Assessment of Dose Proportionality,Absolute Bioavailability,and Immunogenicity Response of CTLA4Ig (BMS-188667), a Novel Immunosuppressive Agent,Following Subcutaneous and Intravenous Administration to Rats

Purpose. The objectives of this study were: to delineate the pharmacokinetics of CTLA4Ig in rats after single and multiple intravenous (IV) and subcutaneous (SC) doses; to assess the relationship of the pharmacokinetic parameters of CTLA4Ig vs dose; to calculate the SC absolute bioavailability; and to assess the antibody response of CTLA4Ig. Methods. A total of 48 (24 male and 24 female) Sprague Dawley rats were divided into eight treatments with 3 rats per gender in each group: a single dose of 10, 80, or 200 mg/kg of CTLA4Ig given either IV or SC and a repeated dose of 10 mg/kg (once every other day for 7 doses over 13 days) given either SC or IV. Serial blood samples were collected up to 43 days after single dose administration and up to 50 days following the administration of the last multiple dose on day 13. The serum concentration of CTLA4Ig and anti-CTLA4Ig antibodies were measured using ELISA assays. Results. After single IV doses, C_max and AUC_inf increased in a dose proportional manner; CL appeared to be dose independent, while both V_ss and T_1/2 increased as the administered dose increased. Following single SC doses, C_max and AUC_inf increased in a linear manner but not proportionally; mean T_max values were prolonged but similar among the three dose levels, while T_1/2 increased as the administered dose increased. The absolute SC bioavailability of CTLA4Ig decreased as the dose increased from 10 (62.5%), 80 (55.7%), and 200 mg/kg (41.1%). Comparison of the AUC_tau values between the first and last doses suggested an accumulation (3.1–4.7) of CTLA4Ig. However, regardless of the route of dosing, AUC_tau after the last dose were comparable to AUC_inf values following the single dose. Anti-CTLA4Ig antibodies were detected at the 10 mg/kg dose level after single or multiple doses for both routes of administration. However, regardless of single or multiple doses, antibody titers were relatively greater for the SC compared to the IV administration. Conclusions. The key findings of this study were: (i) the elimination characteristics of CTLA4Ig were comparable between the SC and IV routes; (ii) the repeated dosing did not alter the pharmacokinetics of CTLA4Ig; (iii) the SC absolute bioavailability tended to decrease as the administered dose increased; and (iv) a greater formation of anti-CTLA4Ig antibodies was observed after SC compared to IV at a single 10 mg/kg dose level; however, after multiple dosing, the formation of antibodies from either of the two routes was relatively slower, and (v) during the study period, no antibodies were observed at either the 80 or 200 mg/kg dose levels regardless of the route of administration.     

Toxicokinetics of bis(2-chloroethoxy)methane following intravenous administration and dermal application in male and female F344/N rats and B6C3F1 mice

In the National Toxicology Program's toxicity studies, rats were more sensitive than mice to Bis(2-chloroethoxy)methane (CEM) - induced cardiac toxicity following dermal application to male and female F344/N rats and B6C3F1 mice. Thiodiglycolic acid (TDGA) is a major metabolite of CEM in rats. It has been implicated that chemicals metabolized to TDGA cause cardiac toxicity in humans. Therefore, the toxicokinetics of CEM and TDGA were investigated in male and female F344/N rats and B6C3F1 mice following a single intravenous administration or dermal application of CEM to aid in the interpretation of the toxicity data. Absorption of CEM following dermal application was rapid in both species and genders. Bioavailability following dermal application was low but was higher in rats than in mice with females of both species showing higher bioavailability than males. CEM was rapidly distributed to the heart, thymus, and liver following both routes of administration. Plasma CEM C_max and AUC_∞ increased proportionally with dose, although at the dermal dose of 400 mg/kg in rats and 600 mg/kg in mice non-linear kinetics were apparent. Following dermal application, dose-normalized plasma CEM C_max and AUC_∞ was significantly higher in rats than in mice (p-value < 0.0001 for all comparisons except for C_max in the highest dose groups where p-value = 0.053). In rats, dose-normalized plasma CEM C_max and AUC_∞ was higher in females than in males: however, the difference was significant only at the lowest dose (p-value = 0.009 for C_max and 0.056 for AUC_∞). Similar to rats, female mice also showed higher C_max and AUC_∞ in females than in male: the difference was significant only for C_max at the lowest dose (p-value = 0.002). Dose-normalized heart CEM C_max was higher in rats than in mice and in females than their male counterparts. The liver CEM C_max was lower compared to that of heart and thymus in both rats and mice following intravenous administration and in rats following dermal application. This is likely due to the rapid metabolism of CEM in the liver as evidenced by the high concentration of TDGA measured in the liver. Dose-normalized plasma and heart TDGA C_max values were higher in rats compared to mice. In rats, females had higher plasma and heart TDGA C_max than males; however, there was no gender difference in plasma or heart TDGA C_max in mice. These findings support the increased sensitivity of rats compared to mice to CEM-induced cardiac toxicity. Data also suggest that, either CEM C_max or AUC can be used to predict the CEM-induced cardiac toxicity. Although, both plasma and heart TDGA C_max was consistent with the observed species difference and the gender difference in rats, the gender difference in mice to cardiac toxicity could not be explained based on the TDGA data. This animal study suggests that toxicologically significant concentrations of CEM and TDGA could possibly be achieved in the systemic circulation and/or target tissues in humans as a result of dermal exposure to CEM.     

