Pharmacokinetic evaluation and relative bioavailability pilot study of fidaxomicin in healthy Chinese subjects: An open, randomized, single-dose, cross-over study.

OBJECTIVE: To compare the pharmacokinetic (PK) characteristics, investigate relative bioavailability, and provide data for potential additional bioequivalence trials between generic fidaxomicin (test (T) formulation) and the original brand (reference (R) formulation) in healthy Chinese subjects. MATERIALS AND METHODS: An open, randomized, single-dose, cross-over study was conducted in 18 healthy Chinese subjects. The subjects randomly received T or R formulations and the alternative formulations were received after a 14-day wash-out period. Blood and fecal samples were collected and tested by liquid chromatography-tandem mass spectrometry (LC-MS/MS). PK parameters were calculated using a non-compartmental model. Relative bioavailability considering commonly established bioequivalence criteria was assessed. RESULTS: Cmax were 3.58 ± 2.74 ng/mL and 6.01 ± 3.93 ng/mL, and AUC0-∞ were 35.71 ± 18.68 h×ng/mL and 52.15 ± 31.31 h×ng/mL for the T and R formulations, respectively. The tmax of both formulations was 5.00 hours. The cumulative fecal excretion rate (Fe0-96h/F) of fidaxomicin and its main active metabolite OP-1118 were similar for both formulations. The geometric mean ratios and 90% confidence intervals (CI) of AUC0-t, AUC0-∞, and Cmax were not completely within the range of 80.00 - 125.00%. Significant within-subject and inter-subject coefficients of variation (> 30%) were found. CONCLUSION: Despite the differences in exposure, PK characteristics and fecal recovery of the two formulations were similar, suggesting that an effective concentration of the generic fidaxomicin could be achieved locally in the gastrointestinal tract. Fidaxomicin was a highly viable drug, thus providing reference for future clinical study design.

Pharmacokinetics and Safety of Single-Dose Amphotericin B Colloidal Dispersion in Healthy Chinese Subjects and Population Pharmacokinetic/Pharmacodynamic Analysis to Inform Clinical Efficacy in Invasive Infections Caused by Candida albicans.

PURPOSE: Amphotericin B colloidal dispersion (ABCD) is a less toxic formulation of amphotericin B for the treatment of invasive fungal infections. The pharmacokinetic (PK) profile and safety of a generic ABCD were investigated after a single dose (0.5 to 1.5 mg/kg) administered as an intravenous infusion in 30 healthy Chinese subjects. METHODS: PK data from healthy Chinese male subjects were applied for developing a population PK model to predict the PK profiles of standard doses (3 or 4 mg/kg) in patients. A 5000-time Monte Carlo simulation of AUC0-24/MIC target was implemented to determine the probability of target attainment (PTA) and cumulative fraction of response (CFR) under standard doses. FINDINGS: The PK profiles of intravenous administration of ABCD were best described by a 3-compartmental model with a time-varying clearance and a dose-dependent volume of distribution in the peripheral compartment. PK/pharmacodynamic (PK/PD) analysis revealed that 3 or 4 mg/kg ABCD once a day resulted in favorable CRF (>98%) with 2-log reduction of Candida albicans. A high PTA (>90%) was achieved at MIC ≤2 mg/L for the dosing regimen of ABCD 3 mg/kg and 4 mg/kg for MIC ≤4 mg/L. IMPLICATIONS: PK/PD analysis indicated that a favorable efficacy of ABCD could be reached at a dose of 3 or 4 mg/kg once daily for 14 to 28 days to treat invasive fungal infections caused by C albicans. ClinicalTrials.gov identifier: NCT03577509.

Effects of Different Component Contents of Colistin Methanesulfonate on the Pharmacokinetics of Prodrug and Formed Colistin in Human.

