, although the range was wide in all cases. Plasma protein binding was high in all subjects measured (mean unbound fraction range 0.7-5.1%), but there were insufficient samples to compare across groups.

CONCLUSION

The formation of metabolites of troglitazone following a single dose is not impaired in the presence of reduced liver function although the capacity to eliminate the metabolites is altered. The clinical significance of the effect of liver disease on the conjugates is not clear.

Elevation of whole-blood glutathione in peritoneal dialysis patients by L-2-oxothiazolidine-4-carboxylate, a cysteine prodrug (Procysteine)

Glutathione is a major cellular antioxidant that protects protein thiols and inhibits cellular damage due to oxygen free radicals. It has been reported previously that patients undergoing dialysis have low levels of blood glutathione, which may lead to increased susceptibility to oxidant stress. L-2-oxothiazolidine-4-carboxylic acid (OTZ) is a cysteine prodrug that raises cellular glutathione levels by increasing delivery of cysteine, the rate-limiting substrate for glutathione synthesis. This study investigates the effect of OTZ on blood glutathione in a blinded, placebo-controlled study of patients with chronic renal failure treated by peritoneal dialysis. Twenty patients were randomly selected to receive OTZ (0.5 g three times a day orally with meals) or placebo for 14 d. Patients visited the clinic for predose blood collection and safety evaluation at baseline (days 3, 7, and 14 and again at 14 d from the last dose [follow-up]). Glutathione concentrations were determined in whole blood by HPLC. OTZ resulted in a significant rise in whole-blood glutathione at days 7 (594 +/- 129 mumol/L) and 14 (620 +/- 108 mumol/L) compared with baseline (544 +/- 139 mumol/L) (P < 0.01 and P < 0.05, respectively). Glutathione was also significantly increased at days 7 and 14 when normalized by hematocrit (Hct) or hemoglobin to correct for anemic status (e.g., 20.7 +/- 5.7 mumol/L per % Hct [day 7] and 20.9 +/- 4.0 mumol/L per % Hct [day 14] versus 18.0 +/- 4.2 mumol/L per % Hct [baseline]; P < 0.05). Glutathione levels did not change in the placebo group at any patient visit, and levels in the OTZ-treated group returned to baseline at follow-up. There were no serious adverse events attributable to OTZ, and the drug appeared to be well tolerated by patients with renal failure treated by continuous ambulatory peritoneal dialysis. Our results show that OTZ increases blood glutathione levels, which may improve antioxidant status in dialysis patients.

Simultaneous determination of an active metabolite and open-ring metabolites by high performance liquid chromatography and pharmacokinetic studies of a penem antibiotic, FCE22891, in dogs

A sensitive high performance liquid chromatographic method for the simultaneous determination of an active metabolite (FCE22101) and open-ring metabolites (P1, P2) of a penem antibiotic, FCE22891, in dog plasma was developed. Plasma samples were pretreated only by ultrafiltration for the determination of the metabolites. The filtrates were directly analyzed by a reversed-phase high-performance liquid chromatographic system using a two-sided bracketing injection technique. The quantitation limits of FCE22101, P1 and P2 were 0.03, 0.1 and 0.15 microgram ml-1, respectively. Analysis of the spiked plasma samples demonstrated the good accuracy and precision of the method. The proposed method was applied to the pharmacokinetic studies of an active metabolite and open-ring metabolites after oral administration of a penem antibiotic, FCE22891, in dogs. In addition, the plasma levels of unchanged FCE22891 and the possible changes of formaldehyde and acyl-L-carnitine levels in plasma, which will be generated from the ester group of FCE22891, were also investigated.

High-performance liquid chromatographic determination of the insulin sensitizing agent DRF-2189 in rat plasma

A high-performance liquid chromatographic method for the determination of DRF-2189, using troglitazone as internal standard, is described. A dichloromethane-ethyl acetate solvent mixture (6:4, v/v) was used as the extraction solvent. A Kromasil C18 column with a mobile phase consisting of 0.05 M phosphate buffer-acetonitrile-methanol (22.5:37.5:40) (pH 5.0) was used at a flow-rate of 1.0 ml/min. The eluate was monitored by using fluorescence detection with excitation and emission wavelengths at 292 nm and 325 nm, respectively. Ratio of peak area of analyte to internal standard was used for quantification of plasma samples. Using this method, the absolute recovery of DRF-2189 from rat plasma was >95% and the limit of quantitation was 50 ng/ml. The intra-day relative standard deviation (R.S.D.) ranged from 1.74 to 7.24% at 1 microg/ml and 1.86 to 3.83% at 10 microg/ml. The inter-day R.S.D.s were 8.34 and 4.91% at 1 and 10 microg/ml, respectively. The method was applied to measure plasma concentrations of DRF-2189 in pharmacokinetic studies in Wistar rats.