A sensitive and simplified HPLC analysis for the determination of fluconazol in human plasma

A sensitive and simplified HPLC assay of fluconazol is described. The calibration curve of fluconazol in plasma ranging 0–10 μ g/ml was linear with the correlation coefficients of 0.9900. The limit of detection was 0.3 μ g/ml. The average recovery of the drug was 89.1±9.05%. After oral administration of single dose(150mg) of fluconazol in man, C_max and T_max were 3 μg/ml and 4hr., respectively.     

Gender effect on the pharmacokinetics of thymoquinone: Preclinical investigation and in silico modeling in male and female rats

Thymoquinone is the most biologically active constituent of Nigella sativa (black seed). A monoterpene compound chemically known as 2-methyl-5-isopropyl-1, 4-quinone. In this study, the gender-dependent pharmacokinetic behavior of thymoquinone in rats was investigated. Thymoquinone was administered orally (20 mg/kg) and intravenously (5 mg/kg) to male and female rats and blood samples were collected at specific time points. Plasma concentration-time curves were plotted and pharmacokinetic parameters were determined using the non-compartmental analysis. In addition, simulations of steady state concentrations of thymoquinone in male and female rats were performed using GastroPlus PK software. After oral administration, the maximum plasma concentration (C_max) of thymoquinone was 4.52 ± 0.092 μg/ml in male rats and 5.22 ± 0.154 μg/ml in female rats (p = 0.002). Similarly, after intravenous administration, the C_max was 8.36 ± 0.132 μg/ml in males and 9.51 ± 0.158 μg/ml in females (p = 0.550). The area under the plasma concentration-time curve (AUC)_0-∞ following oral dosing was 47.38 ± 0.821 μg/ml·h in females and 43.63 ± 0.953 μg/ml·h in males (p = 0.014). Pharmacokinetics and plasma concentration vs. time profiles for multiple oral doses of thymoquinone in rats were predicted using a simulation model to compare the simulation results with the experimental plasma pharmacokinetic data. The differences observed in thymoquinone pharmacokinetics between male and female rats after a single dose were not evident for the simulated steady-state parameters. The findings suggest that the gender difference does not seem to play a significant role in thymoquinone disposition at steady state.     

Pharmacokinetics and bioavailability of the new drug protecor upon peroral administration in rabbits and beagle dogs

A new high-performance liquid chromatographic method with ultraviolet detection has been used to determine the levels of the new cardiotropic drug protecor in the blood of animals (chincilla rabbits, 2.2 ± 0.2 kg; and beagle dogs, 10 ± 0.5 kg). The parameters of protecor pharmacokinetics and bioavailability upon peroral administration of protecor tablets have been determined. Rabbits showed effective absorption of the drug uupon peroral administration in a single dose (100 mg/kg) with a peak concentration in the plasma (C _max= 41 μg/mL) reached within T _max= 3 h followed by rapid removal of the drug from the organism with a half-elimination time T _/12β=1.71 h. Peroral administration of protecor in a single dose (50 mg/kg) in beagle dogs was characterized by C _max= 34.6 μg/mL, T _max = 3 h, and T _/12β=0.75 h. The bioavailability of protecor upon peroral administration was estimated at 90% (rabbits) and 80.7% (beagle dogs). __________ Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 41, No. 12, pp. 3–6, December, 2007.     

Early pharmacokinetics of nasal fentanyl: is there a significant arterio-venous difference?

Objective

We have investigated the arterio–venous difference in the pharmacokinetics of 50 μg fentanyl during the first hour following nasal administration and documented its tolerability in opioid-naïve middle-aged to elderly patients.

