Pharmacokinetics and pharmacodynamics of intravenous dexmedetomidine in healthy Korean subjects

What is known and Objective: Dexmedetomidine is a selective alpha2‐adrenoreceptor agonist used for sedation in critically ill patients. The current study aimed to evaluate the pharmacokinetics (PKs), pharmacodynamics and tolerability of intravenous dexmedetomidine in healthy Korean subjects. Methods: A randomized, double‐blind, placebo‐controlled study with three parallel dosage groups was conducted. Twenty‐four subjects were randomly assigned to placebo or one of three dexmedetomidine dosing regimens, 3 μg/kg/h for 10 min followed by 0·17 μg/kg/h for 50 min (low dose), 6 μg/kg/h for 10 min followed by 0·34 μg/kg/h for 50 min (middle dose) and 3·7 μg/kg/h for 35 min followed by 0·7 μg/kg/h for 25 min (high dose). Serial blood samples for PK analysis were taken up to 12 h. PK parameters were determined using non‐compartmental methods (WinNonlin^®), and a population PK model was developed using nonmem ^®. The sedative effect of dexmedetomidine was assessed by Ramsay sedation score and visual analogue scales/sedation. Adverse events, clinical laboratory tests, electrocardiograms, physical examinations and vital signs were monitored for tolerability assessment. Results: Six subjects were assigned to each of the three active treatment group or placebo group. The AUC_last of the low‐, middle‐ and high‐dose group were 1096·8 ± 119·9 (mean ± SD) ng*h/L, 2643·0 ± 353·2 ng*h/L and 5600·6 ± 411·0 ng*h/L, respectively. PK of dexmedetomidine was best described using a two‐compartment model. The typical value of the population model can be calculated using the following equations: central volume of distribution (L) = 19·9 (age/27)^0·954, peripheral volume of distribution (L) = 59·4, clearance (L/h) = 33·7 (albumin level/4·3)^1·42 and inter‐compartment clearance (L/h) = 67·7. Sedative effects were significantly increased by dexmedetomidine compared to placebo. The blood pressure and heart rate were decreased, but oxygen saturation was maintained stable. What is new and Conclusion: Dexmedetomidine shows linear PK characteristics and dose‐dependent sedative effects. A two‐compartment population PK model was developed for healthy Korean subjects. The PK parameter estimates are similar in Koreans and Caucasians.     

Pharmacokinetics and tolerability of teicoplanin in healthy volunteers after single increasing doses.

In this double-blind, randomized study, five healthy subjects per group received doses of 15, 20, or 25 mg of teicoplanin per kg of body weight, and one subject per group received a 0.9% NaCl placebo as single intravenous infusion over 30 min. Serial blood samples and urine were collected for 13 days postadministration, and concentrations of teicoplanin were determined by microbiological assay. The pharmacokinetic data were analyzed by noncompartmental and compartmental analyses. Laboratory safety tests, audiometry, and serum creatinine clearance measurements were done prior to day 1 and on days 2 and 14. In the three groups, peak levels at the end of the infusion averaged 194, 197, and 253 mg/liter, respectively. Mean concentrations in plasma 24 h after the administration were 10.5, 13.6, and 19.8 mg/liter, respectively. Mean values of volume of distribution at steady state were 0.80, 0.87, and 0.87 liters/kg, respectively. Terminal half-lives averaged 88, 83, and 92 h. Mean total clearance values were 10.9, 11.0, and 11.3 mg/h/kg, respectively, with renal clearance accounting for 75, 81, and 78%, respectively, of the total. The 13-day cumulative mean urinary recovery ranged from 71 to 78% of the dose within the groups. The pharmacokinetics of teicoplanin appears to be linear in the range of administered doses. Teicoplanin was generally well tolerated. Side effects, appearing in five subjects, were represented by fevers, chills, and skin reactions; these adverse reactions were mild, but one episode of rash necessitated the interruption of infusion, and one episode of chills necessitated treatment with corticosteroids. There was no indication of drug-related modifications of laboratory test results.     