Species differences in pharmacokinetics of a hepatoprotective agent, YH439, and its metabolites, M4, M5, and M7, after intravenous and oral administration to rats, rabbits, and dogs

Pharmacokinetic parameters of YH439 and its metabolites, M4, M5, and M7, were compared after iv administration of YH439 to rats (1-10 mg/kg), rabbits (1-10 mg/kg), and dogs (1-20 mg/kg) and oral administration of YH439 to rats (50-500 mg/kg) and dogs (0.5-2 g per whole body weight). After oral administration of YH439 to rats, the F values were 3.67, 1.33, and 0.859% for YH439 oral doses of 100, 300, and 500 mg/kg, respectively. However, the F value increased significantly, 21.2%, after oral administration of YH439-contained mixed micelles (10 mg as free YH439) to rats due to increased water solubility of YH439. Species differences in the pharmacokinetics of YH439 and its metabolites were found. First, M7 was detected in both plasma and urine after both iv and oral administration of YH439 to dogs, whereas it was detected neither in rats nor in rabbits, indicating that considerable amount of M7 was formed from YH439 only in dogs. Second, the AUC (or AUC0-->t) ratios of M4 to YH439 after iv administration of YH439 were 24.6-31.3, 42.2-49.2, and 2200-7640% for rats, rabbits, and dogs, respectively, indicating that formation of M4 after iv administration of YH439 was maximal in dogs. Third, the AUC (or AUC0-->t) ratios of M5 to YH439 after iv administration of YH439 were 103-127, 2.93-3.31, and 92.4-158% for rats, rabbits, and dogs, respectively, indicating that formation of M5 after iv administration of YH439 was minimal in rabbits.

Simultaneous determination of a new hepatoprotective agent, YH439, and its metabolites, M4, M5, and M7 in plasma and urine by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for the simultaneous determination of YH439, and its metabolites (M4, M5, and M7) in human plasma and rat urine using testosterone as an internal standard. The method involved deproteinization (plasma sample) or extraction (urine sample) followed by injection onto a C18 reversed-phase column. The mobile phase was acetonitrile-0.063 M phosphoric acidisopropyl alcohol (38:48:14, v/v/v), and the flow rate was 1.0 ml/min for the two methods. The column effluent was monitored by a UV detector set at 317 nm. The detection limits for YH439, M4, M5, and M7 in human plasma were 50, 40, 50, and 50 ng/ml, respectively, using the deproteinization method, and the corresponding values in rat urine were 50, 100, 50, and 50 ng/ml using the extraction method. No interferences from endogenous substances were found.

Lack of effect of type II diabetes on the pharmacokinetics of troglitazone in a multiple-dose study

Twelve patients with type II diabetes and 12 age-, weight-, and gender-matched healthy subjects participated in a study comparing the pharmacokinetics of troglitazone, metabolite 1 (sulfate conjugate), and metabolite 3 (quinone) after oral administration of 400 mg of troglitazone every morning for 15 days. Serial plasma samples collected after the dose on days 1 and 15 were analyzed for troglitazone, metabolite 1, and metabolite 3 using a validated HPLC method. Steady state plasma concentrations of troglitazone and its metabolites were achieved by the fifth day of troglitazone administration in both groups. Mean day 15 Cmax, tmax, AUC0-24, and Cl/F values of troglitazone were 1.54 micrograms/mL, 3.25 hours, 15.6 micrograms.hr/mL, and 461 mL/min, respectively, in patients with type II diabetes. Corresponding parameter values were 1.42 micrograms/mL, 2.63 hours, 12.5 micrograms.hr/mL, and 558 mL/min, respectively, in healthy subjects. Elimination t1/2 was approximately 24 hours in both groups. Mean day 15 pharmacokinetic parameter values for metabolite 1 and metabolite 3 were similar in the two groups. Ratio of AUC of metabolite 1 to troglitazone was 6.2 and 6.7, respectively, in patients and in healthy subjects. Ratio of AUC of metabolite 3 to troglitazone was 1.1 in both groups. Thus, steady-state pharmacokinetics and disposition of troglitazone and its metabolites in patients with type II diabetes were similar to those in healthy subjects.

Meta-analysis of steady-state pharmacokinetics of troglitazone and its metabolites

The object of this study is to evaluate the effects of age, gender, age-by-gender interaction, Type II diabetes, body weight, race, smoking, and formulation on steady-state pharmacokinetics of troglitazone, Metabolite 1 (sulfate conjugate), and Metabolite 3 (quinone metabolite) following multiple-dose oral administration of troglitazone. Pharmacokinetic parameter estimates [Cl/F (apparent oral clearance), AUC0-24 (area under plasma concentration-time curve), and ratio of AUC for troglitazone to Metabolite 1 and to Metabolite 3] obtained from 84 healthy volunteers and 171 patients with Type II diabetes in 8 studies were analyzed using a graphical method (for race and smoking) or a weighted ANCOVA model incorporating gender, health status (healthy vs Type II diabetes), and formulation as main effects; age, age-by-gender interaction, and body weight as continuous covariates. Ratio of AUC for troglitazone to metabolites was also examined by inspection of log-probit plots. Age, gender, age-by-gender, Type II diabetes, and formulation had negligible effects on troglitazone Cl/F, AUC0-24 (all analytes), and AUC ratio of troglitazone to metabolites. Race and smoking did not appear to influence steady-state pharmacokinetics of troglitazone and its metabolites. Although body weight was a significant covariate for AUC0-24 and Cl/F, the explanatory power of the overall model was weak (R2 < 0.2). Log-probit plots did not reveal a polymorphic distribution in AUC ratio of troglitazone to Metabolite 1 or Metabolite 3. Based on pharmacokinetics, dose adjustment for troglitazone in relation to the demographic factors examined is not required due to their poor predictive ability on steady-state pharmacokinetics of troglitazone and its metabolites.

