Absorption,distribution, metabolism and excretion of gemigliptin,a novel dipeptidyl peptidase IV inhibitor,in rats

Abstract

1.?The absorption, distribution, metabolism and excretion of a novel dipeptidyl peptidase IV inhibitor, gemigliptin, were examined following single oral administration of ¹⁴C-labeled gemigliptin to rats.

2.?The ¹⁴C-labeled gemigliptin was rapidly absorbed after oral administration, and its bioavailability was 95.2% (by total radioactivity). Distribution to specific tissues other than the digestive organs was not observed. Within 7 days after oral administration, 43.6% of the administered dose was excreted via urine and 41.2% was excreted via feces. Biliary excretion of the radioactivity was about 17.7% for the first 24?h. After oral administration of gemigliptin to rats, the in vivo metabolism of gemigliptin was investigated with bile, urine, feces, plasma and liver samples.

3.?The major metabolic pathway was hydroxylation, and the major circulating metabolites were a dehydrated metabolite (LC15-0516) and hydroxylated metabolites (LC15-0635 and LC15-0636).     

Biotransformation and mass balance of faldaprevir,a hepatitis C NS3/NS4 protease inhibitor in rats

Abstract

1.?The metabolism, pharmacokinetics, excretion and tissue distribution of a hepatitis C NS3/NS4 protease inhibitor, faldaprevir, were studied in rats following a single 2?mg/kg intravenous or 10?mg/kg oral administration of [¹⁴C]-faldaprevir.

2.?Following intravenous dosing, the terminal elimination t_1/2 of plasma radioactivity was 1.75?h (males) and 1.74?h (females). Corresponding AUC_0–∞, CL and V_ss were 1920 and 1900?ngEq?·?h/mL, 18.3 and 17.7?mL/min/kg and 2.32 and 2.12?mL/kg for males and females, respectively.

3.?After oral dosing, t_1/2 and AUC_0–∞ for plasma radioactivity were 1.67 and 1.77?h and 11?300 and 17?900 ngEq?·?h/mL for males and females, respectively.

4.?In intact rats, ≥90.17% dose was recovered in feces and only ≤1.08% dose was recovered in urine for both iv and oral doses. In bile cannulated rats, 54.95, 34.32 and 0.27% dose was recovered in feces, bile and urine, respectively.

5.?Glucuronidation plays a major role in the metabolism of faldaprevir with minimal Phase I metabolism.

6.?Radioactivity was rapidly distributed into tissues after the oral dose with peak concentrations of radioactivity in most tissues at 6?h post-dose. The highest levels of radioactivity were observed in liver, lung, kidney, small intestine and adrenal gland.     

Pharmacokinetics,distribution, and disposition of esaxerenone,a novel,highly potent and selective non-steroidal mineralocorticoid receptor antagonist,in rats and monkeys

1.?Esaxerenone (CS-3150) is a novel non-steroidal mineralocorticoid receptor antagonist. The pharmacokinetics, tissue distribution, excretion, and metabolism of esaxerenone were evaluated in rats and monkeys.

2.?Following intravenous dosing of esaxerenone at 0.1–3?mg/kg, the total body clearance and the volume of distribution were 3.53–6.69?mL/min/kg and 1.47–2.49?L/kg, respectively, in rats, and 2.79–3.69?mL/min/kg and 1.34–1.54?L/kg, respectively, in monkeys. The absolute oral bioavailability was 61.0–127% in rats and 63.7–73.8% in monkeys.

3.?After oral administration of [¹⁴C]esaxerenone, the radioactivity was distributed widely to tissues, with the exception of a low distribution to the central nervous system. Both in rats and in monkeys, following oral administration of [¹⁴C]esaxerenone the main excretion route of the radioactivity was feces.

4.?Five initial metabolic pathways in rats and monkeys were proposed to be N-dealkylation, carboxylation, hydroxymethylation, O-glucuronidation, and O-sulfation. The oxidized metabolism was predominant in rats, while both oxidation and glucuronidation were predominant in monkeys.     

Pharmacokinetics of the selective prostacyclin receptor agonist selexipag in rats,dogs and monkeys

1.?This study examined the pharmacokinetics, distribution, metabolism and excretion of the selective prostacyclin receptor agonist selexipag (NS-304; ACT-293987) and its active metabolite MRE-269 (ACT-33679). The compounds were investigated following oral and/or intravenous administration to intact rats, dogs and monkeys, and bile-duct-cannulated rats and dogs.