PURPOSES: To evaluate the effects of component contents in different colistin methanesulfonate (CMS) formulas on their clinical pharmacokinetics of the prodrug CMS and the formed colistin. METHODS: Two CMS formulas (CTTQ and Parkedale) were investigated in a single dose, randomized, open-label, crossover study conducted in 18 healthy Chinese subjects. Both CMS formulas met the requirements of European Pharmacopoeia 9.2 with 12.1% difference in the two major active components (CMS A and CMS B). The PK parameters after a single intravenous infusion of CMS at 2.5 mg/kg were calculated and the steady-state plasma colistin concentrations (Css,avg) following multiple dosing, once every 12 h for 7 days, were simulated with the non-compartment model. RESULTS: The systemic exposure (AUC0-inf) of CMS were 59.49 ± 5.90 h·µg/mL and 51.09 ± 4.70 h·µg/mL, and the AUC0-inf of colistin were 15.39 ± 2.63 h·µg/mL and 12.36 ± 2.10 h·µg/mL for CTTQ and Parkedale, respectively. The ratios (90% CI) of geometric mean of AUC0-inf of CTTQ to Parkedale were 116.38% (112.95%, 119.91%) and 124.49% (120.76%, 128.35%) for CMS and colistin, respectively. The predicted Css,avg (95% CI) were 0.92 (0.85, 0.99) µg/mL and 0.74 (0.69, 0.79) µg/mL for CTTQ and Parkedale, respectively. CONCLUSION: The difference in component content in the two CMS formulas had a significant (P < 0.001) impact on the systemic exposure of colistin in human, thus, warranted essential considerations in clinical applications.

Pharmacokinetics of colistin methanesulfonate (CMS) in healthy Chinese subjects after single and multiple intravenous doses.

The high prevalence of extensively drug-resistant Gram-negative pathogens has forced clinicians to use colistin as a last-line therapy. Knowledge on the pharmacokinetics of colistin methanesulfonate (CMS), an inactive prodrug, and colistin has increased substantially; however, the pharmacokinetics in the Chinese population is still unknown due to lack of a CMS product in China. This study aimed to evaluate the pharmacokinetics of a new CMS product developed in China in order to optimise dosing regimens. A total of 24 healthy subjects (12 female, 12 male) were enrolled in single- and multiple-dose pharmacokinetic (PK) studies. Concentrations of CMS and formed colistin in plasma and urine were measured, and PK analysis was conducted using a non-compartmental approach. Following a single CMS dose [2.36 mg colistin base activity (CBA) per kg, 1 h infusion], peak concentrations (Cmax) of CMS and formed colistin were 18.0 mg/L and 0.661 mg/L, respectively. The estimated half-life (t1/2) of CMS and colistin were 1.38 h and 4.49 h, respectively. Approximately 62.5% of the CMS dose was excreted via urine within 24 h after dosing, whilst only 1.28% was present in the form of colistin. Following multiple CMS doses, colistin reached steady-state within 24 h; there was no accumulation of CMS, but colistin accumulated slightly (RAUC = 1.33). This study provides the first PK data in the Chinese population and is essential for designing CMS dosing regimens for use in Chinese hospitals. The urinary PK data strongly support the use of intravenous CMS for serious urinary tract infections.

Pharmacokinetics and pharmacodynamics of multiple-dose intravenous nemonoxacin in healthy Chinese volunteers.

