Orally active inhibitors of human leukocyte elastase. II. Disposition of L-694,458 in rats and rhesus monkeys

The disposition of L-694,458, a potent monocyclic beta-lactam inhibitor of human leukocyte elastase, was studied in male Sprague-Dawley rats and rhesus monkeys. After iv dosing, L-694,458 exhibited similar pharmacokinetic parameters in rats and rhesus monkeys. The mean values for its plasma clearance, terminal half-life, and volume of distribution at steady state were 27 ml/min/kg, 1.8 hr, and 4.0 liters/kg in rats and 34 ml/min/kg, 2.3 hr, and 5 liters/kg in rhesus monkeys. The bioavailability of a 10 mg/kg oral dose was higher in rats (65%) than in rhesus monkeys (39%). In both species, concentrations of L-694,458 in plasma increased more than proportionally when the oral dose was increased from 10 mg/kg to 40 mg/kg. In monkeys a protracted plasma concentration-time profile was observed at 40 mg/kg, characterized by a delayed T(max) (8-24 hr) and a long terminal half-life (6 hr). [3H]L-694,458 was well absorbed after oral dosing to rats at 10 mg/kg, as indicated by the high recovery of radioactivity in bile (83%) and urine (6%) of bile duct-cannulated rats. Only approximately 5% or less of the radioactivity in bile, urine, and feces was a result of intact L-694,458, indicating that the compound was being eliminated by metabolism, followed by excretion of the metabolites in feces, via bile. Demethylenation of the methylenedioxyphenyl group resulting in the catechol was the primary metabolic pathway in human and rhesus monkey liver microsomes. In rat liver microsomes, the major metabolite was the N-oxide of the methyl-substituted piperazine nitrogen. In rats dosed iv and orally with [3H]L-694,458, concentrations of radioactivity were highest in the lung (the primary target tissue), adrenals, and liver. L-694,458 was unstable in rat blood and plasma, degrading via a pathway believed to be catalyzed by B-esterases and to involve cleavage of the beta-lactam ring and loss of the methylpiperazine phenoxy group. In vitro studies indicated that in human liver, L-694,458 was metabolized by CYP3A and 2C isozymes, and in both monkey and human liver microsomes the compound acted as an inhibitor of testosterone 6beta-hydroxylation.     

Integrated physical and transcript map of 5q31.3-qter

The disposition of S-2-[4-(3-methyl-2-thienyl)phenyl]propionic acid (CAS 155680-07-2, S-MTPPA, code: M-5011) was studied after oral administration to rats, dogs and monkeys using the 14C-labeled drug. After oral dosing, S-MTPPA was well absorbed from the gastrointestinal tract, to the extent of 97.7% in rats. The concentration of S-MTPPA in rat plasma reached a peak (Cmax: 13.07 micrograms/ml) at 15 min (tmax) after dosing and declined with a half-life (t1/2) of 2.5 h. The values of the parameters tmax, Cmax and t1/2 for dogs were 30 min, 26.2 micrograms/ml and 7.0 h, and those for monkeys were 15 min, 12.8 micrograms/ml and 3.0 h, respectively. The radioactivity was widely distributed in tissues and almost completely excreted in urine and feces within 48 h after oral administration to rats. The excretion of radioactivity in bile, urine and feces within 48 h after oral administration of 14C-S-MTPPA to bile duct-cannulated rats amounted to 75.0, 18.6 and 1.4% of the dose, respectively. The drug was metabolized mainly by oxidation of the thiophenyl moiety and by glucuronidation of the carboxyl group in rats and monkeys. The major urinary and fecal metabolite in dogs was identified as the taurine conjugate of MTPPA.     