Stability, blood partition, and pharmacokinetics of a new reversible proton pump inhibitor, YJA-20379-1

The pharmacokinetics of YJA-20379-1 were evaluated after intravenous (i.v.) administration to rats (10-50 mg/kg) and rabbits (10-50 mg/kg), and oral administration to rats (200 and 500 mg/kg). The stability and blood partition between plasma and blood cells were also investigated. After i.v. administration of YJA-20379-1, 10-50 mg/kg, to rats, the pharmacokinetic parameters of YJA-20379-1 were dose-independent, however, they were dose-dependent in rabbits. After oral administration of YJA-20379-1 to rats, the AUC of YJA-20379-1 seemed to increase with increasing doses (73.4 +/- 28.5 and 130 +/- 100 micrograms min/ml for 200 and 500 mg/kg, respectively). The extent of absorption after oral administration (F) was 6.47 and 4.74% for 200 and 500 mg/kg, respectively. The low F values were not due to incomplete absorption and could be due to extensive first-pass metabolism. YJA-20379-1 was unstable in pH solutions of 2-5, 12, and 13, very unstable in pH solutions of 1 and 14, however, stable in pH solutions of 6-11. YJA-20379-1 reached equilibrium rapidly between plasma and blood cells of rabbit blood at 1-5 micrograms/ml, an the mean blood cells/plasma concentration ratio was 5.24 +/- 1.21.

Absorption, distribution, metabolism and excretion of a new, 14C-labelled oxazolidinone MAO-A inhibitor in rat and dog

1. After oral administration of 14C-labelled (5R)-3-[2-((1S)-3-cyano-1-hydroxypropyl)benzothiazol-6-yl]-5-metho xymethyl -2-oxazolidinone (E2011) at a dose of 1 mg/kg, the blood level of radioactivity reached a maximum concentration (Cmax) of 0.545 microgram eq./ml after 0.25 h in the rat and of 0.900 microgram eq./ml after 0.5 h in the dog. In dog plasma, Cmax for radioactivity and unchanged E2011 were 0.862 microgram eq./ml and 0.650 microgram/ml respectively with corresponding Tmax (time at Cmax) of 0.75 and 0.25 h. The unchanged drug in dog plasma was below the detection limit (5 ng/ml plasma) after 24 h. 2. The tissue levels of radioactivity were measured at 0.25 (Tmax), 6, 24, and 168 h after administration to the rat and at 0.5 (Tmax), 24, and 168 h in the dog. The radioactivity was distributed in all tissues examined at Tmax in the rat and dog. The radioactivity levels of the cerebral cortex in the rat and dog were 26 and 36% of the plasma level at Tmax. The radioactivity in tissues decreased at almost the same rate as that in plasma. Plasma protein binding of the unchanged drug in the rat in vitro were about 70% in the range of 0.1-10 micrograms/ml, and those in the dog were about 45% in the same concentration range. 3. Cumulative excretion of radioactivity in the rat was 74.5% in urine and 22.5% in faeces after 7 days. In the dog, 55.5 and 36.5% of the radioactivity administered were excreted in urine and faeces respectively after 7 days. The biliary excretion of radioactivity in the cannulated rat was 23.0% within 48 h. 4. In tlc analysis of plasma and tissues of the rat and dog, the radioactivity for the unchanged drug was much higher than metabolites. In tlc analysis of urine, the same metabolites were detected in the rat and dog, and the radioactivity of a metabolite, IM1, was the highest in the both animals. Eight metabolites were detected in the plasma, tissues and excreta of the rat, and four metabolites in the dog. 5. In conclusion, the absorption, distribution, metabolism and excretion of 14C-labelled E2011 in the rat and dog have been established, and only minor differences were observed between these species.

High-performance liquid chromatographic assay for CI-1004, a dual-inhibitor antiinflammatory agent, in rat, rabbit, dog, monkey and human plasma

CI-1004 and PD 138389 (internal standard, I.S.), were isolated from rat, rabbit, dog, monkey and human plasma by solid-phase extraction with Bond-Elut C18 cartridges. Liquid chromatographic separation was achieved isocratically on a Zorbax Rx-C8 analytical column (250 mm x 4.6 mm I.D). The mobile phase consisted of acetonitrile-20 mM ammonium acetate (65:35, v/v), (pH 4.0). Column temperature was either 40 degrees C (human assay) or 45 degrees C and column effluent was monitored spectrophotometrically at 360 nm. Specificity, chromatographic performance parameters, system repeatability, recovery from matrix, linearity, precision, accuracy and stability were evaluated. Mean retention times (+/-S.D.) of CI-1004 and I.S. were 7.8+/-0.1 and 10.9+/-0.2 at 40 degrees C and 7.7+/-0.2 min and 10.7+/-0.2 min at 45 degrees C. No interfering peaks were observed at the retention time of CI-1004 throughout the validation process. Peak height ratios were proportional to CI-1004 over the concentration range of 7.5-5000 ng/ml in rat, rabbit and monkey plasma and 2.5-5000 ng/ml in dog and human plasma. Recovery of low, medium and high standards of CI-1004 ranged from 82.8-107% from all animal species and recovery of I.S. from rat, rabbit, dog and monkey plasma ranged from 77.5-82.0% and from human plasma was 111%. Assay precision for CI-1004 based on quality control samples was less than or equal to 8.5% C.V. with an accuracy (percentage relative error) of +/-4.7% for all species. Minimum quantitation limit of CI-1004 was 7.5 ng/ml for 0.2 ml rat, rabbit and monkey plasma samples and 2.5 ng/ml for 0.5 ml dog and human plasma samples. The method is suitable for studying the preclinical and clinical pharmacokinetics of CI-1004.

