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 [¹⁴C]-KR31378 to rats. [¹⁴C]-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.     

Pharmacokinetic studies of 2-amino-9-(3-acetoxymethyl-4-isopropoxycarbonyl-oxybut-1-yl)purine, an oral prodrug for the antiviral agent penciclovir.

2-Amino-9-(3-acetoxymethyl-4-isopropoxycarbonyloxybut-1-yl)- purine (SK1899) was tested as an oral prodrug for penciclovir. SK1899 was administered orally to rats and dogs at doses up to 2 and 0.68 mmol/kg, respectively. SK1899 was well absorbed, and the major metabolites detected in plasma and urine were penciclovir, the active antiviral compound, and 6-deoxypenciclovir (M4) in both species. In rats, SK1899 was rapidly and extensively metabolized to penciclovir, which reached the peak plasma concentration (C(max)) of 39.5 microM at 0.5 h after 0.2-mmol/kg dosing. The area under the plasma concentration-time curve (AUC) for penciclovir was 57.5 microM x h. After an oral dose of 0.034 mmol/kg to dogs, extensive conversion of SK1899 to penciclovir also occurred with slower rate of formation of penciclovir from M4 than in rats. The mean C(max) and AUC for penciclovir were 4.5 microM at 2.7 h and 28.2 microM x h, respectively. The 0- to 24-h urinary recovery of penciclovir represented 36.1 and 36.3% of dose to rats and dogs, respectively. Radioactivity was found in fetuses following an oral administration of [(14)C]SK1899 to pregnant rats, but no significant accumulation was observed. Although substantial milk transfer of [(14)C]SK1899 occurred in rats, the radioactivity in milk was rapidly cleared. The values of C(max), AUC, and urinary recovery of penciclovir after dosing with SK1899 to rats and dogs were similar or slightly higher than those from famciclovir. These data indicate that introduction of an isopropoxy carbonate group into one of the two hydroxyl groups of M4 did not significantly alter the oral bioavailability of penciclovir compared with famciclovir.     

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)     

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.     

Distribution to and elimination from tissues following a single or repeated administration of 14C-(+-)-3-(benzyl-methylamino)-2,2-dimethylpropyl methyl 4-(2-fluoro-5-nitrophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedica rbo xylate hydrochloride in rats.

A newly synthesized calcium antagonist, TC-81((+-)-3-benzylmethylamino)-2,2-dimethylpropyl methyl-4-(2-fluoro-5-nitrophenyl)-1,4-dihydro-2,6-dimethyl-3,5- pyridinedicarboxylate hydrochloride, CAS 96515-74-1) was administered to adult male rats, pregnant and lactating rats with a single oral dose or with repeated doses of 0.3 mg/kg for 2 weeks. The distribution to tissues, placental transfer and secretion of the radioactive drug into milk was studied using whole body autoradiography methods and quantitative determination of total radioactivity after autopsy. 14C-TC-81 was distributed rapidly but disproportionately to the tissues after single administration. The highest concentration of radioactivity was observed in the liver. The radioactivity in the various tissues declined slowly comparing to the plasma but at 96 h after dosing the radioactivity was detected only in the liver. The radioactivity penetrated the blood-placental barrier to a low extent after oral administration of 14C-TC-81 to pregnant rats. When 14C-TC-81 was administered to lactating rats, the radioactivity was secreted into the milk with the maximum concentration of radioactivity, 86% of the corresponding plasma concentration. Following 14-day oral treatments of male rats the equivalent concentration in the plasma was increased 1.5 fold as compared to the single treatment. In all tissues, the AUC0-24 h after 1, 7, and 14 days treatment were gradually increased, but these increases were almost the same as or even less than the rise observed in the plasma. After the last dosing, the radioactivity declined slowly with time in most of the tissues.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparative study on the disposition of a new orally active dopamine prodrug, N-(N-acetyl-L-methionyl)-O,O-bis(ethoxycarbonyl)dopamine (TA-870) and dopamine hydrochloride in rats and dogs