Metabolism and disposition of 1,4,7,8-tetrachlorodibenzo-p-dioxin in rats

Metabolism studies of 1,4,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a relatively nontoxic dioxin congener, were undertaken to gain a better understanding of mammalian metabolism of dioxins without the problems associated with the use of the most toxic congener, 2,3,7,8-TCDD. 14C-1,4,7,8-TCDD was dosed to conventional and bile-cannulated rats at a level of 8 mg/kg. The 14C was excreted almost entirely in 72 hours with the major routes of excretion feces and bile. Metabolites were identified from the feces, bile, and urine by GC-MS or negative ion FAB MS and 1H NMR. The two major fecal metabolites were hydroxylated tetra- and triCDDs. Glucuronide and sulfate conjugates of these hydroxyl metabolites were found in the urine and bile. Minor metabolites included dichlorocatechol, dihydroxylated tetra- and triCDDs, and conjugates of these compounds.     

The comparative metabolism of diisopropyl methylphosphonate in mink and rats

This study reports the metabolism of carbon-14labeled diisopropyl methylphosphonate (DIMP) in mink and rats, undertaken to better understand the dose-related mortality reported for mink in a previous study. In both male and female mink and rats, DIMP was rapidly absorbed after oral administration; it was metabolized by a saturable pathway to a single metabolite, isopropyl methylphosphonate (IMPA), which was rapidly excreted, primarily in the urine (90%). Fecal radioactivity, also identified as IMPA, was 1.7-3.1% of the administered dose. Female rats had a slower rate of conversion of DIMP to IMPA and less total excretion of IMPA than male rats. Metabolism of DIMP administered intravenously was not very different from that given orally in both species. These data indicate that mink absorb, metabolize, and excrete DIMP (as IMPA) in a manner very similar to mice, rats, and dogs.     

Disposition of [14C]avitriptan in rats and humans

Avitriptan is a new 5-HT1-like agonist with abortive antimigraine properties. The study was conducted to characterize the pharmacokinetics, absolute bioavailability, and disposition of avitriptan after intravenous (iv) and oral administrations of [14C]avitriptan in rats and oral administration of [14C]avitriptan in humans. The doses used were 20 mg/kg iv and oral in the rat, 10 mg iv in humans, and 50 mg oral in humans. The drug was rapidly absorbed after oral administration, with peak plasma concentrations occurring at 0.5 hr postdose. Absolute bioavailability was 19.3% in rats and 17.2% in humans. Renal excretion was a minor route of elimination in both species, with the majority of the dose being excreted in the feces. After a single oral dose, urinary excretion accounted for 10% of the administered dose in rats and 18% of the administered dose in humans, with the remainder excreted in the feces. Extensive biliary excretion was observed in rats. Avitriptan was extensively metabolized after oral administration, with the unchanged drug accounting for 32% and 22% of the total radioactivity in plasma in rats and humans, respectively. Plasma terminal elimination half-life was approximately 1 hr in rats and approximately 5 hr in humans. The drug was extensively distributed in rat tissues, with a tendency to accumulate in the pigmented tissues of the eye.     

Metabolism and excretion of a new antianxiety drug candidate, CP-93,393, in cynomolgus monkeys: identification of the novel pyrimidine ring cleaved metabolites

