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.

In vivo metabolic investigation of moxifloxacin using liquid chromatography/electrospray ionization tandem mass spectrometry in combination with online hydrogen/deuterium exchange experiments

RATIONALE

Tuberculosis is a leading cause of death from an infectious disease and moxifloxacin is an effective drug as compared to other fluoroquinolones. To date only two metabolites of the drug are known. Therefore, the present study on characterization of hitherto unknown in vivo metabolites of moxifloxacin using liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) is undertaken.

METHODS

In vivo metabolites of moxifloxacin have been identified and characterized by using LC/ESI-MS/MS in combination with an online hydrogen/deuterium (H/D) exchange technique. To identify in vivo metabolites, blood, urine and faeces samples were collected after oral administration of moxifloxacin to Sprague-Dawley rats. The samples were prepared using an optimized sample preparation approach involving protein precipitation, liquid-liquid extraction followed by solid-phase extraction and LC/MS/MS analysis.

RESULTS

A total of nine phase I and ten phase II metabolites of moxifloxacin have been identified in urine samples including N-sulphated, glucuronide and hydroxylated metabolites which are also observed in plasma samples. In faeces samples, only the N-sulphated metabolite is observed. The structures of metabolites have been elucidated based on fragmentation patterns, accurate mass measurements and online H/D exchange LC/MS/MS experiments. Online H/D exchange experiments are used to support the identification and structural characterization of drug metabolites.

CONCLUSIONS

A total of 19 in vivo metabolites of moxifloxacin have been characterized using LC/ESI-MS/MS in combination with accurate mass measurements and online H/D exchange experiments. The main phase I metabolites of moxifloxacin are hydroxylated, decarbonylated, desmethylated and desmethylhydroxylated metabolites which undergo subsequent phase II glucuronidation pathways.

Spectrofluorimetric study of the interaction between europium(III) and moxifloxacin in micellar solution and its analytical application

A sensitive spectrofluorimetric method has been developed for the determination of moxifloxacin (MOX) using europium(III)-MOX complex as a fluorescence probe in the presence of an anionic surfactant, sodium dodecyl benzene sulfonate (SDBS). The fluorescence (FL) intensity of Eu(3+) was enhanced by complexation with MOX at 614 nm after excitation at 373 nm. The FL intensity of the Eu(3+)-MOX complex was significantly intensified in the presence of SDBS. Under the optimum conditions, it was found that the enhanced FL intensity of the system showed a good linear relationship with the concentration of MOX over the range of 1.8 × 10(-11)-7.3 × 10(-9) g mL(-1) with a correlation coefficient of 0.9998. The limit of detection of MOX was found to be 2.8 × 10(-12) g mL(-1) with relative standard deviation (RSD) of 1.25% for 5 replicate determination of 1.5 × 10(-8) g mL(-1) MOX. The proposed method is simple, offers higher sensitivity with wide linear range and can be successfully applied to determine MOX in pharmaceutical and biological samples with good reproducibility. The luminescence mechanism is also discussed in detail with ultraviolet absorption spectra.

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.

Polypyrrole solid phase microextraction: A new approach to rapid sample preparation for the monitoring of antibiotic drugs

Simple or even rapid bioanalytical methods are rare, since they generally involve complicated, time-consuming sample preparation from the biological matrices like LLE or SPE. SPME provides a promising approach to overcome these limitations. The full potential of this innovative technique for medical diagnostics, pharmacotherapy or biochemistry has not been tapped yet. In-house manufactured SPME probes with polypyrrole (PPy) coating were evaluated using three antibiotics of high clinical relevance - linezolid, daptomycin, and moxifloxacin - from PBS, plasma, and whole blood. The PPy coating was characterised by scanning electron microscopy. Influences of pH, inorganic salt, and blood anticoagulants were studied for optimum performance. Extraction yields were determined from stagnant media as well as re-circulating human blood using the heart-and-lung machine model system. The PPy-SPME fibres showed high extraction yields, particularly regarding linezolid. The reproducibility of the method was optimised to achieve RSDs of 9% or 17% and 7% for SPME from stagnant or re-circulating blood using fresh and re-used fibres, respectively. The PPy-SPME approach was demonstrated to meet the requirements of therapeutic monitoring of the drugs tested, even from re-circulating blood at physiological flow rates. SPME represents a rapid and simple dual-step procedure with potency to significantly reduce the effort and expenditure of complicated sample preparations in biomedical analysis.

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.

Liquid chromatography-tandem electrospray mass spectrometry method for determination of serial chiral novel anticholinergic compounds of phencynonate in rat plasma

A sensitive and selective liquid chromatographic-tandem mass spectrometric (LC-MS/MS) method was developed for the determination of serial chiral novel anticholinergic compounds of phencynonate in rat plasma. After a simple protein-precipitation using methanol, the post-treatment samples were separated on a CAPCELL UG120 column with a mobile phase of a mixture of methanol and water (35:65) containing 0.1% formic acid. The serial chiral analytes and internal standard (IS) were all detected by the use of selected reaction monitoring mode (SRM). The method of all serial chiral analytes developed was validated in rat plasma with a daily working range of 0.5-100 ng/ml with correlation coefficient, R(2) > or = 0.99 and a sensitivity of 0.5 ng/ml as lower limit of quantification, respectively. This method was fully validated for the accuracy, precision and stability studies for all serial chiral analytes. The method proved to be accurate and specific, and was applied to the pharmacokinetic study of serial chiral novel anticholinergic compounds of phencynonate in rat plasma.

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.

High-performance liquid chromatography assay for moxifloxacin: Pharmacokinetics in human plasma

A sensitive high-performance liquid chromatographic (HPLC) method for the determination of moxifloxacin in human plasma using fluorescence detection was developed. The drug and an internal standard (norfloxacin) were subjected to precolumn derivatization with 4-chloro-7-nitrobenzodioxazole (NBD-CI). The chromatographic separation was achieved by HPLC using a mixture of acetonitrile-10 mM orthophosphoric acid (pH 2.5) (80:20, v/v) as the mobile phase with isocratically system, a C18 column. The derivative is highly fluorescent at 537 nm, being excited at 464 nm. The linear and reproducible calibration curve over the range was 15-2700 ng/mL of moxifloxacin in human plasma. The limits of detection and quantitation were 6 and 15 ng/mL, respectively. This method was applied in pharmacokinetic studies moxifloxacin preparations in healthy volunteers.

Optimization and validation of the direct HPLC method for the determination of moxifloxacin in plasma

Moxifloxacin (1-cyclopropyl-6-fluoro-1,4-dihydro-8-methoxy-7-[(4aS,7aS)-octahydro-6H-pyrrolo-[3,4-b]pyridin-6-yl]-4-oxo-3-quinolinecarboxylic acid hydrochloride) is new, fourth generation fluoroquinolone with broaden spectrum of antibacterial activity. In the present work simple and rapid RP-HPLC method for the direct determination of moxifloxacin in human plasma is described. Separation of moxifloxacin from plasma components was achieved on Supelco LC-Hisep shielded hydrophobic phase column. The mobile phase consisted of acetonitrile and 0.25mol/dm(3) Na(3)PO(4) (pH 3) in a volume percent ratio (5:95, v/v) and was delivered at a rate of 1mL/min. Fluorescence detection was employed with excitation at 290nm and emission at 500nm. Ofloxacin was used as internal standard and sodium dodecylsulfate solution was used as a displacing agent. Sample preparation was simplified and involved only addition of displacing agent and internal standard and dilution with water. The separation conditions were optimized by the response surface method in two factor space, i.e. the dependence of the retention time on volume percent of acetonitrile and on pH of aqueous phase was optimized. The method was fully validated and validation parameters were: linearity range 3-1300microg/L; correlation coefficient, 0.99986; mean recovery, 92.5%; limit of quantification, 3.0microg/L and limit of detection, 1.0microg/L. Method was applied for the determination of moxifloxacin in human plasma after single or repeated oral doses of 400mg Avelox tablets. The proposed method proved to be rapid and accurate and can be successfully used in pharmacokinetic studies and routine clinical practice.