2.?After oral administration of [¹⁴C]selexipag, selexipag was well absorbed in rats and dogs with total recoveries of over 90% of the dose, mainly in the faeces. Biliary excretion was the major elimination pathway for [¹⁴C]MRE-269 as well as [¹⁴C]selexipag, while renal elimination was of little importance. [¹⁴C]Selexipag-related radioactivity was secreted into the milk in lactating rats.

3.?Plasma was analysed for total radioactivity, selexipag and MRE-269 in rats and monkeys. Selexipag was negligible in rat plasma due to extensive metabolism, and MRE-269 was present in rat and monkey plasma. A species difference was clearly evident when selexipag was incubated in rat, dog and monkey plasma.

4.?Total radioactivity was rapidly distributed to tissues. The highest concentrations were found in the bile duct and liver without significant accumulation or persistence, while there was limited melanin-associated binding, penetration of the blood–brain barrier and placental transfer of drug-related materials.     

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 C_max of radioactivity of 6.45–7.07?μg 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.     

Metabolism,excretion and pharmacokinetics of [14C]glasdegib (PF-04449913) in healthy volunteers following oral administration

1.?The metabolism, excretion and pharmacokinetics of glasdegib (PF-04449913) were investigated following administration of a single oral dose of 100?mg/100 μCi [¹⁴C]glasdegib to six healthy male volunteers (NCT02110342).

2.?The peak concentrations of glasdegib (890.3?ng/mL) and total radioactivity (1043 ngEq/mL) occurred in plasma at 0.75?hours post-dose. The AUC_inf were 8469?ng.h/mL and 12,230 ngEq.h/mL respectively, for glasdegib and total radioactivity.

3.?Mean recovery of [¹⁴C]glasdegib-related radioactivity in excreta was 91% of the administered dose (49% in urine and 42% in feces). Glasdegib was the major circulating component accounting for 69% of the total radioactivity in plasma. An N-desmethyl metabolite and an N-glucuronide metabolite of glasdegib represented 8% and 7% of the circulating radioactivity, respectively. Glasdegib was the major excreted component in urine and feces, accounting for 17% and 20% of administered dose in the 0–120?hour pooled samples, respectively. Other metabolites with abundance <3% of the total circulating radioactivity or dose in plasma or excreta were hydroxyl metabolites, a desaturation metabolite, N-oxidation and O-glucuronide metabolites.

4.?Elimination of [¹⁴C]glasdegib-derived radioactivity was essentially complete, with similar contribution from urinary and fecal routes. Oxidative metabolism appears to play a significant role in the biotransformation of glasdegib.     

Absorption,distribution, metabolism and excretion (ADME) of the ALK inhibitor alectinib: results from an absolute bioavailability and mass balance study in healthy subjects

1.?Alectinib is a highly selective, central nervous system-active small molecule anaplastic lymphoma kinase inhibitor.

2.?The absolute bioavailability, metabolism, excretion and pharmacokinetics of alectinib were studied in a two-period single-sequence crossover study. A 50?μg radiolabelled intravenous microdose of alectinib was co-administered with a single 600?mg oral dose of alectinib in the first period, and a single 600?mg/67?μCi oral dose of radiolabelled alectinib was administered in the second period to six healthy male subjects.

3.?The absolute bioavailability of alectinib was moderate at 36.9%. Geometric mean clearance was 34.5?L/h, volume of distribution was 475?L and the hepatic extraction ratio was low (0.14).

4.?Near-complete recovery of administered radioactivity was achieved within 168?h post-dose (98.2%) with excretion predominantly in faeces (97.8%) and negligible excretion in urine (0.456%). Alectinib and its major active metabolite, M4, were the main components in plasma, accounting for 76% of total plasma radioactivity. In faeces, 84% of dose was excreted as unchanged alectinib with metabolites M4, M1a/b and M6 contributing to 5.8%, 7.2% and 0.2% of dose, respectively.

5.?This novel study design characterised the full absorption, distribution, metabolism and excretion properties in each subject, providing insight into alectinib absorption and disposition in humans.     

