A study of the pharmacokinetics of moxifloxacin by the dynamics of its distribution in the blood plasma and saliva of healthy volunteers: a comparative analysis and possible extrapolation methods

OBJECTIVES

The pharmacokinetics of moxifloxacin in plasma and saliva was investigated in this study.

METHODS

The pharmacokinetics of two specialty drugs of moxifloxacin - reference (Ref) and test (Test) preparation - was studied in 18 healthy volunteers after a single oral dose of 400 mg.

RESULTS

It was found that the concentration of moxifloxacin in saliva 3-24 h after taking the drugs was statistically significantly higher than that in plasma. A high correlation was observed between the concentration of moxifloxacin in plasma and saliva of volunteers after taking of Ref and Test. Some pharmacokinetic parameters, calculated by the concentration of moxifloxacin in saliva and plasma, are statistically different. A technique is proposed for extrapolating the concentration of moxifloxacin in plasma according to its concentration in saliva using the established linear relationship between the moxifloxacin in plasma and saliva of volunteers in time interval of 3-24 h after taking Ref. Based on the obtained extrapolated concentration of moxifloxacin, the pharmacokinetic parameters were calculated for two studied drugs and did not statistically differ from the parameters calculated according to the data in plasma.

CONCLUSIONS

The developed method of concentration extrapolation allows the use of saliva for pharmacokinetic studies of the tablet preparations of moxifloxacin.

Synthesis and evaluation of new 1-oxa-8-azaspiro[4.5]decane derivatives as candidate radioligands for sigma-1 receptors

We report the design, synthesis, and evaluation of a series of 1-oxa-8-azaspiro[4.5]decane and 1,5-dioxa-9-azaspiro[5.5]undecane derivatives as selective σ1 receptor ligands. All seven ligands exhibited nanomolar affinity for σ1 receptors (Ki(σ1) = 0.47 - 12.1 nM) and moderate selectivity over σ2 receptors (Ki(σ2)/ Ki(σ1) = 2 - 44). Compound 8, with the best selectivity among these ligands, was selected for radiolabeling and further evaluation. Radioligand [18F]8 was prepared via nucleophilic 18F-substitution of the corresponding tosylate precursor, with an overall isolated radiochemical yield of 12-35%, a radiochemical purity of greater than 99%, and molar activity of 94 - 121 GBq/μmol. Biodistribution studies of [18F]8 in mice demonstrated high initial brain uptake at 2 min. Pretreatment with SA4503 resulted in significantly reduced brain-to-blood ratio (70% - 75% at 30 min). Ex vivo autoradiography in ICR mice demonstrated high accumulation of the radiotracer in σ1 receptor-rich brain areas. These findings suggest that [18F]8 could be a lead compound for further structural modifications to develop potential brain imaging agents for σ1 receptors.

Selective DYRK1A Inhibitor for the Treatment of Type 1 Diabetes: Discovery of 6-Azaindole Derivative GNF2133

Autoimmune deficiency and destruction in either β-cell mass or function can cause insufficient insulin levels and, as a result, hyperglycemia and diabetes. Thus, promoting β-cell proliferation could be one approach toward diabetes intervention. In this report we describe the discovery of a potent and selective DYRK1A inhibitor GNF2133, which was identified through optimization of a 6-azaindole screening hit. In vitro, GNF2133 is able to proliferate both rodent and human β-cells. In vivo, GNF2133 demonstrated significant dose-dependent glucose disposal capacity and insulin secretion in response to glucose-potentiated arginine-induced insulin secretion (GPAIS) challenge in rat insulin promoter and diphtheria toxin A (RIP-DTA) mice. The work described here provides new avenues to disease altering therapeutic interventions in the treatment of type 1 diabetes (T1D).

Trans-Cyclooctene-Functionalized PeptoBrushes with Improved Reaction Kinetics of the Tetrazine Ligation for Pretargeted Nuclear Imaging

Tumor targeting using agents with slow pharmacokinetics represents a major challenge in nuclear imaging and targeted radionuclide therapy as they most often result in low imaging contrast and high radiation dose to healthy tissue. To address this challenge, we developed a polymer-based targeting agent that can be used for pretargeted imaging and thus separates tumor accumulation from the imaging step in time. The developed targeting agent is based on polypeptide-graft-polypeptoid polymers (PeptoBrushes) functionalized with trans-cyclooctene (TCO). The complementary ¹¹¹In-labeled imaging agent is a 1,2,4,5-tetrazine derivative, which can react with aforementioned TCO-modified PeptoBrushes in a rapid bioorthogonal ligation. A high degree of TCO loading (up to 30%) was achieved, without altering the physicochemical properties of the polymeric nanoparticle. The highest degree of TCO loading resulted in significantly increased reaction rates (77-fold enhancement) compared to those with small molecule TCO moieties when using lipophilic tetrazines. Based on computer simulations, we hypothesize that this increase is a result of hydrophobic effects and significant rearrangements within the polymer framework, in which hydrophobic patches of TCO moieties are formed. These patches attract lipophilic tetrazines, leading to increased reaction rates in the bioorthogonal ligation. The most reactive system was evaluated as a targeting agent for pretargeted imaging in tumor-bearing mice. After the setup was optimized, sufficient tumor-to-background ratios were achieved as early as 2 h after administration of the tetrazine imaging agent, which further improved at 22 h, enabling clear visualization of CT-26 tumors. These findings show the potential of PeptoBrushes to be used as a pretargeting agent when an optimized dose of polymer is used.

[Pharmacokinetic properties of an innovative nootropic agent based on a derivative of 3,7-diazabicyclo[3.3.1]nonane]

The pharmacokinetics and bioavailability of a derivative of 3,7-diazabicyclo[3.3.1]nonane exhibiting a nootropic effect, were studied after a single dose to rats. The pharmacokinetics of the compound was studied after oral and intravenous administration to 270 male rats Sprague Dawley at doses of 2.5 mg/kg, 13 mg/kg and 25 mg/kg. Its distribution in organs and tissues (brain, thymus, heart, lungs, liver, kidneys, and spleen) was also investigated. It was found that after a single intravenous administration, the investigated substance was determined in the blood of animals for 24 h; the half-life was 4.69 h. The relative bioavailability of the 3,7-diazabicyclo[3.3.1]nonane derivative after oral administration was 42.3%, thus suggesting the prospect of creating dosage forms for oral administration. After a single oral administration, the dose dependence of AUC0-t was exponential. The substance is characterized by heterogeneous distribution in the body with preferential accumulation mainly in well-vascularized tissues.

Degradation kinetics and pathways of spirotetramat in different parts of spinach plant and in the soil

Spirotetramat is a new pesticide against a broad spectrum of sucking insects and exhibits a unique property with a two-way systemicity. In order to formulate a scientific rationale for a reasonable spray dose and the safe interval period of 22.4 % spirotetramat suspension concentrate on controlling vegetable pests, we analyzed degradation dynamics and pathways of spirotetramat in different parts of spinach plant (leaf, stalk, and root) and in the soil. We conducted experimental trials under field conditions and adopted a simple and reliable method (dispersive solid phase extraction) combined with liquid chromatography-triple quadrupole tandem mass spectrometry to evaluate the dissipation rates of spirotetramat residue and its metabolites. The results showed that the spirotetramat was degraded into different metabolite residues in different parts of spinach plant (leaf, stalk, and root) and in the soil. Specifically, spirotetramat was degraded into B-keto, B-glu, and B-enol in the leaf; B-glu and B-enol in the stalk; and only B-enol in the root. In the soil where the plants grew, spirotetramat followed a completely different pathway compared to the plant and degraded into B-keto and B-mono. Regardless of different degradation pathways, the dissipation dynamic equations of spirotetramat in different parts of spinach plant and in the soil were all based on the first-order reaction dynamic equations. This work provides guidelines for the safe use of spirotetramat in spinach fields, which would help prevent potential health threats to consumers.

