Pharmacokinetics of 4-acetylaminophenylacetic acid. 1st communication: absorption, distribution, metabolism and excretion in mice, rats, dogs and monkeys after single administration of 14C-labeled compound

Absorption, distribution, metabolism and excretion of 4-acetylaminophenylacetic acid (MS-932) were studied in mice, rats, dogs and monkeys after intravenous or oral administration of 5 or 10 mg/kg of 14C-MS-932. After the intravenous injection of 14C-MS-932, the radioactivity concentrations in the plasma decreased biexponentially. The half-lives of the elimination phase (t1/2, beta) were 2.58 h for mice, 2.35 h for rats, 1.88 h for dogs and 1.24 h for monkeys. After the oral administration of 14C-MS-932, the radioactivity concentrations in the plasma reached maximums between 0.4 and 1.3 h, thereafter decreasing with half-lives similar to those found for the intravenous injection. The systemic availability of this drug was 72-100% in all the species tested. No clear sex-related difference in radioactivity concentrations was found in rat plasma. After both intravenous and oral administrations, in all the species tested, almost all the radioactivity administered was excreted in the urine. Biliary excretion of radioactivity in bile duct-cannulated rats was only 1.42% of the intravenous dose over a 24-h period. Lymphatic absorption of radioactivity was negligible (0.2% of the dose over a 6-h period). After oral administration of 14C-MS-932, the radioactivity concentrations in the rat tissues tested reached maximums within 1 h, decreasing rapidly thereafter similar to the decrease in the concentration in the plasma. Much higher concentrations were present in the kidney and gastro-intestinal tract than in the plasma, whereas the concentrations in the other tissues were lower. Results obtained by whole-body autoradiography were consistent with those obtained for the radioactivity in excised tissues.(ABSTRACT TRUNCATED AT 250 WORDS)     

The absorption, distribution, metabolism and elimination of bevirimat in rats

Bevirimat is the first drug in the class of maturation inhibitors, which treat HIV infection by disrupting the activity of HIV protease enzyme with a mechanism of action distinct from that of conventional protease inhibitors. The absorption, distribution, metabolism and elimination characteristics of single intravenous (25 mg/kg) and oral (25 mg/kg and 600 mg/kg) doses of 14C-bevirimat were studied in male Sprague Dawley and Long Evans rats. Pharmacokinetic and mass-balance studies revealed that bevirimat was cleared rapidly (within 12-24 h) after dosing, although plasma radioactivity was quantifiable up to 168 h. Radioactive metabolites of bevirimat were responsible for approximately 60-80% of plasma radioactivity. Systemically available bevirimat was predominantly (97%) excreted via bile in the faeces, with 相似文献   

Pharmacokinetics of ciprofloxacin. 1st communication: absorption, concentrations in plasma, metabolism and excretion after a single administration of [14C]ciprofloxacin in albino rats and rhesus monkeys

The absorption, disposition, metabolism and excretion of 1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-(1-[U-14C]piperazinyl)-3- quinoline carboxylic acid (ciprofloxacin, Bay o 9867; designated tradename: Ciprobay) were studied following a single intraduodenal (rat), oral and intravenous (rat, monkey) administration, respectively, in the dose range 5 to 30 mg/kg body weight. Ciprofloxacin was absorbed partially (30 to 40%) in both species. Peak plasma concentrations of radioactivity were measured approximately 1 h (rat) or 2 h (monkey) after oral dosing. Terminal half-lives ranging from 26 to 44 h were determined for the elimination of radioactivity from the plasma (observation time up to 48 h after dosing). Nearly identical concentrations of the unchanged drug and total radioactivity were found during the first 7 or 8 h for the monkey after intravenous injection and for the rat also after oral administration, respectively. After reaching maximum concentration of 0.25 microgram/ml after administration of 5 mg/kg to rats and 0.88 microgram/ml after dosing with 30 mg/kg to a rhesus monkey, the unchanged drug was eliminated from plasma corresponding to half-lives ranging from 3 h (rat) and 4.4 h (monkey). The radioactivity was rapidly and completely excreted in both species. After intravenous administration about 51% (rat) and 61% (monkey), respectively, was excreted via the kidney. After oral dosing renal excretion amounted to 6-14% (rat) and 30% (monkey), respectively. Maximum residues in the body (exclusive gastrointestinal tract) of 1% of dose occurred in both species. In urine and feces of rats predominantly the unchanged drug and a conjugate were detected.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic fate of the new angiotensin-converting enzyme inhibitor imidapril in animals. 3rd communication: tissue accumulation after consecutive oral administration of [N-methyl-14C]-imidapril in rats.