Disposition and metabolism of TAK-438 (vonoprazan fumarate), a novel potassium-competitive acid blocker,in rats and dogs

1.?Following oral administration of [¹⁴C]TAK-438, the radioactivity was rapidly absorbed in rats and dogs. The apparent absorption of the radioactivity was high in both species.

2.?After oral administration of [¹⁴C]TAK-438 to rats, the radioactivity in most tissues reached the maximum at 1-hour post-dose. By 168-hour post-dose, the concentrations of the radioactivity were at very low levels in nearly all the tissues. In addition, TAK-438F was the major component in the stomach, whereas TAK-438F was the minor component in the plasma and other tissues. High accumulation of TAK-438F in the stomach was observed after oral and intravenous administration.

3.?TAK-438F was a minor component in the plasma and excreta in both species. Its oxidative metabolite (M-I) and the glucuronide of a secondary metabolite formed by non-oxidative metabolism of M-I (M-II-G) were the major components in the rat and dog plasma, respectively. The glucuronide of M-I (M-I-G) and M-II-G were the major components in the rat bile and dog urine, respectively, and most components in feces were other unidentified metabolites.

4.?The administered radioactive dose was almost completely recovered. The major route of excretion of the drug-derived radioactivity was via the feces in rats and urine in dogs.     

Metabolic disposition of gefitinib,an epidermal growth factor receptor tyrosine kinase inhibitor,in rat,dog and man

1.?Following oral administration of [¹⁴C]-gefitinib to albino and pigmented rats, radioactivity was widely and rapidly distributed, with the highest levels being found in liver, kidney, lung and gastrointestinal tract, but with only low levels penetrating the brain. Levels of radioactivity persisted in melanin-containing tissues (pigmented eye and skin).

2.?Binding to plasma proteins was high (86–94%) across the range of species examined and was 91% in human plasma. Substantial binding occurred to both human serum albumin and α-1 acid glycoprotein.

3.?Following oral and intravenous administration of [¹⁴C]-gefitinib, excretion of radioactivity by rat, dog and human occurred predominantly via the bile into faeces, with <7% of the dose being eliminated in urine.

4.?In all three species, gefitinib was cleared primarily by metabolism. In rat, morpholine ring oxidation was the major route of metabolism, leading to the formation of M537194 and M608236 as the main biliary metabolites. Morpholine ring oxidation, together with production of M523595 by O-demethylation of the quinazoline moiety, were the predominant pathways in dog, with oxidative defluorination also occurring to a lesser degree.

5.?Pathways in healthy human volunteers were similar to dog, with O-demethylation and morpholine ring oxidation representing the major routes of metabolism.     

Absorption,metabolism and excretion of darexaban (YM150), a new direct factor Xa inhibitor in humans

1.?The absorption, metabolism and excretion of darexaban (YM150), a novel oral direct factor Xa inhibitor, were investigated after a single oral administration of [¹⁴C]darexaban maleate at a dose of 60?mg in healthy male human subjects.

2.?[¹⁴C]Darexaban was rapidly absorbed, with both blood and plasma concentrations peaking at approximately 0.75?h post-dose. Plasma concentrations of darexaban glucuronide (M1), the pharmacological activity of which is equipotent to darexaban in vitro, also peaked at approximately 0.75?h.

3.?Similar amounts of dosed radioactivity were excreted via faeces (51.9%) and urine (46.4%) by 168?h post-dose, suggesting that at least approximately half of the administered dose is absorbed from the gastrointestinal tract.

4.?M1 was the major drug-related component in plasma and urine, accounting for up to 95.8% of radioactivity in plasma. The N-oxides of M1, a mixture of two diastereomers designated as M2 and M3, were also present in plasma and urine, accounting for up to 13.2% of radioactivity in plasma. In faeces, darexaban was the major drug-related component, and N-demethyl darexaban (M5) was detected as a minor metabolite.

5.?These findings suggested that, following oral administration of darexaban in humans, M1 is quickly formed during first-pass metabolism via UDP-glucuronosyltransferases, exerting its pharmacological activity in blood before being excreted into urine and faeces.     