Effects of Subcutaneous Pasireotide on Cardiac Repolarization in Healthy Volunteers: a Single‐Center, Phase I, Randomized, Four‐Way Crossover Study

The aim of this study was to evaluate the effects of subcutaneous pasireotide on cardiac repolarization in healthy volunteers. Healthy volunteers were randomized to one of four treatment sequences (n = 112) involving four successive treatments in different order: pasireotide 600 µg (therapeutic dose) or 1,950 µg (maximum tolerated dose) bid by subcutaneous injection (sc), placebo injection and oral moxifloxacin. Maximum ΔΔQTcI occurred 2 hours post-dose for both doses of pasireotide. Mean ΔΔQTcI was 13.2 milliseconds (90% CI: 11.4, 15.0) and 16.1 milliseconds (90% CI: 14.3, 17.9) for the 600 and 1,950 µg bid doses, respectively. Maximal placebo-subtracted change in QTcI from baseline for moxifloxacin was 11.1 (90% CI: 9.3, 12.9) milliseconds. Both pasireotide doses caused a reduction in heart rate: maximal heart rate change compared with placebo occurred at 1 hour for pasireotide 600 µg bid and at 0.5 hours for pasireotide 1,950 µg bid, with heart rate reductions of 10.4 and 14.9 bpm, respectively. At the therapeutic dose of 600 µg, pasireotide has a modest QT-prolonging effect. The relatively small increase of ∼3 milliseconds in ΔΔQTcI in the presence of a 3.25-fold increase in dose suggests a relatively flat dose–effect relationship of pasireotide on ΔΔQTcI in healthy volunteers. No safety concerns for pasireotide were identified during the study.

Identifying the translational gap in the evaluation of drug-induced QTc interval prolongation

AIMS

Given the similarities in QTc response between dogs and humans, dogs are used in pre-clinical cardiovascular safety studies. The objective of our investigation was to characterize the PKPD relationships and identify translational gaps across species following the administration of three compounds known to cause QTc interval prolongation, namely cisapride, d, l-sotalol and moxifloxacin.

METHODS

Pharmacokinetic and pharmacodynamic data from experiments in conscious dogs and clinical trials were included in this analysis. First, pharmacokinetic modelling and deconvolution methods were applied to derive drug concentrations at the time of each QT measurement. A Bayesian PKPD model was then used to describe QT prolongation, allowing discrimination of drug-specific effects from other physiological factors known to alter QT interval duration. A threshold of ≥10 ms was used to explore the probability of prolongation after drug administration.

RESULTS

A linear relationship was found to best describe the pro-arrhythmic effects of cisapride, d,l-sotalol and moxifloxacin both in dogs and in humans. The drug-specific parameter (slope) in dogs was statistically significantly different from humans. Despite such differences, our results show that the probability of QTc prolongation ≥10 ms in dogs nears 100% for all three compounds at the therapeutic exposure range in humans.

CONCLUSIONS

Our findings indicate that the slope of PKPD relationship in conscious dogs may be used as the basis for the prediction of drug-induced QTc prolongation in humans. Furthermore, the risk of QTc prolongation can be expressed in terms of the probability associated with an increase ≥10 ms, allowing direct inferences about the clinical relevance of the pro-arrhythmic potential of a molecule.

Diffusion of Oral and Intravenous 400 mg Once-Daily Moxifloxacin into Lung Tissue at Pharmacokinetic Steady-State

The degree of penetration of an antibiotic into the infection site is an important factor for its therapeutic efficacy, particularly in respiratory tract infections. In the present study, we examined the lung tissue diffusion of moxifloxacin at a dose of 400 mg administered intravenously or orally once-daily, and the results were correlated to microbiological data to estimate the clinical efficacy of moxifloxacin in lower community-acquired respiratory infections. This was a prospective, randomized, parallel-group trial, open-label, single-center study. Patients undergoing lung surgery for bronchial cancer which necessitates the removal of an anatomical piece of lung tissue were randomized into twelve treatment groups, dependent upon the time of surgery and the moxifloxacin formulation, i.v. or oral, administered. During surgery, one blood sample was taken at the time of tissue collection to determine moxifloxacin plasma concentration. At the same time, tissue samples were taken by pulmonary exeresis. A validated new high performance liquid chromatography assay was used to determine moxifloxacin concentrations in plasma and lung tissue. A total of 49 patients (25 for i.v. administration, 24 for oral administration, 44 men and 5 women, mean age, 61 years, mean body weight, 72 kg, mean creatinine clearance was 84 ml/min/1.73 m2) were enrolled. The mean +/- SD steady-state moxifloxacin ratios between lung and plasma concentrations were respectively: 3.53 +/- 1.89 and 4.36 +/- 1.48 for i.v. and oral administration. The mean steady-state moxifloxacin maximal lung concentrations (Cmax) were respectively 12.37 microg/g and 16.21 microg/g for i.v. and oral administration. Moxifloxacin both intravenously and orally exhibits high penetration in lung tissue, with tissue concentrations far above the MIC90s for most of the susceptible pathogens commonly involved, thus underlining its suitability for the treatment of community-acquired, lower respiratory tract infections.

Serum and Prostatic Tissue Concentrations of Moxifloxacin in Patients Undergoing Transurethral Resection of the Prostate

The spectrum of pathogens causing chronic bacterial prostatitis comprises Gram-negative, Gram-positive and atypical microorganisms. Because of its broad spectrum of activity, the group 4 fluoroquinolone moxifloxacin might be a suitable antibiotic for treatment of bacterial prostatitis. The aim of this prospective study was to investigate the penetration of moxifloxacin into prostatic tissue in patients with benign prostatic hyperplasia. Patients received a single dose of moxifloxacin 400 mg in an 1 hour lasting infusion (250 ml) for perioperative prophylaxis before undergoing transurethral resection of the prostate (TURP). Serum concentrations were determined in all patients before infusion, at the end of infusion (time point 0), 0.5, 1 and 2 h after the end of infusion. Patients were randomized for tissue sampling either 0, 0.5, 1 or 2 h after the end of infusion. At beginning of TURP approximately 1 g of tissue was sampled for analysis. Concentrations of moxifloxacin in serum and tissue were determined by HPLC. 39 patients were evaluated. Median serum and prostatic tissue concentrations peaked at 0 h (4.94 mg/ L and 8.50 mg/ kg, respectively). The lowest concentrations were quantified at 2 h after the end of infusion (2.46 mg/ L and 3.88 mg/ kg, respectively). The prostatic tissue concentrations of moxifloxacin were approximately twice as high as in corresponding serum. At the end of infusion the tissue and serum concentrations seemed to be already equilibrated, as their ratios did not differ significantly during the time of investigation. After an intravenous infusion of 400 mg the serum and prostatic tissue concentrations of moxifloxacin were well above the MIC values of most important prostatic pathogens. The high tissue/ serum ratio and the extended antibacterial spectrum suggests active concentration in the prostate which may translate into increased efficacy compared to group 2 and 3 fluoroquinolones in the treatment of chronic bacterial prostatitis.

Biopharmaceutical characterization, metabolism, and brain penetration of the triple reuptake inhibitor amitifadine

Amitifadine (EB-1010, formerly DOV 21,947) is a serotonin-preferring triple reuptake inhibitor that is a drug candidate for major depressive disorder. We investigated several relevant biopharmaceutic and drug-like characteristics of amitifadine using in vitro methodology and additionally determined the in vivo brain to plasma ratio of the drug in rats. Amitifadine was highly plasma protein bound with over 99% of drug bound to human plasma proteins. Using Caco-2 cell lines, amitifadine was bidirectionally highly permeable and showed no evidence of active secretion. Amitifadine was metabolized slowly by human hepatocytes and the major metabolite was the lactam EB-10101. In vitro studies using human liver microsomes demonstrated that EB-10101 was formed by monoamine oxidase A (MAO-A) and a NADPHdependent enzyme, possibly a cytochrome P450 (CYP) isoform. Amitifadine was a moderate inhibitor of the human isoforms of the major drug metabolizing enzymes CYP2D6, CYP3A4, CYP2C9, and CYP2C19 (IC50 = 9 - 100 μM), but was a potent inhibitor of human CYP2B6 (IC50 = 1.8 μM). The brain to plasma ratio for amitifadine varied from 3.7 - 6.5 at various time points, indicating preferential partitioning into rat brain versus plasma. The low affinity for the major drug metabolizing CYP enzymes and metabolism by multiple pathways may reduce pharmacokinetic drug-drug interactions and effects of enzyme polymorphisms. Overall, these studies suggest that amitifadine has drug-like characteristics favorable for drug development.

A randomized, double-blind, placebo-controlled study to evaluate the effect of repeated oral doses of pazopanib on cardiac conduction in patients with solid tumors

PURPOSE

As tyrosine kinase inhibitors have been associated with cardiotoxicity, we evaluated the effect of pazopanib, an inhibitor of vascular endothelial growth factor receptor, platelet-derived growth factor receptor, and c-Kit, on electrocardiographic parameters in patients with cancer.