Methods

Twelve male patients (range in age 47–84 years) scheduled for transurethral resection of the prostate gland received a 100-μl dose of 50 μg fentanyl base as a fentanyl citrate formulation in one nostril. Simultaneous arterial and venous blood samples for analyses of fentanyl were drawn at baseline and at 1, 3, 5, 7, 9, 13, 15, 20, 25, 35, 45 and 60 min after drug administration. Vital signs, sedation and symptoms of local irritation were recorded.

Results

The arterial C_max (maximum serum concentration) of 0.83 ng/ml was nearly twofold higher than the venous C_max of 0.47 ng/ml, and the arterial T_max (time to maximum serum concentration) of 7.0 min was about 5 min shorter than the venous T_max of 11.6 min. The arterial AUC_0-60 (area under the curve from 0 to 60 min after administration) of 21 min*ng/ml was approximately 30% larger than the venous AUC_0-60 of 15 min*ng/ml (all p values?≤?0.005). Venous T_max and C_max did not predict the corresponding arterial values. No significant adverse events were observed.

Conclusion

A significant arterio–venous difference was present after intranasal administration of fentanyl. The short arterial T_max complies with its rapid onset of action. The use of venous concentrations for the prediction of onset time of analgesia should be discouraged. A 50-μg dose of nasal fentanyl was well tolerated by opioid-naïve middle-aged to elderly male patients.

     

Absorption of new HIV-1 protease inhibitor,KNI-272, after intraduodenal and intragastric administrations to rats: Effect of solvent

KNI-272 is a tripeptide drug that has a strong pharmacological potential for treating human immunodeficiency virus type 1 (HIV-1). We have already reported the pharmacokinetic characteristics of KNI-272 after intravenous and intraduodenal (ID) administrations to rats. In this study, KNI-272 was administered to rats as a solution and the effect of four kinds of solvent on the bioavailability (BA) of KNI-272 was determined using rats. The mixtures included propylene glycol (PG) and water (70% PG), a solution of PG (100% PG), a solution of Tween 80 (Tween 80), and a mixture of PG and HCO60, a polyoxyethylated, 60μmol, castor oil derivative (PG:HCO60=7:3). After ID administration to rats at a dose of 50.0 mg kg^?1, the mean peak plasma concentrations, C_max, were 2.58±0.53 (SE) (70% PG), 3.28±0.51 (100% PG), 3.15±0.51 (Tween 80), and 4.66±0.68 μg mL^?1 (PG:HCO60). The highest BA, 44.6%, was obtained after ID administration of KNI-272 dissolved in PG:HCO60. On the other hand, after intragastric (IG) administration of KNI-272 solution in which the drug was dissolved with PG:HCO60, the T_max, the C_max, and the BA were 1.25±0.60h, 2.33±0.65 μg mL^?1, and 24.2%, respectively. The C_max and BA values were equal to half of the values obtained after ID administration of KNI-272 dissolved in the same solution. In this study, as the PG concentration in the solution increased and the other additives (Tween 80 and HCO60) were coadministered, the BA of KNI-272 after ID administration increased. These results suggest that, for the development of an oral dosage form of KNI-272, a non-ionic surfactant that dissolves in the duodenum or small intestine and that enhances the absorption of this drug from the gastrointestinal tract into the enterocytes is needed.     

Pharmacokinetic interactions of almorexant with midazolam and simvastatin, two CYP3A4 model substrates, in healthy male subjects

Purpose

Pre-clinical experiments have shown that almorexant, a dual orexin receptor antagonist, is able to inhibit cytochrome P450 3A4 (CYP3A4). Therefore, a study was conducted to investigate the effects of multiple-dose almorexant on the pharmacokinetics of midazolam and simvastatin, two CYP3A4 model substrates.

Methods

Fourteen healthy male subjects were enrolled in an open-label, randomized, two-way crossover study. Treatment period A consisted of a single oral dose of 2 mg midazolam on day 1 and 40 mg simvastatin on day 3. In treatment period B, subjects received 200 mg almorexant once daily for 9 days together with a single oral dose of midazolam on day 7 and simvastatin on day 9.