Metabolism and excretion of CP-122,721, a non-peptide antagonist of the neurokinin NK1 receptor,in dogs: Identification of the novel cleaved product 5-trifluoromethoxy salicylic acid in plasma

The metabolism and excretion of a potent and selective substance P receptor antagonist, CP-122,721, have been studied in beagle dogs following oral administration of a single 5?mg?kg^?1 dose of [¹⁴C]CP-122,721. Total recovery of the administered dose was on average 89% for male dogs and 95% for female dogs. Approximately 94% of the radioactivity recovered in urine and feces was excreted in the first 72?h. Male bile duct-cannulated dogs excreted a mean of ～56% of the dose in bile, ～11% in feces, and ～25% in urine. The sum of radioactivity in bile and urine indicates >80% of the [¹⁴C]CP-122,721-derived radioactivity was absorbed by the gastrointestinal tract. CP-122,721 was extensively metabolized in dogs, and only a small amount of parent CP-122,721 was excreted as unchanged drug. There were no significant gender-related quantitative/qualitative differences in the excretion of metabolites in urine or feces. The major metabolic pathways of CP-122,721 were O-demethylation, aromatic hydroxylation, and indirect glucuronidation. The minor metabolic pathways included: Aliphatic oxidation at the piperidine moiety, O-dealkylation of the trifluoromethoxy group, and N-dealkylation with subsequent sulfation and/or oxidative deamination. In addition, the novel cleaved product 5-trifluoromethoxy salicylic acid (TFMSA) was identified in plasma. These results suggest that dog is the most relevant animal species in which the metabolism of CP-122,721 can be studied for extrapolating the results to humans.     

Absorption,distribution, metabolism,and excretion of mTOR kinase inhibitor CC-223 in rats,dogs, and humans

1. The absorption, distribution, metabolism, and excretion of CC-223 were studied following a single oral dose of [¹⁴C]CC-223 to rats (3?mg/kg; 90 μCi/kg), dogs (1.5?mg/kg; 10 μCi/kg), and healthy volunteers (20?mg; 200 nCi).

2. CC-223-derived radioactivity was widely distributed in rats. Excretion of radioactivity was rapid and nearly complete from rats (87%), dogs (78%), and humans (97%). Feces was the major excretion pathway for rats (67%) and dogs (70%), whereas urine (57.6%) was the major elimination route for humans. Urine and bile each contained approximately 20% administered radioactivity in rats, whereas bile (20%) played a more important role than urine (<10%) in the excretion of absorbed radioactivity in dogs. Based on excretion data, CC-223 had good absorption, with greater than 56%, 29%, and 57% of the oral dose absorbed in rats, dogs, and humans, respectively.

3. CC-223 was the prominent radioactive component in circulation of rats (>71% of the exposure to total radioactivity) and dogs (≥45.5%), whereas M1 (76.5%) was the predominant circulating metabolite in humans. M1 and M1-derived metabolites accounted for?>66% of human dose. CC-223 was extensively metabolized in rats, dogs, and humans through glucuronidation, O-demethylation, oxidation, and combinations of these pathways.     

Metabolic disposition of AZD8931, an oral equipotent inhibitor of EGFR,HER2 and HER3 signalling,in rat,dog and man

Abstract

1. This series of studies in rats, dogs and humans (Clinicaltrials.gov identifier: NCT01284595) investigated the pharmacokinetics, tissue distribution, metabolism and excretion of the EGFR, HER2 and HER3 signalling inhibitor AZD8931.

2. Single oral or intravenous doses of 2-(4-[4-(3-chloro-2-fluoro[U-¹⁴C]-phenylamino)-7-methoxy-quinazolin-6-yloxy]-piperidin-1-yl)-N-methyl-acetamide difumarate ([¹⁴C]-AZD8931) were administered.

3. AZD8931 absorption was rapid in all species. Following [¹⁴C]-AZD8931 administration to rats, radioactivity was widely and rapidly distributed, with the highest levels in organs of metabolism and excretion (gastrointestinal tract, liver). Following oral and intravenous [¹⁴C]-AZD8931 administration, excretion of radioactivity by all species occurred predominantly via the bile into faeces, with <5% of the dose being eliminated in urine. In all species, AZD8931 was principally cleared by metabolism. The major route of metabolism was hydroxylation and O-demethylation in rat, and aryl ring oxidation in dog. Metabolism of AZD8931 in humans was attributed to three pathways; oxidation and amine or ether cleavage around the piperidine ring with subsequent glucuronide or sulphate conjugation.

4. AZD8931 is largely cleared by metabolism in the rat, dog and human. Excretory profiles indicate that there are no unique human metabolites.     