The metabolism and excretion of a new anxiolytic/antidepressant drug candidate, CP-93,393, ((7S, 9aS)-1-(2-pyrimidin-2-yl-octahydro-pyrido[1, 2-a]-pyrazin-7-yl-methyl)-pyrrolidine-2,5-dione) were investigated in cynomolgus monkeys after oral administration of a single 5 mg/kg dose of 14C-CP-93,393. Urine, bile, feces, and blood samples were collected and assayed for total radioactivity, parent drug, and metabolites. Total recovery of the administered dose after 6 days was 80% with the majority recovered during the first 48 hr. An average of 69% of the total radioactivity was recovered in urine, 4% in bile, and 7% in feces. Mean Cmax and AUC(0-infinity) values for the unchanged CP-93,393 were 143.2 ng/ml and 497.7 ng.hr/ml, respectively, in the male monkeys and 17.2 ng/ml and 13.7 ng.hr/ml, respectively, in the female monkeys. HPLC analysis of urine, bile, feces, and plasma from both male and female monkeys indicated extensive metabolism of CP-93,393 to several metabolites. The identification of metabolites was achieved by chemical derivatization, beta-glucuronidase/sulfatase treatment, and by LC/MS/MS, and the quantity of each metabolite was determined by radioactivity detector. CP-93,393 undergoes metabolism by three primary pathways, aromatic hydroxylation, oxidative degradation of the pyrimidine ring, and hydrolysis of the succinimide ring followed by a variety of secondary pathways, such as oxidation, methylation, and conjugation with glucuronic acid and sulfuric acid. The major metabolites, oxidation on the pyrimidine ring to form 5-OH-CP-93,393 (M15) followed by glucuronide and sulfate conjugation (M7 and M13), accounted for 35-45% of the dose in excreta. Two metabolites (M25 and M26) were formed by further oxidation of M15 followed by methylation of the resulting catechol intermediate presumably by catechol-O-methyl transferase. A novel metabolic pathway, resulting in the cleavage of the pyrimidine ring, was also identified. The metabolites (M18, M20, and M21) observed from this pathway accounted for 8-15% of the dose. Aliphatic hydroxylation of the succinimide ring was a very minor pathway in monkey. 5-Hydroxy-CP-93,393 (M15, 37-49%), its sulfate and glucuronide conjugates (M7 and M13, approximately 34%), and the pyrimidine ring cleaved product (M18, approximately 8%) were the major metabolites in monkey plasma. The identified metabolites accounted for approximately 90, 93, 97, and 92% of the total radioactivity present in urine, bile, plasma, and feces, respectively. The major in vivo oxidative metabolites were also observed after in vitro incubations with monkey liver microsomes.     

Metabolism of linoleamides. I. Absorption, excretion and metabolism of N-(alpha-methylbenzyl)linoleamide in rat and man

1. In urine of rats dosed with N-(alpha-methylbenzyl)linoleamide (MBLA), three dicarboxylic acid monoamides, N-(alpha-methylbenzyl)succinic acid monoamide, N-(alpha-methylbenzyl)glutaric acid monoamide and N-(alpha-methylbenzyl)adipic acid monoamide, were identified. Conjugated alpha-methylbenzylamine, hippuric acid and conjugates of the dicarboxylic acid monoamides were also found in the urine. N-(alpha-Methylbenzyl)succinic acid monoamide was the main metabolite in rats. 2. Biliary excretion of radioactivity was studied in rats, cannulated for collection of bile and duodenal infusion, after oral administration of N-(alpha-methylbenzyl)[1-14C]linoleamide. With constant duodenal infusion of bile, about 7% of the dose was excreted in the bile, while excretion of radioactivity was negligible without bile infusion. 3. The g.l.c. analysis of human urine after oral administration of MBLA revealed that two dicarboxylic acid monoamides were present and N-(alpha-methylbenzyl)succinic acid monoamide was the main metabolite. 4. MBLA was excreted unchanged in the faeces of men who received MBLA to the extent of about 53% dose in 3 days. 5. MBLA was not detected (less than 1 mug/ml) in the serum of a volunteer who had been taking an oral daily dose of 1500 mg of MBLA for 3 months.     

Comparative pharmacokinetics and metabolism of cephapirin in laboratory animals and humans

Comparative drug disposition studies in mice, rats, dogs, and humans indicate that cephapirin, a new semisynthetic cephalosporin antibiotic that exhibits broad-spectrum antimicrobial activity, is metabolized to desacetylcephapirin in these species. Pharmacokinetic analyses of the concentrations of cephapirin and desacetylcephapirin in plasma and urine reveal that the rate and extent of deacetylation decreases from rodents to dogs to humans. The kinetic analyses also suggest that the kidney performs a role not only in the excretion but also in the metabolism of cephapirin to desacetylcephapirin.     