氟康唑胶囊在中国健康男青年的药代动力学及生物等效性

目的：评价两种氟康唑胶囊的生物等效性。方法：以HPLC法测定18名男性健康志愿者单剂量口服两种氟康唑胶囊0.3g后血清中氟康唑浓度,3p97程序求算药动学参数。AUC0→t、AUC0→∞和Cmax对数转换后用3p97程序进行多因素方差分析及双单侧t检验判断90%可信限,tmax用非参数统计Wilcoxon法进行检验。结果：受试制剂和参比制剂的实测tmax分别为（1.8±0.8）h和（1.8±0.8）h,实测Cmax分别为（5.8±1.3）mg/L和（5.8±1.2）mg/L,t1/2分别为（33.3±4.7）h和（34.8±6.7）h,梯形法算得AUC0→t分别为（203.9±45.5）mg/（h·L）和（201.9±37.0）mg/（h·L）,AUC0→∞分别为（237.5±52.1）mg/（h·L）和（239.7±50.4）mg/（h·L）。以市售辉瑞制药有限公司产氟康唑胶囊为参比,海南益尔药业有限公司生产的氟康唑胶囊相对生物利用度F0→t为（100.8±11.1）%,F0→∞为（99.4±9.9）%。非参数统计Wilcoxon法检验结果两药tmax差异无统计学意义,AUC0→t、AUC0→∞和Cmax对数转换后用3p97程序进行多因素方差分析及双单侧t检验结果均拒绝生物不等效假设,受试制剂AUC0→t和Cmax的90%可信限分别落在参比制剂的88.8%～113.2%和86.2%～112.4%。结论：两种制剂生物等效。     

Pharmacokinetics and erythropoietic response to human recombinant erythropoietin in healthy men

To assess the safety, pharmacokinetics, and erythropoietic responses to human recombinant erythropoietin (epoetin beta), single intravenous doses (10, 50, 150, and 500 IU/kg) were administered at monthly intervals to 16 healthy subjects in a two-panel, placebo-controlled, double-blind ascending-dose trial. A 1000 IU/kg dose was subsequently administered in an open manner. Epoetin concentrations were determined in serum and urine by radioimmunoassay. Reticulocyte, hemoglobin, and hematocrit values were serially measured after each dose. Mean epoetin apparent half-lives ranged from 4.42 to 11.02 hours. The apparent volume of distribution was between 40 and 90 ml/kg, consistent with plasma water, and the apparent clearance values ranged from 4 to 15 ml/kg/hr, with both parameters having the highest values at the 10 IU/kg dose level. Clearance tended to decrease as a function of dose. Maximum reticulocyte counts were dose-dependent and occurred 3 to 4 days after the epoetin dose. Epoetin was well tolerated, and no antibodies were detected.     

国产去羟肌苷肠溶胶囊在中国健康男青年体内药物动力学研究

目的:研究国产去羟肌苷肠溶胶囊在中国健康男青年体内的药物动力学.方法:17名健康志愿者分别单剂量口服200 mg去羟肌苷肠溶胶囊后按试验方案采血,用液相色谱-串联质谱法测定血药浓度,DAS 2.0程序计算药物动力学参数.结果:健康受试者单剂量给药200 mg后去羟肌苷的体内过程符合二室模型,主要药物动力学参数分别为tmax(2.4±0.8)h,Cmax(432.0±278.6)μg/L,AUC0-t(1188.8±577.5)μg·h/L,AUC0-∞(1221.6±587.2)μg·h/L,t1/2(1.7±0.3)h,Vd(547.0±373.4)L,CL(218.3±139.1)L/h.结论:国产去羟肌苷肠溶胶囊吸收较片、分散片和散荆为慢,但主要药物动力学参数与其他剂型相近.     