Accumulation characteristics of radioactivity in the organs and tissues, metabolism, and excretion of imidapril hydrochloride ((-)-(4S)-3-[(2S)-2-[[(1S)-1-ethoxycarbonyl-3- phenylpropyl]amino]propionyl]-1-methyl-2-oxoimidazolidine-4-carboxylic acid hydrochloride, imidapril, TA-6366, CAS 89396-94-1), an oral angiotensin-converting enzyme inhibitor, were investigated after consecutive oral administration of [N-methyl-14C]-imidapril at a once-daily dose of 1 mg/kg to male rats for 14 days. During the consecutive oral administration, the plasma radioactivity levels at 1 h after each dose reached steady-state following the 3rd to 4th administered dose; this was about 1.4 times higher than the corresponding plasma levels of the first dose. At 24 h after each administration, the plasma levels attained a steady-state at 3-4 days after the beginning of the consecutive dosing. Examination of the time course of plasma radioactivity after the single and multiple (7 and 14 times) oral administration revealed that the Cmax and AUCO-24 h values slightly, but significantly, increased according to repeated dosing and the beta-phase of the t1/2 of disappearance became longer after consecutive dosing. However, these values were not markedly different among consecutive dosing groups. The extent and rate of excretion of radioactivity in the urine and feces were nearly constant during the periods of consecutive oral administration, and were also similar to those after the single oral administration. Total recovery of radioactivity from urine and feces within 96 h after the final dosing was more than 98% of the total dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics of nimodipine. I. Communication: absorption, concentration in plasma and excretion after single administration of [14C]nimodipine in rat, dog and monkey

Studies on absorption, plasma concentrations and excretion with (+/-)isopropyl-2-methoxyethyl-1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl) -3,5-pyridinedicarboxylate (nimodipine, Bay e 9736, Nimotop) have been conducted in rat, dog and monkey using the carbon-14-labelled substance and a wide range of doses (0.05-10 mg/kg) administered via different routes (intravenous, oral, intraduodenal). Nimodipine was well absorbed in all species. Peak plasma concentrations of radioactivity were determined 28-40 min (male rat), 60 min (female rat), about 3 h (dog) and 7 h (monkey) after administration. Dependent on the observation period (24-216 h) terminal half-lives for the elimination of radioactivity from plasma ranging between 4.6 h (female rat) and 157 h (dog) were observed. Comparing the AUC, the concentration of unchanged [14C]nimodipine in plasma represented only a small (maximally 37% in dogs after i.v. dose) to negligible (about 1%, monkey after oral dosing) part of the total radioactivity. Excretion of radioactivity via feces and urine was rapid in all species after both oral and intravenous dosing. Fecal (biliary) excretion was the major excretory route in rat and dog. The monkeys excreted about 40 to 50% via the urine. Residues in the body never exceeded 1.5% of the dose. [14C]nimodipine and/or its radiolabelled metabolites were secreted in milk of orally dosed lactating rats. Binding of [14C]nimodipine to plasma proteins of rat and dog was about 97%.     