Competitive particle concentration fluorescence immunoassays for measuring anti-diabetic drug levels in mouse plasma

Two competitive particle concentration fluorescence immunoassays were developed to measure blood levels of analogs of anti-diabetic drugs being tested in diabetic mice. Ligands that contained the active pharmacophores were conjugated to PPD for immunization and to beta-phycoerythrin for use as a tracer in the immunoassays. Approximately 90% of 262 compounds assayed were detectable at less than 120 nM in plasma which was well below the estimated therapeutic level of 1 microM for lowering blood glucose. These data were used to define the bioavailability of test compounds and assist in decisions of constructing active analogs. Of additional interest, we noted crossreactivity of one monoclonal antibody for 3 different compound classes that are all known to bind with varying affinities to peroxisome proliferator-activated receptors.

Determination of a new antiulcer agent, YJA-20379-1 in plasma, urine, blood, and tissue homogenates by high-performance liquid chromatography

A high-performance liquid chromatographic method was developed for the determination of a new antiulcer agent, YJA-20379-1, in human plasma and urine, and rat blood and tissue homogenates. The sample preparation was simple: a 2.5-volume of acetonitrile was added to the biological sample to deproteinize it. A 50-microliter aliquot of the supernatant was injected onto a C18 reversed-phase column. The mobile phase employed was methanol--0.1 M Sørensen phosphate buffer of pH7.0--H2O (80:2:15, v/v/v), and was run at a flow-rate of 0.7 ml/min. The column effluent was monitored by ultraviolet detector at 254 nm. The retention time for YJA-20379-1 was approximately 6.3 min. The detection limits for YJA-20379-1 in human plasma and urine, and rat tissue homogenate (including blood) were 50, 100, and 100 ng/ml, respectively. The coefficients of variation of the assay (within-day and between-day) were generally low (below 9.44%) for the human plasma and urine, and rat blood and tissue homogenate. No interference from endogenous substances were found.

Stereoselective determination of a new antidepressant, E2011, and its diastereoisomer as a metabolite by high-performance liquid chromatography

A stereoselective HPLC method has been developed for the determination of E2011 (compound I) and one of its metabolites and diastereoisomers, ER-20593 (compound II), in plasma. The two substances and the internal standard were extracted from plasma, followed by two purification steps. In the first step, a minicolumn, Bond Elut C18, was used and in the second step, another minicolumn, Bond Elut Si, was used for purification of the compounds. After the purification, the compounds were analyzed by HPLC with two Chiralpak AD columns. In this procedure, compounds I and II were stable and there was no chiral inversion. The within-day and the between-day assays were performed in rat plasma, where compounds I and II existed simultaneously. The within-day and the between-day precisions of compound I were 2.0 approximately 10.1% and 1.3 approximately 7.1%, and the within-day and the between-day accuracies were -8.2 approximately +3.0% and -6.6 approximately +4.0% in the concentration range 0.003-10 microg ml(-1). The within-day and the between-day precisions of compound II were 1.7 approximately 16.9% and 0.9 approximately 4.5% and the within-day and the between-day accuracies were -9.0 approximately +2.4% and -5.6 approximately +3.8% in the concentration range of 0.005-0.5 microg ml(-1). QC samples for compound I and II were stable for at least 3 months. The method was applied to measure the levels of compound I and II in the rat plasma after oral administration of compound I.

Pharmacokinetic stereoselectivity of troglitazone, an antidiabetic agent, in the KK mouse

Troglitazone, an oral antidiabetic agent, is an equal mixture of four stereoisomers involving two asymmetric centres. In the present study, the stereoselectivity of in vitro epimerization in plasma and organ homogenate and in vivo plasma disposition in the KK mouse, an animal model of non-insulin-dependent diabetes, was examined. In the incubation experiments at 37 degrees C, there was a fivefold to eightfold acceleration of epimerization at the 5 position of the thiazolidine ring in KK mouse plasma compared with that in buffer. However, no inversion at the 2 position of the chroman ring was observed. In addition, there was an approximately 1.3-fold difference in the epimerization rates among stereoisomers at the 2 position of the chroman ring. However, there were no differences in the values of the equilibrium constants of epimerization, and the ratio of epimerization among stereoisomers at the 5 position of thiazolidine ring was almost unity. The acceleration of epimerization is thought to be due to the high degree of protein binding because of the relationship between the initial epimerization rate and the dilution ratio of the plasma. Although acceleration of epimerization was also observed in the 20% homogenates of liver, kidney, and intestine of the KK mouse, the degree of stereoselectivity was lower than in plasma. The analysis of the plasma disposition after intravenous administration of troglitazone stereoisomers, using a kinetic model, indicated that the metabolic clearance in the liver showed a 2.5-fold maximum difference among stereoisomers and that the stereoselectivity of epimerization was low.

Pharmacokinetics of ebrotidine in rats and dogs

The pharmacokinetics of ebrotidine (N-[(E)-[[[2-[(diaminomethylene)amino] -4-thiazolyl]methyl]thio]ethyl] amino]methylene]-4-bromo-benzenesulfonamide, CAS 100981-43-9, FI-3542) was studied in the rat and dog. After oral (agar suspension) and intravenous administration at 10 mg/kg to rats, ebrotidine was rapidly absorbed. Cmax values averaged 0.498 microgram/ml attained at tmax = 30 min. Distribution was fitted to a two-compartmental model with t1/2 beta = 1 h (i.v.). Clearance (Cl) was 29 ml/min.kg and volume of distribution (Vdss) was 1852 ml/kg. Absolute bioavailability was 22% of the dose administered. After oral (the same tablet formulation as that used for clinical trials) and intravenous administration at 150 mg and 25 mg, respectively, to dogs, absorption of ebrotidine was relatively rapid. Cmax values averaged 2,170 micrograms/ml attained at tmax = 2 h. Distribution was fitted to a two-compartmental model with t1/2 beta = 2.8 h (i.v.). Clearance (Cl) was 600 ml/h.kg and volume of distribution (Vdss) was 1000 ml/kg. Absolute bioavailability, which is variable in this type of drugs, ranges from 29% to 64% of the dose administered.