Pharmacokinetics of meropenem and its metabolite in young and elderly healthy men.

The pharmacokinetics of meropenem and its ring-opened metabolite (ICI 213,689) were investigated with eight young (20- to 34-year-old) and eight elderly (67- to 80-year-old) healthy male volunteers given single 30-min intravenous infusions of 500 mg of meropenem. All subjects had normal age-correlated glomerular function. The mean terminal half-life of meropenem was 1.27 h in the elderly subjects versus 0.81 h in the younger subjects (P less than 0.001). This and similar increases in mean residence time and area under the concentration-time curve were explained by a reduction in total [139 versus 203 ml/(min.1.73 m2); P less than 0.001], renal, and nonrenal clearances in subjects at advanced ages. The apparent volume of distribution and urinary recovery over 8 h were not significantly altered. With the metabolite, prolonged serum half-life and mean residence time, enlarged area under the concentration-time curve, and lower renal clearance but no significant changes in peak plasma concentration or urinary recovery were found in the elderly. The reduction in the renal excretion rate of meropenem and its metabolite corresponds to the age-associated physiological decline in renal function. The capacity to metabolize meropenem may also be slightly impaired in people at advanced ages. Dose reduction of meropenem should be considered for elderly patients.     

进口去羟肌苷肠溶胶囊在中国健康男青年体内药物动力学研究

目的:探讨进口去羟肌苷肠溶胶囊在中国健康男青年体内的药物动力学。方法:18例健康志愿者分别单剂量口服250mg去羟肌苷肠溶胶囊后按试验方案采血,用液相色谱-串联质谱法测定血药浓度,DAS2.0程序计算药物动力学参数。结果:健康受试者单剂量给药250mg后去羟肌苷的体内过程符合二室模型,主要药物动力学参数分别为tmax(1.7±1.0)h,Cmax(604.6±415.1)μg/L,AUC0-t(1381.8±670.0)μg.h/L,AUC0-∞(1408.3±672.7)μg.h/L,t1/2(1.7±0.3)h,Vd(629.4±622.7)L,CL(252.6±206.9)L/h。结论:进口去羟肌苷肠溶胶囊吸收较片、分散片和散剂为慢,但主要药物动力学参数与其他剂型相近。     

Pharmacokinetics and tolerability of extended-release clarithromycin

BACKGROUND: Clarithromycin is a semisynthetic macrolide that exhibits broad-spectrum activity against gram-positive, gram-negative, and atypical respiratory tract and skin/skin structure pathogens, Mycobacterium species, and Helicobacter pylori. It is indicated for the treatment of a wide variety of respiratory and dermatologic infections in children and adults as well as prophylaxis and treatment of Mycobacterium avium complex infection and peptic ulcers due to H. pylori. OBJECTIVE: In this article, we review the results of 3 studies of the steady-state pharmacokinetic profiles of clarithromycin and 14(R)-hydroxy-clarithromycin after multiple oral once-daily doses of 500-mg extended-release (ER) clarithromycin tablets. We also review the drug tolerability in 2 phase III comparative clinical trials of immediate-release (IR) and ER clarithromycin conducted in adults with acute maxillary sinusitis (AMS) and acute exacerbation of chronic bronchitis (AECB). METHODS: In the 3 pharmacokinetic studies, multiple-dose regimens of clarithromycin IR (one 250-mg or 500-mg tablet twice daily) and clarithromycin ER (one or two 500-mg tablets once daily), administered to healthy male and female volunteers, were evaluated. The effect of administration in nonfasting versus fasting conditions was assessed as well. Tolerability information was collected from each adult patient enrolled in phase III efficacy studies conducted to support the application for US Food and Drug Administration approval for the treatment of AMS and AECB. Regimens evaluated were 500 mg IR clarithromycin tablets twice daily or 1000 mg (2 x 500 mg) ER clarithromycin tablets once daily for 7 days (AECB) or 14 days (AMS). RESULTS: Bioavailability of the ER clarithromyin tablet administered with food was equivalent to that of the reference IR tablet, based on area under the plasma concentration-time curve (AUC) for both parent compound and active metabolite. The bioavailability of the ER tablet was 30% lower (based on clarithromycin AUC) when administered under fasting versus nonfasting conditions. Compared with the IR tablet, administration of the ER tablet resulted in significantly lower (P < 0.05) clarithromycin peak plasma concentration (Cmax), delayed time to Cmax, and lower degree of concentration fluctuation, confirming its in vivo extended-release characteristics. The most frequently reported adverse events (AEs) in the phase III clinical trials were diarrhea, abnormal taste, and nausea and were generally mild or moderate. The incidence of AEs was comparable for the 2 formulations. The severity of gastrointestinal AEs was significantly less for the ER formulation than for the IR formulation (P = 0.018), as was the frequency of premature study discontinuation due to gastrointestinal AEs or abnormal taste (P = 0.004). CONCLUSIONS: The results from the 3 pharmacokinetic studies reviewed demonstrate the bioequivalence of the ER and IR formulations and support the use of this clarithromycin ER formulation in a once-daily dosing regimen in phase III clinical trials. The ER tablet should be taken with food to maximize bioavailability. The results of 2 phase III comparative clinical efficacy and safety trials of clarithromycin ER tablets versus IR tablets in AMS and AECB confirm the good tolerability of the ER formulation.     

