Evaluation of the absolute oral bioavailability of the anaplastic lymphoma kinase/c-ROS oncogene 1 kinase inhibitor lorlatinib in healthy participants.

PURPOSE: Lorlatinib is a third-generation tyrosine kinase inhibitor currently approved for the treatment of anaplastic lymphoma kinase (ALK)-positive metastatic non-small cell lung cancer. This open-label, phase 1, randomized two-sequence, two-treatment, two-period, crossover study investigated the absolute oral bioavailability of lorlatinib in healthy participants. METHODS: Eligible participants were randomized to receive two treatments in one of two sequences: lorlatinib 100 mg single oral dose followed by lorlatinib 50 mg intravenous (IV) dose, or lorlatinib IV dose followed by lorlatinib oral dose, each with at least a 10-day washout between successive lorlatinib doses. Blood samples for pharmacokinetics were collected for up to 144 hours (h) after dosing. Validated liquid chromatographic-tandem mass spectrometry was used to determine plasma concentrations of lorlatinib and its benzoic acid metabolite PF-06895751. RESULTS: In total, 11 participants were enrolled (mean age 37.6 years, all male). The adjusted geometric mean (90% confidence interval) for the absolute oral bioavailability was 80.78% (75.73-86.16%). Using non-compartmental analysis, the estimated arithmetic mean elimination plasma half-life of lorlatinib was 25.5 and 27.0 h after the oral and IV doses, respectively. No deaths, serious adverse events (AEs), or severe AEs were reported, and most treatment-emergent AEs were mild in severity, with two events of transaminase increase of moderate severity. All treatment-emergent AEs were resolved by the end of the study. CONCLUSION: Both oral and IV lorlatinib were well-tolerated in healthy participants and oral lorlatinib is highly bioavailable after oral administration.

Hepatic Effects of Pharmacological Doses of Hydroxy-Cobalamin[c-lactam] in Mice.

The vitamin B12 analog hydroxy-cobalamin[c-lactam] (HCCL) impairs hepatic mitochondrial protein synthesis and function of the electron transport chain in rats. We aimed to establish an in vivo model for mitochondrial dysfunction in mice, which could be used to investigate hepatotoxicity of mitochondrial toxicants. In a first step, we performed a dose-finding study in mice treated with HCCL 0.4 mg/kg and 4 mg/kg i.p. for two to four weeks. The plasma methylmalonate concentration was strongly increased at 4 mg/kg starting at three weeks of treatment. We subsequently treated mice daily with 4 mg/kg HCCL i.p. for three weeks and characterized liver function and histology as well as liver mitochondrial function. We found an increase in liver weight in HCCL-treated mice, which was paralleled by hepatocellular accumulation of triglycerides. In liver homogenate of HCCL-treated mice, the complex I activity of the electron transport chain was reduced, most likely explaining hepatocellular triglyceride accumulation. The activity of CPT1 was not affected by methylmalonyl-CoA in isolated liver mitochondria. Despite impaired complex I activity, mitochondrial superoxide anion production was not increased and the hepatocellular glutathione (GSH) pool was maintained. Finally, the mitochondrial DNA content was not altered with HCCL treatment. In conclusion, treatment of mice with HCCL is associated with increased liver weight explained by hepatocellular triglyceride accumulation. Hepatocellular fat accumulation is most likely a consequence of impaired activity of the mitochondrial electron transport chain. The impairment of complex I activity is not strong enough to result in ROS accumulation and reduction of the GSH stores.

Ritonavir-boosted danoprevir plus peginterferon alfa-2a and ribavirin in Asian chronic hepatitis C patients with or without cirrhosis.