Pharmacokinetics of nisoldipine. I. Absorption, concentration in plasma, and excretion after single administration of [14C]nisoldipine in rats, dogs, monkey, and swine

The absorption, disposition and excretion of (+/-) 3-isobutyl-5-methyl 1,4-dihydro-2,6-dimethyl-4-(2-nitrophenyl)-pyridine-3,5-dicarboxylate (nisoldipine, Bay k 5552) have been studied following a single administration of the 14C-labelled compound to rats, dogs, monkey and swine via different routes (intravenous, oral, intraduodenal) in the dose range of 0.05-10 mg.kg-1. [14C]nisoldipine was absorbed rapidly and almost completely. Peak concentrations of radioactivity in plasma were reached 0.9 h (rat), 1.4 h (dog), and 3.6 h (monkey) after oral administration with normalized maximum concentrations being in the same range for all three species (0.49-0.79). The radioactivity was eliminated from plasma with half-lives between 42 h and 54 h within an observation period up to 3 days. The contribution of unchanged [14C]nisoldipine to the concentration of total radioactivity in plasma was low after oral administration (between 0.5% (monkey) and 3.4% (dog) in the peak) indicating an extensive presystemic elimination of this compound. The bioavailability was estimated at 3.4% in rats and 11.7% in dogs. [14C]nisoldipine was highly bound to plasma proteins with free fractions of 0.9-2.9%. The excretion of the radioactivity via urine and feces/bile both after oral and intravenous administration of [14C]nisoldipine occurred rapidly and almost completely within 48 h in all species. Very small residues in the body were recovered at the end of the experiments in rats and dogs (less than 1.6% of the dose). The biliary/fecal route of excretion was preferred in rats, dogs and swine, whereas in monkey 76% of the dose was excreted renally.(ABSTRACT TRUNCATED AT 250 WORDS)     

Absorption, distribution, and excretion of DJ-927, a novel orally effective taxane, in mice, dogs, and monkeys

DJ-927, currently undergoing Phase I clinical trial, is a new orally effective taxane with potent antitumor effects. The absorption, tissue distribution, and excretion of DJ-927 were investigated in mice, dogs, and monkeys after a single oral administration. After oral administration of [14C]DJ-927, radioactivity was rapidly absorbed, with the Cmax occurring within 1-2 h in all species. The blood and plasma radioactivity elimination was biphasic and species-dependent. Elimination half-life of plasma in dogs was much longer than those in monkeys or mice. In mice, radioactivity was rapidly distributed to all tissues except for the central nervous system, especially to adrenal glands, liver, pituitary glands, kidneys, lungs, and spleen. In all species, radioactivity was mainly excreted in feces. Following a single oral administration to mice, more than 80% of the radioactivity was excreted within 48 h; in dogs and monkeys, 80% of the radioactivity was excreted within 168 h. Urinary excretion was less than 7% of radioactive dose in all species. In vitro plasma protein binding of [14C]DJ-927 in the mouse, dog, and monkey plasma ranged from 92-98%. These studies showed that, the novel oral taxane DJ-927 was rapidly absorbed in all three species when administered by the oral route. The long biological half-life and slow elimination of radioactivity were distinctive in particular, compared with commercial taxanes. DJ-927 (as parent compound and its metabolites) is widely distributed to tissues except the brain. These preclinical data are useful for the design of clinical trials of DJ-927 and also for their interpretation.     

Disposition and metabolism of (2S,3S,4R)-N'-cyano-N-(6-amino-3,4-dihydro-3-hydroxy-2-methyl-2-dimethoxy methyl-2H-benzopyran-4-yl)-N'-benzylguanidine, a novel neuroprotective agent for ischemia-reperfusion damage, in rats

The metabolism and disposition of KR31378 (a benzopyran derivative and a novel neuroprotective agent) were investigated following single oral or intravenous administration of [(14)C]-KR31378 to rats. [(14)C]-KR31378 was rapidly absorbed after oral dosing with an oral bioavailability of greater than 71%. The maximum plasma concentration and area under the curve of total radioactivity in rat plasma increased proportionally to the administered dose. KR31378 was distributed over all organs and tissues except for brain, eyeball and testis, and declined by first order kinetics up to 24 h after dosing. Excretion of the radioactivity was 29.5% of the dose in the urine and 58.5% in the feces within 2 days after oral administration. Biliary excretion of the radioactivity in bile duct-cannulated rats was about 66.0% for the first 24 h. KR31378 was extensively metabolized by ring hydroxylation, O-demethylation, oxidation and reduction with subsequent N-acetylation and O-glucuronide conjugation. N-acetylated conjugates (M2, M10, M11, M12, M14, and M15) were identified as the predominant metabolites in rats.     