The pharmacokinetics of a dopamine derivative, TA-870, and dopamine (DA) after oral administration are compared in rats and dogs. The maximum concentrations of free DA in plasma after oral administration of TA-870 were 150 ng/ml in the rat (30 mg/kg) and 234 ng/ml in the dog (33.5 mg/kg). On the contrary, the maximum plasma concentrations after oral administration of DA at an equimolar dose to TA-870 were 12 ng/ml in the rat (12 mg/kg) and 36 ng/ml in the dog (13.5 mg/kg). The AUC values of free DA in plasma after oral administration of TA-870 (30 or 33.5 mg/kg) were 4-6 times higher than those after DA in both animal species. The peak tissue levels of radioactivity in rats after oral administration of [14C]TA-870 (30 mg/kg) were also 5.5 times higher in the liver and 1-2 times higher in other tissues than those after [14C]DA dose (12 mg/kg). In rats, the main excretion route of radioactivity after oral administration of [14C]TA-870 or DA was via the urine. The total recoveries of radioactivity in the urine and feces were 91-96% of the dose within 24 hr for both compounds. Biliary excretion in rats accounted for 19.8% of the dose of [14C]TA-870 and 12.6% of the dose of [14C]DA within 24 hr. These results demonstrate that TA-870 was well absorbed from the digestive tract, extensively metabolized to dopamine, and proved to be an orally usable dopamine prodrug.     

Absorption,distribution, metabolism and excretion of telmesteine,a mucolitic agent,in rat

1. The metabolism and disposition of telmesteine, a muco-active agent, have been investigated following single oral or intravenous administration of (14)C-telmesteine in the Sprague-Dawley rat. 2. (14)C-telmesteine was rapidly absorbed after oral dosing (20 and 50 mg kg(-1)) with an oral bioavailability of >90% both in male and female rats. The C(max) and area under the curve of the radioactivity in plasma increased proportionally to the administered dose and those values in female rats were 30% higher than in male rats. 3. Telmesteine was distributed over all organs except for brain and the tissue/plasma ratio of the radioactivity 30 min after dosing was relatively low with a range of 0.1-0.8 except for excretory organs. 4. Excretion of the radioactivity was 86% of the dose in the urine and 0.6% in the faeces up to 7 days after oral administration. Biliary excretion of the radioactivity in bile duct-cannulated rats was about 3% for the first 24 h. The unchanged compound mainly accounted for the radioactivity in the urine and plasma. 5. Telmesteine was hardly metabolized in microsomal incubations. A glucuronide conjugate was detected in the urine and bile, but the amount of glucuronide was less than 6% of excreted radioactivity.     

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)     

Absorption, plasma concentration, and excretion after single administration of 14C-(+-)-3-(benzylmethylamino)-2,2-dimethylpropyl methyl 4-(2-fluoro-5- nitrophenyl)-1,4-dihydro-2,6-dimethyl-3,5-pyridinedicarboxylate hydrochloride in rats and dogs.

The absorption, plasma concentrations, and excretion of a newly synthesized calcium antagonist, TC-81 ((+-)-3-(benzylmethylamino)-2,2-dimethylpropyl methyl 4-(2-fluoro-5-nitrophenyl)-1,4-dihydro-2,6-dimethyl-3,5- pyridinedicarboxylate hydrochloride, CAS 96515-74-1) were studied following a single oral or intravenous administration of 14C-labelled compound. After oral administration, 14C-TC-81 was rapidly and well absorbed from the gastrointestinal tract. The peak plasma concentrations of radioactivity were observed at 0.5-1 h (rats) and 1-2 h (dogs) h after dosing. The elimination of the radioactivity in plasma was biphasic with a half-life of 3.8-5.2 h (a phase) and 42.9-56.2 h (beta phase) in the rats or 3.2 h (a phase) and 61.5 h (beta phase) in dogs. Maximum plasma concentrations of unchanged drug after oral administration of TC-81 to male rats at the doses of 0.5, 1.0, and 3.0 mg/kg were 1.7, 7.3 and 15.6 ng/ml, respectively. They were attained at 0.5 h after dosing in every dose examined. Plasma levels of unchanged drug declined with a half-life of 0.39-1.15 h. When TC-81 was orally administered to male dogs at the doses of 0.1, 0.2 and 0.5 mg/kg, plasma concentrations of unchanged drug reached the maximum level at 0.5 h after dosing and the values were 0.8, 3.3 and 9.6 ng/ml, respectively. They were eliminated with a half-life of 2.4-2.8 h. The absolute bioavailability of unchanged drug was estimated to be 2.6-7.0% (rats) and 5.3-15.5% (dogs) of the dose.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolism, excretion, and pharmacokinetics of (3-{[4-tert-butyl-benzyl)-(pyridine-3-sulfonyl)-amino]-methyl}-phenoxy)-acetic acid, an EP2 receptor-selective prostaglandin E2 agonist, in male and female Sprague-Dawley rats.

