Pharmacokinetics of fosfosal in rats and dogs

Fosfosal (Disdolen) is a non acetyl derivative of salicylic acid with antiinflammatory and analgesic properties and a greater tolerance than acetylsalicylic acid and lysine acetylsalicylate. In the present work the pharmacokinetics of fosfosal have been studied after oral and intravenous administrations of 100 and 80 mg/kg in rats and dogs, respectively. Plasma concentrations of fosfosal and salicylic acid were determined by an HPLC method. After intravenous administration fosfosal plasma levels decreased rapidly showing a half-life of 2.7 min in rats and 6.7 min in dogs. Fosfosal in plasma is quickly hydrolyzed into salicylic acid producing high concentrations in few minutes after administration. The half-life of salicylic acid was 13.8 and 7.1 h for rats and dogs, respectively. After oral administration only salicylic acid was detected in plasma, indicating that fosfosal, when orally administered, behaves as a prodrug. From the comparison of the AUC for salicylic acid obtained after oral and intravenous administrations it can be deduced that fosfosal it totally absorbed in the two species studied.     

Pharmacokinetics of nizatidine in dogs and rats

1. Plasma levels of nizatidine and two metabolites (N-desmethyl nizatidine and nizatidine S-oxide) were studied in dogs and rats.

2. The time-courses of plasma concentration of nizatidine after i.v. and oral administration to dogs well fitted a two-compartment model. Absorption after oral administration was rapid, and the peak plasma level (C_max) and area under the plasma concentration-time curve (AUC) were proportional to doses. Absolute bioavailability was close to 100%, indicating that nizatidine has a negligible first-pass effect.

3. Nizatidine was eliminated by apparent first-order kinetics after i.v. administration to rats, and the elimination in rats was faster than in dogs. Bioavailability in rats was 72.4%, indicating a slight first-pass effect in rats.

4. When plasma clearance (Cl_p), or volume of distribution (V_d.β), of nizatidine were plotted against animal body weight on a log-log scale, good correlations were obtained for rats, dogs and humans.

5. Peak levels (C_max) of two metabolites were reached at 0.5–1.0?h after oral and i.v. administration of nizatidine to dogs. The elimination curves of the two metabolites were similar to that of nizatidine. Significant relationships were found between doses of nizatidine and C_max or AUC of both metabolites.     

Pharmacokinetics of besulpamide in rats and dogs

The pharmacokinetics of besulpamide were studied in rats and its urinary excretion in rats and dogs. Kinetic characteristics were the same for both male and female rats according to a two-compartment open model. Biological half-life was 1-4 hr, absorption half-life was approximately 10 min and absolute bioavailability was nearly complete (F = 86.4%). In rats, urinary excretion of unchanged besulpamide was 30% after i.v. administration and 7% after oral administration, whereas in dogs after oral administration it was 54%. Values of the area under the plasma concentration-time curve in rats and percent of urinary excretion in dogs show that the kinetics of besulpamide are not dose-related when the drug is administered at doses of 10-50 mg/kg.     

诺必擂停在大鼠和Beagle犬体内的药动学研究

目的:研究诺必擂停在大鼠和Beagle犬体内的药动学过程。方法:通过口服和静注两种给药方式,用高效液相色谱法测定血浆中诺必擂停的浓度。结果:大鼠灌胃给予诺必擂停8、16和32 mg/kg剂量后,血药浓度达峰时间tmax分别为20、30、30 min,峰浓度Cmax分别为(300±171)、(468±122)、(982±449)ng/mL,根据血药浓度AUC计算出的生物利用度F为(14.6±2.7)%。Beagle犬按4 mg/kg单剂量口服给予诺必擂停片后,tmax为(95±12)min,Cmax为(436±88)ng/mL,生物利用度F为(27.4±8.4)%。结论:灌胃给药后诺必擂停在大鼠和Beagle犬体内吸收较快但吸收程度较低,该药在两种动物的药动学参数tmax、t1/2α和t1/2β等存在明显的种属差异。     

