Subacute toxicities and toxicokinetics of DA-8159, a new phosphodiesterase type V inhibitor, after single and 4-week repeated oral administration in rats

The subacute toxicities (10 male and 10 female rats at each dose) and the toxicokinetics (5 male rats at each dose) of DA-8159, a new phosphodiesterase type V (PDE V) inhibitor, were evaluated after single (at day 1) and 4-week (at day 28) oral administration of the drug at doses of 0 (to serve as a control), 20, 80 and 320 mg/kg/day to rats. DA-8159 showed a decrease in body weight gain, clinical signs such as chromodacryohaemorrhoea, ptosis and decreased locomotor activity, an increase in WBC number, changes in parameters related to RBCs, an increase in organ weight of the liver, spleen and lung, and finally microscopic lesions such as cholangiofibrosis and inflammatory cell infiltration in the liver, alveolar macrophage accumulation, and inflammatory cell infiltration in the lung, an increase in bone marrow density and extrahaematopoiesis in the spleen. These changes were observed mainly at a dose of 80 mg/kg or above. While some changes were observed at a dose of 20 mg/kg, these changes were non-specific and transient since this were also observed in control rats. In addition, there was no dose-dependency in these changes. Based on these results, the NOAEL (No-Observed-Adverse-Effect-Level) for DA-8159 in rats was estimated to be 20 mg/kg/day, and the target organs were determined to be liver, bone marrow, spleen, lung and blood cells. After a 4-week oral administration, accumulation of DA-8159 was evident at a dose of 20 mg/kg/day, but was not considerable at toxic doses (80 and 320 mg/kg/day). After a single oral administration, the dose-normalized area under the plasma concentration-time curve from time zero to the last measured time, 24 h, in plasma (AUC(0-24 h)) was significantly different among the three doses (the AUC(0-24 h) based on 20 mg/kg/day was 2.33, 7.00 and 4.19 microg h/ml for 20, 80 and 320 mg/kg/day, respectively). Similar results were also obtained from DA-8164, a metabolite of DA-8159; the AUC(0-24 h) of DA-8164 after dose-normalized to 20 mg/kg/day of DA-8159 were 2.74, 5.00 and 1.68 microg h/ml, respectively.     

Species differences in the formation of DA-8164 after intravenous and/or oral administration of DA-8159, a new erectogenic, to mice, rats, rabbits, dogs and humans

Species differences in the formation of DA-8164 after intravenous and/or oral administration of DA-8159 to mice, rats, rabbits, dogs and humans were investigated. After intravenous administration of DA-8159, the formation of DA-8164 decreased in the order mice, rats, rabbits and dogs; the AUC(DA-8164)/AUC(DA-8159) ratios were 0.479, 0.199, 0.0452 and close to 0 (DA-8164 was below the detection limit in dog plasma), respectively. After oral administration of DA-8159, the formation of DA-8164 was considerable in mice, rats and humans, but almost negligible in dogs; the AUC (or AUC(0-t))(DA-8164)/AUC (or AUC(0-t))(DA-8159) ratios were 2.99, 2.67, 1.39 and 0.0650, respectively. The above data suggested that the formation of DA-8164 was almost negligible after both intravenous and oral administration in dogs. The species differences for the formation of DA-8164 may be due to the involvement of different CYP isozymes for each species and/or a different amount or activity of CYP isozyme if the same CYP isozyme is involved for the formation of DA-8164 for all species. The AUC (or AUC(0-t))(DA-8164)/AUC (or AUC(0-t))(DA-8159) ratios after oral administration were greater than those after intravenous administration in mice, rats and dogs, and this could be due to considerable first-pass (gastric, intestinal and/or hepatic) effects in the species as proved in rats.     