METHODS

This double-blind, placebo-controlled, parallel-group study randomized patients (N = 96) to moxifloxacin (positive control) or placebo on Day 1 followed by pazopanib or placebo 800 mg/day (fasted) on Days 2-8 and 1,600 mg (with food) on Day 9. Treatment effects were evaluated by baseline-adjusted, time-matched, serial Holter electrocardiograms.

RESULTS

Sixty-five patients were evaluable for preplanned analyses. On Day 1, the maximum mean difference in baseline-adjusted, time-matched Fridericia-corrected QT (QTcF) interval in moxifloxacin-treated patients versus placebo was 10.6 ms (90% confidence interval [CI]: 4.2, 17.0). The administration scheme increased plasma pazopanib concentrations approximately 1.3- to 1.4-fold versus the recommended 800 mg once-daily dose. Pazopanib caused clinically significant increases from baseline in blood pressure, an anticipated class effect, and an unexpected reduction in heart rate from baseline that correlated with pazopanib exposure. On Day 9, the maximum mean difference in baseline-adjusted, time-matched QTcF interval in pazopanib-treated patients versus placebo was 4.4 ms (90% CI: -2.4, 11.2). Mixed-effects modeling indicated no significant concentration-dependent effect of pazopanib or its metabolites on QTcF interval.

CONCLUSIONS

Pazopanib as administered in this study achieved supratherapeutic concentrations, produced a concentration-dependent decrease in heart rate, and caused a small, concentration-independent prolongation of the QTcF interval.

Comparison of corneal and aqueous humor penetration of moxifloxacin, gatifloxacin and levofloxacin during keratoplasty

INTRODUCTION

Achieving high antibiotic concentrations is important for preventing and treating postoperative infections. However, no study has simultaneously compared the achieved concentrations of moxifloxacin, gatifloxacin, and levofloxacin in the human cornea and aqueous humor. The authors therefore performed a randomized study to determine the concentrations of 0.5% moxifloxacin, 0.3% gatifloxacin, and 0.5% levofloxacin in the corneal tissue and aqueous humor after topical instillation in patients undergoing penetrating keratoplasty.

METHODS

Patients who required penetrating keratoplasty were eligible for this study. The topical preparations of 0.5% moxifloxacin, 0.3% gatifloxacin, and 0.5% levofloxacin used in the study were preservative free (Japanese formulations). Patients were randomly assigned to one of three sequential drug groups, in which each drug was administered three times before surgery. In each administration cycle, the patients received two drops of each drug at 2-minute intervals. Samples of corneal tissue and aqueous humor were collected during surgery. The concentrations of each drug in the samples were determined by high-performance liquid chromatography.

RESULTS

A total of 63 patients across eight centers in Japan were enrolled in the study. Overall, 61 corneal and 58 aqueous humor samples were evaluated. The concentration (mean±standard deviation) of moxifloxacin in corneal tissues was 12.66±8.93 μg/g, which was significantly higher than that of gatifloxacin (4.71±3.39 μg/g; P<0.0001) and levofloxacin (5.95±4.02 μg/g; P<0.0001). The mean concentration of moxifloxacin in aqueous humor samples was 1.40±1.17 μg/mL, which was significantly higher than that of gatifloxacin (0.65±0.80 μg/mL; P=0.0001) and levofloxacin (0.89±0.86 μg/mL; P<0.05). The sequence of drug administration did not significantly affect the results.

CONCLUSION

These results show that 0.5% moxifloxacin achieved superior ocular concentration than both 0.3% gatifloxacin and 0.5% levofloxacin.

A randomized, crossover, placebo- and moxifloxacin-controlled study to evaluate the effects of bosutinib (SKI-606), a dual Src/Abl tyrosine kinase inhibitor, on cardiac repolarization in healthy adult subjects

Effects of therapeutic and supratherapeutic concentrations of bosutinib, a dual Src/Abl tyrosine kinase inhibitor, on the corrected QT interval (QTc) in 60 healthy adults were assessed, according to ICH-E14 guidelines, in this 2-part, randomized, single-dose, double-blind, crossover, placebo- and open-label moxifloxacin-controlled study. Subjects received placebo, moxifloxacin and bosutinib 500 mg with food (therapeutic) in Part 1. In Part 2, subjects received placebo and bosutinib 500 mg plus ketoconazole (supratherapeutic). ANOVA compared baseline-adjusted QTc for bosutinib with placebo; and bosutinib plus ketoconazole with placebo plus ketoconazole. Primary endpoint was population-specific QT correction (QTcN). Secondary endpoints were Bazett QT correction (QTcB), Fridericia's formula QT correction (QTcF) and individual QT correction (QTcI). Upper bounds for 90% confidence intervals were <10 msec for the mean change in QTcN from placebo at all postdose time points, suggesting that mean therapeutic exposures (C(max) , 114 ng/mL; AUC, 2,330 ng · h/mL) and mean supratherapeutic exposures (C(max) , 326 ng/mL; AUC, 15,200 ng · h/mL) were not associated with QTc changes. Similar results were obtained for QTcB, QTcF and QTcI. No clinically relevant pharmacokinetic/pharmacodynamic relationship was observed between bosutinib concentrations and QTc. No subjects had QTcB, QTcF, QTcI or QTcN >450 msec or change from baseline >30 msec. In summary, therapeutic and supratherapeutic bosutinib exposures are not associated with QTc prolongation in healthy adults.

Contrasting effects of acidic pH on the extracellular and intracellular activities of the anti-gram-positive fluoroquinolones moxifloxacin and delafloxacin against Staphylococcus aureus

In contrast to currently marketed fluoroquinolones, which are zwitterionic, delafloxacin is an investigational fluoroquinolone with an anionic character that is highly active against Gram-positive bacteria. We have examined the effect of acidic pH on its accumulation in Staphylococcus aureus and in human THP-1 cells, in parallel with its activity against extracellular and intracellular S. aureus. Moxifloxacin was used as a comparator. Delafloxacin showed MICs 3 to 5 log(2) dilutions lower than those of moxifloxacin for a collection of 35 strains with relevant resistance mechanisms and also proved to be 10-fold more potent against intracellular S. aureus ATCC 25923. In medium at pH 5.5, this difference was further enhanced, with the MIC decreasing by 5 log(2) dilutions. In infected cells incubated in acidic medium, the relative potency was 10-fold higher than that at neutral pH and the maximal relative efficacy reached a bactericidal effect at 24 h. These results can be explained by a 10-fold increase in delafloxacin accumulation in both bacteria and cells at acidic pH, making delafloxacin one of the most efficient drugs tested in this model. Opposite effects were seen for moxifloxacin with respect to both activity and accumulation. As reported for zwitterionic fluoroquinolones, delafloxacin was found associated with the soluble fraction in homogenates of eukaryotic cells. Taken together, these properties may confer to delafloxacin an advantage for the eradication of S. aureus in acidic environments, including intracellular infections.

Pharmacokinetics of azithromycin and moxifloxacin in human conjunctiva and aqueous humor during and after the approved dosing regimens

PURPOSE

To evaluate the ocular pharmacokinetics of azithromycin and moxifloxacin in human conjunctiva and aqueous humor in subjects undergoing cataract surgery.

DESIGN

Multicenter, open-label, randomized study.

METHODS

Subjects scheduled for routine cataract surgery and with normal-appearing conjunctiva were eligible. One conjunctival biopsy sample and 1 aqueous humor sample were obtained from subjects randomly assigned to 1 of 10 prespecified time points (1 to 312 hours) after treatment initiation of azithromycin ophthalmic solution 1% or moxifloxacin ophthalmic solution 0.5%. Samples were assayed using liquid chromatography tandem mass spectrometry.

RESULTS

Azithromycin 1% provided high concentrations (peak level, 559.7 μg/g) in human conjunctiva that were sustained at levels 1 to 2 orders of magnitude higher than those of moxifloxacin 0.5% throughout the 7-day dosing period and for at least 7 days thereafter. Azithromycin also showed an extended half-life (65.7 hours) in conjunctiva relative to that of moxifloxacin (28.6 hours). Accordingly, the concentration of azithromycin was maintained well above the minimum inhibitory concentration required for inhibition of growth of 90% of tested bacterial isolates for at least 7 days, whereas moxifloxacin conjunctival levels fell to levels at or less than the minimum inhibitory concentration required for inhibition of growth of 90% of tested bacterial isolates approximately 24 hours after the last dose. Peak aqueous humor concentration of moxifloxacin was higher (0.77 μg/mL) than that of azithromycin (0.053 μg/mL). No clinically relevant safety findings were observed.