Penetration of moxifloxacin into sternal bone of patients undergoing routine cardiopulmonary bypass surgery

This study investigated plasma and bone concentrations of moxifloxacin following a single intravenous dose of 400mg to consider its potential role in the treatment of osteomyelitis. Eight patients who underwent routine cardiopulmonary bypass surgery were enrolled in the study. Plasma and bone samples were collected 2h and 5h after the end of infusion. High performance liquid chromatography was used for the determination of moxifloxacin concentrations. Mean plasma concentrations were 3.36 microg/mL and 2.93 microg/mL at 2h and 5h after the end of infusion. The concentrations in the body and manubrium of the sternal bone were 1.65 microg/g and 1.64 microg/g at 2h and 1.4 microg/g and 1.45 microg/g at 5h, respectively. Moxifloxacin showed good penetration into bone and could be considered for the treatment of osteomyelitis.

Pharmacokinetics and milk penetration of moxifloxacin after intravenous and subcutaneous administration to lactating goats

The pharmacokinetics of moxifloxacin was studied following intravenous (IV) and subcutaneous (SC) administration of 5 mg/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 after IV administration could best be described by a two compartment open model. The disposition of SC administered moxifloxacin was best described by a one-compartment model. The plasma moxifloxacin clearance (Cl) for the IV route was 0.43 +/- 0.02 L/kg (mean +/- SE). The steady-state volume of distribution (Vss) was 0.79 +/- 0.08 L/kg. The terminal half-life (t1/2lambdaz) was 1.94 +/- 0.41 and 2.98 +/- 0.48 h after IV and SC administration, respectively. The absolute bioavailability was 96.87 +/- 10.27% after SC administration. Moxifloxacin penetration from blood to milk was quick for both routes of administration and the high AUCmilk/AUCplasma and Cmax-milk/Cmax-plasma ratios reached indicated a wide penetration of moxifloxacin into the milk. From these data, it appears that a 5 mg/kg SC dose of moxifloxacin would be effective in lactating goats against bacterial isolates with MIC < or = 0.20 microg/mL in plasma and MIC < or = 0.40 microg/mL in milk.

Penetration of moxifloxacin into the human pancreas following a single intravenous or oral dose

OBJECTIVES

Failure to prevent secondary infectious complications in acute necrotizing pancreatitis (ANP) is attributable in part to the limited penetration of antimicrobial drugs. As newer quinolones are particularly attractive owing to their antimicrobial activity, for the first time we studied the penetration of moxifloxacin into pancreatic tissue in patients.

PATIENTS AND METHODS

In this prospective, non-comparative clinical trial, 60 patients undergoing elective pancreas resection received a single oral or intravenous (iv) dose of 400 mg moxifloxacin for perioperative antimicrobial prophylaxis. The concentration of moxifloxacin was measured in samples taken from blood and from pancreatic tissue at the beginning and at the end of resection.

RESULTS

Mean moxifloxacin concentrations in pancreatic tissue following iv or oral administration were 3.1+/-0.9 and 2.7+/-1.4 mg/kg at 3-3.7 h post-dose (first sampling) and 3.6+/-1.5 and 3.1+/-1.8 mg/kg at 4.3-5.3 h post-dose (second sampling), respectively. Corresponding mean plasma concentrations of moxifloxacin were 1.8+/-0.5 and 1.2+/-0.6 mg/L (first sampling) and 1.5+/-0.4 and 1.0+/-0.5 mg/L (second sampling), respectively. From first to second sampling, the mean tissue-to-plasma ratios varied from 1.8+/-0.6 to 2.6+/-1.2 (iv) and from 2.4+/-0.8 to 3.1+/-1.2 (oral). Pancreatic tissue concentrations of moxifloxacin exceeded the MIC90 for the relevant pathogens covered by moxifloxacin for at least 5 h after dosing.

CONCLUSIONS

Moxifloxacin has been demonstrated to penetrate efficiently into human pancreatic tissue following iv or oral administration. From a pharmacological perspective, moxifloxacin appears to be promising for prophylaxis and treatment of local pancreas infections. Whether it is beneficial in the prevention and therapy of infectious complications in patients with ANP should be investigated in a controlled clinical trial.

Pharmacodynamics of moxifloxacin and levofloxacin against Streptococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli: simulation of human plasma concentrations after intravenous dosage in an in vitro kinetic model

OBJECTIVES

To compare in an in vitro kinetic model the pharmacodynamics of moxifloxacin and levofloxacin with a concentration-time profile simulating the human free non-protein bound concentrations of 400 mg moxifloxacin intravenous (iv) once daily, 500 mg levofloxacin iv once daily and 750 mg levofloxacin iv once daily against strains of Streptococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae and Escherichia coli with variable susceptibility to fluoroquinolones.

METHODS

The strains used in the study included S. pneumoniae ATCC 6306 (native strain), S. pneumoniae 19397 (double mutation; gyrA and parC), S. pneumoniae 4241 (single mutation; parC), S. aureus ATCC 13709 (native strain), S. aureus MB5 (single mutation; gyrA), E. coli M12 (single mutation; gyrA), E. coli ATCC 25922 (native strain) and K. pneumoniae ATCC 29655 (native strain). The strains were exposed to moxifloxacin and levofloxacin in an in vitro kinetic model simulating the free human serum concentration-time profile of moxifloxacin 400 mg once daily, levofloxacin 500 mg once daily and 750 mg once daily. Repeated samples were taken regularly during 24 h and viable counts were carried out.

RESULTS AND CONCLUSIONS

A correlation was seen between both the area under the serum concentration curve and MIC (AUC/MIC) and the peak concentration/MIC (Cmax/MIC) versus area under the bactericidal killing curve (AUBKC) or Deltalog0-24 cfu/mL. Compiling all data, an AUC/MIC of approximately 100 and a Cmax/MIC of 10 gave a maximal bactericidal effect for both levofloxacin and moxifloxacin. In accordance with the results from others, our study indicated that a lower AUC/MIC was needed for S. pneumoniae in comparison with the Gram-negative bacteria studied. Moxifloxacin yielded higher AUC/MIC and Cmax/MIC against the investigated Gram-positive bacteria in comparison with levofloxacin 500 mg once daily and 750 mg once daily.

Novel conjugate of moxifloxacin and carboxymethylated glucan with enhanced activity against Mycobacterium tuberculosis

Mycobacterium tuberculosis is an intracellular pathogen that persists within macrophages of the human host. One approach to improving the treatment of tuberculosis (TB) is the targeted delivery of antibiotics to macrophages using ligands to macrophage receptors. The moxifloxacin-conjugated dansylated carboxymethylglucan (M-DCMG) conjugate was prepared by chemically linking dansylcadaverine (D) and moxifloxacin (M) to carboxymethylglucan (CMG), a known ligand of macrophage scavenger receptors. The targeted delivery to macrophages and the antituberculosis activity of the conjugate M-DCMG were studied in vitro and in vivo. Using fluorescence microscopy, fluorimetry, and the J774 macrophage cell line, M-DCMG was shown to accumulate in macrophages through scavenger receptors in a dose-dependent (1 to 50 microg/ml) manner. After intravenous administration of M-DCMG into C57BL/6 mice, the fluorescent conjugate was concentrated in the macrophages of the lungs and spleen. Analyses of the pharmacokinetics of the conjugate demonstrated that M-DCMG was more rapidly accumulated and more persistent in tissues than free moxifloxacin. Importantly, therapeutic studies of mycobacterial growth in C57BL/6 mice showed that the M-DCMG conjugate was significantly more potent than free moxifloxacin.