Pharmacokinetic changes of DA-8159, a new erectogenic, after intravenous and oral administration to rats with acute renal failure induced by uranyl nitrate

The pharmacokinetic parameters of DA-8159, a new erectogenic, were compared after intravenous and oral administration of the drug at a dose of 30 mg/kg to control rats and rats with acute renal failure induced by uranyl nitrate (U-ARF). After intravenous administration to rats with U-ARF, the plasma concentrations of DA-8159 were higher than those in control rats. This resulted in a significantly greater area under the plasma concentration-time curve from time zero to time infinity (AUC) of DA-8159 in rats with U-ARF (304 compared with 365 microg min/ml for control rats and rats with U-ARF). The significantly greater AUC in rats with U-ARF was due to significantly slower total body clearance (Cl) of DA-8159 (98.6 compared with 82.2 ml/min/kg). The significantly slower Cl in rats with U-ARF was due to slower renal clearance (1.07 ml/min/kg compared with not calculable, due to impaired kidney function) and nonrenal clearance (97.5 compared with 82.2 ml/min/kg due to slower metabolism) than those in control rats. After oral administration of DA-8159 to rats with U-ARF, the AUC (122 compared with 172 microg min/ml) was significantly greater and Cl(R) was slower (3.47 ml/min/kg compared with not calculable) than those in control rats. The significantly greater AUC in rats with U-ARF could be due to slower Cl of DA-8159 in the rats.     

Negligible pharmacokinetic interaction between oral DA-8159, a new erectogenic, and amlodipine in rats

A pharmacokinetic interaction between oral DA-8159 and amlodipine was evaluated in male Sprague-Dawley rats. In rats pretreated with troleandomycin (a main inhibitor of CYP3A1/2 in rats), the AUC(0-6 h) of amlodipine was significantly greater than the controls (34.5+/-6.01 compared with 28.0+/-4.70 microg min/ml), indicating that amlodipine is metabolized via CYP3A1/2 in rats. It was reported that the metabolism of DA-8159 and the formation of DA-8164 (a metabolite of DA-8159) were mainly mediated via CYP3A1/2 in rats, and amlodipine significantly inhibited the CYP3A2 in rats. Therefore, a pharmacokinetic interaction between the two drugs could be expected. However, after oral administration of DA-8159 at a dose of 30 mg/kg with or without oral amlodipine at a dose of 5 mg/kg to rats, the pharmacokinetic parameters of DA-8159 and DA-8164 were not significantly different between the two groups of rats. Similar results were also obtained from amlodipine between with and without DA-8159. The above data indicated that the pharmacokinetic interaction between oral DA-8159 and amlodipine was almost negligible in rats.     

Effects of omeprazole or cola beverage on the pharmacokinetics of oral DA-8159, a new erectogenic, in rats

The changes in pharmacokinetics of DA-8159 by omeprazole with respect to inhibition of CYP3A1/2 in rats were evaluated. After oral administration of DA-8159 at dose of 30 mg/kg to rats pretreated with oral omeprazole at 30 mg/kg for 1 week, the total area under the plasma concentration-time curve from time zero to time infinity (AUC) of DA-8159 was significantly greater (37.5% increase) than that in control rats. This could be due to inhibition of metabolism of DA-8159 by inhibition of CYP3A1/2 by omeprazole. The AUC(DA-8164 (a metabolite of DA-8159))/AUC(DA-8159) ratio was also smaller (32.4% decrease) with omeprazole. After oral administration of DA-8159 at a dose of 30 mg/kg to rats without or with cola beverage, the pharmacokinetic parameters of DA-8159 and DA-8164 were not significantly different between two groups of rats. This suggested that cola beverage did not have any considerable effects on CYP3A1/2 in rats.     