BACKGROUND AND AIM: Chronic hepatitis C is an important public health problem in Asia. We evaluated the safety, efficacy, and pharmacokinetics of fixed-dose ritonavir-boosted danoprevir plus peginterferon alfa-2a/ribavirin in treatment-naive Asian patients with chronic hepatitis C virus (HCV) genotype (G)1 infection. METHODS: Treatment-naive G1 patients in Taiwan, Thailand, and Korea with serum HCV-RNA level ≥ 105 IU/mL received ritonavir-boosted danoprevir 125/100 mg twice daily plus peginterferon alfa-2a/ribavirin for either 12 (noncirrhotic patients: Arm A, n = 34) or 24 weeks (cirrhotic patients: Arm B, n = 27) in this phase II open-label study. Sustained virologic response was defined as HCV-RNA < 25 IU/mL 12 weeks after end of treatment (SVR12). RESULTS: Similar SVR12 rates were achieved in Arms A (88.2%; 95% confidence interval, 73.4-95.3%) and B (88.9%; 71.9-96.2%). Most patients had G1b infection, among whom SVR12 rates in Arms A and B were 96.7% and 91.7%, respectively. The overall SVR12 rate was 94.0% in noncirrhotic Taiwanese patients (100% in the subset of G1b patients). No patients withdrew for safety reasons. Three (11%) cirrhotic patients (Arm B) experienced serious adverse events, none of which was considered to be related to treatment. No Grade 3/4 alanine aminotransferase elevations were reported. The pharmacokinetic properties of danoprevir were broadly overlapping in noncirrhotic and cirrhotic patients both on Days 1 and 14. CONCLUSIONS: Ritonavir-boosted danoprevir plus peginterferon alfa-2a/ribavirin produced sustained virologic response rates > 90% after 12 weeks' treatment in noncirrhotic and 24 weeks' treatment in cirrhotic Asian patients with G1b infection and was well tolerated. These regimens are well suited to countries where G1b predominates.

Plasma Pharmacokinetics and Routes of Excretion of [14C]-Labeled Arruva, a High-Potency Sweetener, Following Oral Administration to Beagle Dogs.

[14C]-Labeled arruva [sodium/potassium (2R,4R)-2-amino-4-carboxy-4-hydroxy-5-(3-indolyl) pentanoate] was administered as a single gavage dose (10 mg/kg bw) to male and female Beagle dogs and 1 bile duct-cannulated male. The mean peak arruva plasma concentration equivalent of 1.2 µg/g occurred at first sampling time point of 1 hour postdosing. The mean area under the concentration versus time curve from 0 hour postdosing to the last time point was approximately 20 µg·h/g and the mean terminal plasma elimination half-life ranged from 15 hours in females to 21 hours in males. Over 168 hours postdosing, 35% to 50% of the administered arruva was eliminated in the urine with 44% to 53% eliminated in feces; 1.3% of the administered dose was recovered in bile. Arruva and its derivatives were identified using tandem mass spectrometry, and the relative percentage of each substance was quantified via radio high-performance liquid chromatography. Over a 168-hour collection period, combined urine and feces extract data from the 6 noncannulated dogs showed that approximately 91% of the dose was excreted as unchanged parent arruva (41% in urine and 50% in feces). In the cannulated male, 95.3% was excreted as unchanged parent arruva; 50.2% in urine, 43.9% in feces, and 1.3% in bile. Lactone and lactam derivatives of arruva and 1 unidentified substance were detected in urine only during the first 24 hours postdosing with the greatest amounts detected during the first 6 hours of collection; up to 1% of lactone or lactam derivatives were detected in bile samples. Plasma pharmacokinetics data indicated rapid absorption of arruva with the majority of radioactivity located in the feces collected in the first 48 hours.

Stereoselective excretion and first-pass metabolism of clausenamide enantiomers.

Stereoselective differences in pharmacokinetics between clausenamide (CLA) enantiomers have been found after intravenous and oral administration of each enantiomer to rats. The differences could be associated with excretion and first-pass metabolism of two enantiomers. The data from this study demonstrated that (-)CLA was mainly excreted in feces with 13.9% of dose, whereas (+)CLA in bile with 17.2%. A large portion of CLA enantiomers could be transformed into hydroxyl metabolites. In the in vitro metabolic system using rat liver microsomes, it was found that (-)CLA was cleared more than its antipode with peak height ratios [(+)/(-)] from 1.0 to 1.8 at the corresponding substrate concentrations from 0.25 to 2mM. Further study in rabbits showed that two enantiomers underwent an intermediate degree of first-pass metabolism. (-)CLA had lower concentrations and AUC0-8h in the portal vein and heart than those of (+)CLA with rates of hepatic extraction 64.7% for (-)-isomer and 50.8% for (+)-isomer, and intrinsic metabolic clearances of (-) and (+)CLA being 186.3 and 107.2 (l/h), respectively. The first-pass metabolism was involved in CYP3A enzymes in the gut and liver, and different levels of CYP3A1 expression induced by (-)CLA or (+)CLA. Immunohistochemical analyses revealed that (-)-isomer significantly increased the expression of CYP3A1, while (+)-isomer had no obvious effects on it. Taken together, the results provided new evidence that stereoselective pharmacokinetics of CLA enantiomers could be resulted from their stereoselective excretion, first-pass metabolism and induction to metabolizing enzymes, which might be important in understanding the clinic pharmacology of active eutomer, (-)CLA, for treatment of Alzheimer's disease.