Pharmacokinetics and peritoneal penetration of moxifloxacin in peritonitis

OBJECTIVES

To investigate the penetration of moxifloxacin into peritoneal exudate in patients with complicated intra-abdominal infections (cIAIs).

PATIENTS AND METHODS

Patients (n = 10) with evidence of peritonitis who required surgery with drainage of the abdominal cavity received a single intravenous infusion of moxifloxacin, 400 mg, over 1 h. Plasma and peritoneal exudate samples were obtained over 24 h, and moxifloxacin concentrations were measured by HPLC with fluorescence detection.

RESULTS

Plasma moxifloxacin concentrations decreased from a geometric mean of 3.61 mg/L at 1 h to 0.36 mg/L at 24 h. Concentrations in peritoneal exudate were highest 2 h after the start of the infusion, reaching a geometric mean of 3.32 mg/L, and declined to a geometric mean of 0.69 mg/L at 24 h. The exudate/plasma concentration ratio rose from 1.45 at 2 h to 1.91 at 24 h; the 95% confidence intervals for the ratio excluded unity at all time points, suggesting that moxifloxacin penetrates and accumulates in peritoneal exudate. The area under the concentration-time curve (AUC) tended to be greater in exudate; the time to peak concentrations (T(max)) was longer in exudate than in plasma, as were half-life and mean residence time (MRT).

CONCLUSIONS

Following intravenous administration, moxifloxacin penetrated peritoneal exudate in patients with peritonitis, achieving and maintaining concentrations that exceed the MICs for pathogens commonly isolated in cIAIs. These findings support the clinical use of moxifloxacin as treatment for cIAIs.

Correlation between brain/plasma ratios and efficacy in neuropathic pain models of selective metabotropic glutamate receptor 1 antagonists

We have discovered a novel, potent, and selective triazafluorenone series of metabotropic glutamate receptor 1 (mGluR1) antagonists with efficacy in various rat pain models. Pharmacokinetic and pharmacodynamic profiles of these triazafluorenone analogs revealed that brain/plasma ratios of these mGluR1 antagonists were important to achieve efficacy in neuropathic pain models. This correlation could be used to guide our in vivo SAR (structure-activity relationship) modification. For example, compound 4a has a brain/plasma ratio of 0.34, demonstrating only moderate efficacy in neuropathic pain models. On the other hand, antagonist 4b with a brain/plasma ratio of 2.70 was fully efficacious in neuropathic pain models.

Pharmacodynamics of moxifloxacin and levofloxacin simulating human serum and lung concentrations

Fluoroquinolones are known to penetrate well into the infectious foci such as lung mucosa, epithelial lining fluid and alveolar macrophages achieving higher target site concentrations than the corresponding serum levels. In order to integrate the in vitro antibacterial activity and pharmacokinetics of moxifloxacin and levofloxacin, their bactericidal efficacy was assessed by simulating human serum and lung tissue concentrations using Streptococcus pneumoniae, Staphylococcus aureus and Klebsiella pneumoniae as indicator organisms. The bacteria were exposed to fluctuating moxifloxacin and levofloxacin concentrations simulating the drug levels in serum, lung mucosa, epithelial lining fluid and alveolar macrophages. The following parameters were deduced from the kill curves: area under the bactericidal kill curve normalized to the initial inoculum (AUBKC norm), the time needed to reduce the inoculum by 3 log(10) titers, and the initial bactericidal activity. In general, all these three parameters were for all the bacterial isolates having been exposed to moxifloxacin concentration dependent. In contrast, beyond a levofloxacin concentration of optimal bactericidal effect, higher drug concentrations did not further augment the bactericidal activity of levofloxacin. These data demonstrate that not all fluoroquinolones share the same pharmacodynamic targets needed to maximize their antibacterial effect.

Validation of a levofloxacin HPLC assay in plasma and dialysate for pharmacokinetic studies

An HPLC method with fluorescence detection suitable for routine determination of levofloxacin in plasma and dialysate has been validated. Sample preparation was assured by one-step protein precipitation for plasma or direct injection of the dialysate solution, respectively. Separation occurred on an YMC Pro C18 RP column (150 mm x 2 mm) with an acidic binary gradient mobile phase and detection at excitation and emission wavelengths of 296 and 504 nm. The assay was linear between 0.1 and 6 microg/ml for plasma and 0.1 and 5 microg/ml for dialysate with intra- and inter-day precision and accuracy lower than 10%. No degradation of levofloxacin was observed under the applied conditions for both matrices. The method was successfully applied to an in vitro pharmacokinetic study and patient samples as well.

A pharmacodynamic approach to antimicrobial activity in serum and epithelial lining fluid against in vivo-selected Streptococcus pneumoniae mutants and association with clinical failure in pneumonia

OBJECTIVES

Emergence of resistance may be prevented by killing both the parental infecting strain and subsequent less susceptible step-mutants. The present study analyses eradication and resistance selection in Streptococcus pneumoniae with moxifloxacin, levofloxacin and azithromycin, using a parental serotype 3 clinical strain (strain A) and its correspondent step-mutant derivatives resistant to these antibiotics (B, C, D), which were selected in vivo in a patient with pneumonia.

METHODS

Moxifloxacin, levofloxacin and azithromycin MICs were 1, 2 and 0.5 mg/L for the parental strain; 4, 16 and 4 mg/L for isolate B; and 4, 16 and >128 mg/L for isolates C and D, respectively. A pharmacokinetic computerized device was used to simulate serum and epithelial lining fluid (ELF) concentrations. Initial inoculum was approximately 10(8) cfu/mL. Population analysis profiles were performed using plates with increasing antimicrobial concentrations.

RESULTS

In ELF simulations, moxifloxacin showed a bactericidal pattern against all isolates with a minority (approximately 100 cfu/mL) of the surviving population (isolates B, C and D) growing on plates with moxifloxacin concentrations just above those in ELF. Levofloxacin and azithromycin showed a bactericidal pattern only against isolate A, with the whole population of isolates B, C and D growing on plates with levofloxacin concentrations higher (16-64 mg/L) than those in ELF and in plates with azithromycin concentrations as high as 2048 mg/L (for isolates C and D).

CONCLUSIONS

Antimicrobial activity in pulmonary tissue against possible emerging resistant mutants during pneumonia treatment may prevent failures more than the solely activity against the S. pneumoniae parental infecting strain.

Determination of the Newer Quinolones Levofloxacin and Moxifloxacin in Plasma by High-Performance Liquid Chromatography with Fluorescence Detection

A simple, accurate, sensitive, and precise reversed-phase (RP) high-performance liquid chromatographic (HPLC) method with fluorescence detection allowing the sensitive and specific quantitation of the newer fluoroquinolones levofloxacin and moxifloxacin is described. Moxifloxacin is used as the internal standard for the determination of levofloxacin and vice versa. A single-step liquid-liquid extraction from human plasma is sufficient for both quinolones. The method is linear from 0.1 to 15 microg/mL and 0.2 to 7 microg/mL for levofloxacin and moxifloxacin, respectively, covering the clinically relevant plasma concentration range. The limits of quantitation are 0.05 microg/mL (levofloxacin) and 0.2 microg/mL (moxifloxacin). The method is successfully applied to plasma drug level monitoring in a volunteer receiving single therapeutic doses of levofloxacin or moxifloxacin at two different occasions.

Penetration of moxifloxacin into bone in patients undergoing total knee arthroplasty

OBJECTIVES

To investigate plasma and bone moxifloxacin concentrations following oral administration of a single or double dose of the drug, in order to consider its potential role in the treatment of osteomyelitis.