Disposition and metabolism of amosulalol hydrochloride,a new combined α- and β-adrenoceptor blocking agent,in rats,dogs and monkeys

1. The disposition and metabolism of amosulalol hydrochloride, a combined α- and β-adrenoceptor blocking agent, were studied in rats, dogs and monkeys.

2. After oral administration of [¹⁴C]amosulalol hydrochloride, the plasma concentration of radioactivity reached a maximum at 05 to 1 h in all species and declined with half-lives of about 2 h in both rats and monkeys, and of about 4 h in dogs. The ratios of unchanged drug to total radioactivity in the rat and dog plasma were 8 and 43% at 05 h after administration, respectively. The radioactivity in the rat tissues was high in the liver, kidney, blood and pancreas after oral administration.

3. Following oral dosage, the urinary excretion of radioactivity was 26-34% of the dose in rats, 45% in dogs and 46% in monkeys in 48 h. The biliary excretion after oral dosage amounted to 66% and 41% in rats and dogs, respectively.

4. Six metabolites were isolated and identified from the urine of rats and dogs. They were derived from one or two of the following pathways: I, hydroxylation of the 2-methyl group of the methylbenzenesulphonamide ring; II, demethylation of the o-methoxy group of the methoxyphenoxy ring; III, hydroxylation at the 4 or 5 position of the methoxy-phenoxy ring; IV, oxidative cleavage of the C—N bond yielding o-methoxyphenoxy acetic acid. Moreover, some metabolites were metabolized to glucuronide or sulphate.     

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.     

Metabolism of Linoleamides: II. Absorption,Distribution, Excretion and Metabolism of N-[α-Phenyl-β-(p-tolyl)ethyl] linoleamide

1. Absorption, distribution, excretion and metabolism of (-)N-[α-phenyl-β-(p-tolyl)ethyl][¹⁴C]linoleamide (¹⁴C-PTLA) were studied in rats and dogs. Faecal excretion of PTLA was studied in dogs and men by g.l.c.

2. ¹⁴C-PTLA (10 mg/kg) given orally to rats resulted in urinary and faecal excretion of radioactivity of 2 and 93 %, respectively, by male rats and 8 and 87% by female rats in 48 h. Faecal excretion of PTLA in men was similar to that in rats.

3. Distribution of radioactivity in rats and dogs after oral administration of ¹⁴C-PTLA showed that a major part of the dose was not absorbed.

4. N-[α-Phenyl-β-(p-tolyl)ethyl]succinic acid monoamide and N-[α-phenyl-β-(p-tolyl)ethyl]glutaric acid monoamide were detected in the urine of rats dosed orally with ¹⁴C-PTLA.     

Pharmacokinetics,distribution, metabolism,and excretion of the dual reuptake inhibitor [14C]-nefopam in rats

1.?This study examined the pharmacokinetics, distribution, metabolism, and excretion of [¹⁴C] nefopam in rats after a single oral administration. Blood, plasma, and excreta were analyzed for total radioactivity, nefopam, and metabolites. Metabolites were profiled and identified. Radioactivity distribution was determined by quantitative whole-body autoradiography.

2.?The pharmacokinetic profiles of total radioactivity and nefopam were similar in male and female rats. Radioactivity partitioned approximately equally between plasma and red blood cells. A majority of the radioactivity was excreted in urine within 24?hours and mass balance was achieved within 7 days.

3.?Intact nefopam was a minor component in plasma and excreta. Numerous metabolites were identified in plasma and urine generated by multiple pathways including: hydroxylation/oxidation metabolites (M11, M22a and M22b, M16, M20), some of which were further glucuronidated (M6a to M6c, M7a to M7c, M8a and M8b, M3a to M3d); N-demethylation of nefopam to metabolite M21, which additionally undergoes single or multiple hydroxylations or sulfation (M9, M14, M23), with some of the hydroxylated metabolites further glucuronidated (M2a to M2d).

4.?Total radioactivity rapidly distributed with highest concentrations found in the urinary bladder, stomach, liver, kidney medulla, small intestine, uveal tract, and kidney cortex without significant accumulation or persistence. Radioactivity reversibly associated with melanin-containing tissues.     