CONCLUSIONS

Azithromycin 1% demonstrated high, therapeutic levels in the conjunctiva that were maintained up to 7 days after completion of a 1-week dosing regimen. Aqueous humor levels, however, were subtherapeutic with this dosing regimen. In comparison, moxifloxacin achieved lower conjunctival tissue levels, but higher aqueous humor levels.

Multiple species metabolism of PHA-568487, a selective alpha 7 nicotinic acetylcholine receptor agonist

The quinuclidine PHA-0568487(1) is an agonist of the alpha 7 nicotinic acetylcholine receptor that was designed to mitigate the bioactivation associated with the core scaffold and subsequently remove associated liabilities with in vivo tolerability. The drug metabolites of 1 in nonclinical species were identified in plasma and urine of rats, dogs and monkeys receiving oral administrations of 1. The in vitro biotransformation of 1 was subsequently investigated in multiple species employing cryopreserved hepatocytes, hepatic subcellular fractions and recombinantly-expressed human P450 enzymes. In addition, in vitro metabolism of synthetically prepared metabolite precursors were instrumental in the elucidation of several secondary metabolites. The results indicated that the principal biotransformation of 1 was oxidation of the benzo[1,4]dioxane moiety (M8, M10) followed by subsequent oxidation to a range of secondary metabolites (M1-7, M9, M11, M13-15, and M17-18). The carboxylic acids M1 and M2 resulting from the oxidative cleavage of the dioxane ring were the principal metabolites observed in the plasma, urine and hepatocyte incubations across all species (M1 & M2). Quinuclidine oxidation was another pathway of importance, yielding an N-oxide (M12) which was also observed in all species.P450 2D6 and FMO1 catalyze the oxidation of the quinuclidine nitrogen. The N oxidation of the quinuclidine moiety is consistent with previously published accounts of this scaffold's metabolism and, interestingly, may implicate the uncommon quinuclidine moiety as an entity directing the metabolism of this scaffold (e.g., 1) via FMO1 and P450 2D6 oxidation.

Moxifloxacin does not alter ciclosporin pharmacokinetics in transplant patients: a multiple-dose, uncontrolled, single-centre study

BACKGROUND

Moxifloxacin has a broad antibacterial spectrum and rapid bactericidal activity, and is thus a good option for the treatment of bacterial infections in patients who have undergone organ or bone marrow transplantation. Transplant patients also receive immunosuppressant therapy such as ciclosporin.

OBJECTIVE

The primary objective of this study was to assess the steady-state pharmacokinetics of ciclosporin with and without concomitant treatment with moxifloxacin in transplant recipients. A secondary objective was to determine the safety and tolerability of the combined treatment.

METHODS

Patients (n = 9) with stable graft function after bone marrow or renal transplantation and who were already receiving ciclosporin therapy were enrolled into the study. The patients were given ciclosporin (Sandimmun Optoral) capsules twice daily (total daily dosage 150-380 mg/day) throughout the study period. Moxifloxacin (Avolox) tablets 400 mg once daily were given on days 2-8 inclusive. The primary outcome measure was the change in ciclosporin pharmacokinetics on coadministration with moxifloxacin. Secondary outcomes were the steady-state pharmacokinetics of moxifloxacin and ciclosporin plus its metabolites in patients receiving moxifloxacin and ciclosporin concomitantly. Moxifloxacin pharmacokinetic parameters in the presence of ciclosporin were compared with previously published pharmacokinetic data for moxifloxacin in healthy individuals.

RESULTS

No significant changes occurred in the concentration-time curves of ciclosporin and its metabolites following combination therapy with moxifloxacin. The geometric means of whole blood concentrations of ciclosporin and ciclosporin plus its metabolites on day 1 were similar to those on day 8 following combined administration of ciclosporin and moxifloxacin for 7 days. The ratio of combination treatment to monotherapy for ciclosporin was 1.01 (90% CI 0.91, 1.11) for the area under the blood concentration-time curve from time zero to 12 hours at steady state (AUC(12,ss)) and 0.96 (90% CI 0.88, 1.04) for the maximum steady-state blood drug concentration (C(max,ss)). For ciclosporin plus its metabolites the ratio was 1.07 (90% CI 0.99, 1.17) for AUC(12,ss) and 1.03 (90% CI 0.98, 1.09) for C(max,ss). The pharmacokinetic parameters for moxifloxacin were unaffected by the presence of ciclosporin.

CONCLUSIONS

Concomitant administration of moxifloxacin does not alter the pharmacokinetic parameters of ciclosporin or ciclosporin plus its metabolites in immunosuppressed patients. Therefore, no dose adjustments or additional drug monitoring are required when ciclosporin is coadministered with moxifloxacin.

Pharmacokinetics of moxifloxacin in patients undergoing continuous ambulatory peritoneal dialysis

OBJECTIVE

To investigate the effect of continuous ambulatory peritoneal dialysis (CAPD) on plasma and peritoneal fluid concentration and pharmacokinetics of moxifloxacin after administration of one 400 mg dose orally to end-stage renal failure patients undergoing CAPD.

PATIENTS AND METHODS

Blood and peritoneal samples were collected from 8 patients at standard time intervals and concentrations of moxifloxacin were estimated by HPLC analysis with fluorometric and ultraviolet detection. Pharmacokinetic parameters were estimated using standard noncompartmental methods.

RESULTS

Median maximum plasma moxifloxacin concentration was 5.86 mg/L at a median time of 1.25 hours. In serum, median area under the concentration-time curve (AUC(0-->inf)) was 157.95 +/- 100.34 mg.hour/L, median t(1/2) 25.00 hours, median clearance 2.54 L/hour, and median distribution volume 94.90 L. Median peritoneal fluid-to-plasma ratio of moxifloxacin ranged between 0.84 and 1.00, denoting adequate penetration and lack of considerable moxifloxacin removal during CAPD. Maximum moxifloxacin concentration/minimum inhibitory concentration (MIC) and AUC(0-->24)/MIC ratios were above the cutoff points that indicate clinical success.

CONCLUSION

A single 400 mg oral dose of moxifloxacin is safe, presents rapid peritoneal fluid penetration, has similar plasma and peritoneal fluid pharmacokinetics, and should therefore be efficacious in the treatment of CAPD-induced peritonitis.

Moxifloxacin distribution in the interstitial space of infected decubitus ulcer tissue of patients with spinal cord injury measured by in vivo microdialysis

We investigated the distribution of moxifloxacin in the interstitial space of normal and infected subcutaneous tissue in patients with spinal cord injury and decubitus ulcers using in vivo microdialysis. Drug concentrations achieved in serum, saliva, normal and infected tissues showed approximately parallel time profiles. The interstitial tissue fluids reached bactericidal levels for common bacteria found in infected skin lesions. Our findings suggest that moxifloxacin exhibits good and similar penetration into the interstitial space fluid in normal subcutaneous tissue and infected decubitus ulcers in patients with spinal cord injury.

Conjunctival tissue pharmacokinetic properties of topical azithromycin 1% and moxifloxacin 0.5% ophthalmic solutions: a single-dose, randomized, open-label, active-controlled trial in healthy adult volunteers

BACKGROUND

Effective ocular tissue concentrations and prolonged residence times of antibacterial agents are important in treating both acute and chronic diseases. Conjunctival biopsy allows the determination of specific tissue concentration data for topical ophthalmic agents. Drug concentration analysis at various time points following instillation allows interpretation of the residence time and a rationale for dosing frequency.

OBJECTIVE

This study compared the pharmacokinetic parameters of 2 currently available topical ocular antibiotics-azithromycin ophthalmic solution 1% and moxifloxacin ophthalmic solution 0.5%-in the conjunctiva of healthy volunteers after a single topical administration.

METHODS

This single-dose, randomized, open-label, active-controlled clinical trial was conducted at ORA Clinical Research and Development, North Andover, Massachusetts. Subjects were randomly assigned to receive a single dose of azithromycin or moxifloxacin and to undergo biopsy sampling at 30 minutes or 2, 12, or 24 hours after administration. Concentrations of azithromycin and moxifloxacin were determined using liquid chromatography tandem mass spectrometry. Adverse events (AEs) were assessed at all visits using visual acuity measurements, slit-lamp biomicroscopy, and direct questioning.