Metabolism, excretion, and pharmacokinetics of a highly selective EP2 agonist, CP-533,536 (3-{[4-tert-butyl-benzyl)-(pyridine-3-sulfonyl)-amino]-methyl}-phenoxy)-acetic acid), were investigated in male and female Sprague-Dawley rats following an intravenous administration of a single 15 mg/kg dose of [(14)C]CP-533,536. At 144 h after the dose, the cumulative excretion of radioactivity averaged 98.2 +/- 3.44% and 97.0 +/- 4.82% in male and female rats, respectively. The radioactivity was predominantly excreted in feces, reaching 87% of the dose. Mean exposure [area under the concentration-time curve (AUC(0-infinity))] for both CP-533,536 and total radioactivity was higher in female rats than in male rats, whereas the plasma clearance of CP-533,536 and metabolites was lower in female rats compared to male rats. CP-533,536 was extensively metabolized in both male and female rats. The major oxidative pathway was due to the oxidation of the tert-butyl side chain to form the omega-hydroxy metabolite M4 (males, 19.7%; females, 6.5%). M4 was further oxidized to form the omega-carboxy metabolite M3 (males, 32.8%; females 1.66%) or conjugated via sulfation to form metabolite M6 (males 12.7%; females 36.2%). Other metabolites were due to N-oxidation of the pyridine ring (M5) and aromatic hydroxylation (M12), and conjugation with glucuronic acid. The secondary metabolites were due to N-dealkylation of the methyl-phenoxyacetic acid moiety and phase II conjugation. CP-536,536 accounted for about 63 and 72% of the AUC of the total radioactivity for male and female rats, respectively. Gender-related differences in the metabolism and pharmacokinetics were observed. omega-Carboxy metabolite M3 was the major metabolite in male rats, whereas M3-sulfate was identified as the major metabolite in female rats.     

Metabolic fate of the new angiotensin-converting enzyme inhibitor imidapril in animals. 1st communication: absorption, pharmacokinetics and excretion in rats and dogs.

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) is an ester prodrug of the angiotensin-converting enzyme (ACE) inhibitor, 6366 A (CAS 89371-44-8). Absorption, pharmacokinetics and excretion of imidapril were studied in rats and dogs after oral and intravenous administration of [N-methyl-14C]-imidapril and [N-methyl-14C]-6366 A (1 mg/kg). Following oral administration of 14C-labeled imidapril and 6366 A to rats, plasma concentrations of radioactivity were much higher after [N-methyl-14C]-imidapril dosing than after [N-methyl-14C]-6366 A dosing at all time points. Imidapril was relatively rapidly absorbed from the digestive tract and easily metabolized to the pharmacologically active 6366 A after oral dosing in the rats and dogs. Thus, imidapril proved to be an orally usable 6366 A prodrug. More than 62% and 38% of the dose were assumed to be absorbed from the gastrointestinal tract in the rats and dogs, respectively. The in situ absorption study showed that [N-methyl-14C]-imidapril was absorbed from nearly the entire rat small intestine, especially from the jejunum, but hardly absorbed from the stomach. After oral administration, peak levels of radioactivity in the plasma occurred at 1 h in rats and 30 min to 2 h in dogs. The disappearance of unchanged drug from the plasma was much faster in rats than in dogs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic fate of the new angiotensin-converting enzyme inhibitor imidapril in animals. 6th communication: interspecies comparison of pharmacokinetics and excretion of imidapril metabolites in rats, dogs, and monkeys.