Pharmacokinetics of FK027 in rats and dogs

The pharmacokinetics of FK027, a new oral cephalosporin, were investigated in rats and dogs and compared with those of cefaclor, cephalexin and amoxicillin. Upon oral administration to either rats or dogs, FK027 produced higher and more sustained serum levels than the reference drugs, hence a longer half-life. After both oral and intravenous administration, the half-life of FK027 in dogs was approximately three fold that in rats. Although the concentrations of FK027 in rat kidney, liver and spleen were lower than those of cephalexin and amoxicillin, they were sustained similarly to the serum levels. The 24-hour urinary and biliary recovery rates of FK027 in rats after oral dosing with 100 mg/kg were 34.1 and 21.9%, respectively. The urinary excretion of FK027 was significantly lower than that of the reference drugs, however, the biliary excretion was higher. In dogs, 23.4 and 0.2% of the given dose of 40 mg/kg of FK027 was excreted in the 24-hour urine and bile, respectively. Bioavailability of FK027 after oral dosing was 38% in rats and 47% in dogs, as calculated from intravenous data. Binding of FK027 to serum protein in all species was the highest of the test drugs: 63% for human, 93% for dog, 61% for rat serum.     

Pharmacokinetics of dopamine-2 agonists in rats and dogs

The absorption, protein binding, blood-to-plasma ratio, renal excretion, and pharmacokinetics of the dopamine-2 agonists (D2-agonists) 4-(2-di-n-propylaminoethyl)-7-hydroxy-2-(3H)-indolone (1), N-(2'-hydroxy-5'-[N,N-di-n-propylaminoethylphenyl])methanesulfonamide (2), and 4-(2-di-n-propylaminoethyl)-2-(3H)-indolone (3) were examined in dogs and rats. On the basis of relative cumulative urinary recoveries of radiolabeled drug, all three compounds are well absorbed in rats and dogs. In dogs, the free fractions in plasma of unchanged 1, 2, and 3, determined by in vitro studies, were 74, 86, and 63%, respectively, and the protein binding was constant with increasing concentration. The blood-to-plasma partition ratios of the respective compounds were 1.22, 1.14, and 1.16 in dogs, and the ratios were constant with increasing concentration. Large differences between species (dogs, rats, and humans) in protein binding and blood-to-plasma ratios were not seen. The clearances (blood or plasma) of 1 and 2 in dogs were significantly greater than the clearance of 3. The clearance of 3 was almost exclusively nonrenal, whereas 13% of 1 and 2 were recovered unchanged in urine. The steady-state volumes of distribution and the distribution and elimination half-lives of the three compounds were not significantly different. Importantly, the mean residence time of 3 (147 min) in dogs was significantly longer than those of 1 (90 min) and 2 (96 min). The results of analogous studies in rats indicate that 1 and 2 are more rapidly metabolized than 3.     

Pharmacokinetics of flunoxaprofen in rats, dogs, and monkeys

The kinetics of flunoxaprofen, an anti-inflammatory nonsteroidal drug, was studied in rats (Charles River), dogs (beagles), and monkeys (Macaca fascicularis). Plasma levels, after oral and iv administration of 20-40 mg/kg, and urinary excretion were followed for 24-72 h; the determinations were performed by gas chromatography. Levels in various organs and in rat bile were also determined. The pharmacokinetic parameters show noteworthy similarities in the three species studied: high bioavailability, extensive biotransformations with small urinary excretion of unmodified drug, total clearance between 40 and 50 mL/h/kg, and peak plasma levels of approximately 200 micrograms/mL. Rats show a high value in volume of distribution (2 L/kg), whereas dogs and monkeys show a volume of distribution between 0.13 and 0.18 L/kg. In the rat, the half-life of the drug is approximately 70 h, whereas in the dog and monkey, a half-life of approximately 2 h was found.     