This study evaluated the safety and pharmacokinetic/pharmacodynamic profiles of nemonoxacin in healthy Chinese volunteers following multiple-dose intravenous infusion once daily for 10 consecutive days. The study was composed of two stages. In the open-label stage, 500 mg or 750 mg of nemonoxacin (n = 12 each) was administered at an infusion rate of 5.56 mg/min. In the second stage, with a randomized double-blind placebo-controlled design, 500, 650, or 750 mg of nemonoxacin (n = 16 in each cohort; 12 subjects received the drug and the other 4 subjects received the placebo) was given at an infusion rate of 4.17 mg/min. The results showed that, in the first stage, the maximal nemonoxacin concentrations (mean ± SD) at steady state (Cmax_ss) were 9.60 ± 1.84 and 11.04 ± 2.18 µg/ml in the 500-mg and 750-mg cohorts, respectively; the areas under the concentration-time curve at steady state (AUC0-24_ss) were 44.03 ± 8.62 and 65.82 ± 10.78 µg · h/ml in the 500-mg and 750-mg cohorts, respectively. In the second stage, the nemonoxacin Cmax_ss values were 7.13 ± 1.47, 8.17 ± 1.76, and 9.96 ± 2.23 µg/ml in the 500-mg, 650-mg, and 750-mg cohorts, respectively; the AUC0-24_ss values were 40.46 ± 9.52, 54.17 ± 12.10, and 71.34 ± 17.79 µg · h/ml in the 500-mg, 650-mg, and 750-mg cohorts, respectively. No accumulation was found after the 10-day infusion with any regimen. The drug was well tolerated. A Monte Carlo simulation indicated that the cumulative fraction of response of any dosing regimen was nearly 100% against Streptococcus pneumoniae. The probability of target attainment of nemonoxacin therapy was >98% when the MIC of nemonoxacin against S. pneumoniae was ≤1 mg/liter. It is suggested that all of the studied intravenous nemonoxacin dosing regimens should have favorable clinical and microbiological efficacies in future clinical studies. (This study has been registered at ClinicalTrials.gov under registration no. NCT01944774.).

Safety, tolerability, and pharmacokinetics of intravenous nemonoxacin in healthy chinese volunteers.

Nemonoxacin (TG-873870) is a novel nonfluorinated quinolone with potent broad-spectrum activity against Gram-positive, Gram-negative, and atypical pathogens, including vancomycin-nonsusceptible methicillin-resistant Staphylococcus aureus (MRSA), quinolone-resistant MRSA, quinolone-resistant Streptococcus pneumoniae, penicillin-resistant S. pneumoniae, and erythromycin-resistant S. pneumoniae. This first-in-human study was aimed at assessing the safety, tolerability, and pharmacokinetic properties of intravenous nemonoxacin in healthy Chinese volunteers. The study comprised a randomized, double-blind, placebo-controlled, dose escalating safety and tolerability study in 92 subjects and a randomized, single-dose, open-label, 3-period Latin-square crossover pharmacokinetic study in 12 subjects. The study revealed that nemonoxacin infusion was well tolerated up to the maximum dose of 1,250 mg, and the acceptable infusion rates ranged from 0.42 to 5.56 mg/min. Drug-related adverse events (AEs) were mild, transient, and confined to local irritation at the injection site. The pharmacokinetic study revealed that after the administration of 250, 500, and 750 mg of intravenous nemonoxacin, the maximum plasma drug concentration (Cmax) values were 4.826 µg/ml, 7.152 µg/ml, and 11.029 µg/ml, respectively. The corresponding values for the area under the concentration-time curve from 0 to 72 hours (AUC0-72 h) were 17.05 µg · h/ml, 39.30 µg · h/ml, and 61.98 µg · h/ml. The mean elimination half-life (t1/2) was 11 h, and the mean cumulative drug excretion rate within 72 h ranged from 64.93% to 77.17%. Volunteers treated with 250 to 750 mg nemonoxacin exhibited a linear dose-response relationship between the AUC0-72 h and AUC0-∞. These findings provide further support for the safety, tolerability, and pharmacokinetic properties of intravenous nemonoxacin. (This study has been registered at ClinicalTrials.gov under registration no. NCT01944774.).

Establishment of norvancomycin fluorescence polarization immunoassay for therapeutic drug monitoring.