Absorption and excretion of undegradable peptides: role of lipid solubility and net charge

Absorption and excretion of undegradable peptides were investigated with use of octapeptides synthesized from D-amino acids. D-Tyrosine was included in each peptide to permit labeling with 125I, D-glutamic acid or D-lysine were included to vary net electric charge and D-serine or D-leucine were included to vary lipid solubility. Peptides were administered parenterally or orally to normal rats drinking 5% glucose or maltose. Forty-five percent of a lipid-insoluble, negatively charged octapeptide added to the drinking fluid in milligram quantities was absorbed from the intestine and excreted intact in urine; 90% of this peptide was recovered in urine after parenteral injection. In contrast, lipophilic D-octapeptides were largely excreted in feces, even after subcutaneous injection; the amounts excreted in feces were correlated with oil/aqueous partition coefficients. Evidence is presented that lipophilic peptides entering liver cells combine with bile salts to form hydrophilic complexes that are secreted rapidly at high concentration in bile. At physiological concentrations of bile salts (5-40 mM) and nanomolar concentrations of peptide the binding is so complete that these undegradable peptides are rapidly cleared from liver to duodenal fluid in association with the bile salts. After reaching the ileum the bile salts are reabsorbed to blood, leaving the original lipophilic peptides to be excreted in the feces from which they can be extracted, purified and identified by high-pressure liquid chromatography. These mechanisms are discussed in relation to a) the paracellular absorption of peptides and other solutes by solvent drag and b) the delivery and fate of biologically active peptides.     

Synthesis and excretion profile of 1,4-[14C]phenylenebis(methylene)selenocyanate in the rat

1,4-Phenylenebis(methylene)selenocyanate (p-XSC) inhibits chemically induced tumors in several laboratory animal models. To understand its mode of action, we synthesized p-[14C]XSC, examined its excretion pattern in female CD rats and also the nature of its metabolites. p-[14C]XSC was synthesized from alpha,alpha-dibromo-p-[ring-14C]xylene in 80% yield. The excretion profile of p-[14C]XSC (15.8 mg/kg body wt, 200 microCi/rat, oral administration, in 1 ml corn oil) in vivo was monitored by measuring radioactivity and selenium content. On the basis of radioactivity, approximately 20% of the dose was excreted in the urine and 68% in the feces over 3 days. The cumulative percentages of the dose excreted over 7 days were 24% in urine and 75% in feces, similar to excretion rates of selenium. According to selenium measurement, <1% of the dose was detected in exhaled air; radioactivity was not detected. Only 15% of the dose was extractable from the feces with EtOAc and was identified as tetraselenocyclophane (TSC). Most of the radioactivity remained tightly bound to the feces. Approximately 10% of this bound material converted to TSC on reduction with NaBH4. Organic soluble metabolites in urine did not exceed 2% of the dose; sulfate (9 % of urinary metabolites) and glucuronic acid (19.5% of urinary metabolites) conjugates were observed but their structural identification is still underway. Co-chromatography with a synthetic standard led to the detection of terephthalic acid (1,4-benzenedicarboxylic acid) as a minor metabolite. The major urinary conjugates contained selenium. Despite the low levels of selenium in the exhaled air, the reductive metabolism of p-XSC to H2Se cannot be ruled out. Identification of TSC in vivo indicates that a selenol may be a key intermediate responsible for the chemopreventive action of p-XSC.     