PATIENTS AND METHODS

Thirty consecutive patients undergoing total knee arthroplasty were recruited. Three groups, of ten patients each, were formed: group A received moxifloxacin 400 mg orally 2 h (range 1.5-2.5) preoperatively, group B received moxifloxacin 400 mg orally 4 h (range 3.5-4.5) preoperatively and group C received moxifloxacin 400 mg orally 14 h preoperatively, followed by a second dose 2 h (range 1.5-2.5) preoperatively. During surgery, at the time of bone removal, a blood sample and aliquots of cortical and cancellous bone were collected and moxifloxacin concentrations were measured by HPLC.

RESULTS

Mean plasma, cancellous bone and cortical bone concentrations were, respectively: 3.45, 1.89 and 1.43 mg/L for group A; 3.73, 1.81 and 1.56 mg/L for group B; and 6.26, 2.97 and 2.54 mg/L for group C.

CONCLUSIONS

These data show a good penetration of moxifloxacin into both cancellous and cortical bone, with concentrations, after double dosing, exceeding the MIC90 for most pathogens involved in osteomyelitis and the clinic susceptibility breakpoint for Mycobacterium tuberculosis.

Quantitative analysis of Variolin analog (PM01218) in mouse and rat plasma by high-performance liquid chromatography/electrospray ionization tandem mass spectrometry

PM01218 is a novel marine-derived alkaloid and has shown potent growth inhibitory activity against several human cancer cell lines. A rapid and sensitive high performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) method was developed and validated to quantify PM01218 in mouse and rat plasma. The lower limit of quantitation (LLOQ) was 0.05 ng/mL. The calibration curve was linear from 0.05 to 100 ng/mL (R(2)>0.999). The assay was specifically based on the multiple reaction monitoring (MRM) transitions at m/z 278.4-->184.2, no endogenous material interfaced with the analysis of PM01218 and its internal standard from blank mouse and rat plasma. The mean intra- and inter-day assay accuracy remained below 15 and 8%, respectively, for all calibration standards and QC samples. The intra- and inter-day assay precision was less than 12.8 and 8.5% for all QC levels, respectively. The utility of the assay was demonstrated by pharmacokinetics studies of i.v. (bolus) PM01218 on SD rats.

QT prolongation and proarrhythmia by moxifloxacin: concordance of preclinical models in relation to clinical outcome

Moxifloxacin, a fluoroquinolone antibiotic associated with QT prolongation, has been recommended as a positive control by regulatory authorities to evaluate the sensitivity of both clinical and preclinical studies to detect small but significant increases in QT interval measurements. In this study, we investigated effects of moxifloxacin on the hERG current in HEK-293 cells, electrocardiograms in conscious telemetered dogs, and repolarization parameters and arrhythmogenic potentials in the arterially perfused rabbit ventricular wedge model. Moxifloxacin inhibited the hERG current with an IC50 of 35.7 microM. In conscious telemetered dogs, moxifloxacin significantly prolonged QTc at 30 and 90 mg kg(-1), with mean serum Cmax of 8.52 and 22.3 microg ml(-1), respectively. In the wedge preparation, moxifloxacin produced a concentration-dependent prolongation of the action potential duration, QT interval, and the time between peak and end of the T wave, an indicator for transmural dispersion of repolarization. Phase 2 early after-depolarizations were observed in one of five experiments at 30 microM and five of five experiments at 100 microM. The arrhythmogenic potential was also concentration-dependent, and 100 microM ( approximately 18-fold above the typical unbound Cmax exposure in clinical usage) appeared to have a high risk of inducing torsade de pointes (TdP). Our data indicated a good correlation among the concentration-response relationships in the three preclinical models and with the available clinical data. The lack of TdP report by moxifloxacin in patients without other risk factors might be attributable to its well-behaved pharmacokinetic profile and other dose-limiting effects.

Liquid chromatography–tandem mass spectrometry method for determination of phencynonate in rat blood and urine

A sensitive and specific high-performance liquid chromatographic assay with electrospray ionization mass spectrometry detection (LC-ESI-MS) has been developed and validated for the identification and quantification of the novel anticholinergic drug phencynonate in rat blood and urine. The sample pretreatment involves basification and iterative liquid-liquid extraction with ethyl ether-dichloromethane (2:1, v/v) solution, followed by LC separation and positive electrospray ionization mass spectrometry detection. The chromatography was on BetaBasic-18 column (150 mm x 2.1mm i.d., 3 microm). The mobile phase was composed of methanol-water (85:15, v/v), containing 0.5 per thousand formic acid, which was pumped at a flow-rate of 0.2 ml/min. Thiencynonate was selected as the internal standard (IS). Simultaneous MS detection of phencynonate and IS was performed at m/z 358.4 (phencynonate), m/z 364 (thiencynonate), and the selected reaction ion monitoring (SRM) of the two compounds was at 156. Phencynonate eluted at approximately 5.25 min, thiencynonate eluted at approximately 5.10 min and no endogenous materials interfered with their measurement. Linearity was obtained over the concentration range of 1-100 ng/ml in rat blood and 1-500 ng/ml in rat urine. The lower limit of quantification (LLOQ) was reproducible at 1 ng/ml in both of rat blood and urine. The precision measured was obtained from 2.92 to 9.76% in rat blood and 4.17 to 9.76% in rat urine. Extraction recoveries were in the range of 69.57-79.49% in blood and 56.85-64.86% in urine. This method was successfully applied to the identification and quantification of phencynonate in pharmacokinetic studies.

The Integrated Use of Pharmacokinetic and Pharmacodynamic Models for the Definition of Breakpoints

For fluoroquinolones AUC/MIC ratios are known to correlate with clinical outcomes for patients suffering from respiratory tract infections (RTI) and complicated skin and skin structure infections (cSSSI). This paper describes the results of a population PK/PD analysis followed by Monte Carlo simulations to estimate clinical outcome and the microbiological breakpoints for a 400 mg once-daily moxifloxacin (MFX) treatment schedule. Based on PK data from 416 subjects, a non-compartmental population PK model was developed first to describe the expected exposure (AUC) distribution in humans. Height and gender were the main population covariates with moderate influence on PK variability. Albumin, bilirubin, and creatinine clearance (as derived from serum creatinine according to Cockroft and Gault) had a mild effect on AUC. Residual unexplained variability of AUC was low (13.1%). To describe the PD function the MIC distribution pattern of more than 3,000 isolates of S. pneumoniae as the representative pathogen for RTI (MIC90, range: 0.125; 0.006-4 mg/l) was built into the population PK/PD model for RTI, while 126 isolates of methicillin-susceptible Staphylococcus aureus strains (MIC90, range: 0.125; 0.03-4 mg/l) were the basis for the PD function in cSSSI. Simulations for 20,000 (RTI) and 4,000 (cSSSI) subjects were performed to evaluate the AUC/MIC characteristics for moxifloxacin for these two diseases. Overall, a target hit rate was THR = 99% for RTI, while it amounted to THR = 97.5% for cSSSI when applying a threshold of AUIC > 30 [h] as the PK/PD surrogate parameter which is predictive for a positive clinical outcome. A target hit rate of THR = 93.6 % (RTI) and 97.3% (cSSSI), respectively, was predicted when assuming that an AUIC of > 125 [h] is indicative of clinical success (as shown for ciprofloxacin and severe RTIs due to gram-negative infections). In clinical trials with patients receiving 400 mg moxifloxacin once daily for the treatment of community-acquired pneumonia (CAP) success rate was approximately 93.5%. From the simulations performed for RTI an analysis of the overall likelihood of therapeutic failure broken down according to MICs suggests that the risk of a negative clinical outcome at a MIC = 1 mg/l is approximately 0.25% (for MIC = 2 mg/l: predicted likelihood approximately 0.5%) assuming that a cutoff of AUIC = 30 [h] is applicable. Likewise, for cSSSI the probability to fail is predicted as 1.6% at a MIC = 2 mg/l (no strains with MICs between 0.5 and 1 mg/l available from the clinical isolates). These findings are in line with the breakpoint definition of the former National Committee for Clinical Laboratory Standards (NCCLS) for MFX (=1 mg/L to differentiate between susceptible and intermediately susceptible microorganisms; = 2 mg/l to separate intermediate from resistant pathogens). The results of the investigation indicate that the noncompartmental PK/PD model for MFX is suitable to predict clinical outcomes in CAP and cSSSI caused by gram-positive aerobe pathogens. They confirmed that a 400 mg once-daily dosing regimen is suitable to treat these diseases successfully. They are in agreement with the microbiological breakpoints determined by independent methods by the Clinical and Laboratory Standards Institute (CLSI) (former NCCLS).