Pharmacokinetics of triflusal and its main metabolite in rats and dogs.

The methods for determining plasma concentrations of triflusal (2-acetoxy-4-trifluoromethyl benzoic acid) that have been described, do not distinguish between the drug and its main metabolite HTB (2-hydroxy-4-trifluoromethyl benzoic acid). In the present study, we have developed a new analytical technique based on HPLC that enabled us to carry out a pharmacokinetic study of the drug and its metabolite in animals. An intravenous or oral dose of 50 mg/kg was administered to male Sprague-Dawley rats, and 15 mg/kg was administered to beagle dogs. Plasma levels of triflusal and HTB were determined. In rats, triflusal was quickly eliminated from plasma with a biological half-life (t1/2) of 2.7 min and a clearance (Cl) of 73.4 (ml/kg)/min. The elimination of HTB was much slower with a t1/2 of 21.5 h and a Cl of 5.1 (mg/kg)/h. The maximum concentration (Cmax) of triflusal in rats after an oral administration was 8.1 +/- 2.0 micrograms/ml reached between 2.5 and 10 min. The Cmax of HTB was 237.7 micrograms/ml and was achieved at 0.7 h. The bioavailability of triflusal in rats was only 10.6% while the bioavailability of HTB was more than 100% indicating an important first pass effect. In dogs the t1/2 of triflusal was 14.4 +/- 5.9 min and the Cl was 25.1 +/- 4.7 (ml/kg)/min. HTB was also eliminated very slowly with a t1/2 of 71.1 +/- 12.5 h and a Cl of 2.4 +/- 0.3 (ml/kg)/h. The Cmax of triflusal in dogs was 13.3 +/- 2.9 micrograms/ml and was reached after 19.2 +/- 6.1 min (tmax).(ABSTRACT TRUNCATED AT 250 WORDS)     

大鼠和家犬体内加替沙星的测定及药物动力学的研究

目的采用HPLC测定加替沙星在犬和大鼠各组织中的浓度并研究其体内过程。方法家犬po5、102、0 mg.kg-1加替沙星后,测定不同时间血清中浓度,计算药动学参数。大鼠po20 mg.kg-1加替沙星后,测定各组织的药物浓度,并测定尿液、胆汁与粪便累积排泄率。结果加替沙星的犬药动学符合一室模型,AUC0~24和Cmax与剂量平行,Tmax与剂量无关。大鼠po加替沙星后快速分布在各组织中,其中肝、肾、小肠、胃分布最多,大脑未检测到药物。48 h后,尿液、胆汁与粪便中的药物累积排泄率分别为66.2%±8.8%、8.05%±3.08%和3.63%±1.65%。结论加替沙星口服吸收快,消除半衰期长,组织分布广。     

溴泰君(W198)在大鼠和比格狗体内的药代动力学

目的研究溴泰君(W198)在大鼠和比格狗的药代动力学。方法采用HPLC紫外检测方法测定大鼠及比格狗注射W198后血清药物浓度。结果大鼠iv W198 10,20和40 mg·kg^-1 3个剂量的T_1/2β分别为6.60,7.36和6.77 h,AUC_0-24h分别为3.797,7.371和15.192 mg·h·L^-1,V_d分别为7.14,4.33和4.13 L·kg^-1,CL分别为2.83,2.60和2.71 L·(kg·h)^-1。大鼠im W198 20 mg·kg^-1后T_1/2β为11.61 h,AUC_0-24h为4.191 mg·h·L^-1,im的生物利用度为56.9%。比格狗iv W198 5 mg·kg^-1,T_1/2β为11.72 h,AUC_0-24h为12.646 mg·h·L^-1,V_d为0.70 L·kg^-1,CL为0.46 L·(kg·h)^-1。W198与人血浆蛋白的结合率平均为78.0%。结论W198 im的T_1/2β比iv的略长,其生物利用度为56.9%。在10～40 mg·kg^-1剂量内的吸收呈现一级动力学特征。     