Isolation and identification of major urinary metabolites of rifabutin in rats and humans

The antimycobacterial drug rifabutin is extensively metabolized in humans and laboratory animals. About 40% of the dose is excreted in urine as unchanged drug, and lipophilic (extractable with 1-chlorobutane) and polar metabolites. Polar metabolites accounted for 59.1 +/- 2.5% and 88.8 +/- 4.4% of radioactivity in urine collected over 96 hr after intravenous administration of 25 and 1 mg/kg of [14C]rifabutin to Sprague-Dawley rats, respectively. After 48 hr, all urinary radioactivity consisted of polar metabolites. The most abundant polar metabolite, identified by electrospray ionization-MS, collision-induced dissociation-MS, and comparison of HPLC retention times with the synthetic standard, was N-isobutyl-4-hydroxy-piperidine. Lipophilic metabolites accounted for <20% of urinary radioactivity. Major lipophilic metabolites, 25-O-deacetyl-rifabutin, 27-O-demethyl-rifabutin, 31-hydroxy-rifabutin, 32-hydroxy-rifabutin, and 20-hydroxy-rifabutin were isolated from both human and rat urine by HPLC and identified by electrospray ionization-MS, collision-induced dissociation-MS, and NMR spectrometry. In addition, two metabolites formed by the oxidation of the N-isobutyl-piperidyl group of rifabutin were found in the urine of rats, but not humans.     

Comparative studies on the pharmacokinetics of hydrophilic prolinedithiocarbamate, sarcosinedithiocarbamate and the less hydrophilic diethyldithiocarbamate

The pharmacokinetics of the antitoxic and anticarcinogenic compounds diethyldithiocarbamate, prolinedithiocarbamate and sarcosinedithiocarbamate were compared in rats. The bioavailability, the distribution in the organism, the oxidation to thiuramdisulfides, the cleavage to CS2 and the excretion in urine and bile were investigated. The results showed different behaviour of the three compounds. The more toxic diethyldithiocarbamate had a short in vivo half-life, was oxidized to tetraethylthiuramdisulfide in blood, and was metabolized to high yields of CS2 in 24 h. In contrast, prolinedithiocarbamate was more stable in vivo, was found predominantly in the urinary tract and was excreted in urine. The differences could not be explained by the presence of the carboxy group in the latter dithiocarbamate, since sarcosinedithiocarbamate, which also contains a carboxy group, behaved like diethyldithiocarbamate.     

Studies on the toxicology of hexachlorobenzene. II. Identification and determination of metabolites

Female rats were dosed intraperitoneally with 14C-hexaxhlorobenzene. The drug was administered on 2 or 3 occasions. The total doses amounted to 260 and 390 mg/kg 14C-hexachlorobenzene, respectively. Urine and feces from the animals were collected over a period of 4 weeks after the first injection. Both excreta and some tissues of the animals were examined for their content of radioactivity and for hexachlorobenzene and its metabolites. Gas chromatography, isotope dilution analysis, and combined gas chromatography-mass spectrometry were used to identify the metabolites of hexachlorobenzene. In urine pentachlorophenol, tetrachlorohydroquinone, and pentachlorothiophenol were present as major metabolites. One of the isomers of tetrachlorothiophenol was present as a minor metabolite. In the feces pentachlorophenol and pentachlorothiophenol only were identified. At the end of the experiment, carbon-14 excreted with urine and feces amounted to 7% and 27%, respectively, of the radioactivity administered. More than 90% of carbon-14 excreted in urine was contained in the major metabolites. In the feces about 30% of the excreted radioactivity was bound to metabolites and about 70% was contained in the unchanged drug, while in the tissues of the animals only pentachlorophenol was detected in measurable amounts, accounting for 10% of label in blood and less than 0.1% of carbon-14 determined in body fat. Total radioactivity contained in the metabolites detected in the animal body and in the excreta at the end of the experiment accounted for about 16% of the administered radioactivity.     