Subchronic toxicity and toxicokinetics of LZB, a new proton pump inhibitor, after 13-week repeated oral administration in dogs

The subchronic toxicity and toxicokinetics of a novel proton pump inhibitor, pymeprazole (LZB), were investigated in beagle dogs by daily oral administration for 13 consecutive weeks. Three test groups received doses of 30, 100 and 300 mg/kg/day of LZB. Rabeprazole of 60 mg/kg/day was used as positive control. The 13-week repeated oral doses of LZB resulted in objective signs of mild gastrointestinal disturbance for high-dose group animals. One individual dog of high-dose group was found to be lethargy and astasia at the last month of administration; for hematology, mild anemia was observed at high-dose females; for clinical chemistry, higher cholest, trigly and gastrin were observed at high-dose females, higher ASAT, ALAT, cholesterol, triglyceride and gastrin at high-dose males were also observed; for histopathology, the primary effects of LZB were related to gastric mucosa of high-dose group seen by H and E or Grimelius stain. Impairment of surface epithelium was observed by SEM. The treat-related effects basically were reversible for a 4-week drug-free period. As for positive control group, 13-week oral administration of rabeprazole resulted in more severe toxicity than high-dose group of LZB although much lower dose was employed. The accumulation of LZB after 13-week oral administration was not notable at the toxic dose of 300 mg/kg/day. The toxic dose was considered to be 100mg/kg/day and the no-observed-adverse-effect level (NOAEL) to be 30 mg/kg/day, which is much higher than other PPIs. The toxicological target could be stomach, liver, hematological system and nervous system.     

Pharmacokinetic changes of DA-8159, a new erectogenic, and one of its metabolites, DA-8164 after intravenous and oral administration of DA-8159 to spontaneously hypertensive rats and DOCA-salt-induced hypertensive rats

The pharmacokinetics of DA-8159 and one of its metabolites, DA-8164, were compared after intravenous and oral administration of DA-8159 at a dose of 30 mg/kg to spontaneously hypertensive rats (SHRs) at 16 and 6 weeks old and their respective age-matched control normotensive Kyoto-Wistar rats (KW rats), and deoxycorticosterone acetate-salt-induced hypertensive rats (DOCA-salt rats) at 16 weeks old and their age-matched control Sprague-Dawley rats. After oral administration of DA-8159 to 16-week-old SHRs, the AUC values of both DA-8159 (157 versus 103 microg min/ml) and DA-8164 (215 versus 141 microg min/ml) were significantly greater, but the values of DA-8159 were reversed in 16-week-old DOCA-salt rats (125 versus 200 microg min/ml). However, the AUC values of both DA-8159 and DA-8164 were not significantly different between the 6-week-old SHRs and their control rats. The above AUC differences in 16-week-old SHRs may be due to neither hereditary characteristics of SHRs nor the hypertensive state itself.     

Subacute toxicity and toxicokinetics of a new antibiotic,DW-224a,after single and 4-week repeated oral administration in dogs

The subacute toxicity and toxicokinetics of a new fluoroquinolone antibiotic, DW-224a, were evaluated after single (on the 1st day) and 4-week (on the 28th day) oral administration of the drug at doses of 0 (to serve as a control), 10, 30, and 90 mg/kg/d, to male and female dogs (n=3 for male and female dogs for each dose). During the test period, clinical signs, mortality, body weight, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weight and histopathology were examined. The 4-week repeated oral dose of DW-224a resulted in vomiting, salivation, increased serum cholesterol level, and atrophy of thymus and testes. The target organ was determined to be the thymus and testes. The absolute toxic dose of DW-224a was 30 mg/kg and the level at which no adverse effects were observed was 10 mg/kg for both sexes. There were no significant gender differences in the pharmacokinetic parameters of DW-224a for each dose after both single and 4-week oral administration. The pharmacokinetic parameters of DW-224a were dose independent after a single oral administration; the time to reach the peak plasma concentration (T(max)) and the dose-normalized area under the plasma concentration-time curve from time zero to 24 h in plasma (AUC(0-24 h)) were not significantly different among the three doses. The accumulation of DW-224a after 4-week oral administration was not notable at the toxic dose of 90 mg/kg/d. For example, after 4-week administration, the dose-normalized AUC(0-24 h) value at 90 mg/kg/d (7.69, 7.05 microg h/ml) was not significantly greater than that at 10 mg/kg/d. After 4-week oral administration, the dose-normalized C(max) and AUC(0-24 h) at 90 mg/kg/d were not significantly higher and greater, respectively, than those after a single oral administration.     