Results

Concomitant administration of midazolam with almorexant at steady-state levels, achieved within 4–5 days, resulted in an increase of 1.2-fold [90 % confidence interval (CI) 1.0–1.4], 1.4-fold (90 % CI 1.2–1.6), and 1.3-fold (90 % CI 1.2–1.4) in the maximum plasma concentration (C_max), area under the concentration–time curve from time 0 to infinity (AUC_0-∞), and terminal half-life (t_1/2), respectively, of midazolam; the time to peak plasma concentration (t_max) was unchanged. Whereas C_max and t_max were not influenced by almorexant, the AUC_0-∞ of hydroxy-midazolam increased by 1.2-fold (90 % CI 1.1–1.4) and the t_1/2 by 1.3-fold (90 % CI 1.0–1.5). Concomitant administration of simvastatin with almorexant at steady-state resulted in an increase of 2.7-fold (90 % CI 2.0–3.7) and 3.4-fold (90 % CI 2.6–4.4) in C_max and AUC_0-∞, respectively, for simvastatin; the t_1/2 and t_max were unchanged. The C_max and AUC_0-∞ of hydroxyacid simvastatin both increased by 2.8-fold, with 90 % CIs of 2.3–3.5 and 2.2–3.5, respectively; the t_max increased by 2 h and the t_1/2 was unchanged. The urinary 6-β-hydroxycortisol/cortisol ratio was unaffected by almorexant.

Conclusions

Our results suggest that the observed interaction was caused by the inhibition of CYP3A4 activity, most probably at the gut level.     

Influence of CYP2C19 polymorphism on the pharmacokinetics of nelfinavir and its active metabolite

AIMS

This study reports the pharmacokinetics of nelfinavir, its active metabolite, M8, and active moiety (nelfinavir + M8) in volunteers genotyped for CYP2C19 as extensive metabolizer (*1*1; n = 38), heterozygous poor metabolizer (PM) (*1*2; n = 22) and homozygous PM (*2*2; n = 6).

METHODS

Subjects received nelfinavir at normal dose (3.5 days of 1250 mg q12h) or high dose (1250 mg q12h for 3 days and single dose of 3125 mg on day 4). Steady-state plasma samples were analysed by high-performance liquid chromatography/ultraviolet assay to determine pharmacokinetics.

RESULTS

At steady state, the mean C_max was 42% [95% confidence interval (CI) 19, 69] and 63% (95% CI 20, 122) higher, and mean AUC was 51% (95% CI 24, 83) and 85% (95% CI 32, 159) higher for *1*2 and *2*2 compared with *1*1 subjects, respectively. For M8, the mean C_max and AUC were 35% (95% CI 6, 55) and 33% (95% CI −3, 56), respectively, lower for *1*2 compared with *1*1 subjects. M8 was not detectable in *2*2 subjects. The mean C_max and AUC values for the active moiety were higher by 30–35% for the *1*2 and *2*2 compared with *1*1 subjects.

CONCLUSIONS

Mutation in CYP2C19 increased the systemic exposure of nelfinavir and reduced the exposure of M8. No significant differences were noted among the heterozygous (*1*2) and homozygous (*2*2) PMs. These changes are not considered to be clinically relevant and hence the use of nelfinavir does not require prior assessment of CYP2C19 genotype.     

大鼠重复ig给予N-［（3-烯丙基-2-羟基）苯亚甲基-2-（4-苄基-高哌嗪-1-基）乙酰肼富马酸盐的药动学研究

目的 采用高效液相色谱-串联质谱法（HPLC-MS/MS）测定SD大鼠血浆中N-［（3-烯丙基-2-羟基）苯亚甲基］-2-（4-苄基-高哌嗪-1-基）乙酰肼富马酸盐（SM-1）,并计算大鼠重复ig给药的药动学参数,评价SM-1的药动学特征。方法 将60只健康SPF级SD大鼠随机分为阴性对照组、溶媒对照组和SM-1低、中、高剂量组,每组16只动物（阴性对照组和溶媒对照组为6只动物）,雌雄各半。每天ig给药1次,各组分别给予水、溶媒或SM-1 50、100、200 mg·kg^-1,给药体积10 mL·kg^-1,连续给药4周,于首次给药和末次给药阶段进行药动学采血测定。采用经验证的HPLC-MS/MS法测定SD大鼠血浆中SM-1浓度。使用Phoenix WinNonlin 7.0软件进行血药浓度-时间数据分析与药动学参数计算。结果 SD大鼠ig给予SM-1后,在50～200 mg·kg^-1剂量,SD大鼠体内的平均峰浓度（C_max）及药时曲线下面积（AUC_0～t）随剂量的增加而增加,各剂量组动物平均C_max及AUC_0～t比值与剂量比相近。连续给药后,低、中、高剂量组均未出现明显的蓄积。雌性大鼠SM-1的暴露高于雄性大鼠。结论 连续给药28 d后,SM-1在大鼠体内未出现明显的蓄积,雌性大鼠SM-1的暴露高于雄性大鼠。     