Pharmacokinetics of ebrotidine in healthy volunteers. A summary

Several clinical pharmacokinetic studies of ebrotidine (N-[(E)-[[2-[[[2-[(diaminomethylene)amino]-4-thiazolyl] methyl]thio]ethyl]amino]methylene]-4-bromo-benzenesulfonamide, CAS 100981-43-9, FI-3542) administered by oral route in single and multiple doses to healthy volunteers have been performed. Dosage levels were 150, 300, 400, 500, 600 and 800 mg. Plasma concentrations of unchanged ebrotidine and its major metabolite, ebrotidine sulfoxide, excreted in the urine were determined. The main pharmacokinetic parameters were calculated from the experimental data. Absorption was relatively rapid (Imax = 2 h) and unrelated to dose. Drug behavior was considered as reasonably linear: Cmax = 364-1168 ng/ml and AUC0-12 h = 1427-5997 ng.h/ml (doses from 150 mg to 800 mg). The mean values of terminal elimination half-life (t1/2 beta) ranged from 13.9 to 20.3 h (doses of 400, 600 and 800 mg). After multiple dosing there was no drug accumulation, and no significant changes in the mean values of the main pharmacokinetic parameters were observed. The steady state was reached from the second day of administration, 10-24% of the ebrotidine administered dose was excreted in urine mainly as its major metabolite, ebrotidine sulfoxide, as well as unchanged drug and other minor metabolites. These percentages were constant and independent of the dose administered.

Determination of protein binding of troglitazone stereoisomers by fluorometric titration

Determination of the protein binding of troglitazone is difficult because of its high adsorption to filters and membranes and the instability of the stereoisomers. We attempted to assess the protein binding of four stereoisomers of troglitazone in the plasma and albumin from several species by the method using fluorescent probes. The inhibition constants (Ki) for the stereoisomers of troglitazone were obtained from the decreases in fluorescence intensity of dansylsarcosine caused by competitive inhibition. Each stereoisomer of troglitazone displaced dansylsarcosine, a typical specific fluorescent probe for the diazepam binding site on human serum albumin (HSA). The highest binding affinity for dansylsarcosine was observed with HSA (dissociation constant, Kd,1 = 0.5 microM), while it was lowest in the mouse (Kd,1 = 18 microM). The Ki values for KK and ddY mouse plasma and mouse and rat albumin were in the range 2-15 microM, and there were no large variations among stereoisomers, the maximum differences being twofold. For human plasma and albumin, the displacement could not be accounted for by a simple competitive inhibition. Comparison between unbound fraction (fu) values calculated from thus obtained Ki values and those of a mixture of the four stereoisomers determined by high-performance frontal analysis showed that the fu values obtained by fluorometric titration were higher, while the relative differences among the stereoisomers in terms of animal species and strain were comparable for the two methods. Small differences in protein binding among stereoisomers of troglitazone may not be the major reason for their stereoselective pharmacokinetics.

Tolerability and pharmacokinetics of ebrotidine in healthy subjects given single and repeated oral doses

The tolerability and safety of ebrotidine (N-[(E)-[[2-[[[2-[(diaminomethylene)amino]-4-thiazolyl]methyl] thio]ethyl]amino]methylene]-4-bromo-benzenesulfonamide, CAS 100981-43-9, FI-3542) and its basic pharmacokinetic parameters were determined after its oral administration to healthy volunteers. Sixteen subjects were selected to participate in two different studies: an increasing single dose study to determine the maximal tolerated dose (from 25 to 1600 mg), and a multiple dose study (stepped doses from 400 to 1600 mg daily for 12 days). The results of the studies showed that ebrotidine has a good tolerability. Vital signs and laboratory tests were not influenced by the study treatment. No clinically relevant adverse effects were reported during the investigation. Ebrotidine reached peak plasma concentrations 2-3 h after oral administration. Its elimination half-life ranged from 9 to 14 h. In conclusion, ebrotidine was well tolerated after administration of oral single doses of up to 1600 mg, and after repeated administration of up to 800 mg/12 h for 12 days.

Pharmacokinetic study of ebrotidine administered in multiple doses to healthy volunteers for 4 days

The safety of ebrotidine (N-[(E)-[[2-[[[2-[(diaminomethylene)amino]-4- thiazolyl]methyl]thio]ethyl]amino] methylene]-4-bromo-benzenesulfonamide, CAS 100981-43-9, FI-3542), a new H2-receptor antagonist with gastroprotective activity, was assessed and its main pharmacokinetic parameters were determined in order to establish the dose linearity after the repeated administration of three different dose levels. The study was carried out in a group of 8 healthy volunteers of either sex, aged between 20 to 29 years. Oral doses of ebrotidine were administered in a randomized, single-blind design. Volunteers remained in the Unit for two days at each of the three study phases with washout intervals of 2 weeks and received seven doses of ebrotidine (150, 300 and 500 mg b.i.d). Pharmacological evaluation included vital signs, laboratory tests, adverse events and blood and urine samplings for pharmacokinetic analysis. Ebrotidine was determined by high performance liquid chromatography (HPLC) with UV detection. The results showed a good tolerability of ebrotidine after the administration of seven doses for 4 days, with no changes in the vital signs or laboratory parameters. No clinically significant dose-related adverse events were reported during the study. The absorption of ebrotidine was relatively rapid (tmax approximately 2 h) and linear within the dose range from 150 to 500 mg. Drug biotransformation was linear with doses tested, and no metabolic saturation occurred. The terminal elimination half-life of ebrotidine was between 7 and 11 h or even longer. There was no accumulation of ebrotidine and the steady state was reached, regardless of the dose administered, within the first 24-48 h.