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 and dose-dependency of LB30870 in rats, dogs, and monkeys

This study was to examine the pharmacokinetics of LB30870, a thrombin inhibitor, after IV and oral administration to rats, dogs, and monkeys. In rats and dogs, LB30870 showed linear pharmacokinetics after IV and oral administration. The oral bioavailability (BA) in rats was about 30 % with high inter-subject variability in the time to reach peak plasma concentration (T_max). Oral absorption of a solution and prototype tablet formulations of LB30870 were tested in dogs. T_max was 30 min and the BA values were 40.8–43.1 % with solution formulation. BA values after oral administration of the two tablet formulations at the dose of 100 mg/dog were 27.0 and 30.8 %. T_max were 60 min in the tablet formulation, indicating that the disintegration and dissolution of tablets caused delay in T_max compared to solution formulation. After IV administration of LB30870 to monkeys, the plasma concentrations decreased bi-exponentially and BA was 15.0 % after oral (20 mg/kg) dosing. In summary, linear pharmacokinetics of LB30870 were observed in both rats and dogs. The differences in BA among species could be due to difference in absorbed fraction and/or the first pass extraction (pre-systemic elimination) of LB30870.     

Pharmacokinetics and metabolism of the novel muscarinic receptor agonist SNI-2011 in rats and dogs

In this study, the pharmacokinetics of SNI-2011 ((+/-)-cis-2-methylspiro[1,3-oxathiolane-5,3'-quinuclidine]monohydrochloride hemihydrate, cevimeline, CAS 153504-70-2), a novel muscarinic acetylcholine receptor agonist developed for the treatment of Sj?gren's syndrome, in rats and dogs were determined following intravenous or oral administration using liquid chromatography/mass spectrometry (LC/MS). The in vitro metabolism of SNI-2011 was also evaluated with rat and dog liver microsomes. After oral administration, plasma concentrations of SNI-2011 reached to Cmax within 1 h in both species, suggesting that SNI-2011 was quickly absorbed, and then decreased with a t1/2 of 0.4-1.1 h. The bioavailability was approximately 50% and 30% in rats and dogs, respectively. Major metabolites in plasma were both S- and N-oxidized metabolites in rats and only N-oxidized metabolite in dogs, indicating that a large species difference was observed in the metabolism of SNI-2011. Sex difference was also observed in the pharmacokinetics of SNI-2011 in rats, but not in dogs. In the in vitro study, chemical inhibition and pH-dependent studies revealed that the sulf-oxidation and N-oxidation of SNI-2011 were mediated by cytochrome P450 (CYP) and flavin-containing monooxygenase (FMO), respectively, in both species. In addition, CYP2D and CYP3A were mainly responsible for the sulfoxidation in rat liver microsomes.     

Pharmacokinetics of LB20304, a new fluoroquinolone,in rats and dogs

The pharmacokinetics of LB20304 was investigated following intravenous (IV) and oral administration to rats and dogs. Additionally,in vitro metabolism and serum protein binding studies were also conducted. The total body clearance, apparent volume of distribution, terminal half-life, and extent of bioavailability were 21.8 ml/min/kg, 2265 ml/kg, 93.6 min, and 30.8% for rats; and 7.95 ml/min/kg, 4144 ml/kg, 363 min, and 81.1% for dogs, respectively. LB20304 was stable in the liver microsome containing NADPH generating system and its serum protein binding was 58.5–65.8% for rats, 19.1–26.6% for dogs, and 56.9–59.6% for humans. Its tissue concentration levels in liver, stomach, small intestine, and kidney were 9.5 to 26.1 times greater than plasma level, but the concentration in testis was quite low and that in brain was negligible in rats. The 48 hr urinary recovery of the dose was 44% for IV dosing and 14% for oral dosing, whereas the 48 hr biliary recovery of the dose was 6.4% for IV dosing and 4.5% for oral dosing in rats. In summary, the pharmacokinetic properties of LB20304 were characterized by its good oral absorption, long plasma half-life, and good tissue distribution.     