马来酸曲美布汀缓释片在中国健康男青年体内药物动力学研究

目的:探讨马来酸曲美布汀缓释片在中国健康男青年体内的药物动力学。方法:10例健康志愿者分别单剂量口服300 mg马来酸曲美布汀缓释片后按试验方案采血,用高效液相色谱法测定血药浓度,DAS 2.0程序计算药物动力学参数。结果:健康志愿者单剂量给药300 mg后马来酸曲美布汀的体内过程符合一室模型,主要药物动力学参数分别为tmax(4.0±0.9)h,Cmax(545.0±232.9)μg/L,AUC0-t(2 987±1 185)μg.h/L,AUC0-∞(3 053±1 209)μg.h/L,t1/2(3.6±1.1)h,Vd(589.6±234.8)L,CL(121±68)L/h。结论:马来酸曲美布汀缓释片吸收明显滞后于普通片,显示出缓释特征,但主要药物动力学参数与其他剂型相近。     

Pharmacokinetics of posaconazole coadministered with antacid in fasting or nonfasting healthy men

Posaconazole is a potent broad-spectrum azole antifungal agent in clinical development for the treatment of invasive fungal infections. This study evaluated the potential for a pH-dependent pharmacokinetic interaction between posaconazole and an antacid (Mylanta), under fasting and nonfasting conditions. Twelve men completed this randomized, four-period crossover, single-dose study. Subjects received 200 mg of posaconazole following a 10-h fast, with 20 ml of Mylanta and a 10-h fast, with 20 ml of Mylanta and a high-fat breakfast, and with a high-fat breakfast alone. Antacid coadministration had no statistically significant effects on posaconazole bioavailability under fasting or nonfasting conditions. In the fasting state, antacid slightly increased the relative oral bioavailability of posaconazole by 15% (P = 0.296); in the nonfasting state, antacid decreased the relative bioavailability of posaconazole by 12% (P = 0.352). Food increased the relative oral bioavailability of posaconazole by 400% (P = 0.001). In conclusion, the effect of antacid on posaconazole exposure in the fasting or nonfasting state was small and is not considered clinically significant.     