Pharmacokinetics of a three-way drug interaction between danoprevir, ritonavir and the organic anion transporting polypeptide (OATP) inhibitor ciclosporin.

BACKGROUND: Danoprevir (RG7227) is a potent macrocyclic inhibitor of the hepatitis C virus NS3/4A protease, which is currently in development in combination with low-dose ritonavir for the treatment of chronic hepatitis C infection. Danoprevir is a substrate of cytochrome P450 3A4, and the organic anion transporting polypeptides (OATP) 1B1 and 1B3. OBJECTIVE: The objective of this study was to evaluate the effect of a potent OATP inhibitor, ciclosporin, on danoprevir pharmacokinetics, when administered as danoprevir/ritonavir. The effect of danoprevir/ritonavir on ciclosporin pharmacokinetics was also investigated. METHODS: This was a single-dose, randomized, open-label, two-sequence, three-period, crossover study in healthy volunteers. In the first period, subjects were randomized to receive either a single oral dose of danoprevir 100 mg in combination with ritonavir 100 mg or a single oral dose of ciclosporin 100 mg. After a 14-day washout, patients were crossed over to receive the opposite treatment. In period 3, all subjects received the combination of danoprevir/ritonavir and ciclosporin following a 14-day washout from period 2. Blood samples were collected serially with each dose for pharmacokinetic assessment. Pharmacokinetic parameters were estimated using non-compartmental analysis. Geometric mean ratios (GMRs) and 90 % confidence intervals (CIs) were used to compare pharmacokinetic parameters [maximum concentration (C max), area under the concentration-time curve from time zero to infinity (AUC∞), and concentration 12 h post-dose (C 12h)] of danoprevir/ritonavir and ciclosporin when administered alone or in combination. Measures of safety and tolerability were also evaluated. RESULTS: A total of 18 subjects were enrolled, and 17 completed the study. The C max, AUC∞, and C 12h GMRs (90 % CI) when danoprevir/ritonavir and ciclosporin were co-administered versus danoprevir/ritonavir or ciclosporin alone were 7.22 (5.42-9.62), 13.6 (11.2-16.6), and 22.5 (17.4-29.3), respectively, for danoprevir, 1.97 (1.72-2.27), 2.23 (2.07-2.42), and 2.50 (2.22-2.81), respectively, for ritonavir, and 1.42 (1.29-1.57), 3.65 (3.27-4.08), and 6.15 (5.32-7.11), respectively, for ciclosporin. All treatments were well tolerated, with no laboratory abnormalities, and no clinically significant changes in vital signs, electrocardiograms, or physical examinations observed. CONCLUSIONS: A significant drug-drug interaction was observed between ciclosporin and danoprevir/ritonavir, leading to substantial increases in exposure to danoprevir and a lesser impact on exposure to ritonavir. Therefore, co-administration of danoprevir/ritonavir with potent OATP inhibitors should be undertaken with appropriate precautions.

Impact of low-dose ritonavir on danoprevir pharmacokinetics: results of computer-based simulations and a clinical drug-drug interaction study.