RESULTS

Forty-eight subjects (mean age, 40.0 years; 48% female; 96% white, 2% black, and 2% Asian) underwent conjunctival biopsy. Mean (SD) concentrations of azithromycin in conjunctival tissue (lower limit of quantitation [LLOQ], 1 microg/g for 1-mg biopsy specimen) were 131 (89), 59 (19), 48 (24), and 32 (20) microg/g at 30 minutes and 2, 12, and 24 hours, respectively (median values, 117, 69, 46, and 30 microg/g). Mean concentrations concentrations of moxifloxacin in conjunctival tissue (LLOQ, 0.05 microg/g for 1-mg biopsy sample) were 1.92 (2.03), 3.77 (8.98), 0.02 (0.04), and 0.01 (0.02) microg/g at 30 minutes and 2, 12, and 24 hours, respectively (median values, 1.12, 0.12, <0.05, and <0.05 microg/g). Thirteen subjects (6 in the azithromycin group and 7 in the moxifloxacin group) experienced 20 AEs, 11 of which were considered possibly related to study treatment, and 15 of which were ocular (most commonly conjunctival hemorrhage).

CONCLUSIONS

In this single-dose study of 2 currently available topical ocular antibiotics in healthy volunteers, therapeutic concentrations were achieved with both agents. Both treatments were well tolerated in the population studied. Clinical Trials Identification Number: NCT00564447.

Disposition kinetics of moxifloxacin in lactating ewes

The present study was planned to investigate the plasma disposition kinetics and the pattern of moxifloxacin elimination in the milk of lactating ewes (n=6) following a single intravenous (IV) bolus or intramuscular (IM) injections at a dosage of 5 mg/kg in all animals. A crossover study was carried out in two phases separated by 21 days. Plasma and milk samples were collected serially for 72 h and moxifloxacin concentrations were assayed using high performance liquid chromatography with fluorescence detection. A two-compartment open model best described the decrease of moxifloxacin concentration in the plasma after IV injection. The disposition after IM administration moxifloxacin was best described by a one-compartment model. Following IV administration, the distribution half-life (t(1/2alpha)) was 0.22+/-0.02 h. The elimination half-life was 1.77+/-0.23 h. The volume of distribution at steady state (V(dss)) was 0.84+/-0.12L/kg, the total body clearance (Cl(tot)) was 0.34+/-0.04 L/h/kg and the area under the curve (AUC) was 14.74+/-2.16 microg h/mL. Following IM administration, the mean T(max), C(max), t(1/2el) and AUC values for plasma data were 1.45+/-0.02 h, 2.21+/-0.27 microg/mL, 2.68+/-0.19 h and 14.21+/-2.35 microg h/mL. The IM bioavailability was 96.35+/-17.23% and the in vitro protein binding of moxifloxacin ranged from 32-37%. Penetration of moxifloxacin from the blood into milk was rapid and extensive, and the moxifloxacin concentrations in milk exceeded those in plasma from 1h after administration. The kinetic values AUC(milk)/AUC(plasma) and C(maxmilk)/C(maxplasma) ratios indicated a wide penetration of moxifloxacin from the bloodstream to the mammary gland. The in vitro minimum inhibitory concentration (MIC) of moxifloxacin for Mannheimia haemolytica was found to be 0.035 microg/mL.

Toxicity and uptake of cyclic nitramine explosives in ryegrass Lolium perenne

Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (CL-20) are cyclic nitramines used as explosives. Their ecotoxicities have been characterized incompletely and little is known about their accumulation potential in soil organisms. We assessed the toxicity and uptake of these explosives in perennial ryegrass Lolium perenne L. exposed in a Sassafras sandy loam (SSL) or in a sandy soil (DRDC, CL-20 only) containing contrasting clay contents (11% and 0.3%, respectively). A 21-d exposure to RDX, HMX or CL-20 in either soil had no adverse effects on ryegrass growth. RDX and HMX were translocated to ryegrass shoots, with bioconcentration factors (BCF) of up to 15 and 11, respectively. In contrast, CL-20 was taken up by the roots (BCF up to 19) with no translocation to the shoots. These studies showed that RDX, HMX, and CL-20 can accumulate in plants and may potentially pose a risk of biomagnification across the food chain.

In vitro permeation characteristics of moxifloxacin from oil drops through excised goat, sheep, buffalo and rabbit corneas

The objective of present investigation was to study the in vitro permeation characteristics of moxifloxacin from oil drops through freshly excised goat, sheep, buffalo and rabbit corneas. Moxifloxacin, 0.043 to 0.048% (w/v) ophthalmic solutions with or without (0.5% v/v) benzyl alcohol were made in arachis, castor, cottonseed, olive, soybean, sunflower and sesame oils. Permeation studies were conducted by putting 1 ml oil formulation on cornea (0.50 cm2) fixed between donor and receptor compartments of an all glass modified Franz diffusion cell and measuring the drug permeated in receptor (containing 10 ml bicarbonate ringer, pH 7.4 at 37 degrees C under stirring) by spectrophotometry at 291 nm, after 120 min. Post permeation corneal hydration was measured to assess corneal damage. The study was designed with paired corneas i.e. one cornea of an animal received formulation without benzyl alcohol while the contralateral cornea received formulation with benzyl alcohol. Moxifloxacin ophthalmic solution in castor oil showed maximum permeation with all the corneas. Addition of benzyl alcohol, a preservative, to oil drops reduced permeation of moxifloxacin from each oil drop, with corneas of all the species. Partition experiments with moxifloxacin oil drops and phosphate buffer (pH 7.4) indicated higher partitioning of drug in the oil phase, in presence of benzyl alcohol. Thus results of permeation are consistent with the partition characteristics of drug between oil and aqueous phase. Corneal hydration obtained with all the formulations was between 75 to 80% indicating no corneal damage.

Rifampicin Reduces Plasma Concentrations of Moxifloxacin in Patients with Tuberculosis

BACKGROUND

The long duration of the current tuberculosis (TB) treatment is demanding and warrants the development of new drugs. Moxifloxacin shows promising results and may be combined with rifampicin to shorten the duration of TB treatment. Rifampicin induces the phase II metabolic enzymes that are involved in the biotransformation of moxifloxacin. Therefore, the interaction between rifampicin and moxifloxacin should be investigated.

PATIENTS AND METHODS

Nineteen Indonesian patients with pulmonary TB who were in the last month of their TB treatment completed a 1-arm, 2-period, fixed-order pharmacokinetic study. In phase 1 of the study, they received 400 mg of moxifloxacin every day for 5 days in addition to 450 mg of rifampicin and 600 mg of isoniazid 3 times per week. In phase 2 of the study, after a 1-month washout period, patients received moxifloxacin for another 5 days (without rifampicin and isoniazid). A 24-h pharmacokinetic curve for moxifloxacin was recorded on the last day of both study periods, and its pharmacokinetic parameters were evaluated for an interaction with rifampicin, using a bioequivalence approach.

RESULTS

Coadministration of moxifloxacin with rifampicin and isoniazid resulted in an almost uniform decrease in moxifloxacin exposure (in 18 of 19 patients). The geometric means for the ratio of phase 1 area under the curve to phase 2 area under the curve and for the ratio of phase 1 peak plasma concentration to phase 2 peak plasma concentration were 0.69 (90% confidence interval, 0.65-0.74) and 0.68 (90% confidence interval, 0.64-0.73), respectively. The median time to reach peak plasma concentration for moxifloxacin was prolonged from 1 h to 2.5 h when combined with rifampicin and isoniazid (P=.003).

CONCLUSIONS

Coadministration of moxifloxacin with intermittently administered rifampicin and isoniazid results in reduced moxifloxacin plasma concentrations, which is most likely the result of induced glucuronidation or sulphation by rifampicin. Further studies are warranted to evaluate the impact of the interaction on the outcome of TB treatment.

In vitro pharmacodynamics of moxifloxacin versus levofloxacin against 4 strains of Streptococcus pneumoniae: 1 wild type, 2 first-step parC mutants, and 1 pump mutant

Levofloxacin binds topoisomerase IV, whereas moxifloxacin preferentially binds DNA gyrase. Most 1st-step pneumococcal mutants have alterations in the parC gene of topoisomerase IV. Because of differential binding affinity, moxifloxacin may have superior activity against 1st-step mutants compared with levofloxacin. The purpose of this work was to compare rates and extent of bacterial killing of genetically characterized Streptococcus pneumoniae with moxifloxacin and levofloxacin. Four strains of S. pneumoniae were used: a wild type, 2 first-step parC mutants, and a pump mutant. Using an in vitro pharmacodynamic model run in duplicate, we exposed bacteria to unbound moxifloxacin and levofloxacin peaks of 2 and 4.5 mg/L, respectively, which emulated clinical dosing. Additional experiments were done in which the area under the curve (AUC)/MIC ratio of 1 agent was matched to the competing drug's clinical dose AUC/MIC ratio. Time kill curves were analyzed for rate and extent of bacterial kill and regrowth. Pre- and postexposure MIC and polymerase chain reaction (PCR) testing were done. Moxifloxacin and levofloxacin displayed similar rates and extent of bacterial kill for the wild type, efflux pump type, and parC mutant 27-1361B. Moxifloxacin initially achieved a faster rate of kill, regardless of the AUC/MIC ratio, against parC mutant 7362 (P < 0.05) but not an advantage in time to 3 log kill. Postexposure MIC values were elevated for strain 7362 in 2 moxifloxacin experiments and 1 levofloxacin experiment. Post-PCR analysis revealed new gyrA mutations for all 3 isolates. Both moxifloxacin and levofloxacin are effective against multiple strains of S. pneumoniae.