Absorption, distribution and excretion of 2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate in rats, dogs and monkeys

Absorption, distribution and excretion of 2,4-diamino-6-(2,5-dichlorophenyl)-s-triazine maleate (MN-1695) were studied in rats, dogs and monkeys after administration of [14C]-MN-1695. MN-1695 was found to be well absorbed from the small intestine after oral administration in all species examined. Plasma level of unchanged MN-1695 reached a maximum at 1 to 4 h after oral administration of [14C]-MN-1695 in rats, dogs and monkeys. The mean elimination half-life of unchanged MN-1695 from plasma was about 3, 4 and 50 h in rats, dogs and monkeys, respectively. Tissue levels of radioactivity after oral administration of [14C]-MN-1695 in rats indicated that [14C]-MN-1695 was distributed throughout the body and the radioactivity in tissues disappeared with a rate similar to that in plasma. A stomach autoradiogram after intravenous administration of [14C]-MN-1695 in the rat revealed the radioactivity localized in the gastric mucosa where MN-1695 was assumed to exert its pharmacological activity. In pregnant rats, [14C]-MN-1695 was distributed to the fetus with levels similar to maternal blood levels. After oral administration of [14C]-MN-1695 in rats, 39 to 46% of the dose was excreted into the urine and 50 to 63% of the dose into the feces, within 96 h. In dogs, about 40% of the dose was excreted into the urine and about 50% of the dose into the feces, within 6 days after oral administration. In monkeys, within 14 days after oral administration, about 60 and 30% of the dose were excreted into the urine and feces, respectively, and the main excretion route was the urine.(ABSTRACT TRUNCATED AT 250 WORDS)     

The pharmacokinetics and metabolism of idazoxan in the rat

1. [2'-14C]Idazoxan was rapidly and completely absorbed after its oral administration to rats. 2. After administration of either [2'-14C] or [6,7-3H]idazoxan, radioactivity was taken up by a wide range of tissues and became localized, especially in the organs of metabolism and excretion. Quantitative distribution patterns were route-dependent such that oral dosing resulted in lower radioactivity concentrations in all tissues apart from liver. 3. Clearance of idazoxan (94-144 ml/min per kg) was due mostly to metabolism and was independent of dose. Oral bioavailability in male rats at low oral doses of idazoxan (10 mg/kg) was about 1%, but increased with increasing dose to 23% at 100 mg/kg. Oral bioavailability in female rats was considerably higher than in male rats, at all doses studied. Brain idazoxan levels were in equilibrium with those in plasma, but ten-fold higher. 4. Elimination of radioactivity after administration of 14C-idazoxan was via the urine and the faeces (about 75% and 20% of dose respectively) and occurred essentially in the 24 h period immediately after dosing. By 96 h after dosing, elimination was virtually complete, with less than 0.5% dose remaining in the carcasses. 5. Biotransformation was by hydroxylation at positions 6 and 7 to form phenolic metabolites, which were excreted as glucuronide and sulphate metabolites in urine, but unconjugated in faeces. Other minor metabolic routes were 5-hydroxylation or oxidative degradation of the imidazoline ring, but these pathways were of quantitatively minor importance in the rat.     