Pharmacokinetics,safety, and tolerability of oral posaconazole administered in single and multiple doses in healthy adults

The pharmacokinetics, safety, and tolerability of posaconazole, an investigational triazole antifungal, were evaluated following the administration of rising single and multiple oral doses. A total of 103 healthy adults were enrolled in two phase I trials. Each study had a double-blind, placebo-controlled, parallel-group design with a rising single-dose (RSD) or rising multiple-dose (RMD) scheme. In the RSD study, subjects received single doses of posaconazole oral tablets (50 to 1200 mg) or placebo. In the RMD study, subjects received posaconazole oral tablets (50 to 400 mg) or placebo twice daily for 14 days. By using model-independent methods, the area under the plasma concentration-time curve and the maximum concentration in plasma were determined and used to assess dose proportionality. In the RSD study, the levels of posaconazole in plasma increased proportionally between the 50- and 800-mg dose range, with saturation of absorption occurring above 800 mg. Dose proportionality was also observed in the RMD study. In both studies, the apparent volume of distribution was large (range, 343 to 1341 liters) and the terminal-phase half-life was long (range, 25 to 31 h). Posaconazole was well tolerated at all dose levels, and the adverse events were not dose dependent. No clinically significant changes in clinical laboratory test values or electrocardiograms were observed. Following the administration of single and twice-daily rising doses, the level of posaconazole exposure increased in a dose-proportional manner. The long elimination-phase half-life of posaconazole supports once- or twice-daily dosing in clinical trials; however, additional studies are required to determine if further division of the dose will enhance exposure.     

Pharmacokinetics and tolerability of modafinil tablets in Chinese subjects

Objective:  To investigate the pharmacokinetics and tolerability of modafinil in Chinese subjects.
Methods:  Twelve healthy volunteers were given an escalating single dose of modafinil (100, 200 and 400 mg) in a three-period study (study 1). Another 12 volunteers received 100 mg twice daily for 7 days in multiple-dose study (study 2). Blood samples were taken from 0 to 60 h for study 1. And samples for study 2 were collected before administration on three consecutive morning and then from 0 to 60 h after the last dose. Pharmacokinetic parameters were calculated and compared with results from published data.
Results:  In study 1, C _max and area under the concentration–time curve of modafinil and modafinil acid were increased proportionally with dose levels; t _1/2 was independent on the dose levels. In study 2, the steady state was reached on day 4, and mean trough plasma concentration of modafinil was 1·36 ± 0·34  μ g/mL. Apparent plasma clearance and apparent volume of distribution were lower in 100 mg twice-daily group than those in 100 mg single group. The adverse events were mild and moderate in study 1 and 2.
Conclusions:  In this pharmacokinetic study, modafinil was safe and well tolerated by young healthy Chinese subjects. The major pharmacokinetic parameters of modafinil in Chinese subjects are similar to those reported in Caucasians although the half-life seems to be longer in the former than in the latter. This apparent difference requires investigation.     

Pharmacokinetics,safety, and tolerability of ceftolozane/tazobactam in healthy Japanese,Chinese, and white subjects

Ceftolozane/tazobactam, a novel antibacterial with potent activity against Gram‐negative pathogens, was developed for treatment of complicated urinary tract infections, including pyelonephritis, and intra‐abdominal infections. A phase 1 pharmacokinetic (PK) study of ceftolozane/tazobactam in healthy Japanese, Chinese, and white volunteers was conducted to assess the potential effect of ethnicity on PK. The PK of ceftolozane, tazobactam, and tazobactam metabolite M1 was compared after single 1.5‐ and 3‐g intravenous doses of ceftolozane/tazobactam. Ten Japanese, nine Chinese, and ten white subjects were enrolled, and 27 completed all doses of study medication. Dose‐normalized PK parameters for ceftolozane and tazobactam were similar among Japanese, Chinese, and white subjects (at 1.5‐g and 3‐g doses, ceftolozane area under the plasma concentration–time curve from zero to infinity [AUC_0–∞] = 166.3, 165.9, and 185.5 h μg/mL, respectively, and 157.7, 158.5, and 181.2 h μg/mL, respectively; tazobactam AUC_0–∞ = 48.5, 43.2, and 50.1 h μg/mL, respectively, and 47.3, 43.7, and 50.0 h μg/mL, respectively. The 90% CIs of their ratio estimates were within the range 0.80 to 1.25 with the exception of AUC_0–∞ for ceftolozane after the 3‐g dose (0.79). The cumulative amount of ceftolozane and tazobactam excreted in urine was similar among ethnic groups. For all groups, treatment‐emergent adverse events (AEs) were mild; no deaths or serious AEs were reported. The PK of ceftolozane/tazobactam was approximately dose proportional (i.e. doubling the dose approximately doubles the exposure) and similar among the groups. No dosage adjustment is needed for ceftolozane/tazobactam in Japanese and Chinese patients.     