To establish a rapid and simple fluorescence polarization immunoassay method for determination of norvancomycin serum concentration, we collected 300 serum samples from the patients receiving norvancomycin in the hospitals localized in Shanghai, China. The drug concentrations were measured by the established HPLC method and FPIA with vancomycin kit. A FPIA algorithm for the determination of norvancomycin concentration was established according to the correlation between the FPIA and HPLC results. The methods and algorithm were validated in another 70 clinical samples. HPLC determination showed a good linear correlation within the range of 0.5-100 mg l(-1) of norvancomycin concentrations. The method was validated via extraction recovery, intra- and inter-day methodological recovery and stability of norvancomycin in serum. Correlation analysis between the measurements of HPLC and FPIA in 300 serum samples gave the linear regression equation: (concentration by HPLC)=0.760 × (concentration by FPIA)-0.577 (P<0.001, R(2)=0.982). An algorithm was derived from this correlation for measuring the serum norvancomycin concentrations with FPIA. When it was validated in additional 70 serum samples from patients, 'FPIA algorithm' showed good accuracy versus HPLC: 'FPIA algorithm'=0.93 (HPLC)+0.63, R(2)=0.962, and 94.3% of the results from FPIA algorithm fell within the range of -20%/+20% of HPLC. This algorithm developed in this study can be easily used for determination of norvancomycin using TDx analyzer with vancomycin kit indirectly. It may also be useful for norvancomycin therapeutic drug monitoring.

Circadian rhythm in serum iron levels.

This study was aimed at assessing the circadian rhythm of serum iron levels in Chinese healthy subjects. The project was conducted in 19 healthy, Chinese male subjects following a 4-day diet equilibration. Blood samples were collected on day 5 at 0800, 1000, 1200, 1400, 1600, 1800, 2000, and 2400 hours to determine endogenous serum iron concentrations. Iron concentrations were determined using an inductively coupled plasma mass spectrometry. Iron concentration was decreased from morning to afternoon. The minimum value of iron level was 1,987 µg/L at 2000 hours while the maximum was 2,229 µg/L at 1000 hours, and 2,278 µg/L at 1400 hours, respectively, the amplitude was 291 µg/L. This study indicates that when assessing the bioequivalence of iron formulations, baseline levels of iron (obtained before dosing) should not be subtracted simply from the amount obtained on the drug dosing day to yield the net effect of iron formulation administration. More valid methods to optimize the design of such bioequivalence studies should be taken into consideration.

Comparative bioavailability of ferrous succinate tablet formulations without correction for baseline circadian changes in iron concentration in healthy Chinese male subjects: a single-dose, randomized, 2-period crossover study.

BACKGROUND: Ferrous succinate is used for the treatment of iron deficiency anemia. Determining the bioavailability of iron products is a challenge, because iron is naturally present in the blood and some tissues. Therefore, bioequivalence evaluation of ferrous formulations can be affected by the presence of endogenous iron species. Little information regarding the pharmacokinetics of ferrous supplements is available in the healthy Chinese population. OBJECTIVES: The aim of the study was to assess the comparative bioavailability of 200-mg of a test (ferrous succinate,100 mg × 2, Hunan Huana Pharmaceutical Co., Ltd., Hunan, China) and reference (Sulifei, 100 mg × 2, Nanjing Jinling Pharmaceutical Co., Ltd., Nanjing, China) formulation in healthy Chinese male subjects. The study was conducted to meet Chinese State Food and Drug Administration regulatory requirements for approval of a generic formulation of ferrous succinate. METHODS: This study utilized a single-dose randomized, 2-period, crossover design with alternate assignment of subjects to treatment (a single 200-mg [100 mg × 2]) or reference formulation groups. Both groups underwent a 4-day diet equilibration before 2 days of treatment and, finally, a 4-day washout period for the bioequivalence study. Blood samples were collected at 8:00 am on every diet equilibration day, 0 (baseline), 1, 2, 3, 4, 4.5, 5, 6, 9, 12, 24, and 36 hours after drug administration. Iron concentrations were determined using an inductively coupled plasma mass spectrometry. Subjects in both groups were given a standardized diet, with known amounts of iron and calories. The formulations were assumed to be bioequivalent if the 90% CI ratios for C(max) were within 70% to 143% and AUC(0-last) were within 80% to 125%-criteria established by the Chinese Food and Drug Administration. Tolerability was monitored throughout the study by assessing clinical parameters (vital signs, chemistry laboratory) and subject reports. RESULTS: Twenty healthy Han Chinese male subjects (mean age, 26.8 years [range, 20-39 years]; weight, 61.9 kg [range, 52-72 kg]; body mass index, 21.5 kg/m(2) [range,19.1-23.8 kg/m(2)]; and baseline iron values, 1271 µg/L [range 1113-1429 µg/L]) were enrolled and completed the study. Without baseline correction for endogenous iron compound, the mean C(max) measurements of iron for the test and reference formulations were 2981 [621.1] and 3028 [707.4] µg/L, respectively; AUC(0-last) values were 48,460 [9242] and 48,390 [8420] µg/L/h, respectively; T(max) values were 4.3 [1.6] and 3.7 [1.3] hours. The 90% CIs for the ratios of C(max) and AUC(0-last) were 89.9% to 109.2% and 92.5% to 107.7%. No significant difference was found between groups with regard to pharmacokinetic parameters. Both test and reference formulations were well tolerated, with only 2 (10%) subjects who received the reference formulation complaining of mild heartburn that resolved after approximately 1 hour. Another subject (5%) complained of nausea 10 minutes after the test administration, which resolved within 2 hours. The relative bioavailability of the test-reference preparations was 101.6%. CONCLUSION: In this single-dose crossover study in healthy Chinese male subjects, the test and reference formulations of ferrous succinate 200-mg (100 mg × 2,) tablets met the criteria for assuming bioequivalence as defined by the Chinese Food and Drug Administration. Both formulations were well tolerated. Chinese Clinical Trials registration number: ChiCTR-TRC-11001646.