Influence of cholestyramine on the pharmacokinetics of rosiglitazone and its metabolite,desmethylrosiglitazone, after oral and intravenous dosing of rosiglitazone: Impact on oral bioavailability,absorption, and metabolic disposition in rats

The possible influence of the bile acid-sequestering agent cholestyramine (CSA), which is a basic co-medication in hypercholesterolemic patients, on the pharmacokinetics of rosiglitazone (RGL) and its circulating metabolite desmethylrosiglitazone (DMRGL) was investigated following a single oral and intravenous dose of RGL to Wistar rats. The pharmacokinetic parameters of RGL and DMRGL were evaluated following oral or intravenous administration of RGL to rats at 10?mg?kg^?1 with and without pre-treatment (0.5?h before RGL administration) of CSA at 0.057, 0.115, 0.23 and 0.34?g?kg^?1 doses. With an increase in CSA dose there was dose-dependent decrease in area under the curve (AUC)_(0?∞) and C_max with no change in T_max, K_el and t_1/2 values for both RGL and DMRGL following oral administration of RGL. The oral bioavailability of RGL was reduced by 19.9, 35.6, 53.8 and 72.0% in rats following pre-treatment with CSA at 0.057, 0.115, 0.230 and 0.340?g?kg^?1, respectively. There was no change in the above-mentioned pharmacokinetic parameters for RGL and DMRGL in rats when RGL was given intravenously following pre-treatment with the above-mentioned oral doses of CSA. Another objective of the study was to determine the effect of staggered oral CSA dosing at 1, 2 and 4?h after oral RGL administration at 10?mg?kg^?1. AUC_(0?∞) of RGL and DMRGL was reduced following CSA staggered administration at 1?h, whereas 2- and 4-h staggered dose administration of CSA had no effect on the AUC_(0?∞) of RGL and DMRGL. Irrespective of CSA staggered dose administration there was no change in other pharmacokinetic parameters, namely C_max, T_max, K_el and t_1/2. The apparent formation rate constant (K_f) of DMRGL was also calculated to show that only the absorption of RGL was affected, not the apparent formation rate of DMRGL. The authors also studied the in vitro adsorption of RGL (100, 250, 500?µg?ml^?1) at various pH conditions (pH 2, 4 and 7) and different concentrations of CSA (15, 30, 60 and 120?mg?ml^?1). The percentage binding of CSA was in the range 50–72% (at pH 2), 74–89% (at pH 4) and 97–100% (at pH 7). In conclusion, we carried out a systematic investigation demonstrating mechanistically the interaction potential of RGL when co-administered with CSA. The applicability of the metabolite data after intravenous and oral dosing and pH-based binding experiments further adds credence to the key findings.     

Pharmacokinetic behaviour in polymorphonuclear leucocytes of N,N-dimethylcarbamoylmethyl α,2-dimethyl-5H-[1]benzopyrano[2,3-b]-pyridine-7-acetate (Y-23023), a new prodrug type of antiinflammatory agent,and indomethacin after oral administrations in rats

Abstract— N,N-Dimethylcarbamoylmethyl α,2-dimethyl-5H-[1]-benzopyrano[2,3-b]pyridine-7-acetate (Y-23023) is a prodrug developed as a new non-steroidal anti-inflammatory drug (NSAID). Y-23023 is rapidly hydrolysed to an active metabolite, α,2-dimethyl-5H-[1]benzopyrano[2,3-b]pyridine-7-acetic acid (M₁) following its absorption and then exhibits a strong anti-inflammatory activity. We have examined the pharmacokinetic behaviour in polymorphonuclear leucocytes (PMNs) of M₁ and of indomethacin after oral administration to rats of Y-23023 and indomethacin, respectively. Y-23023 was rapidly absorbed, producing a mean C_max (1·13 μg mL^?1) of M₁ after 1 h in plasma. Indomethacin was less rapidly absorbed, producing a mean C_max (3·38 μg mL^?1) after 3 h in plasma. The mean AUC of M₁ and indomethacin in plasma were 5·45 μg h mL^?1 and 22·49 μg h mL^?1, respectively. The mean t_max, C_max and AUC of M1 in PMNs were 1 h, 11·1 ng (41 pmol)/10⁸ cells and 58·6 ng (164 pmol) h/10⁸ cells, respectively. The same parameters for indomethacin in the PMNs were 3 h, 15·4 ng (57 pmol)/10⁸ cells and 95·2 ng (266 pmol) h/10⁸ cells, respectively. The PMNs/plasma ratio of M₁ was about 2·8 times that of indomethacin. These results indicate that the association of M₁, an active metabolite of Y-23023, from blood to the PMNs is greater than that of indomethacin.     