Pharmacokinetics and tolerability of oseltamivir combined with probenecid

Oseltamivir is an inhibitor of influenza virus neuraminidase, which is approved for use for the treatment and prophylaxis of influenza A and B virus infections. In the event of an influenza pandemic, oseltamivir supplies may be limited; thus, alternative dosing strategies for oseltamivir prophylaxis should be explored. Healthy volunteers were randomized to a three-arm, open-label study and given 75 mg oral oseltamivir every 24 h (group 1), 75 mg oseltamivir every 48 h (q48h) combined with 500 mg probenecid four times a day (group 2), or 75 mg oseltamivir q48h combined with 500 mg probenecid twice a day (group 3) for 15 days. Pharmacokinetic data, obtained by noncompartmental methods, and safety data are reported. Forty-eight subjects completed the pharmacokinetic analysis. The study drugs were generally well tolerated, except for one case of reversible grade 4 thrombocytopenia in a subject in group 2. The calculated 90% confidence intervals (CIs) for the geometric mean ratios between groups 2 and 3 and group 1 were outside the bioequivalence criteria boundary (0.80 to 1.25) at 0.63 to 0.89 for group 2 versus group 1 and 0.57 to 0.90 for group 3 versus group 1. The steady-state apparent oral clearance of oseltamivir carboxylate was significantly less in groups 2 (7.4 liters/h; 90% CI, 6.08 to 8.71) and 3 (7.19 liters/h; 90% CI, 6.41 to 7.98) than in group 1 (9.75 liters/h; 90% CI, 6.91 to 12.60) (P < 0.05 for both comparisons by analysis of variance). The (arithmetic) mean concentration at 48 h for group 2 was not significantly different from the mean concentration at 24 h for group 1 (42 ± 76 and 81 ± 54 ng/ml, respectively; P = 0.194), but the mean concentration at 48 h for group 3 was significantly less than the mean concentration at 24 h for group 1 (23 ± 26 and 81 ± 54 ng/ml, respectively; P = 0.012). Alternate-day dosing of oseltamivir plus dosing with probenecid four times daily achieved trough oseltamivir carboxylate concentrations adequate for neuraminidase inhibition in vitro, and this combination should be studied further.     

Pharmacokinetics and tolerability of multiple-dose rosuvastatin: An open-label, randomized-sequence, three-way crossover trial in healthy Chinese volunteers