Permeability and concentration of levofloxacin in epithelial lining fluid in patients with lower respiratory tract infections.

The purpose of the study was to assess the bactericidal effects of a single oral dose of levofloxacin (LVFX) by examining the concentration of LVFX in alveolar epithelial lining fluid (ELF) from patients with lower respiratory tract infections (LRTI). Forty patients with LRTI took 500 mg of LVFX and then received a fiberoptic bronchoscopic procedure randomly 1, 4, 8, 12, or 24 hours following dosing. Bronchoalveolar lavage fluid and blood were collected at the time of the bronchopulmonary procedure, and the LVFX concentration was determined. The mean peak concentrations of LVFX in plasma and ELF were achieved at 1.5 hours (4.07 mg/L) and 1 hour (3.44 mg/L), respectively. The AUC(24h) samples were 50.12 mg . h/L and 34.51 mg . h/L, respectively. The permeability of LVFX, which was estimated based on the ratio of LVFX concentration in tissue fluids to that in plasma, was 0.78 on average across all time points. After a single dose of LVFX in patients with LRTI, the drug rapidly distributed into bronchopulmonary tissue, thereby suggesting this dose is capable of achieving the concentration in target organs required for bactericidal efficacy.

Population pharmacokinetics of oral levofloxacin 500 mg once-daily dosage in community-acquired lower respiratory tract infections: results of a prospective multicenter study in China.