The pharmacokinetics and excretion of the main metabolites 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) were investigated in rats, dogs, and monkeys after oral or intravenous administration of [N-methyl-14C]-imidapril and [alanine-3-14C]-imidapril. After oral administration of 14C-labeled imidapril to rats and dogs, the plasma concentrations of the pharmacologically active metabolite, 6366 A (M1, CAS 89371-44-8), reached a peak at 1-2 h in rats and at 2-6 h in dogs. The disappearance half-lives of M1 from plasma were much longer in dogs (6.3-9.3 h) than in rats (0.9-2.3 h). At the point of peak plasma radioactivity, the major radioactive metabolites in the plasma were M2, followed by M3, M4 greater than M1 in rats; in dogs, M2 and M3 followed by M1 greater than M4. After intravenous administration of [N-methyl-14C]-imidapril to rats and dogs, plasma levels of M1 reached a peak at the first measuring time of 5 min in rats and at about 2 h in dogs. The half-lives of plasma M1 levels were similar to those after oral dosing. At 1 h after dosing, the major metabolites in plasma were M1 followed by M2 in both rats and dogs. Irrespective of the route of administration, unchanged imidapril disappeared more rapidly from the plasma in rats than in dogs.(ABSTRACT TRUNCATED AT 250 WORDS)     

Metabolic fate of the new anti-ulcer drug enprostil in animals. 3rd communication: tissue accumulation after consecutive oral administration of [3H]-enprostil in rats

Accumulation characteristics of radioactivity in organs and tissues were investigated after oral administration of [3H]-enprostil ((+/-)-11a,15a-dihydroxy-9-oxo-16-phenoxy-17,18,19,20-tetranorp r osta-4,5,13(t)- trienoic acid methyl ester, TA-84135) to male rats once a day (20 micrograms/kg/d) for 1, 7 or 14 days. [3H]-Enprostil was found to be partially metabolized in vivo to volatile tritium (3H2O). The ratios of volatile tritium to total radioactivity in plasma increased with repeated administration of [3H]-enprostil and the levels of volatile tritium were almost equilibrated within 7 days of drug administration. The formation rate of volatile tritium was estimated to be 1-2% of the single dose. The blood levels of non-volatile radioactivity at 1 h after each daily dosing were nearly constant. The levels at 24 h, however, increased with repeated dosing. The levels of non-volatile radioactivity in most tissues at 1 h after the multiple administration (7 and 14 times) were higher than those after the single dose. At 24 h, levels were noticeable after multiple dosing even in the tissues in which levels below the detection limit were found after the single dose. From the comparison of the multiple-dose groups, the levels in most tissues attained steady state within 7 times dosing. The daily excretions of radioactivity in the urine, feces and expired air were constant throughout the period of consecutive administration. The total recovery of administered dose was 92%, which was similar to that achieved in the single-dosing group. As described above, the retention of non-volatile radioactivity was observed in most tissues.(ABSTRACT TRUNCATED AT 250 WORDS)     

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.     

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 physiological disposition of the anti-tussive agent, 1,2,3,4a,9b-hexahydro-8,9b-dimethyl-4-[3-(4-methylpiperazin-1-yl)propionamido]dibenzofuran-3-one dihydrochloride Azipranone, in man, rat, dog and baboon.

1. The absorption, tissue distrigution, elimination and biotransformation of the anti-tussive agent Azipranone labelled with 14C have been investigated after oral dosing to rat, dog, baboon and man and parenteral administration to rat and baboon. 2. Levels of radioactivity in plasma were maximal within 20 min of dosing in the rat and after 1-2 h in the remaining species. The concn. declined thereafter with a half-life estimated at 1, 3-4 and 18-24 h for rat, dog, and baboon and man respectively. 3. Three human volunteers excreted 53, 62 and 70% of the radioactivity in the urine in 96 h while the remaining species excreted 50-70% of the dose in the faeces in the same period. 4. Radioactivity was rapidly and extensively eliminated in the bile of both rat and baboon after administration of [14C]Azipranone. 5. The 24 h urine samples from all species contained ten major and a similar number of minor radioactive components. 6. In hepatic microsomal preparations, biotransformations of Azipranone are catalysed by enzymes requiring both NADPH2 and cytochrome-P450.     