Influence of activated charcoal on the pharmacokinetics of moxifloxacin following intravenous and oral administration of a 400 mg single dose to healthy males

AIMS

To evaluate the extent to which enterohepatic recycling circulation contributes to moxifloxacin bioavailability in healthy, males by administration of activated charcoal and to evaluate the efficacy of activated charcoal administration in decreasing systemic concentrations of moxifloxacin in the event of overdose.

METHODS

Nine healthy males, mean age 34 years (range 23-45 years) participated in a single centre, randomized, nonplacebo-controlled, three way crossover study. The pharmacokinetics of moxifloxacin in plasma and urine were determined for up to 96 h following a 400 mg single dose randomly administered on three separate occasions with a minimum washout phase of 1 week. Treatment A was 400 mg moxifloxacin IV as a 1 h infusion, treatment B was 400 mg moxifloxacin IV as a 1 h infusion with oral activated charcoal (5 g directly before the start of the infusion, 5 g immediately after the end of the infusion, and 10 g at 2, 4 and 8 h after the start of the infusion), treatment C was 400 mg oral moxifloxacin with activated charcoal (10 g 15 min before and at 2, 4 and 8 h after drug administration). The subjects underwent a series of clinical and laboratory tests.

RESULTS

Single 400 mg doses of moxifloxacin (PO and/or IV) were safe and well tolerated. The bioavailability of moxifloxacin was significantly decreased when given with charcoal (AUC = 35.5 (IV reference) vs 5.40 (PO) vs 28.5 (IV) mg l(-1) h). Concurrently peak concentrations were lowered C(max) = 3.38 (IV reference) vs 0.62(PO) vs 2.97 (IV) mg l(-1)) by approximately 85% (P < 0.05) following oral administration and by 20% after IV treatment (P < 0.05). Bioavailability amounted to 15.4% (95% confidence interval 9.6, 25.0%) for treatment B while it was 80.4% (95% confidence interval 76.3.6, 84.6%) for treatment C. Terminal half-lives were not affected. The kinetics of urinary excretion corroborated these findings.

CONCLUSIONS

The results of this study show that moxifloxacin undergoes pronounced enteric recycling after systemic uptake. In addition, these findings confirm that activated charcoal may be useful in treating moxifloxacin overdose by preventing its absorption.

Pharmacokinetic-pharmacodynamic integration of moxifloxacin in rabbits after intravenous, intramuscular and oral administration

The pharmacokinetics of moxifloxacin was studied following intravenous (i.v.), intramuscular (i.m.) and oral dose of 5 mg/kg to healthy white New Zealand rabbits (n = 6). Moxifloxacin concentrations were determined by HPLC assay with fluorescence detection. The moxifloxacin plasma concentration vs. time data after i.v. administration could best be described by a two-compartment open model. The disposition of i.m. and orally administered moxifloxacin was best described by a one-compartment model. The plasma moxifloxacin clearance (Cl) for the i.v route was (mean +/- SD) 0.80 +/- 0.02 L/h.kg. The steady-state volume of distribution (Vss) was 1.95 +/- 0.18 L/kg. The terminal half-life (t(1/2lambdaz)) was (mean +/- SD) 1.84 +/- 0.12, 2.09 +/- 0.05 and 2.15 +/- 0.07 h after i.v., i.m. and oral, respectively. Minimal inhibitory concentration (MIC) assays of moxifloxacin against different strains of S. aureus were performed in order to compute pharmacodynamic surrogate markers. From these data, it is concluded that a 5 mg/kg dose moxifloxacin would be effective by i.m. and oral routes in rabbits against bacterial isolates with MIC < or = 0.06 microg/mL and possibly for MIC < or = 0.12 microg/mL, but in the latter case a higher dose would be required.

Biliary secretion of moxifloxacin in obstructive cholangitis and the non-obstructed biliary tract

BACKGROUND

Biliary secretion of antibiotic agents into the bile is considerably compromised by biliary obstruction, a precondition of bacterial cholangitis. Moxifloxacin may be advantageous according to secretion and antimicrobial spectrum.

AIM

To establish the secretion of moxifloxacin into obstructed and non-obstructed bile.

METHODS

Biliary excretion of moxifloxacin was determined in plasma and bile of 10 patients with biliary obstruction and cholangitis and 10 patients without biliary obstruction 30 min after administration of 400 mg of moxifloxacin intravenously.

RESULTS

The plasma concentration of moxifloxacin was similar in both groups (4.45 +/- 1.58 microg/mL; 4.33 +/- 1.23 microg/mL). The concentration of moxifloxacin in the bile was significantly lower in patients with biliary obstruction than without (4.63 +/- 3.94 microg/mL; range 0.71-14.40; vs. 16.90 +/- 13.77 microg/mL; range 1.79-42.50; P = 0.043). Although significantly different, the penetration index was extensively high in those without biliary obstruction (4.41 +/- 4.40; range 0.35-14.45) but still sufficient in those patients with obstructive cholangitis (1.02 +/- 0.74; range 0.29-2.83; P = 0.035).

CONCLUSION

These findings are suggestive of an active secretion mechanism for moxifloxacin into the obstructed bile, producing a biliary concentration sufficiently above the minimal inhibitory concentrations for most of the expected bacteria.

Clearance of moxifloxacin during continuous haemofiltration (CVVHF) in vitro

BACKGROUND/AIMS

The clearance of moxifloxacin is reported to be unaltered in the presence of renal insufficiency. There is little information about the clearance of intravenous moxifloxacin in renal replacement therapies during intensive care. The aim of this study was to determine the clearance of moxifloxacin during continuous veno-venous haemofiltration (CVVHF) in vitro.

METHODS

The elimination of moxifloxacin (reservoir with 600 mL of washed human erythrocytes, 100 mL of NaHCO3 and various amounts of Ringer solution and human albumin to give a total volume of 1000 mL, pH 7.35 +/- 0.5; haematocrit 41 +/- 2) during CVVHF in vitro with two filter conditions (during priming, after priming), three protein concentrations (human albumin: 0 g/L, 20 g/L, 40 g/L) and two filtration velocities [(i) standard condition: blood flow at 100 mL/min and turnover of 2 L/h; (ii) blood flow at 50 mL/min and turnover of 1 L/h] were investigated.

RESULTS

A new filter needs 20 min of priming before moxifloxacin reaches a steady relative filtration rate. The sieving coefficient with 0 g/L albumin was 1.07, with 20 g/L 0.90 and with 40 g/L 0.80. Under standard filtration conditions (i) the renal clearance was between 26.7 and 35.7 mL/min, and under the altered conditions (ii) it was 15.2 mL/min.

CONCLUSION

During CVVHF in vitro we found filtration clearances of moxifloxacin of the same order as its renal clearance in healthy subjects. The high sieving coefficient, nearly independent of blood protein concentration, would suggest that moxifloxacin is filtered almost as freely as creatinine. These results do not indicate a need for dose adjustment under appropriate haemofiltration conditions and normal hepatic function.