The disposition of clavulanic acid in man

Following oral administration of potassium 14C-clavulanate to four human subjects, at least 73% of the radioactive dose was absorbed. The mean absolute bioavailability was 64%. Absorption was rapid with peak plasma concentrations of radioactivity and clavulanic acid (2-6 micrograms/ml) occurring between 45 min and three hours after dosing. Values for the volume of distribution at steady-state and terminal half-life of clavulanic acid in the plasma were 12.01 and 0.8 h respectively. Following intravenous administration of clavulanic acid to the same subjects, the clearance, and volume of distribution at steady-state were 0.21 l/min, and 12.01, respectively. Clavulanic acid was the major radioactive component present in 0-24 h urine following oral dosing (23% of the dose). The two major metabolites were 2,5-dihydro-4-(2-hydroxyethyl)-5-oxo-1H-pyrrole-3-carboxylic acid (15% of the dose) and 1-amino-4-hydroxybutan-2-one (8.8% of the dose). Clavulanic acid and 1-amino-4-hydroxybutan-2-one were the major components in plasma following oral administration (52 and 21% of plasma radioactivity respectively at two hours after dosing). The major route of excretion of radioactivity following oral administration was via the urine (73% of the dose). Most of this radioactivity was excreted in the first 24 h after dosing (68% of the dose). The renal clearance of clavulanic acid was 0.1 l/min. Elimination of radioactivity also occurred via the expired air (17% of the dose) and the faeces (8% of the dose).     

Evidence for a different metabolic behaviour of cytidine diphosphate choline after oral and intravenous administration to rats

Radioactivity plasma decay was studied in rats after intravenous and oral administration of cytidine diphosphate [methyl-14C]choline at doses of 25 and 300 mg/kg. The kinetics fitted well with a two compartment open model and showed a long lasting elimination phase with a half-life ranging from 2.0 to 2.6 days for the two doses and the two administration routes. Absorption of cytidine diphosphate choline radioactivity was complete after oral treatment with the low dose and accounted for 94.5% of the dose when 300 mg/kg of cytidine diphosphate [methyl-14C]choline were administered. However the distribution of radioactivity in tissues, urine and expired air suggest metabolic differences, at least from a quantitative point of view, between the oral and intravenous treatments. In particular, the higher excretion of radioactivity associated with trimethylamine in urine found when cytidine diphosphate [methyl-14C]choline was given orally, suggest that the compound may be metabolized, at least in part, previous to its gastrointestinal absorption.     

Pharmacokinetics of falintolol II. Absorption, distribution and elimination from tissues and organs following ocular administration and intravenous injection of falintolol in albino rabbits

The absorption, distribution and elimination of falintolol maleate was studied in various ocular and extraocular tissues and organs following ocular instillation, intravenous injection of a 0.5% 14C-falintolol ophthalmic solution and repeated ocular instillations of a 1% non-labeled falintolol ophthalmic solution into albino New Zealand rabbits. Falintolol was distributed in all studied tissues and organs after both routes of administration. After ocular instillation, levels of total radioactivity were distinctly higher in ocular tissues than after intravenous injection. Thus, the level was 475 times more important in cornea, 72 times in aqueous humor and 36 times in iris and ciliary body after ocular instillation. On the other hand, levels of total radioactivity in extraocular tissues and organs were 30-50% higher after intravenous injection compared to ocular instillation of the same dose. Peak levels of total radioactivity were generally achieved between 30 min and 1 h after ocular instillation, while 1.5 h after intravenous injection an increase in the declining part of the curve occurred. This increase, characteristic of an enterohepatic reabsorption, was also observed in blood and plasma 1 h after intravenous injection. Urinary elimination was the major means of excretion since 79.6% of total radioactivity was found in urine 6 h after intravenous injection and 74.5% 12 h after ocular instillation. But after ocular instillation, only 5% was excreted as unchanged falintolol. Whatever the route of administration, after single or repeated application, no drug accumulation was evident.     