BACKGROUND AND OBJECTIVE: Danoprevir, a potent, selective inhibitor of the hepatitis C virus (HCV) NS3/4A protease, is metabolized by cytochrome P450 (CYP) 3A. Clinical studies in HCV patients have shown a potential need for a high danoprevir daily dose and/or dosing frequency. Ritonavir, an HIV-1 protease inhibitor (PI) and potent CYP3A inhibitor, is used as a pharmacokinetic enhancer at subtherapeutic doses in combination with other HIV PIs. Coadministering danoprevir with ritonavir as a pharmacokinetic enhancer could allow reduced danoprevir doses and/or dosing frequency. Here we evaluate the impact of ritonavir on danoprevir pharmacokinetics. METHODS: The effects of low-dose ritonavir on danoprevir pharmacokinetics were simulated using Simcyp, a population-based simulator. Following results from this drug-drug interaction (DDI) model, a crossover study was performed in healthy volunteers to investigate the effects of acute and repeat dosing of low-dose ritonavir on danoprevir single-dose pharmacokinetics. Volunteers received a single oral dose of danoprevir 100 mg in a fixed sequence as follows: alone, and on the first day and the last day of 10-day dosing with ritonavir 100 mg every 12 hours. RESULTS: The initial DDI model predicted that following multiple dosing of ritonavir 100 mg every 12 hours for 10 days, the danoprevir area under the plasma concentration-time curve (AUC) from time zero to 24 hours and maximum plasma drug concentration (C(max)) would increase by about 3.9- and 3.2-fold, respectively. The clinical results at day 10 of ritonavir dosing showed that the plasma drug concentration at 12 hours postdose, AUC from time zero to infinity and C(max) of danoprevir increased by approximately 42-fold, 5.5-fold and 3.2-fold, respectively, compared with danoprevir alone. The DDI model was refined with the clinical data and sensitivity analyses were performed to better understand factors impacting the ritonavir-danoprevir interaction. CONCLUSION: DDI model simulations predicted that danoprevir exposures could be successfully enhanced with ritonavir coadministration, and that a clinical study confirming this result was warranted. The clinical results demonstrate that low-dose ritonavir enhances the pharmacokinetic profile of low-dose danoprevir such that overall danoprevir exposures can be reduced while sustaining danoprevir trough concentrations.

Pharmacokinetics and antiviral activity of PHX1766, a novel HCV protease inhibitor, using an accelerated Phase I study design.

BACKGROUND: PHX1766 is a novel HCV NS3/4 protease inhibitor with robust potency and high selectivity in replicon studies (50% maximal effective concentration 8 nM). Two clinical trials investigated the safety, tolerability, pharmacokinetics and antiviral activity of PHX1766 in healthy volunteers (HV) and chronic hepatitis C patients, by use of a dose-adaptive overlapping clinical trial design. METHODS: Two randomized, double-blind, placebo-controlled clinical trials were conducted. Single doses of PHX1766 or placebo were administered to 25 HV and six HCV genotype 1-infected patients (50 mg once daily -1,000 mg once daily, 250 mg twice daily and 100 mg of a new formulation of PHX1766 once daily). Multiple doses of PHX1766 or placebo were administered to 32 HV and seven HCV genotype 1-infected patients (50 mg once daily -800 mg twice daily). RESULTS: Oral administration of PHX1766 was safe and well tolerated at all dose levels with rapid absorption (time at which concentration maximum is reached of 1-4 h) and with mean terminal half-lives of 4-23 h. Multiple doses of PHX1766 800 mg twice daily in HCV patients produced an area under the plasma concentration-time curve from time of drug administration to the last time point with a measurable concentration after dosing accumulation ratio of 2.3. The mean maximal observed HCV RNA decline was 0.6 log(10) IU/ml in the first 24 h in the single-dose protocol and 1.5 log(10) IU/ml after 6 days of PHX1766 dosing. CONCLUSIONS: An overlapping, dose-adaptive single-dose and multiple-dose escalating design in HV and HCV-infected patients proved to be highly efficient in identifying a therapeutic dose. Although in vitro replicon studies indicated a robust HCV RNA viral decline of PHX1766, the study in HCV patients demonstrated only modest viral load reduction.

Treatment of chronic hepatitis C patients with the NS3/4A protease inhibitor danoprevir (ITMN-191/RG7227) leads to robust reductions in viral RNA: a phase 1b multiple ascending dose study.

BACKGROUND & AIMS: Danoprevir is a potent and selective inhibitor of the hepatitis C virus (HCV) NS3/4A serine protease. The present study assessed the safety, pharmacokinetics, and antiviral activity of danoprevir in a randomized, placebo-controlled, 14-day multiple ascending dose study in patients with chronic HCV genotype 1 infection. METHODS: Four cohorts of treatment-naïve (TN) patients (100 mg q12 h, 100 mg q8 h, 200 mg q12 h, 200 mg q8 h) and one cohort of non-responders (NR) to prior pegylated interferon alfa-ribavirin treatment (300 mg q12 h) were investigated. RESULTS: Danoprevir was safe and well tolerated; adverse events were generally mild, transient and were not associated with treatment group or dose level. Danoprevir displayed a slightly more than proportional increase in exposure with increasing daily dose and was rapidly eliminated from the plasma compartment. Maximal decreases in HCV RNA were: -3.9 log(10)IU/ml and -3.2 log(10)IU/ml in TN receiving 200 mg q8 h and 200 mg q12 h, respectively. End of treatment viral decline in these two cohorts was within 0.1 log(10)IU/ml of the viral load nadir. HCV RNA reduction in NR was more modest than that observed in upper dose TN cohorts. The overall incidence of viral rebound was low (10/37) and was associated with the R155K substitution in NS3 regardless of the HCV subtype. CONCLUSIONS: Danoprevir was safe and well tolerated when administered for 14 days in patients with chronic HCV genotype 1 infection. Treatment resulted in sustained, multi-log(10) IU/ml reductions in HCV RNA in upper dose cohorts. These results support further clinical evaluation of danoprevir in patients with chronic HCV.