Penetration of moxifloxacin into the human aqueous humour after oral administration

AIMS

To determine the pharmacokinetics of moxifloxacin, a new generation fluoroquinolone, in the anterior chamber of the human uninflamed eye.

METHODS

35 patients undergoing cataract surgery received two doses of 400 mg of oral moxifloxacin with a 12 hour interval and were divided into six groups. Moxifloxacin levels in aqueous humour and serum were determined by a microbiological agar well diffusion technique at 2, 4, 6, 8, 10, and 12 hours after the second dose in each group respectively.

RESULTS

Mean moxifloxacin levels in the anterior chamber were 1.20 (SD 0.35) microg/ml at the 2 hours group, 1.22 (0.48) microg/ml at the 4 hours group, 1.20 (0.45) microg/ml at the 6 hours group, 1.58 (0.38) microg/ml at the 8 hours group, 1.37 (0.44) microg/ml at the 10 hours group, and 1.23 (0.55) microg/ml at the 12 hours group. The mean ratio of aqueous to serum moxifloxacin level was 38%.

CONCLUSION

Moxifloxacin penetrates well into the anterior chamber of the human uninflamed eye after oral administration, reaching early significant levels, which are maintained for at least 12 hours and are much higher than the MIC(90) values of Gram positive and Gram negative pathogens commonly implicated in intraocular infections with the exceptions of fluoroquinolone resistant staphylococci, MRSA, and Pseudomonas aeruginosa.

The impact of mechanical ventilation on the moxifloxacin treatment of experimental pneumonia caused by Streptococcus pneumoniae

OBJECTIVE

Streptococcus pneumoniae is a leading cause of community-acquired pneumonia and is responsible for early-onset ventilator-associated pneumonia as well. In intensive care units, community-acquired pneumonia is still associated with a mortality rate of up to 30%, especially when mechanical ventilation is required. Our objective was to study to what extent MV could influence the efficacy of moxifloxacin in a rabbit model of pneumonia.

DESIGN

Prospective experimental study.

SETTING

University hospital laboratory.

SUBJECTS

Male New Zealand White rabbits (n = 75).

INTERVENTIONS

S. pneumoniae (16089 strain; minimal inhibitory concentration for moxifloxacin = 0.125 mg/L) was instilled intrabronchially. Four hours later, a human-like moxifloxacin treatment was initiated in spontaneously breathing (SB) and mechanically ventilated (MV) animals. Untreated rabbits were used as controls. Survivors were killed 48 hrs later. Pneumonia was assessed and moxifloxacin pharmacokinetics were analyzed.

MEASUREMENTS AND MAIN RESULTS

Moxifloxacin treatment was associated with an improvement in survival in the SB animals (13 of 13 [100%] vs. eight of 37 [21.6%] controls). The survival rate was less influenced by treatment in MV rabbits (seven of 15 [46.1%] vs. one of eight [12.5%] controls). The lung bacterial burden was greater in MV compared with SB rabbits (5.1 +/- 2.4 vs. 1.6 +/- 1.4 log10 colony-forming units/g, respectively). Nearly all the untreated animals presented bacteremia as reflected by a positive spleen culture. No bacteremia was found in SB animals treated with moxifloxacin. In contrast, three of 13 (23.1%) moxifloxacin-treated and MV animals had positive spleen cultures. The apparent volume of distribution of moxifloxacin was lower in MV compared with SB rabbits.

CONCLUSIONS

In our model of moxifloxacin-treated S. pneumoniae pneumonia, mechanical ventilation was associated with a higher mortality rate and seemed to promote bacterial growth as well as systemic spread of the infection. In addition, the volume of distribution of moxifloxacin was reduced in the presence of mechanical ventilation. Although the roles of factors such as anesthesia, paralysis, and endotracheal tube insertion could not be established, these results suggest that mechanical ventilation may impair host lung defense, rendering antibiotic therapy less effective.

Simultaneous determination of levofloxacin, gatifloxacin and moxifloxacin in serum by liquid chromatography with column switching

Liquid chromatography with a column-switching technique was developed for simultaneous direct quantification of levofloxacin, gatifloxacin and moxifloxacin in human serum. Serum samples were injected on a LiChroCART 4-4 pre-column (PC) filled with a LiChrospher 100 RP-18, 5 microm where fluoroquinolones (FQs) were purified and concentrated. The FQs were back-flushed from the PC and then separated on a Supelcosil ABZ+ Plus (150 mm x 4.6 mm i.d.) analytical column with a mobile phase containing 10 mM phosphate buffer (pH 2.5), acetonitrile (88:12, v/v) and 2mM tetrabutyl ammonium bromide. The effects of ion-pair reagents, buffer type, pH and acetonitrile concentrations in the mobile phase on the separation of the three FQs were investigated. Fluorescence detection provided sufficient sensitivity to achieve a quantification limit of 125 ng/ml for levofloxacin and moxifloxacin; 162.5 ng/ml for gatifloxacin with a 5 microl sample size. The on-line process of extraction avoids time-consuming treatment of the samples before injection and run time is shortened. The recovery, selectivity, linearity, precision and accuracy of the method are convenient for pharmacokinetic studies or routine assays.

Moxifloxacin—Warfarin Interaction: A Series of Five Case Reports

OBJECTIVE:

To report 5 cases of a moxifloxacin—warfarin drug interaction, all resulting in elevated international normalized ratios (INRs) and clinically significant hemorrhage in one case.

CASE SUMMARIES:

Between January 2002 and January 2004, 4 men and 1 woman (age range 63–92 y) were retrospectively identified as having significantly elevated INR results shortly after being prescribed moxifloxacin with concomitant warfarin therapy.

DISCUSSION:

This is the second series of case reports describing an interaction between warfarin and moxifloxacin. The current moxifloxacin product monograph indicates this drug has no significant effect on the pharmacokinetics of R- or S-warfarin or the prothrombin time (INR). A moxifloxacin—warfarin interaction probably led to prolonged hospitalization in 2 cases and significant gastrointestinal hemorrhage in one case. In 3 of the 5 cases, a moxifloxacin—warfarin interaction was assessed as probable, and in the remaining 2 cases, a moxifloxacin—warfarin interaction was assessed as possible by use of the Naranjo probability scale.

CONCLUSIONS:

Healthcare professionals should consider moxifloxacin for the potential to interact with warfarin. Routine, frequent INR monitoring for patients previously stabilized on warfarin during initiation and discontinuation of moxifloxacin may help detect this potential interaction.

Effects of Enteral Feeding on the Oral Bioavailability of Moxifloxacin in Healthy Volunteers

BACKGROUND AND OBJECTIVE

Moxifloxacin is a new generation fluoroquinolone antimicrobial agent used worldwide. In clinical practice in intensive care units, moxifloxacin may be frequently administered through a nasogastric feeding tube. In the absence of an oral liquid formulation and since the multivalent cations contained in enteral feeds may potentially impair absorption of moxifloxacin administered via this route, we studied the effect of concomitant enteral feeding on the pharmacokinetics and tolerability of moxifloxacin administered as a crushed tablet through the nasogastric tube.

PARTICIPANTS AND METHODS

This was a single-centre, open-label, randomised, controlled, nonblinded, three-way crossover study. Twelve young healthy volunteers (nine females and three males) aged 20-42 years were included in the study. Each participant received three separate treatment regimens in a randomised fashion: an intact moxifloxacin 400 mg tablet (regimen A, reference treatment), a crushed moxifloxacin 400 mg tablet as a suspension through a nasogastric tube with water (regimen B) and a crushed moxifloxacin 400 mg tablet as a suspension through a nasogastric tube with enteral feeding (regimen C). A washout period of 1-week followed each treatment. Concentrations of moxifloxacin in serum were measured by a validated high-performance liquid chromatography method. Pharmacokinetic parameters were calculated by noncompartmental methods. Additionally, the primary parameters indicative for changes in absorption (area under the serum concentration-time curve from time zero to infinity [AUC(infinity)] and peak serum concentration [C(max)]), were tested for bioequivalence, assuming log-normally distributed data using ANOVA.