Quantification of the effects of troglitazone on insulin sensitivity and beta-cell function in Watanabe heritable hyperlipidemic rabbits: a minimal model analysis

Troglitazone is a newly developed antidiabetic drug that has been shown to improve insulin resistance and hyperinsulinemia both in diabetic animal models and in patients with non-insulin-dependent diabetes mellitus. The Watanabe heritable hyperlipidemic (WHHL) rabbit, an animal model of familial hypercholesterolemia, is characterized by hyperinsulinemia, which reflects insulin resistance. In this study to determine the effects of troglitazone on glucose and insulin metabolism in WHHL rabbits, we quantified the rate of glucose utilization (glucose tolerance index [Kg]), sensitivity of first-phase posthepatic insulin secretion to glucose (phi1), sensitivity of second-phase posthepatic insulin secretion to glucose (phi2), insulin sensitivity to glucose disposal ([Si] inversely related to insulin resistance), insulin-independent glucose disposal (glucose effectiveness [Sg]), and rate of insulin clearance (Ki) by incorporating our previously reported two-compartment model of a glucose/insulin system with the glucose disappearance model of Bergman. Galvin insulin sensitivity (GIS) was also computed for comparison with Bergman Si. When troglitazone was administered as a food admixture (24 mg/d per animal) for 6 months, it did not significantly affect beta-cell function as measured by phi2, glucose tolerance as measured by Kg, or Sg, but increased both Si and Ki and reduced phi1, leading to a decreased plasma insulin response during the intravenous glucose tolerance test (IVGTT). Si was strongly and significantly correlated with GIS. These data indicate that in WHHL rabbits, troglitazone improves insulin sensitivity and posthepatic insulin clearance without affecting beta-cell function or glucose tolerance.

Metabolism and excretion of the novel antipsychotic drug ziprasidone in rats after oral administration of a mixture of 14C- and 3H-labeled ziprasidone

The metabolism and excretion of ziprasidone (5-[2-[4-(1,2-benzisothiazol-3-yl)piperazin-1-yl]ethyl]-6-++ +chloroindolin-2-one hydrochloride hydrate) were studied in Long Evans rats after oral administration of a single dose of a mixture of 14C- and 3H-labeled ziprasidone. The radioactive dose was quantitatively recovered over 7 days in both male and female rats. The percentage of the dose excreted in urine, bile, and feces of rats was 21.6, 19.2, and 55.6%, respectively. The total excretion in urine and bile suggested that at least 41% of the drug was absorbed. Absorption of ziprasidone was rapid, and the mean plasma concentrations of the unchanged drug and metabolites were slightly higher in the female rats than in the males. The maximal plasma concentrations for ziprasidone and metabolites were reached at 1 hr in both male and female rats. Based on AUC (0-12 hr) values, approximately 59 and 52% of the circulating radioactivity (average of 14C and 3H) was attributable to metabolites in male and female rats, respectively. Ziprasidone was extensively metabolized in rats, and only a small amount of ziprasidone was excreted as unchanged drug. Twelve metabolites were identified by ion spray LC/MS, using a combination of parent ion and product ion scanning techniques. The structures of eight metabolites were unambiguously confirmed by coelution on HPLC with synthetic standards, and four additional metabolites were partially identified. There was a gender-related difference in the excretion of urinary metabolites in Long Evans rats. The major route of metabolism in male rats involved N-dealkylation. In female rats the major metabolites were due to oxidation at the benzisothiazole ring. Based on the structures of these metabolites, four major and two minor routes of metabolism of ziprasidone were identified. The major routes included 1) N-dealkylation of the ethyl side chain attached to the piperazinyl nitrogen, 2) oxidation at the sulfur, resulting in the formation of sulfoxide and sulfone, 3) oxidation on the benzisothiazole moiety (other than sulfur), and 4) hydration of the C==N bond and subsequent oxidation at the sulfur of the benzisothiazole moiety. The minor routes involved N-oxidation on the piperazine ring and hydrolysis of the oxindole moiety.

Meloxicam pharmacokinetics in renal impairment

AIMS

The aim of the present study was to determine how the pharmacokinetics of meloxicam are affected by kidney dysfunction and consequently to define the appropriate dose for the use of meloxicam in patients with mild or moderate renal impairment.

METHODS

Meloxicam was administered to subjects with mild (creatinine clearance 41-60 ml min-1) to moderate (20-40 ml min-1) renal impairment compared with normal renal function (> 60 ml min-1). Thirty-eight subjects received meloxicam 15 mg once daily over 9 days. Meloxicam plasma concentrations were determined from blood samples taken during the study and pharmacokinetic parameters calculated according to noncompartmental methods.

RESULTS

Subjects with no or mild renal impairment showed similar pharmacokinetic profiles (geometric mean AUCSS (%gCV) 55 (33%) vs 55 (38%) micrograms ml-1 h). Subjects with moderate renal impairment demonstrated lower total plasma meloxicam concentrations (AUCSS 35 (50%) micrograms ml-1 h, with corresponding higher plasma clearance (P = 0.013) compared with subjects with no renal impairment. However, this was combined with higher meloxicam free fractions in moderately impaired subjects such that free meloxicam concentrations were similar in all three groups. Meloxicam was well tolerated with few adverse events occurring and no difference in incidence observable between groups.