[Antimicrobial blood concentrations in burns. A five years' retrospective survey]. / Concentrations sanguines d'antibiotiques chez les patients brûlés. Etude rétrospective sur cinq ans.

The monitoring of antimicrobial agents is a routine in our unit. We reviewed the results either of peak-and-through concentrations (peak and through is one sample) or concentrations at steady state (Css) of all antimicrobials given over five years (2001 to 2005) and studied the antimicrobials with at least 20 samples. We found 706 samples in 122 patients, the antimicrobials being amikacin, amoxicillin, ceftazidime, ciprofloxacin, cloxacillin, gentamicin, imipenem, ofloxacin, tobramycin and vancomycin. When comparing samples in witch the concentrations were above a value thought to be predictive of efficacy to those were not, we could notice: that no parameter about patients or burn surface was predictable for achieving targeted blood concentration; that usual regimen could not achieve targeted concentrations, excepted with ceftazidime, provided it was used in continuous infusion; that, with the other beta-lactams, continuous infusion was more likely to achieve targeted blood concentrations; that, with fluoroquinolones, both higher and more frequent injections were needed; that, with aminoglycosides used once a day, the dosage had to be higher than usually recommended. We conclude that antimicrobial regimen should be altered in burns and that a monitoring of blood concentrations should be performed in these patients.

Isolevuglandins covalently modify phosphatidylethanolamines in vivo: detection and quantitative analysis of hydroxylactam adducts.

Levuglandins (LGs) and isolevuglandins (isoLGs, also called "isoketals" or "isoKs") are extraordinarily reactive products of cyclooxygenase- and free radical-induced oxidation of arachidonates. We now report the detection in vivo and quantitative analysis of LG/isoLG adducts that incorporate the amino group of phosphatidylethanolamines (PEs) into LG/isoLG-hydroxylactams. Notably, LC-MS/MS detection of these hydroxylactams is achieved with samples that are an order of magnitude smaller and sample processing is much simpler and less time consuming than required for measuring protein-derived LG/isoLG-lysyl lactams. A key feature of our protocol is treatment of biological phospholipid extracts with phospholipase A(2) to generate mainly 1-palmitoyl-2-lysoPE-hydroxylactams from heterogeneous mixtures of phospholipids with a variety of acyl groups on the 2 position. Over 160% higher mean levels of LG/isoLG-PE-hydroxylactam (P<0.001) were detected in liver from chronic ethanol-fed mice (32.4+/-6.3 ng/g, n=6) compared to controls (12.1+/-1.5 ng/g, n=4), and mean levels in plasma from patients with age-related macular degeneration (5.2+/-0.4 ng/ml, n=15) were elevated approximately 53% (P<0.0001) compared to those of healthy volunteers (3.4+/-0.1 ng/ml, n=15). Just as LG/isoLG-protein adducts provide a dosimeter of oxidative injury, this study suggests that LG/isoLG-PE-hydroxylactams are potential biomarkers for assessing risk for oxidative stress-stimulated diseases.

Synthesis, ex vivo and in vitro hydrolysis study of an indoline derivative designed as an anti-inflammatory with reduced gastric ulceration properties.

The compound 1-(2,6-dichlorophenyl)indolin-2-one (1), planned as a pro-drug of diclofenac (2), was easily synthesized in 94% yield by an intramolecular reaction in the presence of coupling agent (i.e., EDC). Compound 1 showed anti-inflammatory and analgesic activity without gastro-ulcerogenic effects. The chemical and enzymatic hydrolysis profile of the lactam derivative 1 does not indicate conversion to diclofenac (2). This compound is a new non-ulcerogenic prototype for treatment of chronic inflammatory diseases.