Pharmacokinetics and N-acetylation metabolism of S-methyl-l-cysteine and trans-S-1-propenyl-l-cysteine in rats and dogs

1.?Pharmacokinetics and N-acetylation metabolism of S-methyl-L-cysteine (SMC) and trans-S-1-propenyl-L-cysteine (S1PC) were examined in rats and dogs. SMC and S1PC (2–5?mg/kg) were well absorbed in both species with high bioavailability (88–100%).

2.?SMC and S1PC were excreted only to a small extent in the urine of rats and dogs. The small renal clearance values (<0.03?l/h/kg) indicated the extensive renal reabsorption of SMC and S1PC, which potentially contributed to their long elimination half-lives (>5?h) in dogs.

3.?S1PC, but not SMC, underwent N-acetylation extensively in vivo, which can be explained by the relative activities of N-acetylation of S1PC/SMC and deacetylation of their N-acetylated forms, N-acetyl-S1PC/N-acetyl-SMC, in the liver and kidney in vitro. The activities for S1PC N-acetylation were similar to or higher than those for N-acetyl-S1PC deacetylation in liver S9 fractions of rat and dog, whereas liver and kidney S9 fractions of rat and dog had little activity for SMC N-acetylation or considerably higher activities for N-acetyl-SMC deacetylation.

4.?Our study demonstrated that the pharmacokinetics of SMC and S1PC in rats and dogs was characterized by high bioavailability and extensive renal reabsorption; however, the extent of undergoing the N-acetylation metabolism was extremely different between SMC and S1PC.     

Pharmacokinetics of carbamazepine polymorphs and dihydrate in rats,related to dogs and humans

Species differences in the oral pharmacokinetics and absolute bioavailability (F _abs ) of carbamazepine polymorphs (form I and form III) and dihydrate were studied. The pharmacokinetics of each form was investigated in rats following a single oral/intravenous administration of 10 mg/kg and an oral dose of 80 mg/kg, which were compared with the published data obtained from dogs and humans. No significant differences were found in their C _max, T _max, AUC_0−∞ and F _abs among the forms at the low dose. However, significant differences were observed at the high dose. The Fabs of each form was markedly reduced with increasing of doses in species (e.g. F _abs in rats ranged from > 82% to 38.4%–56.0%). At a comparable dose, the C _max, and AUC_0−∞ of rats and humans were about 3–10 times higher than in dogs. The absorption rate of form III in rats exhibited a similar trend to that in humans, and was far higher in dogs. A multi-peak phenomenon in plasma curves was observed in rats and humans, but not in dogs. In conclusion, rats appear to be a better predictor of carbamazepine polymorphs absorbed in humans, and form III may be more suitable as a pharmaceutical crystal.     

Pharmacokinetics and body distribution of amiodarone and desethylamiodarone in rats after oral administration