Effects of the moderate CYP3A4 inhibitor, fluconazole, on the pharmacokinetics of fesoterodine in healthy subjects

AIMS

To assess the effects of fluconazole, a moderate CYP3A4 inhibitor, on the pharmacokinetics (PK) and safety/tolerability of fesoterodine.

METHODS

In this open-label, randomized, two-way crossover study, 28 healthy subjects (18–55 years) received single doses of fesoterodine 8 mg alone or with fluconazole 200 mg. PK endpoints, including the area under the plasma concentration–time curve from 0 to infinity (AUC(0,∞)), maximum plasma concentration (C_max), time to C_max (t_max), and half-life (t_1/2), were assessed for 5-hydroxymethyl tolterodine (5-HMT), the active moiety of fesoterodine.

RESULTS

Concomitant administration of fesoterodine with fluconazole increased AUC(0,∞) and C_max of 5-HMT by approximately 27% and 19%, respectively, with corresponding 90% confidence intervals of (18%, 36%) and (11%, 28%). There was no apparent effect of fluconazole on 5-HMT t_max or t_½. Fesoterodine was generally well tolerated regardless of fluconazole co-administration, with no reports of death, serious adverse events (AEs) or severe AEs. Following co-administration of fesoterodine with fluconazole, 13 subjects (48%) experienced a total of 40 AEs; following administration of fesoterodine alone, six subjects (22%) experienced a total of 19 AEs. The majority of AEs were of mild intensity. There were no clinically significant changes in laboratory or physical examination parameters.

CONCLUSION

Fesoterodine 8 mg single dose was well tolerated when administered alone or with fluconazole. Based on the observed increase in 5-HMT exposures being within the inherent variability of 5-HMT pharmacokinetics, adjustment of fesoterodine dose is not warranted when co-administered with a moderate CYP3A4 inhibitor provided they are not also inhibitors of transporters.     

Safety,Tolerability, Pharmacokinetics and Pharmacodynamics of Recombinant Human Parathyroid Hormone after Single‐ and Multiple‐Dose Subcutaneous Administration in Healthy Chinese Volunteers

Abstract: Recombinant human parathyroid hormone [rhPTH(1–84)] represents a new class of anabolic agents for the treatment of osteoporosis. The present study was designed to assess the safety, tolerability, pharmacokinetics and pharmacodynamics of rhPTH(1–84) after single‐ and multiple‐dose subcutaneous administration in healthy Chinese volunteers. Six cohorts of 32 volunteers received a single dose of rhPTH(1–84) at 0.5–5.0 μg/kg, and two cohorts of 12 volunteers received 2.0 and 3.0 μg/kg of rhPTH(1–84) once daily for 7 consecutive days to assess its safety and tolerability. The results indicated that rhPTH(1–84) appeared to be safe and well tolerated. Additionally, pharmacokinetics of rhPTH(1–84) and its active N‐terminal fragment rhPTH(1–34) were investigated after administration of single 1.0, 2.0 and 4.0 μg/kg doses of rhPTH(1–84) in 30 other volunteers and after multiple doses of 2.0 μg/kg once daily for 7 consecutive days. The pharmacokinetic parameters for rhPTH(1–84) and rhPTH(1–34) after subcutaneous administration of a single dose of 1.0, 2.0 and 4.0 μg/kg were as follows: C_max = (110.54 ± 59.18), (149.70 ± 50.61) and (372.52 ± 94.96) pg/mL; (53.93 ± 6.27), (61.12 ± 11.28) and (89.04 ± 7.08) pg/mL, respectively. AUC_0–10 = (268.87 ± 47.72), (538.93 ± 146.89) and (1364.11 ± 176.82) pg hr/mL; (197.20 ± 50.78), (207.15 ± 72.08) and (344.05 ± 77.06) pg hr/mL, respectively. t_1/2 = (2.34 ± 1.93), (2.58 ± 1.18) and (2.74 ± 1.31) hr; (3.37 ± 1.82), (4.39 ± 3.79), and (3.99 ± 1.85) hr, respectively. Plasma C_max and AUC values of rhPTH(1–84) and rhPTH(1–34) were found to be dose proportional. The pharmacokinetic parameters for rhPTH(1–84) and rhPTH(1–34) after administration of multiple doses of 2.0 μg/kg were as follows: C_{ss_max} = (164.96 ± 52.61) and (75.05 ± 7.31) pg/mL; C_{ss_min} = (6.99 ± 7.73) and (2.05 ± 2.82) pg/mL; AUC_ss = (567.26 ± 118.41) and (306.02 ± 77.55) pg hr/mL; t_1/2 = (1.81 ± 0.89) and (2.27 ± 1.11) hr; DF = (6.93 ± 2.64) and (6.00 ± 1.37), respectively. After multiple doses, the pharmacokinetic parameters for rhPTH(1–84) were consistent with those after single dose. However, the mean C_max and AUC_0–10 of rhPTH(1–34) after multiple dosing were significantly higher than the corresponding values obtained after single‐dose administration. Serum total calcium and phosphate concentrations increased and decreased significantly at 4 hr post‐dosing, respectively.     