RESULTS

All moxifloxacin treatment regimens were well tolerated. The AUC(infinity) was slightly, but not statistically significantly, decreased in treatments with regimens B and C. AUC(infinity) (geometric means 39.6 [regimen A] vs 36.1 [regimen B] vs 36.1 mg.h/L [regimen C] and point estimates 91% for B : A and C : A) indicated bioequivalence of the treatments. Bioequivalence criteria of AUC(infinity) and C(max) were met upon retrospective statistical analysis. Likewise C(max) after moxifloxacin administration through nasogastric tube with water (regimen B) and with tube feed (regimen C) were slightly decreased (geometric means 3.20 [regimen A] vs 3.05 [regimen B] vs 2.83 mg/L [regimen C]; point estimates 88% for B : A, and 95% for C : A). They were within the range seen in other studies conducted with oral administration of the drug. No statistically significant differences were observed in time to reach C(max) (t(max); median 1.75 [regimen A] vs 1.00 [regimen B] vs 1.75 hours [regimen C]). Thus, the rate of absorption of moxifloxacin was not affected by administration through a nasogastric tube. This route of ingestion seems to be associated with a slight loss of bioavailability independent of the carrier medium used (water vs enteral feed); no clinically relevant interaction with the multivalent cations contained in the enteral feed was observed, indicating that moxifloxacin and enteral nutrition can be administered concomitantly.

CONCLUSION

There was no clinically relevant effect of enteral feeding on the pharmacokinetics of oral moxifloxacin in healthy volunteers. This result has to be evaluated in patients, particularly those from the intensive care unit, who are characterised by severe infectious and/or concomitant diseases that might influence absorption of moxifloxacin.

Pharmacokinetics of moxifloxacin in patients undergoing continuous venovenous haemodiafiltration

OBJECTIVE

Moxifloxacin is an 8-methoxy quinolone with a broad range of activity against clinically important pathogens. Therefore it is frequently administered in severe respiratory tract infections. Continuous venovenous haemodiafiltration (CVVHDF) is an important extracorporeal renal replacement therapy for intensive care patients suffering from sepsis and multiple organ failure. The aim of this study was to investigate the pharmacokinetics of intravenous moxifloxacin in anuric critically ill patients undergoing CVVHDF.

PATIENTS AND METHODS

Pharmacokinetic analysis was performed in nine intensive care patients with acute renal failure and suspected or proven infection sensitive to moxifloxacin, who received moxifloxacin 400 mg intravenously once daily. The concentration of moxifloxacin in serum and ultradiafiltrate was determined by HPLC.

RESULTS

Peak and trough serum concentrations were 3.76 +/- 2.02 mg/L and 0.24 +/- 0.14 mg/L, respectively, at the arterial port after the first dose. The mean elimination half-life was 9.87 +/- 3.26 h, the volume of distribution 270 +/- 133 L and the calculated AUC0-24 18.41 +/- 8.46 mg.h/L. Total clearance was 19.09 +/- 8.22 L/h and the clearance of haemodiafiltration 1.63 +/- 0.33 L/h.

CONCLUSIONS

The pharmacokinetics of moxifloxacin in critically ill patients with acute renal failure undergoing CVVHDF was comparable to healthy subjects and patients without renal impairment. We recommend 400 mg of intravenous moxifloxacin once per day in anuric patients during CVVHDF.

Gabapentin-lactam, but not gabapentin, reduces protein aggregates and improves motor performance in a transgenic mouse model of Huntington?s disease

Gabapentin (GBP), an anti-convulsant widely used in the treatment of neuropathic pain syndromes, has been suggested to have neuroprotective properties. There is evidence, however, that the neuroprotective properties attributed to GBP are rather associated with a derivative of GBP, gabapentin-lactam (GBP-L), which opens mitochondrial ATP-dependent K+ channels, in contrast to GBP. We explored whether GBP and GBP-L may attenuate the course of a monogenetic autosomal neurodegenerative disorder, Huntington's disease (HD), using a transgenic mouse model. R6/2 mice treated with GBP-L performed walking on a narrow beam better than mice receiving no treatment, vehicle or GBP, suggesting a beneficial effect of GBP-L on motor function. In addition, a marked reduction of neuronal nuclear and cytoplasmic inclusions was observed in brains of mice treated with GBP-L. The pharmacokinetics of GBP-L yielded a mean plasma concentration near the EC50 of GBP-L to open mitochondrial ATP-dependent K+ channels. These findings support the role of GBP-L as a novel neuroprotective substance in vivo.

Determination of gabapentin-lactam in serum of patients under gabapentin therapy

Gabapentin (1-(aminomethyl)cyclohexane acetic acid, CAS 601 42-96-3, GBP, Neurontin) and its derivative gabapentin-lactam (8-aza-spiro[5,4]decan-9-one, GBP-L) were determined by HPLC in the serum of patients with focal epilepsy treated with GBP. In patients in whom serum was acquired within 3 h after oral intake, GBP-L could be detected at concentrations up to 8.2 micromol/l. As GBP-L has been previously shown to exert neuroprotective effects in a similar concentration range, this finding suggests that clinically relevant effects of GBP-L may occur in patients treated with GBP. The possible neuroprotective efficacy of GBP-L should be the subject of further preclinical and clinical investigations.

Concentrations of moxifloxacin in serum and synovial fluid, and ex vivo bactericidal activity against arthritis-causing pathogens

Three doses of moxifloxacin 400 mg qd were administered orally to 20 candidates for knee arthroscopy (mean age, 71.2 years). The procedure was scheduled at four different points of time after the last dose: 2, 6, 12, and 24 h. Five patients were studied at each point of time. Drug levels were determined by the bioassay method. Bactericidal activity against four bacterial pathogens (two strains of each) was studied on serum and synovial fluid samples obtained during arthroscopy using the NCCLS guidelines. Mean (+/-S.D.) peak serum and synovial fluid concentrations were 3.46 +/- 0.78 mg/L and 3.42 +/- 0.51 mg/L, respectively. Levels above 1.0 mg/L were detected as long as 24 h. The peak bactericidal titers were (in serum and synovial fluid, respectively) 1:18.3 and 1:32 against Staphylococcus aureus, 1:18.3 and 1:22.6 against Streptococcus pyogenes, 1:45.2 and 1:64.0 against Klebsiella pneumoniae, and 1:2.3 and 1:1.7 against Pseudomonas aeruginosa. Bactericidal titers >1:2 were documented against the first three pathogens up to 24 h after dosing. On the basis of its pharmacokinetic and pharmacodynamic characteristics, moxifloxacin seems to be an excellent candidate for the treatment of joint infections, except those caused by P. aeruginosa.

Moxifloxacin penetration into human gastrointestinal tissues

OBJECTIVE

Moxifloxacin is a recently developed fourth-generation methoxyquinolone with a broad spectrum of activity against both Gram-positive and Gram-negative aerobic bacteria and anaerobes. The aim of the present study was to assess the penetration of moxifloxacin into gastrointestinal (GI) mucosal tissues to evaluate its potential role as an antimicrobial drug in bacterial infections of the GI tract.

PATIENTS AND METHODS

Twenty-eight patients undergoing GI-tract surgery received 400 mg of moxifloxacin twice pre-operatively [eight patients orally (po) and 20 patients intravenously (iv)], of whom 22 completed the study. Mucosal tissues (three stomach, three small bowel and 16 colon) and serum samples were collected and moxifloxacin concentrations were measured by HPLC.