Background: Rosuvastatin has been reported to be beneficial in the treatment of dyslipidemia. The C_max and AUC_0−t of rosuvastatin were reported to be ~2 to 4 times higher in Chinese subjects compared with white subjects after administration of a single 1-mg/kg dose.Objectives: The aims of this study were to assess the pharmacokinetics and tolerability of multiple doses of rosuvastatin in healthy Chinese volunteers.Methods: This open-label, randomized-sequence, 3-way crossover trial consisted of three 7-day treatment periods and two 10-day washout periods. Healthy volunteers were randomly allocated to 1 of 3 daily treatment regimens: rosuvastatin 5, 10, or 20 mg. To assess the pharmacokinetics and tolerability of rosuvastatin, blood samples were drawn before dosing (hour 0) on days 5, 6, and 7 and 0.5, 1, 1.5, 2, 3, 4, 5, 6, 8, 12, 15, 24, 36, 48, 72, and 96 hours after the final dose was administered on day 7. A validated HPLC-MS/MS method was used to determine rosuvastatin levels. A 2-compartment pharmacokinetic model was fitted to the plasma concentration-time profiles obtained for each volunteer. Adverse events (AEs) were monitored throughout the study via subject interview, vital signs, and blood sampling. Serious AEs were those requiring hospitalization, treatment discontinuation, or resulting in death.Results: Twelve healthy Chinese volunteers (6 men: mean [SD] age, 21.8 [1.7] years; weight, 62.3 [5.8] kg; height, 174.3 [7.2] cm; 6 women: age, 20.8 [1.2] years; weight, 53.2 [4.7] kg; height, 161.3 [4.3] cm) participated in and completed the trial. The mean (SD) steady-state C_max was significantly greater after ro-suvastatin administration in the 20-mg group compared with the 5-mg group (37.69 [29.83] vs 6.17 [6.03] ng/mL; P = 0.04). The t_1/2 was significantly greater in the 20-mg group (15.51 [6.43] hours) compared with the 5-mg group (5.65 [5.08] hours; P = 0.001) and the 10-mg group (8.58 [5.17] hours; P = 0.002). The mean AUC_0−t was significantly greater in the 20-mg group compared with the 5-mg group (349.16 [257.20] vs 40.63 [39.31] ng/mL/h; P = 0.02). All AEs were considered by the investigators to be mild in intensity, with the exception of 2 cases of abdominal discomfort (1 man and 1 woman, both in the 5-mg dose group). Two women in the 20-mg group experienced dizziness and cold sweats simultaneously. In the 10-mg group, 1 woman had abdominal discomfort and nausea and 1 woman had jaw pain. All reported AEs were considered possibly related to study drug administration.Conclusions: In this small study in healthy Chinese volunteers, rosuvastatin systemic exposure appeared to be dose-proportional over the dosing range of 5 to 20 mg with multiple-dose administration. There was no accumulation of rosuvastatin in the body with the 5- and 10-mg doses. However, the results suggest that rosuva-statin might accumulate when the dose is increased to 20 mg. No serious AEs occurred in any of the 3 dosing groups.     

Pharmacokinetics, safety, and tolerability of ascending single intravenous doses of oritavancin administered to healthy human subjects

Oritavancin (LY333328 diphosphate) is a novel glycopeptide antimicrobial agent with potent microbiological activity in vitro against Gram-positive bacteria. A single-dose, open-label, noncontrolled, dose-escalation study in 11 healthy human subjects was carried out to evaluate the safety and pharmacokinetics of oritavancin. One subject at each dose level received a single intravenous dose of 0.02, 0.03, 0.05, 0.08, 0.125, 0.20, and 0.325 mg/kg infused over 1 hour and four subjects each received a single-dose of 0.5 mg/kg. Safety and tolerability were evaluated by monitoring adverse events and laboratory parameters. Oritavancin pharmacokinetics were assessed by blood, urine, and fecal sampling. The plasma concentrations of oritavancin after the end of infusion followed a multiexponential decline over a 2-week period. Median (range) C(max) for the 0.5 mg/kg dose group was 6.5 (4.7-7.6) microg/mL. In every subject, plasma concentrations declined to < or =10% of the C(max) within 24 hours. Following a short, constant-rate infusion, the pharmacokinetics of oritavancin were linear across a total dose range from 3.66-44.6 mg. Renal clearance was approximately 0.457 mL/min. The mean (range) plasma terminal half-life of oritavancin was 195.4 (135.8-273.8) hours across all dose levels from 0.05-0.5 mg/kg. Less than 5% and 1% of administered drug were recovered in the urine and feces, respectively, after 7 days. This first time in man evaluation of oritavancin revealed that single doses of oritavancin of up to and including 0.5 mg/kg were safe and well tolerated. Although no clinically relevant changes in renal, hepatic and hematologic indices from baseline were observed, five subjects did manifest asymptomatic and transient elevations of hepatic transaminase concentrations. Because this study was not placebo-controlled and enrolled a small number of subjects, the safety and pharmacokinetic profiles of oritavancin need to be confirmed in additional studies.     