The pharmacokinetics and body distribution of amiodarone and desethylamiodarone were studied in rats after single oral administration of 100 mg/kg and 200 mg/kg of amiodarone. The time-course of the concentrations of the drug and its main metabolite was determined by high performance liquid chromatography in serum and tissues up to 24 h. The mean absorption half-life of amiodarone was 1.83 h for both dosages and the mean elimination half-life was 15 h after the 100 mg/kg dosage and 105 h after the 200 mg/kg dosage. The mean bioavailability of oral amiodarone ranged from 17% to 60% with an average of 39%. Desethylamiodarone, the major metabolite of amiodarone, was present over the 24 h period of observation in relatively low levels of 30 to 60 ng/ml after the 100 mg/kg dose and 50 to 110 ng/ml after the 200 mg/kg dose respectively, which is circa 4% and 7% of the corresponding parent drug level. Amiodarone is preferentially distributed in decreasing order in lung, liver, thyroid gland, kidney, heart, adipose tissue, muscle tissue and brain. The metabolite desethylamiodarone exhibited a distribution pattern comparable to the parent drug. However, its maximum concentrations in serum and tissues were consistently lower than the corresponding amiodarone concentrations and varied from 18 to 55% (mean 27%), depending on the acute oral dose applied and on the kind of tissue. The amiodarone tissue/serum concentration ratios were high in lung tissue (60-100) and moderate to high in the other tissues except brain (3-60), and indicate an extensive distribution of the drug with the lung as an organ with specific binding sites or uptake mechanisms and adipose tissue as a reservoir with a large storage capacity. The metabolite tissue/serum concentration ratios were very high in lung tissue (500-800), high in renal, thyroid, liver and adipose tissue (80-200) and moderate in the other tissues except for brain (20-60); they indicate a very extensive distribution of desethylamiodarone with, primarily, lung and to some lesser extent kidney, liver and thyroid gland as organs with sites of metabolism and/or specific binding sites or uptake mechanisms and fat as a reservoir for the drug. A marked increase in the accumulation of amiodarone and desethylamiodarone was observed in adipose tissue after chronic oral administration, whereas the rise in kidney and brain was less pronounced and in the remaining tissues it was insignificant. Our data suggest that the rat is a good model for describing the single oral dose pharmacokinetics and body distribution of amiodarone and desethylamiodarone in man.     

Pharmacokinetics and body distribution of amiodarone and desethylamiodarone in rats after intravenous administration

The pharmacokinetics and body distribution of amiodarone and desethylamiodarone were investigated in rats following a single intravenous dose of 100 mg/kg and 150 mg/kg of amiodarone. The decline in serum and tissue concentrations of amiodarone and desethylamiodarone are described by biexponential functions. All aspects of the typical kinetic profile of the drug and its major metabolite, desethylamiodarone, are discussed. Amiodarone is preferentially distributed in decreasing order in thyroid gland, lung, kidney, liver, heart, adipose tissue, skeletal muscle and brain. The metabolite desethylamiodarone showed a distribution pattern which is similar to that observed for the parent drug. Our study indicates an extensive distribution of amiodarone, with the thyroid gland and lung as organs with specific binding sites or uptake mechanisms and adipose tissue as a depot with a large storage capacity. We also found a very extensive distribution of the metabolite desethylamiodarone with mainly lung and thyroid gland and to some lesser extent kidney, liver and heart as organs with sites of metabolism and/or specific binding sites or uptake mechanisms and fat as a reservoir for the drug. Our data demonstrate the advantages of intravenous loading dosages of amiodarone over oral doses, since considerably higher and longer lasting effective serum and tissue concentrations of amiodarone are reached while lower quantities of the less cardio-active metabolite are formed.     

Pharmacokinetics of pyridostigmine in dogs

The pharmacokinetics of the cholinesterase inhibitor pyridostigmine has been studied in six male Beagle dogs after iv infusion and after oral doses as an immediate-release syrup and as an extended-release tablet, all at a level of approximately 0.6 mg/kg. Pyridostigmine was characterized as a drug of relatively long terminal half-life (8.3 h +/- 2.1 SD), low systemic clearance (13 mL/min/kg +/- 1 SD) and high volumes of distribution (Vd lambda z, 8.7 L/kg +/- 1.9 SD and Vdss, 3.9 L/kg +/- 0.9 SD). The ratio of mean residence times in tissues and plasma was greater than 4, indicating a high affinity of peripheral tissues for the drug. This ratio was about twofold higher in three of the dogs than in the others. Pyridostigmine was slowly and incompletely bioavailable in these dogs; the systemic availability was 44.4% +/- 4.3 SD from the syrup and 33.6% +/- 9.5 SD from the tablet. Pyridostigmine disposition in these dogs was largely determined by distribution processes.