Hyperglycemia delays terminal depolarization and enhances repolarization after peri-infarct spreading depression as measured by serial diffusion MR mapping

The absorption, distribution, and excretion of GT31-104, a novel bile acid sequestrant, was studied in rats and dogs after both acute and subchronic oral administration. The polyallylamine backbone of GT31-104 was labeled with tritium and one of the alkyl side chains was labeled with 14C. The mean blood and plasma concentration of [3H, 14C]GT31-104 in rats, in both treatment regimens, was negligible at all time points, with the highest amount observed being 0.69 microgram eq/g blood; in dogs the mean blood and plasma concentration of [3H, 14C]GT31-104 was below the limit of quantitation (< 0.001% total dose) at all time points. In both rats and dogs, the mean total urinary excretion of [3H, 14C]GT31-104 was approximately 0.06% of the total dose. The fecal excretion data indicates that both 3H- and 14C-derived radioactivity was excreted entirely in the feces. Mean total radioactivity excreted in the feces ranged from approximately 95 to 105% in the rats and 92 to 102% in the dogs. Across the different treatment regimens, in both species, tissue concentrations were negligible (< 0.01% total dose) and no differences in tissue profile were noted, indicating that there was no effect of pretreatment on [3H, 14C]GT31-104 absorption. GT31-104 was extracted with water, and the water-soluble portion contained radioactivity that would correlate to approximately 0.19% of the 3H dose and 0.41% of the 14C dose; this portion probably accounted for the negligible radioactivity observed systemically. Analysis of gastrointestinal (GI) tract tissues with contents indicated that GT31-104 is rapidly cleared from the GI tract. These data indicate that GT31-104 is not absorbed from the GI tract in rats and dogs.     

Excretion of DNA adducts of 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline, PhIP-dG, PhIP-DNA and DiMeIQx-DNA from the rat

The heterocyclic aromatic amines, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) and 2-amino-3,4,8-trimethylimidazo[4,5-f]quinoxaline (4,8-DiMeIQx) are formed during frying of meat. PhIP and 4,8-DiMeIQx have, after metabolic activation, been shown to form adducts with DNA at the C8 of guanine both in vitro and in vivo. In order to investigate possible urinary biomarkers for estimation of the genotoxic dose of PhIP and 4,8-DiMeIQx, [3H]PhIP-dG, [3H]PhIP-DNA and [14C]4,8-DiMeIQx-DNA were injected i.p. to rats and the excretion of radioactivity in urine and faeces were measured. For all three [3H]PhIP-dG, [3H]PhIP-DNA and [14C]4,8-DiMeIQx-DNA 15-20% of the dose were excreted in the urine and 80-85% of the dose were excreted in the faeces. Urinary excretion showed maximum to 24 h (90%) with a rapid decline, 10% to 48 h and 0% to 72 h. Faecal excretion also showed maximum to 24 h (60%) with a slower decline, 30% to 48 h and 10% to 72 h. HPLC analysis of samples of urine and extracts from faeces, from rats dosed with [3H]PhIP-dG, showed that approximately 90% of the radioactivity co-eluted with PhIP-dG, indicating that PhIP-dG is excreted unmetabolized. HPLC analysis of samples of urine and extracts from faeces, from rats dosed with [3H]PhIP-DNA, showed that approximately 85% of the radioactivity co-eluted with PhIP-dG, indicating that PhIP-DNA adducts is mainly excreted as nucleoside adducts. Approximately 5% of the radioactivity excreted in the urine co-eluted with PhIP-G, indicating loss of deoxyribose. HPLC analysis of samples of urine and extracts from faeces, from rats dosed with [14C]4,8-DiMeIQx-DNA, showed that approximately 90% of the radioactivity co-eluted with 4,8-DiMeIQx-dG, indicating that 4,8-DiMeIQx-DNA adducts is mainly excreted as nucleoside adducts. Man is able to eliminate compounds of a higher mol. wt in the urine than the rat, the percentage of PhIP-dG and 4,8-DiMeIQx eliminated in the urine of man would therefore be expected to be higher than in the rat. Measurement of urinary nucleoside adducts of PhIP and 4,8-DiMeIQx could therefore provide a basis for the development of a biomonitoring strategy for the genotoxic dose of these food derived HAA.     