Effects of CYP3A4*1G and CYP3A5*3 polymorphisms on pharmacokinetics of tylerdipine hydrochloride in healthy Chinese subjects

1. The aim of this analysis was to explore the influence of CYP3A4*1G and CYP3A5*3 polymorphisms on the pharmacokinetics of tylerdipine in healthy Chinese subjects.

2. A total of 64 and 63 healthy Chinese subjects were included and identified as the genotypes of CYP3A4*1G and CYP3A5*3, respectively. Plasma samples were collected for up to 120?h post-dose to characterize the pharmacokinetic profile following single oral dose of the drug (5, 15, 20, 25 and 30?mg). Plasma levels were measured by a high-performance liquid chromatography-mass spectrometry (LC-MS/MS). The pharmacokinetic parameters were calculated using non-compartmental method. The maximum concentration (C_max) and the area under the curve (AUC_0–24?h) were all corrected by the dose given.

3. In the wild-type group, the mean dose-corrected AUC_0–24?h was 1.35-fold larger than in CYP3A4*1G carriers (p?=?.018). Among the three CYP3A5 genotypes, there showed significantly difference (p?=?.008) in the t_1/2, but no significant difference was observed for the AUC_0–24?h and C_max. In subjects with the CYP3A5*3/*3 genotype, the mean t_1/2 was 1.35-fold higher than in CYP3A5*1/*1 group (p?=?.007). And the t_1/2 in CYP3A5*3 carriers also was 1.32-fold higher than in the wild-type group (p?=?.004).

4. CYP3A4*1G and CYP3A5*3 polymorphisms may influence tylerdipine pharmacokinetic in healthy Chinese subjects.

     

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.     

A conscious rat model involving bradycardia and hypotension after oral administration: a toxicokinetical study of aconitine

1.?A model of aconitine-induced bradycardia and hypotension, which is similar to aconitine poisoning in humans, was constructed in conscious rats by oral administration.

2.?Blood pressure (BP) and heart rate (HR) of Sprague-Dawley rats were measured using a volume pressure recording (VPR) system. The pharmacokinetics of toxic doses of aconitine and its metabolites were analyzed using UPLC-MS/MS.

3.?The HR was significantly decreased by 29% at 2?h after oral administration of 200?μg/kg aconitine. When the dose was increased to 400?μg/kg, systolic BP and diastolic BP were significantly decreased by 11% and 12% at 2?h after the administration, except when bradycardia occurred at 2?h and 4?h. The drug concentration-time curve showed a double-peak phenomenon in rats administered a 400?μg/kg dose. The AUC_0–12?h value in the 400?μg/kg group significantly increased 0.8-fold compared to the 200?μg/kg group. Moreover, a high plasma concentration of 16-O-demethyaconitine was found in the rats that received two toxic doses.

4.?In conclusion, bradycardia and hypotension are induced in conscious rats by a toxic dose of aconitine (400?μg/kg), and there was no significant difference in dose-normalized AUC_0–12?h values between oral administrations of 200?μg/kg and that of 400?μg/kg. However, the dose-normalized C_max and AUC_0–12?h values in 200?μg/kg and 400?μg/kg groups were significantly smaller than those in 100?μg/kg group. The metabolites of aconitine, 16-O-demethyaconitine, and benzoylaconitine may also contribute to the hypotensive response.     