Factors influencing the protein binding of a new phosphodiesterase V inhibitor, DA-8159, using an equilibrium dialysis technique

Various factors influencing the protein binding of DA-8159 to 4% human serum albumin (HSA) were evaluated using an equilibrium dialysis technique at an initial DA-8159 concentration of 5 microg/mL. It took approximately 8 h incubation to reach an equilibrium between 4% HSA and an isotonic phosphate buffer of pH 7.4 containing 3% of dextran ('the buffer') using a Spectra/Por 2 membrane (mol. wt. cut-off: 12,000--14,000) in a water bath shaker kept at 37 degrees C and at a rate of 50 oscillations per min. The extent of binding was dependent on DA-8159 concentrations, HSA concentrations, incubation temperature, buffer pH, and alpha-1-acid glycoprotein (AAG) concentrations. The binding of DA-8159 in heparinized human plasma (93.9%) was significantly higher than in rats (81.4%), rabbits (80.4%), and dogs (82.2%), and this could be due to differences in AAG concentrations in plasma.     

Subacute toxicity and toxicokinetics of CJ-10882, a type IV phosphodiesterase inhibitor, after 4-week repeated oral administration in dogs.

The subacute toxicity and toxicokinetics of a type IV phosphodiesterase inhibitor, CJ-10882, were evaluated after single (on the 1st day) and 4-week (on the 27th day) oral administration of the drug, in doses of 0 (to serve as a control), 2, 10 and 50 mg/kg/day, to male and female dogs (n=3 for male and female dogs for each dose). During the test period, clinical signs, mortality, body weight, food consumption, ophthalmoscopy, urinalysis, hematology, serum biochemistry, gross findings, organ weight and histopathology were examined. The 4-week repeated oral doses of CJ-10882 resulted in salivation, vomiting, and atrophy of the thymus. The absolute toxic dose was 50 mg/kg/day and the level at which no adverse effects were observed was 2 mg/kg/day for male and female dogs. There were no significant gender differences in the pharmacokinetic parameters of CJ-10882 for each dose after both single and 4-week oral administration. The pharmacokinetic parameters of CJ-10882 were dose independent after a single oral administration; the time to reach a peak plasma concentration (T(max)) and the dose-normalized area under the plasma concentration-time curve from time zero to 8 h in plasma (AUC(0-8 h)) were not significantly different among three doses. The accumulation of CJ-10882 after 4-week oral administration was not notable at the toxic dose of 50 mg/kg/day. For example, after 4-week administration, the dose-normalized AUC(0-8 h) value at 50 mg/kg/day (0.132 microg h/ml) was not significantly greater than that at 10 mg/kg/day (0.131 microg h/ml). After 4-week oral administration, the dose-normalized C(max) and AUC(0-8 h) at 50 mg/kg/day were not significantly higher and greater, respectively, than those after the single oral administration.     

Interspecies pharmacokinetic scaling of DA-8159, a new erectogenic, in mice, rats, rabbits and dogs, and prediction of human pharmacokinetics

Time-averaged total body clearance (Cl) and apparent volume of distribution at steady state (V(SS)) of DA-8159 after intravenous administration to mice (30 mg/kg), rats (30 mg/kg), rabbits (30 mg/kg) and dogs (3 mg/kg) were analysed as a function of species body weight (W) using the allometric equation for interspecies scaling, and were used to predict those in humans. Significant linear relationships were obtained between log Cl (l/h) and log W (kg) (r = 0.992; p = 0.0079) and log V(SS) (l) and log W (kg) (r = 0.999; p < 0.0001). The corresponding allometric equations were Cl = 4.36 W(0.492) and V(SS) = 6.41 W(0.911). These allometric equations were extrapolated to predict the Cl and V(SS) for DA-8159 in humans based on the 70 kg body weights. In addition, concentrations in the plasma-time profile predicted using the four animal data fitted to a complex Dedrick plot of animal data. Our results indicated that the DA-8159 data obtained from four laboratory animals could be utilized to generate preliminary estimates of the pharmacokinetic parameters in humans. These parameters can serve as guidelines for better planning of clinical studies.     