Identification and quantification of the atypical metabolite ornithine-lactam in human plasma by liquid chromatography-tandem mass spectrometry (LC-MS/MS).

In the late 1970s the atypical metabolite of ornithine, ornithine-lactam, has been observed in urine samples of patients suffering from hyperornithinemia. However, not least due to insufficient analytical methods, until now there are no data available about ornithine-lactam in human plasma. Here, we describe a new method, which is, for the first time, suitable to identify and quantify ornithine-lactam in human EDTA-plasma. The method was validated according to the requirements of the FDA guidance for bioanalytical method validation. The analytes were extracted on mixed mode cation exchange SPE columns, separated on a silica analytical HPLC column working in the HILIC mode and detected on a tandem mass spectrometer equipped with an ESI ion source. As internal standard newly synthesized stable isotope labeled D(6)-ornithine-lactam was used. The calibration function was linear in the range of 0.1-5 microM. Intra- and inter-day precision and accuracy was better than 14% at all concentration levels. In EDTA-plasma samples from 30 volunteers ornithine-lactam concentrations ranging from 0.136 to 0.653 microM were determined. These concentrations correlated significantly (p<0.001, R(2)=0.784) to those of ornithine in EDTA-plasma.

Reduction of in-source collision-induced dissociation and thermolysis of sulopenem prodrugs for quantitative liquid chromatography/electrospray ionization mass spectrometric analysis by promoting sodium adduct formation.

Six chromatographically resolved sulopenem prodrugs were monitored for their potential to undergo both in-source collision-induced dissociation (CID) and thermolysis. Initial Q1 scans for each prodrug revealed the formation of intense [Prodrug2 + H]+, [Prodrug2 + Na]+, [Prodrug + Na]+, and [Sulopenem + Na]+ ions. Non-adduct-associated sulopenem ([Sulopenem + H]+) along with several additional lower mass ions were also observed. Product ion scans of [Prodrug3 + Na]+ showed the retention of the sodium adduct in the collision cell continuing down to opening of the beta-lactam ring. In-source CID and temperature experiments were conducted under chromatographic conditions while monitoring several of the latter ion transitions (i.e., adducts, dimers and degradants/fragments) for a given prodrug. The resulting ion profiles indicated the regions of greatest stability for temperature and declustering potential (DP) that provided the highest signal intensity for each prodrug and minimized in-source degradation. The heightened stability of adduct ions, relative to their appropriate counterpart (i.e., dimer to dimer adduct and prodrug to prodrug adduct ions), was observed under elevated temperature and DP conditions. The addition of 100 microM sodium to the mobile phase further enhanced the formation of these more stable adduct ions, yielding an optimal [Prodrug + Na]+ ion signal at temperatures from 400 to 600 degrees C. A clinical liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for sulopenem prodrug PF-04064900 in buffered whole blood was successfully validated using sodium-fortified mobile phase and the [PF-04064900 + Na]+ ion for quantitation. A conservative five-fold increase in sensitivity from previously validated preclinical assays using the [PF-04064900 + H]+ precursor ion was achieved.

In vitro metabolism of KBH-A40, a novel delta-lactam-based histone deacetylase (HDAC) inhibitor, in human liver microsomes and serum.

1. The metabolism of KBH-A40, a novel delta-lactam-based histone deacetylase (HDAC) inhibitor, was investigated in vitro using human liver microsomes and serum. After 60-min incubation in human liver microsomes with beta-nicotinamide adenine dinucleotide phosphate (NADPH) or uridine diphosphate glucuronic acid (UDPGA), the residual KBH-A40 was 90.6% +/- 5.1% and 28.9% +/- 2.0% (t(1/2) = 26 min), respectively, suggesting that KBH-A40 is likely predominantly metabolized by glucuronidation, rather than by cytochrome P450 (CYP)-mediated oxidation. Consistently, KBH-A40 glucuronide was the only metabolite identified following incubations of KBH-A40 with human liver microsomes in the presence of both NADPH and UDPGA. 2. KBH-A40 was not notably degraded when incubated with human serum for 60 min. In contrast, KBH-A40 was rapidly hydrolysed to its carboxylic acid form in rat serum (t(1/2) = 13 min). 3. Taken collectively, the results suggest that KBH-A40 is likely metabolized in man predominantly by glucuronidation of its hydroxamic acid moiety, with negligible biotransformation elsewhere in the molecule.