Metabolism and disposition of [14C]5-amino-o-cresol in female F344 rats and B6C3F1 mice

The metabolism and disposition of [(14)C]5-amino-o-cresol (AOC) in female F344 rats following oral, intravenous, and dermal administration and in female B6C3F1 mice following oral administration were studied. Greater than 80% of a single oral dose (4.0-357 mg kg(-1)) or intravenous dose (2.7 mg kg(-1)) was excreted in urine within 24 h. When the dosing site was protected from grooming, less than 10% of the dermal dose (2.5 and 26 mg kg(-1), rinsed off after 6 h) was absorbed within 24 h, and most of the absorbed radioactivity was excreted in urine. For the unprotected dermal dose, grooming played a major role in the absorption of AOC. Very little AOC-derived radioactivity was present in the surveyed tissues after 24 or 72 h regardless of route, dose level, or species. Five urinary metabolites were identified: 5-acetamido-1,4-dihydroxy-2-methylbenzene glucuronide, AOC O-glucuronide, AOC O-sulfate, N-acetyl-AOC O-glucuronide, and N-acetyl-AOC O-sulfate.     

Metabolism and disposition of (RS)-2-methoxy-3-(octadecylcarbamoyloxy)propyl 2-(3-thiazolio)ethyl phosphate (MOTP) in rats and dogs

1. Metabolites (RS)-4-[(3-hydroxy-2-methoxy)propoxycarbonylamino]butanoic acid (I) and (RS)-2-[(3-hydroxy-2-methoxy)propoxycarbonylamino]acetic acid(II) were isolated from urine after i.v. administration of (RS)-2-methoxy-3-(octadecyl-[14C]carbamoyloxy)propyl 2-(3-thiazolio)ethyl phosphate (14C-MOTP) to rats and characterized by t.l.c., g.l.c.-mass spectrometry and p.m.r. spectrometry. 2. After i.v. administration of 14C-MOTP, the plasma concentration of the drug declined biphasically with half-lives of 0.22 and 3.94 h in rats, and 0.81 and 8.00 h in dogs. In rats and dogs, unchanged MOTP was the main 14C component in the plasma, together with a small amount of I and II. 14C-MOTP was highly bound to plasma protein of both animals. 3. Five min after i.v. administration of 14C-MOTP to rats, 14C was widely distributed in tissues, with the highest conc. in the lung and the lowest in the eye. The distribution of 14C was relatively slow in some tissues. In most tissues, 14C decreased to low levels at 96 h, except in the Harder's gland. 4. Elimination of 14C-MOTP was almost complete within 120 h in rats and 144 h in dogs. In both species, the administered 14C was excreted largely in the urine as I and II, with the remainder appearing in the faeces and the expired air. Biliary excretion and reabsorption of 14C were detected in rats. 5. During repeated i.v. administration of 14C-MOTP to rats for 7 days, the conc. of 14C in plasma and most tissues attained steady state within 5 days, except in Harder's gland, where the level rose gradually until the seventh day of dosing. Within 6 days after the last dosing, 96% of the injected dose was eliminated from the body.     

Metabolic fate of the new Ca++-channel blocking agent (+)-(2S,3S)-3-acetoxy-8-chloro-(2-(dimethylamino)ethyl)-2,3-dihydro- 2-(4-methoxyphenyl)-2,5-benzothiazepin-4-(5H)-one maleate. Distribution, excretion and protein binding in rats and dogs