Effects of enzyme inducers and inhibitors on the pharmacokinetics of intravenous DA-8159, a new erectogenic, in rats

In order to find what types of hepatic microsomal cytochrome P450 (CYP) isozymes are involved in the metabolism of DA-8159 and in the formation of DA-8164 in rats, enzyme inducers, such as dexamethasone, phenobarbital, 3-methylcholanthrene and isoniazid, and enzyme inhibitors, such as troleandomycin and quinine, were pretreated in rats. After a 1 min intravenous administration of DA-8159 at a dose of 30 mg/kg to rats pretreated with dexamethasone (a main inducer of CYP3A1/2 in rats), the total areas under the plasma concentration-time curve from time zero to time infinity (AUC) values of DA-8159 (283 versus 349 microg min/ml) and DA-8164 (98.0 versus 79.8 microg min/ml) were significantly smaller and greater, respectively, than those in control rats. However, the AUC values of DA-8159 were not significantly different after pretreatment with phenobarbital, isoniazid and 3-methylcholanthrene (main inducers of CYP2B1/2, 2E1 and 1A1/2, respectively, in rats). In rats pretreated with troleandomycin (a main inhibitor of CYP3A1/2 in rats), the AUC values of DA-8159 (435 versus 370 microg min/ml) and DA-8164 (34.8 versus 76.5 microg min/ml) were significantly greater and smaller, respectively. However, in rats pretreated with quinine (a main inhibitor of CYP2D1 in rats), the AUC of DA-8159 was comparable to that in control rats. The above data indicate that DA-8159 was metabolized and DA-8164 was formed mainly via CYP3A1/2 in rats.     

Pharmacokinetics of DA-8159, a new erectogenic, after intravenous and oral administration to rats: hepatic and intestinal first-pass effects

The purposes of this study were to report dose-independent (after intravenous administration) and dose-dependent (after oral administration) area under the curve of plasma concentration versus time from time zero to time infinity (AUC), and gastric, intestinal, and/or hepatic first-pass effects (after intravenous, intraportal, intragastric, and intraduodenal administration) of DA-8159 [5-[2-propyloxy-5-(1-methyl-2-pyrollidinylethylamidosulfonyl)phenyl]-1-methyl-3-propyl-1,6-dihydro-7H-pyrazolo(4,3-d)pyrimidine-7-one], a new erectogenic, in rats. After intravenous administration at doses of 5, 10, and 30 mg/kg, the AUCs and time-averaged total body clearances (CLs) were dose-independent. However, the AUCs were dose-dependent after oral administration at doses of 20, 30, 50, and 100 mg/kg. This result could be due to saturation of first-pass effects at high doses. The extent of absolute oral bioavailability (F) of DA-8159 was 38.0% at a dose of 30 mg/kg. Considering almost complete absorption of DA-8159 from rat gastrointestinal tract ( approximately 99% of oral dose of 30 mg/kg), the low F could be due to considerable hepatic, gastric, and/or intestinal first-pass effects. After intravenous administration at three doses, the CLs were considerably slower than the reported cardiac output in rats, suggesting almost negligible first-pass effect of DA-8159 in the heart and lung. The AUCs were not significantly different between intragastric and intraduodenal administration of DA-8159 at a dose of 30 mg/kg (131 and 127 microg x min/mL), suggesting that gastric first-pass effect of DA-8159 was almost negligible in rats. However, the values were significantly smaller than that after intraportal administration (311 microg x min/mL), indicating considerable intestinal first-pass effect of DA-8159 in rats of approximately 58% of the oral dose. Approximately 23% of DA-8159 at a dose of 30 mg/kg absorbed into the portal vein was eliminated by the liver (hepatic first-pass effect) based on AUC difference between intravenous and intraportal administration (the value, 23%, was equivalent to approximately 9.6% of oral dose). The low F of DA-8159 after oral administration at a dose of 30 mg/kg to rats was mainly due to considerable intestinal ( approximately 58%) first-pass effects.     