Lymphatic absorption and metabolism of orally administered testosterone undecanoate in man

[3H]-testosterone undecanoate ([3H]TU) was administered orally to 4 patients with a thoracic duct catheter after neck dissection surgery. Appearance of radioactivity in lymph, plasma and urine was measured at different times. Metabolites of TU in these fluids were investigated. Peak levels of radioactivity appeared simultaneously in lymph and plasma (2.5-5 h after administration) while the excretion in urine was highest approximately 2 h after the plasma and lymph peak. The main compounds appearing in the lymph were TU and 5alpha-dihydrotestosterone undecanoate (5alpha-DHTU), but 5beta-DHTU could not be detected. In plasma almost all metabolites were probably conjugated. During the first 24 h approximately 40% of the administered radioactivity was excreted in the urine. The total amount of radioactivity excreted in the urine during the first week was 45-48%. The predominant urinary metabolites were testosterone- and androsterone-glucuronide. The results indicate that TU is metabolized partly in the intestinal wall. The remaining TU and newly-formed 5alpha-DHTU, at least partly, are absorbed via the lymphatic system.     

Wide distribution of [3H](-)-epigallocatechin gallate, a cancer preventive tea polyphenol, in mouse tissue

The increasing recognition of green tea and tea polyphenols as cancer preventives has created a need for a study of their bioavailability. For this purpose, we synthesized [3H] (-)-epigallocatechin gallate ([3H]EGCG) with a specific activity of 48.1 GBq/mmol and directly administered the solution into the stomachs of CD-1 female or male mice. Radioactivity in the digestive tract, various organs, blood, urine and feces was measured with an oxidizer at various times after administration and significant radioactivity was found in the previously reported target organs of EGCG and green tea extract (digestive tract, liver, lung, pancreas, mammary gland and skin), as well as other organs (brain, kidney, uterus and ovary and testes) in both sexes. Incorporation of radioactivity in the cells was confirmed by microautoradiography. Within 24 h, 6.6 (females) and 6.4% (males) of total administered radioactivity was excreted in the urine and 37.7 and 33.1% in feces. HPLC analysis of urine from both sexes revealed that 0.03-0.59% of administered [3H]EGCG, along with at least five metabolites, was excreted. In addition, we found that a second, equal administration to female mice after a 6 h interval enhanced tissue levels of radioactivity in blood, brain, liver, pancreas, bladder and bone 4-6 times above those after a single administration. These results suggest that frequent consumption of green tea enables the body to maintain a high level of tea polyphenols and this paper is the first pharmacological evidence of a wide distribution of [3H]EGCG in mouse organs, indicating a similar wide range of target organs for cancer prevention in humans.     

Metabolic disposition of 14C-bromfenac in healthy male volunteers

The metabolic disposition of 14C-bromfenac, an orally active, potent, nonsteroidal, nonnarcotic, analgesic agent was investigated in six healthy male subjects after a single oral 50-mg dose. The absorption of radioactivity was rapid, producing a mean maximum plasma concentration (Cmax) of 4.9 +/- 1.8 microg x equiv/mL, which was reached 1.0 +/- 0.5 hours after administration. Unchanged drug was the major component found in plasma, and no major metabolites were detected in the plasma. Total radioactivity recovered over a 4-day period from four of the six subjects averaged 82.5% and 13.2% of the dose in the urine and feces, respectively. Excretion into urine was rapid; most of the radioactivity was excreted during the first 8 hours. Five radioactive chromatographic peaks, a cyclic amide and four polar metabolites, were detected in 0- to 24-hour urine samples. Similarity of metabolite profiles between humans and cynomolgus monkeys permitted use of this animal model to generate samples after a high dose for structure elucidation. Liquid chromatography/mass spectrometry (LC/MS) analysis of monkey urine samples indicated that the four polar metabolites were two pairs of diastereoisomeric glucuronides whose molecular weight differed by two daltons. Enzyme hydrolysis, cochromatography, and LC/MS experiments resulted in the identification of a hydroxylated cyclic amide as one of the aglycones, which formed a pair of diastereoisomeric glucuronides after conjugation. Data also suggested that a dihydroxycyclic amide formed by the reduction of the ketone group that joins the phenyl rings formed the second pair of diastereoisomeric glucuronides. Further, incubation of various reference standards in control (blank) urine and buffer with and without creatinine indicated that the hydroxy cyclic amide released from enzyme hydrolysis can undergo ex vivo transformations to a condensation product between creatinine and an alpha-keto acid derivative of the hydroxy cyclic amide that is formed by oxidation and ring opening. Further experiments with a dihydroxylated cyclic amide after reduction of the keto function indicated that it too can form a creatinine conjugate.     