CONCLUSIONS

On the basis of these results there is no necessity for a dosage adjustment when administering meloxicam to patients with mild to moderate renal impairment.

Automated sample preparation using membrane microtiter extraction for bioanalytical mass spectrometry

The development and application of membrane solid phase extraction (SPE) in 96-well microtiter plate format is described for the automated analysis of drugs in biological fluids. The small bed volume of the membrane allows elution of the analyte in a very small solvent volume, permitting direct HPLC injection and negating the need for the time consuming solvent evaporation step. A programmable liquid handling station (Quadra 96) was modified to automate all SPE steps. To avoid drying of the SPE bed and to enhance the analytical precision a novel protocol for performing the condition, load and wash steps in rapid succession was utilized. A block of 96 samples can now be extracted in 10 min., about 30 times faster than manual solvent extraction or single cartridge SPE methods. This processing speed complements the high-throughput speed of contemporary high performance liquid chromatography mass spectrometry (HPLC/MS) analysis. The quantitative analysis of a test analyte (Ziprasidone) in plasma demonstrates the utility and throughput of membrane SPE in combination with HPLC/MS. The results obtained with the current automated procedure compare favorably with those obtained using solvent and traditional solid phase extraction methods. The method has been used for the analysis of numerous drug prototypes in biological fluids to support drug discovery efforts.

Riluzole. A review of its pharmacodynamic and pharmacokinetic properties and therapeutic potential in amyotrophic lateral sclerosis

Riluzole, a benzothiazole, affects neurons by 3 mechanisms: by inhibiting excitatory amino acid release, inhibiting events following stimulation of excitatory amino acid receptors and stabilising the inactivated state of voltage-dependent sodium channels. It has demonstrated neuroprotective activity in vivo and in vitro. Results from 2 randomised double-blind placebo-controlled trials in patients with amyotrophic lateral sclerosis (ALS; motor neuron disease) have demonstrated that riluzole can extend survival and/or time to tracheostomy. After 18 months, the relative risk of death or tracheostomy with riluzole 100 mg/day was reduced by 21%. Although riluzole slowed the rate of deterioration in muscle strength in the first trial, this was not confirmed in the second, larger trial. Riluzole had no effect on any other functional or secondary variable. Gastrointestinal effects, anorexia, asthenia, circumoral paraesthesia and dizziness were reported more frequently with riluzole than placebo. Elevated alanine aminotransferase levels were observed in 10.6 versus 3.8% of patients treated with riluzole 100 mg/day versus placebo, leading to treatment withdrawal in 3.8 versus 2.1% of patients. In conclusion, riluzole is the first drug that has been shown to have an effect on survival in patients with ALS. Although the effect of riluzole was modest, it has allowed some insight into the pathogenesis of ALS from which future gains may be made.

Determination of pramipexole (U-98,528) in human plasma by high-performance liquid chromatography with atmospheric pressure chemical ionization tandem mass spectrometry

A highly sensitive and selective HPLC-MS-MS method was developed for the determination of pramipexole in human plasma. The analytes, pramipexole and BHT-920 (internal standard), were extracted from plasma at basic pH with methyl tert.-butyl ether (MTBE). MTBE was evaporated to dryness and reconstituted in 100 microliters of (95:5) methanol-water. Chromatographic separation was achieved on a Zorbax SB-CN column with a mobile phase of (15:5:80) water-0.1 M ammonium acetate-methanol. The analytes were detected utilizing HPLC in conjunction with atmospheric pressure chemical ionization (APCI) tandem mass spectrometry (MS-MS). The assay was linear in the concentration ranges of 50 to 5000 pg/ml. The analysis of pooled quality controls (150, 750, and 3000 pg/ml) demonstrated excellent precision with relative standard deviations (R.S.D.) (n = 18) of 7.2%, 5.3% and 5.2%, respectively. The method is accurate with all intra-day (n = 6) and overall (n = 18) mean values being less than 11.7% from theoretical.

Effects of the antihypoxic and neuroprotective drug, lubeluzole, on repolarization phase of canine heart assessed by monophasic action potential recording

The cardiovascular effects of the antihypoxic and neuroprotective drug, lubeluzole, were investigated using beagle dogs anesthetized with halothane. Endocardial-contact electrode catheter was used for continuous monitoring of monophasic action potential (MAP), which could provide a precise information of repolarization phase. Intravenous administration of an efficacious dose of lubeluzole (0.63 mg/kg, n = 6) slightly decreased both the heart rate and the blood pressure. It did not change PQ interval and QRS width, while it significantly prolonged QT interval, corrected QT (QTc) and the duration of the MAP during the observation period over 60 min. The effects of drug on repolarization phase were late-onset and long-lasting compared with the time course of plasma drug concentrations, which changed as predicted by the two-compartment theory of pharmacokinetics. Additional injection of lubeluzole (2.5 mg/kg, n = 6) showed qualitatively similar changes to those of lower dose, and did not induce the cardiovascular collapse in any dog. Neither afterdepolarization nor ventricular escaped beat was detected during the observation period. The drug concentration in cardiac tissue was correlated linearly with the plasma drug concentration at 60 min after the second drug administration. These results indicate that lubeluzole exerts only minor cardiovascular effects except the prolongation of the repolarization period. The monitoring of plasma drug concentration may be helpful to estimate the steady-state distribution of drug to the heart, but less helpful to predict the QT prolongation. In future clinical trials, care must be taken with patients, especially those at risk to have prolonged repolarization.