Pharmacokinetics and tolerability of gemifloxacin (SB-265805) after administration of single oral doses to healthy volunteers

Gemifloxacin (known as SB-265805 or LB-20304) is a potent, novel fluoroquinolone compound with a broad spectrum of antibacterial activity. The pharmacokinetics and tolerability of oral gemifloxacin were characterized in healthy male volunteers after a single dose of 20, 40, 80, 160, 320, 600, or 800 mg. Multiple serum and urine samples were collected and analyzed for gemifloxacin using high-performance liquid chromatography with fluorescence detection. Safety assessments included vital signs, 12-lead electrocardiogram readings, hematology, clinical chemistry, urinalysis, and adverse-experience monitoring. Gemifloxacin was rapidly absorbed after all doses. Maximum concentrations of gemifloxacin in serum (C(max)) were achieved approximately 1 h after dosing, after which concentrations in serum declined in a biexponential manner. Values of C(max) and the area under the concentration-time curve in serum from 0 h to infinity (serum AUC(0-infinity)) increased linearly with dose. Serum AUC(0-infinity) values (mean +/- standard deviation) were 0.65+/-0.01, 1.28+/-0.22, 2.54+/-0.31, 5.48+/-1.24, 9.82+/-2.70, 24.4+/-7.1, and 31.4+/-7.6 microg. h/ml following 20-, 40-, 80-, 160-, 320-, 600-, and 800-mg doses, respectively. The terminal phase elimination half-life was independent of dose, with an overall mean of 7.4+/-2.0 h. The profiles indicated that the pharmacokinetic profile is suitable for a once-daily dosing regimen. Approximately 25 to 40% of the administered dose was excreted unchanged in the urine, and renal clearance (ca. 150 ml/min) was independent of dose. There were no significant changes in clinical chemistry, hematology, or urinalysis parameters, vital signs, or 12-lead electrocardiogram readings in subjects, irrespective of dose. The results of these studies support the further investigation of once-daily administration of gemifloxacin.     

Pharmacokinetics of the triazole antifungal agent genaconazole in healthy men after oral and intravenous administration.

The pharmacokinetics of genaconazole, a potent new difluorophenyl-triazole antifungal agent, was studied in 12 healthy male volunteers following a single oral or intravenous administration of the drug. In a randomized two-way crossover design, each volunteer received either two 50-mg genaconazole tablets orally or a parenteral preparation containing 100 mg of genaconazole given as a 30-min intravenous infusion. Both dosage regimens were well tolerated. Blood and urine samples were collected up to 10 days after drug administration. Concentrations of genaconazole in plasma and urine were determined by a specific high-performance liquid chromatography assay with a limit of quantitation of 0.1 microgram/ml. Pharmacokinetic evaluation following oral and intravenous doses indicated that mean values for the area under the concentration-time curve from 0 h to infinity (137 and 136 micrograms.h/ml), half-life (50 and 49 h), volume of distribution (52 and 52 liters), and clearance (12 and 12 ml/min) were independent of the route of drug administration. The oral and intravenous administrations of genaconazole yielded virtually superimposable plasma concentration-time curves, resulting in an absolute bioavailability of 100%. Amounts of unchanged genaconazole found in urine samples from 0 to 240 h after oral and intravenous doses were comparable, and urinary excretion accounted for 76 and 78% of the administered dose, respectively. Renal clearances for the two routes of administration were also similar, and renal clearance accounted for over 80% of the total body clearance. The 100% absolute bioavailability of genaconazole regardless of the route of administration provides greater dosing flexibility in various clinical settings than currently exists.