Perspectives on antibiotics for postoperative endophthalmitis prophylaxis: Potential role of moxifloxacin

To aid the cataract surgeon's understanding of rational approaches to antimicrobial prophylaxis and place the European Society of Cataract & Refractive Surgeons (ESCRS) postoperative endophthalmitis study in perspective, a review was conducted of published and unpublished data on intracameral antibiotic use during cataract surgery and the antimicrobial efficacy, pharmacodynamics, ocular penetration, and safety of moxifloxacin. The ESCRS-sponsored study of postoperative endophthalmitis prophylaxis reported rates of presumed infectious postoperative endophthalmitis of 0.07% with intracameral cefuroxime treatment and 0.34% in control groups. Postoperative endophthalmitis after cefuroxime use was mostly due to cefuroxime-resistant gram-positive bacteria. Intracameral cefuroxime also requires extemporaneous compounding, has short-term stability, and carries a risk for hypersensitivity. Moxifloxacin, a fourth-generation fluoroquinolone, has potent and rapid bactericidal activity against the most common gram-positive postoperative endophthalmitis pathogens, has excellent ocular penetration after topical administration, and is available in a self-preserved ophthalmic formulation that has been shown safe and effective in preventing endophthalmitis when administered intracamerally in an animal model. Available data suggest that the optimum antibiotic regimen and route of delivery for cataract surgery antimicrobial prophylaxis require further study. Moxifloxacin offers many theoretical advantages that make it an attractive first-line choice for topical use and of interest for intracameral administration.

Allometric scaling of marbofloxacin, moxifloxacin, danofloxacin and difloxacin pharmacokinetics: a retrospective analysis

The purpose of this study was to examine the allometric analyses of marbofloxacin, moxifloxacin, danofloxacin and difloxacin using pharmacokinetic data from the literature. The parameters of interest (half-life, clearance and volume of distribution) were correlated across species as a function of body weight using an allometric approach (Y = aWb). Results of the allometric analysis indicated similarity between clearance and volume of distribution as they relate to body weight for all drugs. The elimination half-life was independent of body mass for all fluoroquinolones except moxifloxacin. Results of the analysis suggest that allometric scaling can be used as a tool for predicting pharmacokinetic parameters for fluoroquinolones.

Levocetirizine does not prolong the QT/QTc interval in healthy subjects: results from a thorough QT study

OBJECTIVE

To conduct a thorough QT study of levocetirizine, a non-sedating antihistamine, in accordance with International Conference on Harmonisation (ICH) E14 guidance.

METHODS

The study was designed as a single-dose, placebo and positive-controlled, four-way crossover, randomised trial in which 52 healthy male and female subjects participated. Levocetirizine (5 and 30 mg) and placebo were administered double-blind, and the positive control, moxifloxacin (400 mg), was open-label. Electrocardiograms (ECGs) were obtained by continuous Holter monitoring at various time points (three per time point) during a 24-h period at baseline and after each treatment. The ECGs were read centrally in a blinded manner. QT intervals were corrected for heart rate using a gender- and study-specific correction (QTcSS) and Fridericia's correction (QTcF). The largest QTc time-matched and baseline-subtracted difference between each active drug and the placebo (largest delta delta QTcSS) was derived from a mixed-effect analysis of variance.

RESULTS

The one-sided 95% upper limits of the largest delta delta QTcSS for levocetirizine were 5.7 ms (5 mg) and 3.9 ms (30 mg), with mean estimates of 2.9 and 1.1 ms, respectively. Similar results were obtained for the delta delta QTcF data. Statistically, moxifloxacin significantly lengthened the QTcSS, with a one-sided 95% lower limit of the largest delta delta QTcSS of 10.5 ms and a mean estimate of 13.4 ms. There was no relationship between the measured delta QTcSS and the plasma concentration of levocetirizine, whereas a statistically significant linear relationship was observed with the plasma concentration of moxifloxacin [slope estimate 0.004 ms/(ng/mL); 95% confidence interval: 0.003-0.005].

CONCLUSIONS

Overall, the results of this thorough QT study indicate that the methodology of the trial was valid and sensitive enough to demonstrate the absence of effect of levocetirizine at both therapeutic (5 mg) and supra-therapeutic (30 mg) doses on cardiac repolarisation.

64Cu-Labeled Triphenylphosphonium and Triphenylarsonium Cations as Highly Tumor-Selective Imaging Agents

This report presents synthesis and evaluation of the 64Cu-labeled triphenylphosphonium (TPP) cations as new radiotracers for imaging tumors by positron emission tomography. Biodistribution properties of 64Cu-L1, 64Cu-L2, 64Cu-L3, and 99mTc-Sestamibi were evaluated in athymic nude mice bearing U87MG human glioma xenografts. The most striking difference is that 64Cu-L1, 64Cu-L2, and 64Cu-L3 have much lower heart uptake (<0.6% ID/g) than 99mTc-Sestamibi ( approximately 18% ID/g) at >30 min p.i. Their tumor/heart ratios increase steadily from approximately 1 at 5 min p.i. to approximately 5 at 120 min p.i. The tumor/heart ratio of 64Cu-L3 is approximately 40 times better than that of 99mTc-Sestamibi at 120 min postinjection. Results from in vitro assays show that 64Cu-L1 is able to localize in tumor mitochondria. The tumor is clearly visualized in the tumor-bearing mice administered with 64Cu-L1 as 30 min postinjection. The 64Cu-labeled TPP/TPA cations are very selective radiotracers that are able to provide the information of mitochondrial bioenergetic function in tumors by monitoring mitochondrial potential in a noninvasive fashion.

Comparison of the QT interval response during sinus and paced rhythm in conscious and anesthetized beagle dogs

INTRODUCTION

The aim of the present study was to compare sensitivity in detecting the drug-induced QT interval prolongation in three dog models: conscious telemetered at sinus rhythm and conscious and anesthetized dogs during atrial pacing. The test substances used represent different chemical classes with different pharmacological and pharmacokinetic profiles.

METHOD

Dofetilide and moxifloxacin were tested in all models, whereas cisapride and terfenadine were tested in the conscious telemetered and paced models. All substances were given as two consecutive 1.5-h intravenous infusions (infusions 1 and 2). The individual concentration-time courses of dofetilide, moxifloxacin, and cisapride were linked to the drug-induced effects on the QT interval and described with a pharmacokinetic-pharmacodynamic model to obtain an estimate of the unbound plasma concentrations at steady state that give a 10- and 20-ms drug-induced QT interval prolongation (CE10ms and CE20ms).

RESULTS

In the conscious telemetered, conscious paced, and anesthetized dog models, the mean CE10ms values were 1.4, 4.0, and 2.5 nM for dofetilide and 1300, 1800, and 12,200 nM for moxifloxacin. For cisapride, the CE10ms values were 8.0 and 4.4 nM in the conscious telemetered and conscious paced dog models. The drug-induced QT interval prolongation during the last 30 min of infusions 1 and 2 was comparable in the conscious models, but smaller in the anesthetized dog model. Terfenadine displayed a marked delay in onset of response, which could only be detected by the extended ECG recording.

DISCUSSION

All dog models investigated detected QT interval prolongation after administration of the investigated test substances with similar sensitivity, except for a lower sensitivity in the anesthetized dogs following moxifloxacin administration. The conscious telemetered dog model was favorable, mainly due to the extended continuous ECG recording, which facilitated detection and quantification of delayed temporal differences between systemic exposure and drug-induced QT interval prolongation.