RESULTS

The highest tissue concentrations were detected in the mucosa of the stomach (10.9 +/- 5.1 mg/kg), followed by colon mucosa (7.8 +/- 7.1 mg/kg after iv; 6.6 +/- 3.6 mg/kg after po) and small bowel mucosa (5.4 +/- 0.5 mg/kg). The tissue-to-serum ratio of moxifloxacin was 2.0 +/- 1.6 in the small bowel mucosa, 5.8 +/- 3.4 and 6.8 +/- 3.9 in the colon mucosa after po and iv administration, respectively, and 9.7 +/- 5.7 in the stomach mucosa.

CONCLUSION

Moxifloxacin penetrates into and accumulates in the mucosa of the stomach, small bowel and colon. The clinical applicability of moxifloxacin administration for bacterial GI-tract infections should be investigated in controlled trials.

Sinus tissue concentration of moxifloxacin after a single oral dose

Moxifloxacin is a new fluoroquinolone antimicrobial approved for the treatment of acute bacterial rhinosinusitis. In order to assess its distribution pattern into the paranasal sinuses, and specifically to evaluate how the histopathologic changes associated with chronic inflammation affect its tissue penetration, we conducted the present investigation, a randomized, open-label, single dose, sinus-tissue pharmacokinetic study with oral moxifloxacin. Twenty adult subjects, selected for surgery because of recalcitrant chronic rhinosinusitis, were preoperatively randomly allocated to receive a tablet of 400 mg moxifloxacin 3 or 4 hours before the procedure. During the operation, tissue samples were collected at specific sinonasal sites, and the concentration levels of the antimicrobial in the different parts of the paranasal sinuses were assayed. Simultaneously, the degree of inflammation at each site was evaluated. We found that moxifloxacin was distributed extensively throughout the sinuses, in both inflamed and noninflamed mucosae, but tended to be concentrated in maxillary sinus cysts. The tissue-to-blood ratios exceeded 4:1 at most sites, with mucosal concentration levels well above the MIC90 values of the drug against a wide range of microorganisms. We concluded that the oral moxifloxacin tissue kinetics provides an extremely potent antimicrobial activity in all parts of the sinuses, regardless of the inflammatory status of the mucosa.

Penetration of moxifloxacin into healthy and inflamed subcutaneous adipose tissues in humans

The present study addressed the ability of moxifloxacin to penetrate into healthy and inflamed subcutaneous adipose tissues in 12 patients with soft tissue infections (STIs). Penetration of moxifloxacin into the interstitial space fluid of healthy and inflamed subcutaneous adipose tissues was measured by use of in vivo microdialysis following administration of a single intravenous dosage of 400 mg in six diabetic and six nondiabetic patients with STIs. For the entire study population, the mean time-concentration profile of free moxifloxacin in plasma was identical to the time-concentration profile of free moxifloxacin in tissue (P was not significant). For healthy and inflamed adipose tissues for the diabetic subgroup, the mean moxifloxacin areas under the concentration-time curves (AUCs) from 0 to 8 h (AUC(0-8)s) were 8.1 +/- 7.1 and 3.7 +/- 1.9 mg.h/liter, respectively (P was not significant). The ratios of the mean AUC(0-8) for inflamed tissue/AUC(0-8) for free moxifloxacin in plasma were 0.5 +/- 0.4 for diabetic patients and 1.2 +/- 0.8 for nondiabetic patients (P was not significant). The ratios of the AUCs from 0 to 24 h for free moxifloxacin in plasma/MIC at which 90% of isolates are inhibited were >58 and 121 h for Streptococcus species and methicillin-sensitive Staphylococcus aureus, respectively. Concentrations of moxifloxacin effective against clinically relevant bacterial strains are reached in plasma and in inflamed and healthy adipose tissues. Thus, the pharmacokinetics of moxifloxacin in tissue and plasma support its use for the treatment of STIs in diabetic and nondiabetic patients.

Voltammetric behaviour and determination of moxifloxacin in pharmaceutical products and human plasma

The oxidative behaviour of moxifloxacin was studied at a glassy carbon electrode in different buffer systems using cyclic, differential pulse, and Osteryoung square-wave voltammetry. The oxidation process was shown to be irreversible over the entire pH range studied (2.0-10.0) and was diffusion-controlled. The methods were performed in Britton-Robinson buffer and the corresponding calibration graphs were constructed and statistical data were evaluated. When the proposed methods were applied at pH 6.0 linearity was achieved from 4.4 x 10(-7) to 1.0 x 10(-5) mol L(-1). Applicability to tablets and human plasma analysis was illustrated. Furthermore, a high-performance liquid chromatographic method with diode-array detection was developed. A calibration graph was established from 4.0 x 10(-6) to 5.0 x 10(-5) mol L(-1) moxifloxacin. The described methods were successfully employed with high precision and accuracy for estimation of the total drug content of human plasma and for pharmaceutical dosage forms of moxifloxacin.

Serum Bactericidal Activity of the Methoxyfluoroquinolones Gatifloxacin and Moxifloxacin against Clinical Isolates of Staphylococcus Species: Are the Susceptibility Breakpoints Too High?

Healthy volunteers received a single dose of gatifloxacin and moxifloxacin (400 mg each), and serum samples were obtained from these volunteers over a 24-h period. Prolonged (> or =12 h) serum bactericidal activity (SBA) was observed for both agents against staphylococcal isolates with minimum inhibitory concentrations (MICs) of gatifloxacin of < or =0.5 mug/mL. In strains with gatifloxacin MICs of 1.0 mug/mL, SBA was observed for < or =6 h, and, for isolates with gatifloxacin MICs of 2.0 mug/mL, little or no SBA was observed for either drug. The relative lack of SBA against less susceptible strains of staphylococci suggests that the current susceptibility breakpoint concentration (MIC, 2.0 mug/mL) for these methoxyfluoroquinolones against Staphylococcus is too high.

Identification of metabolites of a substance P (neurokinin 1 receptor) antagonist in rat hepatocytes and rat plasma

[3R,5R,6S]-3-(2-cyclopropyloxy-5-trifluoromethoxyphenyl)-6-phenyl-1-oxa-7-azaspiro[4.5]decane is a substance P (Neurokinin 1 receptor) antagonist. Substance P antagonists are proven in concept to have excellent potential for the treatment of major depression, and they allow superior and sustained protection from acute and delayed chemotherapy-induced emesis. The metabolism of this compound was investigated in rat hepatocytes, and circulating rat plasma metabolites were identified following oral and intravenous dosing. The turnover in rat hepatocytes within 4 h was about 30%, and the major metabolites were identified as two nitrones and a lactam associated with the piperidine ring. Although these metabolites were also observed in rat plasma, the major circulating metabolite was a keto acid following oxidative de-amination of the piperidine ring. Liquid chromatography/tandem mass spectrometry and nuclear magnetic resonance were used to confirm the structure of the latter metabolite. A mechanism leading to the formation of the keto acid metabolite has been suggested, and most intermediates were observed in rat plasma.

Quantitative analysis of bencynonate in human plasma using a deuterated internal standard by gas chromatography-mass spectrometry with selected-ion monitoring

A gas chromatographic-mass spectrometric method is described for the quantitative analysis of bencynonate in human plasma. Deuterated bencynonate served as the internal standard and selected-ion monitoring of the fragments of bencynonate and internal standard permitted the quantitation of bencynonate down to 25 pg/ml of plasma. The assay is linear for plasma bencynonate concentrations in the range 25 pg/ml-3 ng/ml. At 0.25 ng/ml the recovery and coefficient of variation are 54.3% and 19.1%, respectively. Application of the method to clinical studies gave data for the pharmacokinetics and relative bioavailability of bencynonate in man.