Distribution and excretion of radiolabeled temoporfin in a murine tumor model

The biodistribution and excretion of temoporfin (tetra[m-hydroxyphenyl]chlorin, m-THPC), a recently developed photosensitizer, was investigated in BALB/c mice. [14C]temoporfin was administered intravenously (0.73 mumol/kg) to tumor-free mice or to mice implanted with the Colo 26 colorectal carcinoma. Blood, tissue and fecal samples were collected for 35 days and 10 days postdose from tumor-free mice and tumor-bearing mice, respectively. Blood concentrations fell rapidly such that at later time points they were indistinguishable from background counts. Tumor concentrations rose to a peak of 0.34 microgram temoporfin equivalents/mL at 2 days and then declined in parallel (log plot) with the blood concentrations. Tumor: tissue ratios at 2 days for skin, adipose tissue and skeletal muscle underlying the tumor were 1.5, 2.3 and 3.8, respectively. By 4 days the corresponding values were 1.6, 3.4 and 4.0. Nearly 40% of the administered radioactivity was excreted in the feces in the first 24 h and more than 80% had been excreted by 20 days. Less than 0.2% of the dose was recovered from the urine. An elimination half-life of 10-12 days was calculated from the excretion data.     

The metabolic fate of the coronary vasodilator 4-(3,4,5-Trimethoxycinnamoyl)-1-(N-pyrrolidinocarbonylmethyl)piperazine (cinepazide) in the rat, dog and man

1. An oral dose of the coronary vasodilator 4-(3,4,5-trimethoxy[14C]cinnamoyl)-1-(N-pyrrolidinocarbonylmethyl)piperazine was well absorbed and more than 60% of the dose was excreted within 24 h. In 5 days, rats, dogs, and man excreted in the urine and faeces respectively 36.7% and 58.3%, 33.4% and 68.6%, and 61.3% and 38.1% dose. Faecal radioactivity was probably excreted via the bile. 2. Plasma concentrations of radioactivity reached a maximum within about 1 h in all three species and declined fairly rapidly (t0.5 less than 3 h). For several hours, more than 50% of the plasma radioactivity was due to unchanged drug. After correction for dose and body weight (normalization), peak plasma concentrations of unchanged drug in man, rat and dog were in the approximate ratio 100 :30:1. 3. Similar metabolites were excreted by the three species, but the relative proportions differed. Rats and man excreted 17.2% and 15.9% respectively as unchanged drug in the urine whereas dogs excreted only 3.6%. Rat bile and urine contained 4.3% and 9.8% dose respectively as glucuronides of the mono-O-demethylated compounds and dog and human urine contained 9.0% and 2.6% respectively of these metabolites. The corresponding pyrrolidone accounted for 2.5%, 5.5% and 5.1% respectively in rat, dog and human urine. Complete O-demethylation also occurred since 4-(3,4,5-trihydroxycinnamoyl)-1-(N-pyrrolidinocarbonylmethyl)piperazine was present in rat faeces (22.1% dose).