Pharmacokinetics of ciprofloxacin. 2nd communication: distribution to and elimination from tissues and organs following single or repeated administration of [14C]ciprofloxacin in albino rats

1-Cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-7-(1-[U-14C]piperazinyl)-3-quinoline carboxylic acid (ciprofloxacin, Bay o 9867; designated tradename: Ciprobay) was administered to male and to pregnant albino rats with single intravenous or oral doses of 5 or 10 mg/kg body weight and with repeated oral doses of 5 mg/kg (7 consecutive daily administrations to male rats). Following a single intravenous administration the [14C]ciprofloxacin related radioactivity was distributed rapidly and differentiated to the body. Compared to plasma high concentrations were determined in kidney, liver, skeleton muscle, pancreas, testes and cartilage, low concentrations occurred in brain and adipose tissue. In some selected tissues radioactivity was largely due to unchanged [14C]ciprofloxacin (57% to 100%). A good penetration of total radioactivity into tissues and organs with a similar distribution pattern as detected after intravenous dosing also occurred after a single oral administration. Highest concentrations were determined 1 h after dosing. Compared to plasma most tissues and organs showed higher concentrations and higher AUC-values. For brain and eye low values were determined. Compared to plasma a longer mean residence time of radioactivity was calculated for brain, eye, eye-wall, testes and blood cells. 6 d after single administration the radioactive residues in the body exclusive gastrointestinal tract amounted to less than 0.1% of the dose. Following a seven-day treatment the distribution pattern of total radioactivity in the body did not differ essentially from that after single dosing. Compared to single dosing AUC-values higher by the factor 2 to 4 were calculated after repeated administration for plasma and most of the tissues and organs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolism of 8-chloro-6-(o-chlorophenyl)-1-methyl-4H-s-triazolo [4,3-alpha] [1,4] benzodiazepine, triazolam, a new central depressant. I. Absorption, distribution and excretion in rats, dogs and monkeys.

1. Peak radioactivity in the blood was reached at 30 min after i.p. and 1 h after oral dosing of [14C]triazolam to rats. In dogs, peak blood level was observed at 30 min after oral dosing. 2. Daily dosing of triazolam to male rats for 21 days caused a gradual increase in blood level, with peak at 1 h after dosing. 3. The rate of binding of triazolam plus its metabolites to plasma protein of rats was about 30% at 15 min and 6 h. 4. In rats, the majority of the activity of the intra-intestinally administered [14C]triazolam was found in the small intestines in 6 h. 5. About 58% of the oral dose and 77% of the i.p. dose were recovered in the bile of rats in 48 h after dosing. When the bile from one rat was introduced into the duodenum of a second rat, approximately 37% was recovered in the bile of the second animal in 24 h. 6. In male rats, high radioactivity was seen in the liver, kidneys, adrenals and heart, and low in the CNS. By 96 h after dosing, radioactivity in the liver, blood and kidneys was very low, and was undetectable in other tissues and organs. Radioactivity levels in tissues after daily dosing for 7, 14 and 21 days did not differ appreciably from single administration. 7. In monkeys, activity was high in the liver, kidneys and skin following oral administration and low in the CNS. 8. After oral administration of [14C]triazolam to pregnant rats, the activity in the uterus and placenta was higher than that in the maternal blood. The activity in the foetus was low. 9. In rats given [14C]triazolam orally or i.p., 85% and 12% of the oral dose, and 82% and 14% of the i.p. dose were recovered in the faeces and urine, respectively, in 96 h. The rate of cumulative faecal and urinary excretion after repeated dosing was similar to the single dosing with 80% and 14% of the activity recovered, respectively, in faeces and urine in 6 days. In dogs, 50% of the oral dose was found in the faeces and 40% in the urine. 10. Radioactivity in the milk of rats was maximal at 4 h after oral dosing. It declined to 34% of the peak level 48 h later.     