[Blood and respiratory diffusion of antibiotics. A critical analysis of predictive parameters for clinical effectiveness]. / 05--diffusion sérique et respiratoire des antibiotiques. Analyse critique des paramètres prédictifs d'efficacité clinique.

The implementation of a treatment for lower respiratory tract infections must integrate a pharmacokinetic/pharmacodynamic (PK-PD) approach of antibiotic dosing. The activity of beta-lactam antibiotics is best predicted by the duration of time during which serum concentrations exceed the MIC (T>MIC). T>MIC of 30-40% is sufficient to achieve clinical cure in immunocompetent patients. This threshold is achieved with amoxicillin for penicillin susceptible or resistant Sreptococcus pneumoniae and with amoxicillin-clavulanate and ceftriaxone for S. pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. For macrolides, the activity is best predicted by T>MIC and for azithromycin and telithromycin by area-under-the-curve/MIC (AUC/MIC). Sufficient PK-PD values are only achieved for macrolides against susceptible strains of S. pneumoniae and against M. catarrhalis; for telithromycin, an AUC/MIC>25, which is necessary for bacterial eradication, is achieved in>99% of patients for S. pneumoniae and M. catarrhalis and>90% of patients for H. influenzae. For fluoroquinolones, both peak/MIC and AUC/MIC are predictors of clinical and bacteriological efficacy. AUC/MIC required ratios vary according to pathogens and severity of diseases from 48 to 125. These thresholds are reached for respiratory pathogens; for S. pneumoniae, AUC/MIC90 ratios of levofloxacin and moxifloxacin are 96 and 192, respectively; the presence of a mutation in parC increases the risk for the acquisition of additional mutations and failure.

[Pharmacokinetics of (-)-clausenamide and its major metabolite 6-hydroxyl-clausenamide in beagle dogs by HPLC/MS].

UNLABELLED: To establish a sensitive and accurate method to study the pharmacokinetics of (-)-clausenamide [(-)-clau] and its major metabolite 6-hydroxyl-clausenamide (6-OH-clau) in the plasma of the Beagle dog. METHODS: (-)-Clau was orally administered to six Beagle dogs at the dose of 30 mg x kg(-1), venous blood from front leg was sampled and plasma was separated for analysis. After extraction with ethyl acetate, the plasma samples were analyzed by HPLC/MS and the mobile phase was a mixture of methanol-water-acetic acid (60: 40: 0. 8) at the flow rate of 1.0 mL x min(-1). The API-ES positive ion SIM detection was carried out for the detection of both (-)-clau ([M + H] (+), m/z 298 ) and 6-OH-clau ([M + H - H2 O](+), m/z 296) with glipzide (glip) ([M + H](+), m/z 446) as internal standard. The pharmacokinetic parameters were calculated by 3P97 software. RESULTS: There was good linear relationship ( r > 0. 999) between the SIM responses and the concentrations for (-)-clau and 6-OH-clau at the range from 1.0 to 200 ng x mL(-1) and 0.2 to 40.0 ng x mL(-1), respectively. The absolute recovery was greater than 85%. The plasma concentration-time curves of (-)-clau and 6-OH-clau were both best fitted to a two-compartment model. The C(max) of (-)-clau and 6-OH-clau were (21 +/- 10) ng x mL(-1) and (3.9 +/- 2.2) ng x mL(-1), T(max) were (0.8 +/- 0.5) h and (1.3 +/- 0.5) h, T 1/2 alpha were (0.9 +/- 0.6) hand (1.4 +/- 0.6) h, T 1/2 beta were (19 +/- 23) hand (13 +/- 12) h, AUC(0-24 h) were (69 +/- 14) h x ng x mL(-1) and (12 +/- 7) h x ng x mL(-1) respectively. CONCLUSION: The established HPLC/MS method was sensitive and specific for the determination of (-)-clau. It was shown that the absorption and first phase elimination of (-)-clau were very quick in Beagle dogs, but the terminal elimination was very slow. The plasma concentration profile of its major metabolite 6-OH-clau was similar to (-)-clau and the AUC was relatively small in comparison with (-)-clau.

Quantification of faropenem in human plasma by high-performance liquid chromatography.