A highly sensitive canine telemetry model for detection of QT interval prolongation: Studies with moxifloxacin, haloperidol and MK-499

INTRODUCTION

Preclinical evaluation of delayed ventricular repolarization manifests electrocardiographically as QT interval prolongation and is routinely used as an indicator of potential risk for pro-arrhythmia (potential to cause Torsades de Pointes) of novel human pharmaceuticals. In accordance with ICH S7A and S7B guidelines we evaluated the sensitivity and validity of the beagle dog telemetry (Integrated Telemetry Services (ITS)) model as a preclinical predictor of QT interval prolongation in humans.

METHODS

Cardiovascular monitoring was conducted for 2 h pre-dose and 24 h post-dosing with moxifloxacin (MOX), haloperidol (HAL), and MK-499, with a toxicokinetic (TK) evaluation in a separate group of dogs. In both cardiovascular and TK studies, MOX (0, 10, 30 and 100 mg/kg), HAL (0, 0.3, 1, 3 mg/kg) and MK-499 (0, 0.03, 0.3 and 3 mg/kg) were administered orally by gavage in 0.5% methylcellulose. Each dog received all 4 doses using a dose-escalation paradigm. Inherent variability of the model was assessed with administration of vehicle (0.5% methylcellulose) alone for 4 days.

RESULTS

Significant increases in QT(c) were evident with 10, 30 and 100 mg/kg of MOX (C(max)< or =40 microM), 0.3, 1 and 3 mg/kg of HAL (C(max)< or =0.36 microM) and 0.3 and 3 mg/kg of MK-499 (C(max)< or =825 nM) with peak increases of 45 (20%), 31 (13%), and 45 (19%) ms, respectively (p< or =0.05).

DISCUSSION

In conclusion, we have demonstrated that the ITS-telemetry beagle dog exhibits low inherent intra-animal variability and high sensitivity to detect small but significant increases in QT/QT(c) interval ( approximately 3-6%) with MOX, HAL and MK-499 in the same range of therapeutic plasma concentrations attained in humans. Therefore, this dog telemetry model should be considered an important preclinical predictor of QT prolongation of novel human pharmaceuticals.

Differential aqueous and vitreous concentrations of moxifloxacin and ofloxacin after topical administration one hour before vitrectomy

PURPOSE

To investigate the penetration of ofloxacin and moxifloxacin into the aqueous and vitreous after topical administration one hour before vitrectomy surgery.

DESIGN

Prospective, randomized, double-blind case series study.

METHODS

Twenty-seven patients undergoing vitrectomy were randomized to receive either topical ofloxacin 0.3% or moxifloxacin 0.5% every 10 minutes for one hour before surgery. Aqueous and vitreous samples were obtained and analyzed using high-performance liquidation chromatography.

RESULTS

The moxifloxacin aqueous (1.576 +/- 0.745 microg/ml) and vitreous (0.225 +/- 0.013 microg/ml) levels were significantly higher than the ofloxacin aqueous (0.816 +/- 0.504 microg/ml) (P = .0009) and vitreous (0.225 +/- 0.013 microg/ml) [P = .0054] levels, respectively. The mean moxifloxacin aqueous and vitreous levels exceeded the minimum inhibitory concentration for 90% of isolates (MIC(90)) for a wide variety of bacteria implicated in endophthalmitis. In contrast, the aqueous level of ofloxacin exceeded the MIC(90) of only a few organisms.

CONCLUSIONS

Moxifloxacin applied every 10 minutes during the hour before vitrectomy penetrated the eye significantly better than ofloxacin.

Pharmacodynamic assessment based on mutant prevention concentrations of fluoroquinolones to prevent the emergence of resistant mutants of Streptococcus pneumoniae

The objective of this study was to investigate the relationship between pharmacokinetic and pharmacodynamic parameters, on the basis of the mutant prevention concentration (MPC) concept, and the emergence of resistant mutants of Streptococcus pneumoniae to fluoroquinolone antibacterials. Some clinical isolates with various MIC and MPC values of moxifloxacin and levofloxacin were exposed under conditions simulating the time-concentration curves observed when moxifloxacin (400 or 80 mg, once a day) or levofloxacin (200 mg, twice a day) was orally administered by using an in vitro pharmacodynamic model. The decrease in susceptibility was evaluated by altering the population analysis profiles after moxifloxacin or levofloxacin treatment for 72 h. When the area under the concentration-time curve from 0 to 24 h (AUC(0-24))/MPC and peak concentration (C(max))/MPC were above 13.41 and 1.20, respectively, complete eradication occurred and no decrease in susceptibility was observed. On the other hand, when AUC(0-24)/MPC and C(max)/MPC were below 0.84 and 0.08, respectively, the susceptibility decreased. However, the time inside the mutant selective window and the time above the MPC did not show any correlation with the decrease in susceptibility. These results suggest that AUC(0-24)/MPC and C(max)/MPC are important parameters for predicting the emergence of resistant mutants and that higher values indicate greater effectiveness.

In vivo efficacy of moxifloxacin compared with cloxacillin and vancomycin in a Staphylococcus aureus rabbit arthritis experimental model

We investigated the efficacies of moxifloxacin, cloxacillin, and vancomycin in a rabbit model of Staphylococcus aureus arthritis. No significant difference between therapeutic regimens was observed after a 7-day treatment. Oral moxifloxacin could be a suitable alternative to standard parenteral therapy for S. aureus arthritis.

Dexamethasone as adjuvant therapy to moxifloxacin attenuates valve destruction in experimental aortic valve endocarditis due to Staphylococcus aureus

Although the beneficial effects of dexamethasone have frequently been investigated in various serious-infection settings, insufficient data on valve histology and cardiac function for infective endocarditis are available. The efficacy of moxifloxacin for the treatment of experimental aortic valve endocarditis due to methicillin-susceptible Staphylococcus aureus and the long-term effects of dexamethasone were evaluated in the current study. Sixty-eight rabbits were randomly assigned to four groups: A, B, C, and D. Group A consisted of 18 animals and functioned as a control group. Groups B and C consisted of 11 and 23 subjects, respectively, which received moxifloxacin for 5 days in a human-like pharmacokinetic simulation. Group D consisted of 16 animals that were administered moxifloxacin plus dexamethasone (0.25 mg/kg of body weight twice a day intravenously). The group B animals were sacrificed a day after the completion of treatment, and group C and D animals were sacrificed after 12 days in order to monitor any possible relapse and allow microbiological, histopathological, and echocardiographic evaluation of the long-term effects of glucocorticoids. No differences in survival, sterilization rates, or inflammatory infiltration and calcification of valve tissue were observed among the treated groups. However, the degrees of valve damage and collagenization were significantly worse, the fibroblast content was higher, and fractional shortening of the left ventricle fluctuated significantly in group C compared to group D (all groups, P < 0.05). We concluded that dexamethasone treatment for experimental S. aureus endocarditis attenuates valve destruction and preserves overall cardiac function without impeding the efficacy of moxifloxacin.

The influence of continuous venovenous haemodialysis on the pharmacokinetics of multiple oral moxifloxacin administration to patients with severe renal dysfunction

AIM

We investigated single dose and steady-state pharmacokinetics of moxifloxacin in eight venovenous haemodialysis patients.

METHODS

Plasma, dialysate and urine pharmacokinetic parameters for moxifloxacin and its main metabolites were calculated after single and multiple (7 days) dosing with 400 mg day(-1).

RESULTS

Moxifloxacin pharmacokinetics after a single dose and at steady state (multidose day 7) were comparable in patients with impaired renal function and healthy subjects (geometric mean/%CV AUC mg l(-1) h single dose 37.0/24.3 in haemodialysis patients vs. 29.8/22.6 in healthy subjects, 95% CI for ratio of haemodialysis patients to healthy subjects 99.34%, 154.60%; steady state 40.4/29.1 haemodialysis patients vs. 33.9/20.1 in healthy subjects, 95% CI for ratio of haemodialysis patients to healthy subjects 90/39%, 156.93%). In haemodialysis patients plasma concentrations of moxifloxacin at steady-state were elevated compared with those after a single 400 mg dose (AUC mg l(-1) h, geometric mean/%CV, 40.4/29.1) compared with 37.0/24.3; 95% CI for ratio of steady-state to single dose 87.29%, 136.52%, as were concentrations of metabolite M1 3.21/34.6 compared with 2.02/45.3, 95% CI for ratio of steady state to single dose 14.21%, 175.07%. Haemodialysis cleared about 9% of the dose as unchanged moxifloxacin.

CONCLUSIONS

No dose adjustments are required for venovenous haemodialysis patients on oral moxifloxacin therapy.