Absorption,tissue distribution and elimination of 4-[(3)h]-epigallocatechin gallate in beagle dogs

Polyphenols found in tea are potent antioxidants and have inhibitory activity against tumorigenicity. The purpose of the described study was to assess the absorption, tissue distribution, and elimination of epigallocatechin gallate (EGCG), the principal catechin found in green tea, in a nonrodent species. 4-[(3)H]-EGCG was administered to beagle dogs by intravenous (IV) and oral routes. Following IV administration of 25 mg/kg, radioactivity in the bloodstream resided predominantly in the plasma. Distribution occurred during the first hour, and the plasma levels of total radioactivity declined with a mean half-life of approximately 7 hours. The apparent volume of distribution (0.65 l/kg) indicated wide distribution, and the total body clearance (1.01 ml/min-kg) was low. A subsequent single oral dose (250 mg/kg) was rapidly absorbed, with peak plasma levels at about 1 hour after administration, followed by elimination with a mean half-life of 8.61 hours. The mean area under the curve (AUC) for total radioactivity was approximately 20% of the value following IV administration (corrected for dose administered). Excretion of radioactivity in the feces predominated over urinary excretion following both IV and oral administration of [(3)H]-EGCG. Tissue distribution was determined 1 hour after an IV dose (25 mg/kg) administered after 27 days of oral treatment with EGCG (250 mg/kg/day) to mimic chronic consumption of tea. Radioactivity was distributed to a variety of epithelial tissues; the highest concentrations were observed in the liver and gastrointestinal tract tissues. Repeat dose oral administration of EGCG resulted in significantly lower blood radioactivity compared to the concentration following a single dose. These results are generally in accord with previous studies in rodents and indicate that, after oral administration, EGCG (as parent compound and metabolites) is widely distributed to tissues where it can exert a chemopreventive effect.     

The metabolic disposition of C-labelled carmoisine in the rat after oral and intravenous administration

The absorption, distribution and excretion of the red azo dye carmoisine (Ext. D & C No. 10) was studied in male rats. [14C]Carmoisine was administered in a dose of 200 mg/kg (25 microCi) by gavage or in the same dose (200 mg/kg; 3 microCi) by intravenous injection, and radioactivity was measured in blood, tissue, faeces and urine at different times after dosing. After oral administration of the dye, no radioactivity was detected in the brain, adipose tissue, muscle, testes, spleen or lung, and recovery of the administered activity in faeces and urine was almost complete by 32 hr. The radioactivity profile of the blood indicated rapid but poor absorption of [14C]carmoisine, a maximum radioactivity content corresponding to 0.01% of the dose per ml of blood being reached within 10 min. The decay curve for 14C radioactivity in the blood after iv injection of [14C]carmoisine indicated rapid distribution to the tissues and could be described in terms of a two-compartment mathematical model. The highest levels of radioactivity occurred in the gastro-intestinal tract and liver after the injection but after 24 hr no radioactivity was detectable in these or other tissues. All the radioactivity was recovered in the faeces and urine in the 24 hr following iv injection, the 79% of the dose present in faeces indicating active excretion of the dye and its metabolites in the bile and poor reabsorption from the intestine. The bioavailability of [14C]carmoisine, calculated from the blood-radioactivity curves after oral and iv administration, was less than 10%.     

Pharmacokinetics, tissue distribution, and excretion of sitafloxacin, a new fluoroquinolone antibiotic, in rats, dogs, and monkeys