A simple, sensitive and specific high-performance liquid chromatography (HPLC) method with ultraviolet detection (315 nm) was developed and validated for quantitation of faropenem (CAS 106560-14-9), the newest addition to the group of beta-lactam antimicrobials, in human plasma. Following solid-phase extraction using Waters Oasis SPE cartridges, the analyte and internal standard (hydrochlorothiazide, CAS 58-93-5) were separated using an isocratic mobile phase of 10 mmol/L acetate buffer (pH adjusted to 7.0 with dilute acetic acid) / methanol / triethyl amine (70/30/0.03, v/v/v) on reverse phase Waters symmetry C18 column. The lower limit of quantitation was 200 ng/mL, with a relative standard deviation of less than 2 %. A linear range of 200 to 25000 ng/mL was established. This HPLC method was validated with between-batch and within-batch precision of 1.6 to 2.3 % and 0.4 to 1.6 %, respectively. The between-batch and within-batch bias was -3.1 to 5.3 % and -6.0 to 1.5 %, respectively. Frequently coadministered drugs did not interfere with the described methodology. The stability of faropenem in plasma was excellent, with no evidence of degradation during sample processing (autosampler) and 30 days storage in a freezer. This validated method is sensitive, simple and repeatable enough to be used in pharmacokinetic studies.

Comparative disposition of [14C]ertapenem, a novel carbapenem antibiotic, in rat, monkey and man.

1. The disposition and metabolism of ertapenem, a carbapenem antibiotic, was examined in rat, monkey and man. Sprague-Dawley rats and Rhesus monkeys were given, by intravenous administration, radiolabelled doses of ertapenem (60 and 30 mg kg(-1), respectively), and healthy normal volunteers received a single fixed dose of 1000 mg. Urine and faeces were collected for determination of total radioactivity. 2. In healthy volunteers, [14C]ertapenem was eliminated by a combination of hydrolytic metabolism to a beta-lactam ring-opened derivative and renal excretion of unchanged drug. Approximately equal amounts were excreted as a beta-lactam ring-opened metabolite and unchanged drug (36.7 and 37.5% of dose, respectively). A secondary amide hydrolysis product accounted for about 1% of the dose in man. About 10% of the administered radioactivity was recovered in faeces, which suggested that a minor fraction underwent biliary and/or intestinal excretion. 3. In animals, a greater fraction of the dose was eliminated via metabolism; excretion of unchanged drug accounted for 17 and 5% of dose in rats and monkeys, respectively. In monkeys, the beta-lactam ring-opened and amide hydrolysis metabolites accounted for 74.8 and 7.59% of the dose, respectively, whereas in rats, these metabolites accounted for 31.9 and 20% of dose, respectively. 4. In vitro studies with fresh rat tissue homogenates indicated that lung and kidney were the primary organs involved in mediating formation of the beta-lactam ring-opened metabolite. The specific inhibitor of dehydropeptidase-I, cilastatin, inhibited the in vivo and in vitro metabolism of ertapenem in rats, which suggested strongly that the hydrolysis of ertapenem in lung and kidney was mediated by this enzyme.

Pharmacokinetic interactions of ceftazidime, imipenem and aztreonam with amikacin in healthy volunteers.

The common usage of extended spectrum beta-lactams co-administered with amikacin in everyday clinical practice for infections by multidrug-resistant isolates has created the need to search for pharmacokinetic interaction. Eighteen healthy volunteers were enrolled in the study; six were administered 1g of ceftazidime singly intravenously or combined with 0.5 g of amikacin; six received 0.5 g of imipenem singly or combined with 0.5 g of amikacin and six 1g of aztreonam singly or combined with 0.5 g of amikacin. Blood and urine samples were collected at regular time intervals and apparent serum levels were determined by a microbiological assay. Co-administration of ceftazidime and amikacin resulted in higher C(max) and AUC for amikacin than when administered alone. Co-administration of imipenem and amikacin resulted in higher C(max) for imipenem than when administered alone. The tested interactions did not affect plasma half-life (t(1/2)) and clearance rate of any antimicrobial compared with its single administration. All tested drugs were mainly eliminated by glomerular filtration. It is concluded that co-administration of ceftazidime, imipenem or aztreonam with amikacin in healthy volunteers might affect C(max) and AUC without influencing any other pharmacokinetic parameter. The probable clinical endpoint is that giving ceftazidime, imipenem or aztreonam with amikacin might result in a transient elevation of beta-lactam serum levels without further affecting the complete pharmacokinetic profile of each drug as obtained after administration of the drug alone.