Effects of rifampin and multidrug resistance gene polymorphism on concentrations of moxifloxacin

Treatment regimens combining moxifloxacin and rifampin for drug-susceptible tuberculosis are being studied intensively. However, rifampin induces enzymes that transport and metabolize moxifloxacin. We evaluated the effect of rifampin and the human multidrug resistance gene (MDR1) C3435T polymorphisms (P-glycoprotein) on moxifloxacin pharmacokinetic parameters. This was a single-center, sequential design study with 16 volunteers in which sampling was performed after four daily oral doses of moxifloxacin (400 mg) and again after 10 days of combined rifampin (600 mg) and moxifloxacin. After daily coadministration of rifampin, the area under the concentration-time curve from 0 to 24 h (AUC(0-24)) for moxifloxacin decreased 27%. Average bioequivalence between moxifloxacin coadministered with rifampin and moxifloxacin alone was not demonstrated: the ratio of geometric means (RGM) of the moxifloxacin AUC(0-24) was 73.3 (90% confidence intervals [CI], 64.3, 83.5) (total P value, 0.87 for two one-sided t tests). Peak moxifloxacin concentrations, however, were equivalent: the RGM of the maximum concentration of the drug in serum was 93.6 (90% CI, 80.2, 109.3) (total P value, 0.049). Concentrations of the sulfate conjugate metabolite of moxifloxacin were increased twofold following rifampin coadministration (AUC(0-24), 1.29 versus 2.79 mug.h/ml). Concomitant rifampin administration resulted in a 27% decrease in the mean moxifloxacin AUC(0-24) and a marked increase in the AUC(0-24) of the microbiologically inactive M1 metabolite. Additional studies are required to understand the clinical significance of the moxifloxacin-rifampin interaction.

In Vitro Efficacy and Pharmacodynamic Indices for Antibiotics against Coagulase-Negative Staphylococcus Endophthalmitis Isolates

PURPOSE

To compare pharmacodynamic indices and minimal inhibitory concentrations for vancomycin, gatifloxacin, moxifloxacin, linezolid, and combined quinupristin and dalfopristin for historic and current human coagulase-negative staphylococcus (CoNS) endophthalmitis isolates.

DESIGN

Experimental study.

PARTICIPANTS

Fifty-nine CoNS endophthalmitis isolates retrieved from patients at the Bascom Palmer Eye Institute from 1993 through 2006.

METHODS

Coagulase-negative staphylococcal endophthalmitis isolates were recovered from the microbiology specimen bank, rehydrated, and processed for susceptibility testing using standard microbiological protocols. E tests were used to determine and compare mean inhibitory concentration for 50% of isolates (MIC50) and mean inhibitory concentration for 90% of isolates (MIC90) values. Peak concentration (C(max)) was defined as the maximum attainable aqueous concentration using topical or oral therapy, or both. The MIC50 and MIC90 values for each antibiotic are the minimum concentrations that inhibit 50% and 90% of CoNS endophthalmitis isolates, respectively. Significance was determined by the McNemar test. Pharmacodynamic indices (C(max)/MIC) were calculated using determined MIC values and published intraocular drug concentrations for topical and oral dosing. The pharmacodynamic index was defined as the achievable aqueous humor concentration of an antibiotic divided by the concentration of the antibiotic required to inhibit a specified percentage of microbiologic isolates.

MAIN OUTCOME MEASURES

Pharmacodynamic indices for new and conventional antibiotics.

RESULTS

General in vitro susceptibility patterns in descending order were vancomycin (100%), linezolid (100%), quinupristin and dalfopristin (98%), moxifloxacin (48%), and gatifloxacin (47%). The corresponding MIC50 and MIC90 values were vancomycin, 2 microg/ml and 3 microg/ml, respectively; linezolid, 1 microg/ml and 4 microg/ml; quinupristin and dalfopristin, 0.25 microg/ml and 0.5 microg/ml; moxifloxacin, 0.75 microg/ml and > or =32 microg/ml; and gatifloxacin, 2 microg/ml and > or =32 microg/ml. Pharmacokinetic indices (C(max)/MIC90) for topical dosing were all <1. There was a significant difference in the percent of isolates susceptible to combined quinupristin and dalfopristin, vancomycin, and linezolid compared with moxifloxacin and gatifloxacin. There was no statistical significance in CoNS susceptibility between the tested fluoroquinolones.

CONCLUSIONS

Vancomycin, linezolid, and combined quinupristin and dalfopristin were more effective in vitro than fluoroquinolones against CoNS in the current study. Reported aqueous concentrations of the antibiotics used in this study failed to provide adequate coverage for 90% of the CoNS endophthalmitis isolates.

Cross-over assessment of serum bactericidal activity of moxifloxacin and levofloxacin versus penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae in healthy volunteers

We compared the serum bactericidal activity (SBA) of moxifloxacin and levofloxacin against penicillin-susceptible and penicillin-resistant Streptococcus pneumoniae in 12 healthy volunteers. Each subject received 3 days of oral moxifloxacin 400 mg daily and levofloxacin 750 mg daily, respectively, with a 2- to 4-week washout period between regimens. Blood was drawn at 6 time points after the third dose of each antibiotic. Mean serum bactericidal titers (MSBTRs) for moxifloxacin were 4-fold higher than the mean titers for levofloxacin at each time point. For each drug, MSBTRs at each time point were the same or within one 2-fold dilution when analyzed according to the penicillin susceptibility of the strains or the sex of the subjects. The difference in SBA of the 2 drugs may have implications for the emergence of resistance and clinical outcome.

Pharmacokinetics and milk penetration of moxifloxacin after intramuscular administration to lactating goats

The pharmacokinetics of moxifloxacin was studied following intramuscular administration of 5mg/kg to healthy lactating goats (n=6). Moxifloxacin concentrations were determined by high performance liquid chromatography assay with fluorescence detection. The moxifloxacin plasma concentration versus time data could best be described by a one-compartment model. The plasma moxifloxacin clearance (Cl) was mean standard deviation (+/-SD) 0.49+/-0.14 L/h kg. The apparent volume of distribution (V(z)) was 0.83+/-0.20 L/kg. The terminal half-life (t(1/2 lambda z)) was 1.31+/-0.64 h. Moxifloxacin penetration from blood to milk was rapid and the high AUC(milk)/AUC(plasma) and C(max-milk)/C(max-plasma) ratios reached indicated a good penetration of moxifloxacin into the milk.

Thorough QT Study with Recommended and Supratherapeutic Doses of Tolterodine

The objective of our study was to determine the QTc effects of tolterodine. A crossover-design thorough QT study of recommended (2 mg twice daily) and supratherapeutic (4 mg twice daily) doses of tolterodine, moxifloxacin (400 mg once daily), and placebo was performed. Electrocardiograms (ECGs) and pharmacokinetic samples were obtained on days 1-4; time-matched baseline ECGs were taken on day 0. Mean placebo-subtracted change from baseline Fridericia-corrected QT (QTcF) during peak drug exposure on day 4 was the primary end point. Mean QTcF prolongation of moxifloxacin was 8.9 ms (machine-read) and 19.3 ms (manual-read). At recommended and supratherapeutic tolterodine doses, mean QTcF prolongation was 1.2 and 5.6 ms (machine-read), respectively, and 5.0 and 11.8 ms (manual-read), respectively. The QTc effect of tolterodine was lower than moxifloxacin. No subject receiving tolterodine exceeded the clinically relevant thresholds of 500 ms absolute QTc or 60 ms change from baseline. In conclusion, tolterodine does not have a clinically significant effect on QT interval.

Vitreal penetration of oral and topical moxifloxacin in humans

PURPOSE

To investigate the vitreal penetration of moxifloxacin after oral and topical administration.

DESIGN

Prospective, nonrandomized clinical trial.

METHODS

Twenty-four patients were assigned to one of four dosing groups: control (n = 3), which received no medication; oral (n = 8), which received two 400 mg oral doses of moxifloxacin before surgery; topical (n = 8), which received one drop of topical moxifloxacin 0.5% every 15 minutes for the hour preceding surgery; and combined (n = 5), which received two 400 mg oral doses and one drop of topical moxifloxacin 0.5% hourly for 18 hours prior to surgery. Vitreous samples were obtained and analyzed.

RESULTS

Control, below quantifiable levels; oral, 1.553 +/- 0.33 microg/ml; topical, 0.027 microg/ml; and combined, 2.219 +/- 0.71 microg/ml. One topical patient developed postoperative endophthalmitis.

CONCLUSIONS

In contrast to topical moxifloxacin, oral moxifloxacin achieves significant levels in the noninflamed human vitreous.