Distribution, excretion and protein binding of (+)-(2S,3S)-3-acetoxy-8-chloro-(2-(dimethylamino)ethyl)-2,3-dihydro- 2-(4-methoxyphenyl)-2,5-benzothiazepin-4-(5H)-one maleate (TA-3090) in rats and dogs were investigated after oral (30 mg/kg (rats), 2 mg/kg(dogs] and intravenous (3 mg/kg (rats), 0.2 mg/kg (dogs) administration of 14C-TA-3090. Plasma level of radioactivity in rats reached plateau (6.04 micrograms equiv. of TA-3090 free base/ml) 1 h after oral administration. The plateau level continued at least up to 6 h. The plasma concentration of the unchanged drug (free base) reached the maximum (425 ng/ml) at 45 min after oral administration, and then decreased with a half-life of 1.16 h. Plasma level of radioactivity after intravenous administration to rats rose gradually up to 1 h and thereafter it was kept constant for 6 h. Plasma concentration of the unchanged drug decreased with half-lives of 0.43 h (alpha phase) and 1.33 h (beta phase) after intravenous administration. In dogs, the peak level of plasma radioactivity after oral administration was 227 ng/ml at 1 h. The Cmax, Tmax and t1/2 of unchanged drug were 31 ng/ml, 1.34 h and 4.13 h, respectively. The plasma levels of total radioactivity and unchanged drug after intravenous administration to dogs were 146 and 142 ng/ml at 1 min, respectively. The t1/2 of the plasma radioactivity were 0.02 h (alpha) and 4.02 h (beta). Those of unchanged drug were 0.03 h (alpha) and 1.66 h (beta).(ABSTRACT TRUNCATED AT 250 WORDS)     

The disposition of radioactivity after administration of the anthelminthic methyl-14C-5-cyclopropylcarbonyl-2-benzimidazole carbamate (ciclobendazole) to rats and dogs

1. The disposition of radioactivity has been studied in rats and dogs after administration of a new anthelminthic agent, 14C-labelled methyl-5-cyclopropylcarbonyl-2-benzimidazole carbamate (14C-ciclobendazole). 2. An oral dose of 14C-ciclobendazole (4 mg/kg) to rats was rapidly absorbed and about 70% and 20% of the dose was excreted in the faeces and urine, respectively, during 2 days. Bile duct cannulated rats excreted about 80% of the dose in 48-h bile, about 2% in the faeces and about 10% in the urine showing that an oral dose was well-absorbed and that some enterohepatic circulation probably occurred. The excretion of radioactivity in the bile was less after i.v. administration. 3. An oral dose of 14C-ciclobendazole (4 mg/kg) to dogs was mainly eliminated during 2 days with about 80% of the dose in the faeces and only about 10% in the urine. Anaesthetised bile duct-cannulated dogs, excreted between 26% and 35% of an oral dose in the bile during 24 h and up to 58% of an oral dose was absorbed at this time. 4. The tissue distribution of radioactivity in rats and dogs after single or multiple oral doses of 14C-ciclobendazole (4 mg/kg) showed that there was no unusual accumulation or localisation of radioactivity in the measured tissues. Highest concentrations were present in the intestinal tract, liver and kidneys, organs associated with biotransformation and excretion and also in the lungs and adrenals. 5. After oral administration of 14C-ciclobendazole to rate at three different dose levels (4, 40 and 400 mg/kg), peak plasma levels occurred at 15-30 min and declined with similar half-lives (about 20 h). A comparison of peak concentrations and areas under the plasma concentration-time relationships showed that the absorption of ciclobendazole was probably dose-dependent, a lower proportion probably being absorbed at higher doses. After repeated daily oral dosing with 14C-ciclobendazole (4 mg/kg), there were no significant changes in either the daily plasma concentrations or the biological half-life measured after the last dose, indicating that ciclobendazole probably did not induce or inhibit its own metabolism when dosed repeatedly at 4 mg/kg. 6. A comparison of the areas under the plasma concentration-time relationships after oral, i.p. and i.v. administration of 14C-ciclobendazole to rates indicated that there was no signigicant uptake by the liver during first pass and that an oral dose was well absorbed by rats. 7. The peak plasma concentration in the dog, after an oral dose of 14C-ciclobendazole (4 mg/kg) was reached at about 30 min and declined with a half-life of about 3 h. 8. Ciclobendazole was probably well-absorbed by rats and dogs and excreted more rapidly by the latter species than by the former Relatively higher plasma concentrations of drug and/or metabolites were thus achieved in rats than in dogs.