Assessment of Toxicokinetics and Toxicodynamics Following Intravenous Administration of Etoposide Phosphate in Beagle Dogs

The toxicokinetics and toxicodynamics of etoposide phosphate (BMY-40481), a water soluble phosphate ester derivative of etoposide, were investigated in beagle dogs (N = 4) following 5 min i.v. infusion doses equivalent to 57, 114 and 461 mg/m² of etoposide. The doses were administered in sequence starting with the low dose. There was a 28 day wash-out period between the doses. Serial blood samples were collected over 32 hr and the levels of intact BMY-40481 and etoposide in plasma were measured using validated HPLC assays. Hematology profiles were obtained at pre-dose, and twice a week post-dose for 28 days to correlate systemic exposure to etoposide and hematologic toxicity. Following i.v. administration, plasma concentrations of BMY-40481 declined rapidly. For the 3 doses, mean t_1/2 of BMY-40481 ranged from 0.11 - 0.17 hr (6.6-11 min). The mean C_max and AUC values of BMY-40481 ranged from 1.72 - 40.5 µg/ml and 0.16 - 4.14 hr.µg/ml, respectively. Both systemic clearance and steady state volume of distribution of BMY-40481 decreased significantly at the high dose. In contrast, the mean C_max and AUC values of etoposide ranged from 5.46 - 39.4 µg/ml and 2.28 - 22.6 hr.µg/ml, respectively. C_max occurred at the end of infusion (5 min) at all dose levels, indicating that etoposide was rapidly formed from BMY-40481. The apparent systemic clearance (range: 342 - 435 ml/min/m²) and apparent steady state volume of distribution (range: 21.5 - 26.6 1/m²) of etoposide were dose-independent. The AUC of etoposide was significantly correlated with hematologic toxicity, i.e., percent decreases in white blood count (WBC), absolute neutrophil count (ANC) and platelets. The relationship was best described by the sigmoid E_max model for WBC and ANC, and by a simple linear model for platelets. Hemoglobin showed slight decreases which did not correlate with etoposide AUC. In summary, BMY-40481 is rapidly and extensively converted to etoposide; etoposide exhibits linear kinetics; and except for hemoglobin, hematologic toxicity is significantly correlated with etoposide exposure.     

LC-MS/MS测定大鼠血浆中K15的浓度及其在药动学研究中的应用

目的 建立SD大鼠血浆中（3AS,4S,6AR）-四氢-4-甲氧基-呋喃并[3,4-B]呋喃-2（3H）-酮（K15）的LC-MS/MS测定方法,并进行K15的药动学研究。方法 分别灌胃及静脉注射给予大鼠不同剂量K15后,从眼眶静脉丛取血,并采用LC-MS/MS测定大鼠血浆中K15的浓度变化。利用DAS药动学软件拟合主要药动学参数AUC、C_max、T_max、T_1/2等。结果 大鼠血浆中的内源性杂质不干扰K15的测定,日内精密度4.53%~6.60%,日间精密度5.19%~8.14%,准确度为96.10%~102.49%。K15的线性范围为25~1 000 ng·mL^-1,r=0.998 5。K15的定量下限为25 ng·mL^-1（RSD=12.7%,n=6）。150,450和1 000 mg·kg^-1灌胃给药的生物利用度分别为79.5%,44.4%和57.0%。结论 该方法适用于K15在大鼠中的药动学研究。K15在大鼠中的药动学为非线性动力学,灌胃给予大鼠后在其体内具有一定的系统暴露量,但没有随给药剂量呈线性增加。在给药剂量为100和450 mg·kg^-1时,其在体内的C_max没有显著性增高,但是在1 000 mg·kg^-1时,C_max显著增加。随着给药剂量的增加,K15在大鼠体内的T_1/2显著增加,提示K15在大鼠体内的暴露时间随剂量的增加显著延长。     

Pharmacokinetics of a new histamine H2-receptor antagonist,Z-300, in rat and dog

1. The plasma level of Z-300 reached a maximum (C_max) at 30?min after the oral administration of Z-300 to dog, and disappeared from the systemic circulation with a halflife of 8-9 h. The bioavailability of Z-300 was 52% after the oral administration of Z-300, 3?mg/kg. At doses ranging from 3 to 30?mg/kg, C_max and AUC (area under the plasma concentration-time curve) were proportional to the dose. 2. The plasma level of Z-300 reached C_max at 10?min after the oral administration of Z-300 to rat, and disappeared from the systemic circulation with a half-life of 0.8-1.6 h. The bioavailability of Z-300 was 39% after the oral administration of Z-300, 10?mg/kg, and there was a non-linear relationship between the plasma level-time profile of Z-300 and the administered dose (3-50?mg/kg). 3. The binding of Z-300 to plasma protein was 92% in man, 65% in dog and 25% in rat. It is suggested that these species differences were due to the content of α₁-acid glycoprotein (α₁-AG), because Z-300 bound more strongly to α₁-AG than to albumin.