Pharmacokinetic changes of DA-8159, a new erectogenic, after intravenous and oral administration to rats with diabetes mellitus induced by streptozotocin

Intravenous administration of DA-8159, 30 mg/kg, to rats with diabetes mellitus induced by streptozotocin (DMIS), AUC of DA-8164 (a metabolite) was significantly smaller in rats with DMIS (57.9 compared with 81.8 microg x min/mL). This may be due to more contribution of significantly faster clearance of DA-8164 than that of significantly greater formation of DA-8164 in the rats. For example, the CL of DA-8164 was significantly faster (9.68 compared with 6.29 mL/min/kg) after intravenous administration of DA-8164, 10 mg/kg, to rats with DMIS and in vitro intrinsic clearance for the formation of DA-8164 was significantly faster (1.92 compared with 1.59 microL/min/mg protein) in hepatic microsomal fraction of rats with DMIS due to significant increase in expression of CYP3A1(23) in the rats. DA-8164 was formed mainly via CYP3A1/2 in rats. After intravenous administration of DA-8159, renal clearance was significantly faster in rats with DMIS (5.79 compared with 2.80 mL/min/kg) due to urine flow-dependent renal clearance of DA-8159 in rats. After oral administration of DA-8159, the AUC values of both DA-8159 and DA-8164 were not significantly different between two groups of rats. Although the exact reason is not known it may be due to changes in first-pass effect of DA-8159 in rats with DMIS.     

Pharmacokinetics of intravenous and oral DA-8159, a new erectogenic, in rats with protein-calorie malnutrition

Influence of dietary protein deficiency on the pharmacokinetics of DA-8159 and one of its metabolites, DA-8164, was investigated after intravenous and oral administration of DA-8159 at a dose of 30 mg kg(-1) to male Sprague-Dawley rats allowed free access to a 23% (control) or 5% (protein-calorie malnutrition, PCM) casein diet for 4 weeks. The total area under the plasma concentration-time curve from time zero to time infinity (AUC) values of DA-8164 were significantly smaller after both intravenous (87.0 vs 162 microg min mL(-1)) and oral (144 vs 319 microg min mL(-1)) administration of DA-8159 to PCM rats. This could be due to the decrease in CYP3A1/2 (50-60%) in the rats because DA-8164 was mainly formed via CYP3A1/2 in rats. This could be supported by significantly slower in-vitro CL(int) (2.04+/-0.646 vs 3.15+/-0.693 microL min(-1) (mg protein)(-1)) for the formation of DA-8164 in hepatic microsomal fraction of PCM rats. After intravenous administration of DA-8159, the AUC values of DA-8159 were not significantly different between the two groups of rats although the AUC of DA-8164 was significantly smaller in PCM rats, and this may be due to the minor metabolic pathway of DA-8164 in rats. However, after oral administration of DA-8159, the AUC of DA-8159 was significantly greater in PCM rats (194 vs 122 microg min mL(-1)). This was not due to enhanced absorption of DA-8159 from the gastrointestinal tract in the rats but may be due to a decreased intestinal first-pass effect of DA-8159 in the rats.     