Preclinical metabolism and disposition of luseogliflozin,a novel antihyperglycemic agent

Abstract

1. We investigated the metabolism and disposition of luseogliflozin, a sodium-glucose cotransporter 2 (SGLT2) inhibitor, in rats and dogs, as well as in vitro metabolism in rats, dogs and humans. In addition, we studied its localization in the rat kidney.

2. [¹⁴C]Luseogliflozin was rapidly and well absorbed (>86% of the dose) after oral administration to rats and dogs. The drug-derived radioactivity was mainly excreted via the feces in both species.

3.?The predominant radioactivity component in the excreta was associated with the metabolites, with only a minor fraction of unchanged luseogliflozin. The major metabolites were two glucuronides (M8 and M16) in the rats, and the O-deethylated form (M2) and other oxidative metabolites (M3 and M17) in the dogs.

4. The in vitro metabolism in dog and human hepatocytes was significantly slower than that in the rat hepatocytes. The biotransformation in animal hepatocytes was similar to that observed in vivo. Incubation with human hepatocytes resulted in the formation of metabolites, including M2, M3, M8 and M17, via multiple metabolic pathways.

5. [¹⁴C]Luseogliflozin was well-distributed to its target organ, the kidney, and was found to be localized in the renal cortex, which shows SGLT2 expression. This characteristic distribution was inhibited by preinjection of phlorizin, an SGLT inhibitor, suggesting that the renal radioactivity was associated with SGLT2.     

The metabolism and excretion of prochloraz,an imidazole-based fungicide,in the rat

1. Following oral administration of prochloraz (1-[N-propyl-N-2-(2,4,6-trichlorophenoxy)ethylcarbamoyl]imidazole) at 100mg/kg body weight to rats, the compound underwent extensive metabolism, the primary route appearing to be opening of the imidazole ring followed by hydrolysis of the alkyl chain. The major metabolites were 2,4,6-trichlorophenoxyacetic acid and 2-(2,4,6-trichlorophenoxy)ethanol, which is present mainly as a glucuronide conjugate. Ring hydroxylation occurred to produce several minor metabolites. No unchanged prochloraz was excreted in the urine.

2. Tissue residues 96?h after dosing were generally < 1?mg prochloraz equivalents/kg tissue. The highest residues were found in the liver (2˙8–5˙1?mg prochloraz equivalents/kg tissue) and kidney (1˙5–2˙1?mg prochloraz equivalents/kg tissue), the principal organs of metabolism and excretion. Residues in female rats were generally slightly higher than those found in males.

3. The metabolites were quantitatively excreted within 96?h, with > 50% of the dosed radioactivity being found in the 0–24?h excreta. Urinary excretion accounted for 65% dose in male and 41% in female rats, respectively.     

Disposition and pharmacokinetics of temozolomide in rat

1.?Temozolomide, an imidazotetrazine derivative, is a cytotoxic alkylating agent of broad-spectrum antitumour activity. The absorption, metabolism, distribution and excretion of temozolomide have been investigated in male and female Sprague–Dawley and Long–Evans rats following single oral or intravenous dose administration of 200?mg?m^?2 non-radiolabelled or ¹⁴C-radiolabelled temozolomide. The distribution of ¹⁴C-temozolomide was also evaluated by whole-body autoradiography in male Sprague–Dawley rats. Plasma concentrations of temozolomide and its active metabolite 3-methyl-(triazen-1-yl)imidazole-4-carboxamide (MTIC) were determined by high-performance liquid chromatography (HPLC) with ultraviolet detection. Plasma, urine and faeces were profiled by HPLC with radiochemical detection.

2.?Temozolomide was rapidly and extensively (>90%) absorbed and widely distributed in tissues. The distribution pattern of radioactivity was gender independent. Penetration into the brain following oral or intravenous administration was 35–39% based on the brain/plasma AUC ratio.

3.?Following intravenous or oral administration, temozolomide was primarily eliminated renally (75–85% of the dose) as either unchanged drug, a carboxylic acid analogue, AIC (a degradation product) and a highly polar unidentified peak. Biliary excretion was minimal (1.4–1.6%). The pharmacokinetics (oral versus intravenous) were similar and gender independent. The absolute oral availability was 96–100%. Temozolomide was rapidly eliminated (t_1/2 = 1.2?h) and converted to MTIC.

4.?Systemic exposure to MTIC was about 2% that of temozolomide. Overall, the disposition of temozolomide in rats was similar to that observed in humans.