The pharmacokinetics, tissue distribution and excretion of sitafloxacin (CAS 127254-12-0, DU-6859a) were investigated in rats, dogs, and monkeys following single intravenous or single oral administration of 14C-labelled sitafloxacin at a dose of 4.69 mg/kg. Following single administration of the oral dose, serum concentrations of radioactivity peaked at 0.5 h in rats, 2.3 h in dogs, and 2.5 h in monkeys. The apparent absorption ratios of 14C-sitafloxacin based on the AUC0-infinity were 31%, 51%, and 93% in rats, dogs, and monkeys, respectively. In rats, the drug-related radioactivity had been distributed to most organs and tissues 30 min after oral dosing, and had been essentially eliminated after 24 h. The highest levels of radioactivity were observed in the kidneys and liver, whereas the concentrations in the cerebrum and spinal cord were much lower than the serum value. The urinary recoveries of radioactivity after intravenous dosing were 45.5 % in rats, 32.3 % in dogs, and 77.8 % in monkeys. In bile duct-cannulated rats, 57.8 % of the orally administered radioactivity was excreted in the bile within 48 h, and at least 45 % of the sitafloxacin-related material secreted in the bile was re-absorbed from the gastrointestinal tract. These results indicate that sitafloxacin is rapidly absorbed and widely distributed into various tissues. Sitafloxacin-related material is eliminated primarily through both renal and biliary excretion in rats, and possibly in dogs, whereas renal excretion is the major route of elimination in monkeys.     

Absorption,distribution and excretion of nilvadipine,a new dihydropyridine calcium antagonist,in rats and dogs

1. The absorption, distribution and excretion of nilvadipine have been studied in male rats and dogs after an i.v. (1 mg/kg for rats, 0.1 mg/kg for dogs) and oral dose (10 mg/kg for rats, 1 mg/kg for dogs) of ¹⁴C-nilvadipine.

2. Nilvadipine was rapidly and almost completely absorbed after oral dosing in both species; oral bioavailability was 4.3% in rats and 37.0% in dogs due to extensive first-pass metabolism. The ratios of unchanged drug to radioactivity in plasma after oral dosing were 0.4–3.5% in rats and 10.4–22.6% in dogs. The half-lives of radioactivity in plasma after i.v. and oral dosing were similar, i.e. 8–10h in rats, estimated from 2 to 24 h after dosing and 1.5 d in dogs, estimated from 1 to 3 d. In contrast, plasma concentrations of unchanged drug after i.v. dosing declined biexponentially with terminal phase half-lives of 1.2 h in rats and 4.4 h in dogs.

3. After i.v. dosing to rats, radioactivity was rapidly distributed to various tissues, and maintained in high concentrations in the liver and kidneys. In contrast, after oral dosing to rats, radioactivity was distributed mainly in liver and kidneys.

4. With both routes of dosing, urinary excretion of radioactivity was 21–24% dose in rats and 56–61% in dogs, mainly in 24 h. After i.v. dosing to bile duct-cannulated rats, 75% of the radioactive dose was excreted in the bile. Only traces of unchanged drug were excreted in urine and bile.     

Pharmacokinetics, metabolism and excretion of an inhibitor of inducible nitric oxide synthase, L-NIL-TA, in dog

1. The pharmacokinetics, metabolism and excretion of L-NIL-TA, an inducible nitric oxide synthase inhibitor, were investigated in dog. 2. The dose of [14C]L-NIL-TA was rapidly absorbed and distributed after oral and intravenous administration (5 mg kg-1), with Cmax of radioactivity of 6.45-7.07 microg equivalents g-1 occurring at 0.33-0.39-h after dosing. After oral and intravenous administration, radioactivity levels in plasma then declined with a half-life of 63.1 and 80.6-h, respectively. 3. Seven days after oral and intravenous administrations, 46.4 and 51.5% of the radioactive dose were recovered in urine, 4.59 and 2.75% were recovered in faeces, and 22.4 and 22.4% were recovered in expired air, respectively. The large percentages of radioactive dose recovered in urine and expired air indicate that [14C]L-NIL-TA was well absorbed in dogs and the radioactive dose was cleared mainly through renal elimination. The mean total recovery of radioactivity over 7 days was approximately 80%. 4. Biotransformation of L-NIL-TA occurred primarily by hydrolysis of the 5-aminotetrazole group to form the active drug L-N6-(1-iminoethyl)lysine (NIL or M3), which was further oxidized to the 2-keto acid (M5), the 2-hydroxyl acid (M1), an unidentified metabolite (M2) and carbon dioxide. The major excreted products in urine were M1 and M2, representing 22.2 and 21.2% of the dose, respectively.