Pharmacokinetic interaction between DA-8159, a new erectogenic, and metformin in rats: competitive inhibition of metabolism via hepatic CYP3A1/2

BACKGROUND AND PURPOSE: Erectile dysfunction is highly prevalent in diabetic patients and PDE V inhibitors are effective and safe for the treatment of erectile dysfunction in men with diabetes. Therefore, in this study we investigated whether a pharmacokinetic interaction occurs between DA-8159 and metformin, as both drugs are metabolized via hepatic CYP3A1/2 in rats. EXPERIMENTAL APPROACH: DA-8159 (30 mg kg(-1)) and metformin (100 mg kg(-1)), both separately and together, were administered to rats either intravenously or orally. The V (max), K (m), CL(int), apparent inhibition constants (K (i)), [I]/K (i) and concentrations of each drug in the liver and intestine were then measured. KEY RESULTS: After i.v. administration of both drugs simultaneously, the AUC of DA-8159 and metformin was significantly greater (21.2 and 33.9% increase for DA-8159 and metformin, respectively) than that of each drug alone. After p.o. administration of the drugs, the AUC of metformin was also significantly greater (20.7% increase) in the presence of DA-8159 than in its absence. However, the AUC of DA-8159 was similar in the absence and presence of metformin. CONCLUSIONS AND IMPLICATIONS: The significantly greater AUC of metformin and DA-8159 after i.v. administration of both drugs and of metformin after p.o. administration of both drugs is probably due to competitive inhibition for the metabolism of these drugs via hepatic CYP3A1/2. However, the similar AUCs of DA-8159 in the absence and presence of metformin, after p.o. administration, indicates that the dose of metformin used was insufficient to inhibit the hepatic and intestinal metabolism of DA-8159.     

Dose-dependent pharmacokinetics of KR-31378, a new neuroprotective agent for ischaemia-reperfusion damage in dogs

Dose-dependent pharmacokinetic parameters of KR-31378, a new neuroprotective agent for ischaemia-reperfusion damage, were evaluated after intravenous and oral administration of the drug at doses of 5, 10 and 25 mg/kg to male beagle dogs. After intravenous administration, the dose-normalized (based on 5 mg/kg) areas under the plasma concentration-time curve from time zero to time infinity (AUC values, 725, 1450 and 2300 micro g min/ml for 5, 10 and 25 mg/kg, respectively) were significantly different among the three dose ranges studied; the value increased more proportionally as the dose increased. This could be due to slower total body clearance (Cl) with increasing doses (6.90, 3.46 and 2.17 ml/min/kg). The slower Cl value with increasing doses may be due to saturable metabolism of KR-31378 in dogs. After oral administration, the dose-normalized (based on 5 mg/kg) AUC values (833, 1450 and 1920 micro g min/ml) at 5 mg/kg were significantly smaller than those at 10 and 25 mg/kg. Note that the AUC values were comparable (not significantly different) between intravenous and oral administration at all doses studied, indicating that the absorption of KR-31378 from the gastrointestinal tract was essentially complete and the first-pass (gastric, intestinal and/or hepatic first-pass) effects were almost negligible in dogs.     

Safety profile of thalidomide after 53 weeks of oral administration in beagle dogs.

Fifty-six adult beagle dogs (28 male, 28 female) were orally administered thalidomide at 43, 200, or 1000 mg/kg/day for 53 weeks. Sixteen (2/sex/dose group) and 32 (4/sex/dose group) dogs were euthanized and necropsied after 26 and 53 weeks of dosing, respectively. The remaining 8 animals (2/sex/group; high-dose and control groups) were dosed for 53 weeks, euthanized, and necropsied at 58 weeks after a 5-week recovery period. There were no deaths during the study. The only observed clinical signs attributable to thalidomide administration were green-colored urine, white-colored fecal residue presumed to be unchanged thalidomide, enlarged and/or blue coloration of female mammary tissue, and prolonged estrus. There were no thalidomide-related changes in body weights, food consumption, electrocardiography, ophthalmoscopy, neurological function, and endocrine function. The mostly slight and/or transient variations observed in some hematology and blood chemistry values of dosed dogs were considered to be toxicologically insignificant and were supported by the lack of histopathologic correlates. The only gross finding attributable to thalidomide was a yellow-green discoloration of the femur, rib, and/or calvarium that was observed at each euthanization interval including recovery. There was no microscopic correlate for this finding. No thalidomide-related microscopic changes were seen in any of the organs and tissues at 26 weeks. Mammary duct dilatation and/or glandular hyperplasia observed in females at 53 and 58 weeks and hepatic bile pigment exhibited by high-dose males at 53 weeks were microscopic changes considered to be thalidomide-related. There was no gross and histopathologic evidence of any tumors. In summary, thalidomide at up to 1000 mg/kg/day for 53 weeks did not induce any major systemic toxicity or tumors in dogs. The NOAEL was 200 mg/kg/day.     