This study aimed to explore the pharmacokinetic features of levofloxacin (LVFX) in Chinese patients with infections and to confirm oral LVFX 500 mg once daily as an optimal treatment regimen based on pharmacokinetic-pharmacodynamic (PK-PD) analysis. A total of 1052 plasma samples from 164 Chinese adult patients with community acquired lower respiratory tract infections (CALRTIs) and 18 healthy volunteers were used for population PK analysis. LVFX 500-mg tablets were given once daily. A nonlinear mixed effects model (NONMEM) program was used for population PK model-building and a two-compartment model with first-order absorption process was established. Creatinine clearance (CL(cr)) and body weight were identified as intrinsic factors which significantly affected oral clearance (CL(t)/F) and the apparent volume of distribution of the central compartment (V1/F), respectively. The final model is described as follows: CL(t)/F (l/h) = (8.97 + 0.917 x (CL(cr) (ml/min)-100.92) x 60/1000) x exp (eta(CLt/F)). V1/F (l) = (85.3 + 1.22 x (weight (kg)-60.75)) x exp (eta(V1/F)). Q/F (l/h) = 0.351. V2/F (l) = 6.81. k(a) (h(-1)) = 1.44 x exp(eta(ka)). Based on the population PK model, mean C(max) and AUC(0-24h) in CALRTI patients were estimated as 5.13 microg/ml and 58.98 microg.h/ml, respectively. A subgroup analysis showed that patients with mild renal dysfunction (50 ml/min < or = CL(cr) < 80 ml/min) had 34% higher AUC(0-24h) values compared to patients with normal renal function (CL(cr) > or = 80 ml/min). Postmodeling simulation using final population PK estimates also showed that C(max) and AUC(0-24h) increased markedly in patients with severe renal dysfunction. The results indicate that LVFX dosage adjustment should be individualized on the basis of the CL(cr), especially in those with CL(cr) less than 50 ml/min. None of the PK parameters had any correlation with the occurrence of adverse events. PK-PD analysis indicated that, in patients treated with LVFX 500 mg once daily, the AUC(0-24h)/MIC ratio exceeded the target for those major CALRTI pathogens isolated. In addition, the C(max)/MIC ratio reached 5 for Streptococcus pneumoniae, indicating that the emergence of LVFX-resistant S. pneumoniae could be prevented during the therapy with this dosage regimen. These results demonstrate that oral LVFX 500 mg once daily has favorable PK parameters and PK-PD features in patients with CALRTIs, and the results strongly support this dosage regimen for the treatment of CALRTI.

Selective method for the determination of cefdinir in human plasma using liquid chromatography electrospray ionization tandam mass spectrometry.

A sensitive and selective liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method was developed for the determination of cefdinir in human plasma. After a simple protein precipitation using trichloracetic acid, the post-treatment samples were applied to a prepacked RP18 Waters SymmetryShield column interfaced with a triple quadrupole tandem mass spectrometer. Positive electrospray ionization was employed as the ionization source. The mobile phase consisted of methanol-water-formic acid (25:75:0.075, v/v/v). The analyte and I.S. cefaclor were both detected by the use of selected reaction monitoring mode. The method was linear in the concentration range of 5-2,000 ng/ml. The lower limit of quantification was 5 ng/ml. The intra- and inter-day relative standard deviation across three validation runs over the entire concentration range was less than 4.3%. The accuracy determined at three concentrations (36, 360 and 1,800 ng/ml for cefdinir) ranged from 99.6 to 106.7% in terms of recovery. The chromatographic run time for each plasma sample was less than 3 min. The method herein described was successfully applied for the evaluation of pharmacokinetic profiles of cefdinir capsule in 12 healthy volunteers.

[Study on bioequivalence of domestic bambuterol capsules and imported tablets by high performance capillary zone electrophoresis].

AIM: To study bioequivalences of bambuterol and its metabolites terbutaline in 20 healthy male volunteers. METHODS: A single oral dose of domestic bambuterol capsule or imported bambuterol tablet was given according to a randomized 2-way cross-over design. The plasma bambuterol and terbutaline concentrations were determined by high performance capillary zone electrophoresis (HPCZE). RESULTS: The pharmacokinetic parameters of the capsule and tablet of bambuterol: AUC0-1 were (72 +/- 18) and (72 +/- 13) microgram.h.L-1, Cmax were (8.1 +/- 1.8) and (9.2 +/- 2.3) microgram.L-1, Tmax were (3.6 +/- 1.3) and (3.7 +/- 1.0) h, respectively; terbutaline: AUC0-t were (129 +/- 32) and (130 +/- 34) microgram.h.L-1, Cmax were (7.8 +/- 2.2) and (8.5 +/- 2.9) microgram.L-1, Tmax were (5.4 +/- 0.8) and (5.6 +/- 1.1) h, respectively. The bioavaiability of the capsule was (100 +/- 16)% (bambuterol) and (101 +/- 13)% (terbutaline). CONCLUSION: The results demonstrated that the two preparations of bambuterol and terbutaline were bioequivalent by analysis of variance, with two-one sided test at 90% confidential level.