The fate of a thiazolidinedione antidiabetic agent in rat and dog

1. The fate of [14C]BRL 49653C, a novel thiazolidinedione antidiabetic agent, has been studied following oral administration to the rat and dog. 2. Clearance was almost exclusively by metabolism, with only small amounts of unchanged BRL 49653 being excreted by either species. 3. Phase I metabolism resulted in ring hydroxylation, N-demethylation and oxidative removal of the pyridinylamino function to yield a phenoxyacetic acid derivative. 4. Sulphation of phase I metabolites occurred in both species, but glucuronidation was only observed in the rat. 5. The parent compound was the major circulating component in both species at early times, but at later times sulphate conjugates of phase 1 metabolites were predominant.

A long-term study to evaluate the safety and efficacy of meloxicam therapy in patients with rheumatoid arthritis

Meloxicam is a new non-steroidal anti-inflammatory drug (NSAID), which has a higher activity against cyclooxygenase-2 (COX-2) than against cyclooxygenase-1 (COX-1), with potentially high anti-inflammatory and analgesic action. This study was designed to assess the long-term safety and efficacy of meloxicam 15 mg daily. Three hundred and fifty-seven patients (aged 19-84 yr, mean 56 yr) with rheumatoid arthritis (RA) received meloxicam 15 mg orally once daily, for up to 18 months. Sixty-six per cent of patients remained on therapy for 18 months. Mean global efficacy, assessed by each patient on a visual analogue scale (0 cm = excellent, 10 cm = useless), was 3.32 +/- 3.1 cm at the last study visit (all patients included) and 2.33 +/- 2.25 cm after 18 months. Health status, general condition, morning stiffness, grip strength of right hand, Ritchie joint index, pain in the morning and pain at night all improved significantly. Efficacy was maintained through the study. Only 11.4% of patients discontinued prematurely due to lack of efficacy. Mean global tolerance was good. Twenty-eight per cent of patients experienced gastrointestinal (GI) adverse events, 21% musculoskeletal system disorders, 18% skin disorders and 15% respiratory disorders. Only 13.7% of patients discontinued due to adverse events. Severe GI effects, such as perforation, ulcer and bleeding, occurred in only three patients (0.8%). Withdrawals due to GI adverse events occurred in 3.9% of patients. Meloxicam 15 mg once daily was effective and compared favourably with standard NSAIDs regarding tolerance when administered to patients with RA over an 18 month period.

Simultaneous quantitation of pioglitazone and its metabolites in human serum by liquid chromatography and solid phase extraction

A high-performance liquid chromatographic (HPLC) method for the simultaneous determination of pioglitazone (U-72107) and its potential metabolites (M-1 to M-6) in human serum was developed. The method involved a solid phase extraction (SPE) of pioglitazone, its metabolites, and the internal standard (U-92573) from serum using C18 SPE columns with an elution solvent of 0.5 ml of acetonitrile-water (35:65, v/v). Separation of the eight analytes was achieved within 20 min using a reversed-phase Zorbax RX-C8 analytical column (250 mm x 4.6 mm i.d., 5 microns particle size) with a mobile phase of acetonitrile-water (40:60, v/v) containing 3 ml acetic acid per liter mobile phase (apparent pH 5.5). An ultraviolet detector operated at 269 nm was used with a linear response observed from 0.02 to 2 micrograms ml-1 for these analytes except for M-4 which was best fitted with a polynomial regression. Limit of quantitation was found to be 0.02 microgram ml-1 for pioglitazone, M-3, M-5, and M-6; 0.04 microgram ml-1 for M-2 and M-4; and 0.5 microgram ml-1 for M-1 when using a 0.5 ml serum sample for extraction. Obtained from the method validation, intra- and inter-assay precision was < or = 9% and accuracy ranged from -8.2 to 13.4% for all analytes. The applicability of this method has been demonstrated by successfully analyzing clinical serum samples. The strategies in the HPLC characterization and in the SPE procedure development for this method are discussed as well.

Effects of the novel neuroprotective agent, riluzole, on human brain function and behavior: I. Double-blind, placebo-controlled EEG mapping and psychometric studies under normoxia

In a double-blind, placebo-controlled, crossover study, the encephalotropic and psychotropic properties of single oral doses of the novel neuroprotective agent, riluzole, were investigated utilizing EEG mapping and psychometry. Twenty healthy young volunteers received randomly at weekly intervals, placebo, 50, 100 and 200 mg riluzole. EEG recordings and evaluation of 9 noopsychic and 5 thymopsychic variables were carried out at 0, 2, 4, 6 and 8 h after oral drug administration. EEG maps on the multivariate analysis demonstrated that all three doses induced significant changes in human brain function, as compared with placebo, between 2 and 8 h, with effect only increasing slightly with dose. EEG maps on univariate analysis demonstrated generally an increase of delta/theta, decrease of alpha and beta power, as well as a slowing of the centroid of the total power spectrum, which suggests sedative properties of the drug. Only after the two highest doses at 6 h were some different findings observed. Multivariate statistics on psychometry failed to show any significant effects on the noopsyche, while for the thymopsyche, all three doses of riluzole produced a deterioration. The latter was characterized by a decrease in drive and wakefulness as well as deterioration in well-being, mood and affectivity. Thus, under normoxia, in all three doses riluzole produced neurophysiologically a sedative effect, accompanied at the behavioral level by a deterioration in the thymopsyche, which may be expected from a drug with antiglutamatergic effects in normals.