Subchronic toxicity and toxicokinetics of MCC-555, a novel thiazolidinedione, after 270-day repeated oral administration in dogs

MCC-555, a treatment candidate for type 2 diabetes, is a novel thiazolidinedione which has comparatively high anti-diabetic efficacy. The present study was conducted to evaluate its toxicity and toxicokinetics in beagle dogs by oral administration at doses of 0, 6.67, 20 or 40mg/kg/day for 270 days. A 30-day recovery period was included at the end of the study to evaluate the reversibility of the toxic effects. During the treatment and recovery periods, the effects of the test agent on mortality, body weight, food consumption, hematology, serum biochemistry, urinalysis, electrocardiogram (ECG), organ weights, bone marrow and histopathology were examined. There were no treatment-related mortalities. Vomiting was observed in dogs receiving 40mg/kg/day during administration, but the dogs recovered within 1h after oral administration. Significant increases in total bilirubin and alkaline phosphatase were observed in dogs receiving the 40mg/kg/day dose during the treatment period, but the levels returned toward normal during the 30-day recovery period. Mild hydropic or fatty degeneration in the liver and inflammatory cell infiltration in the hepatic lobule or portal area was also observed sporadically without a dose-dependent relationship at the end of treatment and recovery periods. The most apparent toxicity in dogs was in the digestive system. However, these toxic effects of MCC-555 were transient and reversible. The accumulation of MCC-555 after 270-day oral administration was not notable at the toxic dose of 40mg/kg/day and the no-observed-adverse-effect level (NOAEL) was 20mg/kg/day. No differences in toxicokinetics of MCC-555 were observed between male and female dogs and no significant accumulation of MCC-555 was observed in tissues after 270 days of repeated treatments. MCC-555 distribution into different organs showed a higher penetration in the liver, kidneys and testes, followed by the ovaries and uterus. Metabolites and the metabolic style of MCC-555 are to be approved.     

Toxicity study of a new camptothecin anti-cancer agent CKD-602 in dogs: 4-Week continuous intravenous dose by infusion pump and 4-week repeated intravenous dose

In evaluating toxicity, one of the most important factors is the administration method, because it can affect the exposure and absorbance level of the test article, and, consequently, influence the interpretation of toxicity test results. Continuous intravenous (IV) administration is a widely used administration method for anti-cancer drugs in clinical settings. Previous studies have reported the toxic effects of the test article following repeated IV dosing of CKD-602, a novel camptothecin-derivative anti-tumor agent that was developed by Chong Kun Dang Pharmaceutical Corporation in Seoul, Korea. However, CKD-602-related toxicities induced by IV infusion administration have not yet been evaluated, although the drug is more widely used in clinical settings. In the present study, CKD-602 was administered using a continuous IV infusion pump and using repeated IV administration at doses of 0, 0.003, or 0.01 mg/kg/day for 4 weeks to compare and evaluate the drug-induced toxicities using the two different administration methods. Higher mortality, more severe clinical symptoms, increased complete blood count, serum biochemistry, and histopathology were demonstrated when CKD-602 was administered using the 4-week continuous IV infusion pump method compared with the repeated IV administration method. Based on these results, we conclude that the administration of CKD-602 using the 4-week continuous IV infusion pump method can elicit more severe toxicity than that using 4-week repeated IV dosing method. Thus, more attention should be paid to the administration of CKD-602 using continuous IV infusion in the clinical setting.