Adjusting surface coverage of Pt nanocatalyst decoration for selectivity control in CMOS-integrated SnO2 thin film gas sensors

Smart gas-sensor devices are of crucial importance for emerging consumer electronics and Internet-of-Things (IoT) applications, in particular for indoor and outdoor air quality monitoring (e.g., CO2 levels) or for detecting pollutants harmful for human health. Chemoresistive nanosensors based on metal-oxide semiconductors are among the most promising technologies due to their high sensitivity and suitability for scalable low-cost fabrication of miniaturised devices. However, poor selectivity between different target analytes restrains this technology from broader applicability. This is commonly addressed by chemical functionalisation of the sensor surface via catalytic nanoparticles. Yet, while the latter led to significant advances in gas selectivity, nanocatalyst decoration with precise size and coverage control remains challenging. Here, we present CMOS-integrated gas sensors based on tin oxide (SnO2) films deposited by spray pyrolysis technology, which were functionalised with platinum (Pt) nanocatalysts. We deposited size-selected Pt nanoparticles (narrow size distribution around 3 nm) by magnetron-sputtering inert-gas condensation, a technique which enables straightforward surface coverage control. The resulting impact on SnO2 sensor properties for CO and volatile organic compound (VOC) detection via functionalisation was investigated. We identified an upper threshold for nanoparticle deposition time above which increased surface coverage did not result in further CO or VOC sensitivity enhancement. Most importantly, we demonstrate a method to adjust the selectivity between these target gases by simply adjusting the Pt nanoparticle deposition time. Using a simple computational model for nanocatalyst coverage resulting from random gas-phase deposition, we support our findings and discuss the effects of nanoparticle coalescence as well as inter-particle distances on sensor functionalisation.

Effect of albumin substitution on pharmacokinetics of piperacillin/tazobactam in patients with severe burn injury admitted to the ICU

BACKGROUND

Pathophysiological changes in severely burned patients alter the pharmacokinetics (PK) of anti-infective agents, potentially leading to subtherapeutic concentrations at the target site. Albumin supplementation, to support fluid resuscitation, may affect pharmacokinetic properties by binding drugs. This study aimed to investigate the PK of piperacillin/tazobactam in burn patients admitted to the ICU before and after albumin substitution as total and unbound concentrations in plasma.

PATIENTS AND METHODS

Patients admitted to the ICU and scheduled for 4.5 g piperacillin/tazobactam administration and 200 mL of 20% albumin substitution as part of clinical routine were included. Patients underwent IV microdialysis, and simultaneous arterial plasma sampling, at baseline and multiple timepoints after drug administration. PK analysis of total and unbound drug concentrations under steady-state conditions was performed before and after albumin supplementation.

RESULTS

A total of seven patients with second- to third-degree burns involving 20%-60% of the total body surface were enrolled. Mean (SD) AUC0-8 (h·mg/L) of total piperacillin/tazobactam before and after albumin substitution were 402.1 (242)/53.2 (27) and 521.8 (363)/59.7 (32), respectively. Unbound mean AUC0-8 before and after albumin supplementation were 398.9 (204)/54.5 (25) and 456.4 (439)/64.5 (82), respectively.

CONCLUSIONS

Albumin supplementation had little impact on the PK of piperacillin/tazobactam. After albumin supplementation, there was a numerical increase in mean AUC0-8 of total and unbound piperacillin/tazobactam, whereas similar Cmax values were observed. Future studies may investigate the effect of albumin supplementation on drugs with a higher plasma protein binding.

Comparison of ultrafiltration and microdialysis for ceftriaxone protein-binding determination

BACKGROUND

High protein binding (PB) of antibiotics has an impact on their antimicrobial activity. It has been questioned whether in vitro PB determination can capture the dynamic and concentration-dependent PB of highly bound antibiotics.

OBJECTIVES

This clinical study compared in vitro ultrafiltration (UF) and in vivo IV microdialysis (MD) methods to determine ceftriaxone PB.

METHODS

Six healthy male volunteers received a single IV 2 g dose of ceftriaxone. Unbound ceftriaxone plasma concentrations were measured with MD and venous plasma sampling with subsequent UF. Pharmacokinetic parameters were determined using non-compartmental pharmacokinetic analysis. Non-linear mixed-effects modelling was used to quantify the PB. The PTA was estimated.

RESULTS

The Cmax of ceftriaxone total plasma concentration (297.42 ± 21.0 mg/L) was approximately 5.5-fold higher than for free concentrations obtained with UF (52.83 ± 5.07 mg/L), and only 3.5-fold higher than for free concentrations obtained with MD (81.37 ± 26.93 mg/L). Non-linear, saturable PB binding was confirmed for both UF and MD. Significantly different dissociation constants (Kd) for the albumin/ceftriaxone complex were quantified: in UF it was 23.7 mg/L (95% CI 21.3-26.2) versus 15.9 mg/L (95% CI 13.6-18.6) in MD. Moreover, the estimated number of binding sites (95% CI) per albumin molecule was 0.916 (0.86-0.97) in UF versus 0.548 in MD (0.51-0.59). The PTA obtained with MD was at most 27% higher than with UF.

CONCLUSIONS

In vitro UF versus in vivo intravasal MD revealed significantly different PB, especially during the distribution phase. The method of PB determination could have an impact on the breakpoint determination and dose optimisation of antibiotics.

Effect of the human endotoxin challenge on tedizolid tissue penetration

The effects of the human endotoxin challenge on tissue pharmacokinetics are unknown. In the present study, we aimed to assess the effect of the endotoxin challenge on interstitial fluid pharmacokinetics of tedizolid in healthy volunteers using intramuscular microdialysis. Eight healthy male subjects were treated with 200 mg of tedizolid phosphate for 6 days. On Day 6, an intravenous bolus of lipopolysaccharide (LPS) (2 ng/kg body weight) was administered. LPS infusion did not affect plasma pharmacokinetics of tedizolid. In contrast, following LPS infusion, median muscle tissue fAUC (0.83 [0.75-1.15] vs. 1.14 [1.11-1.43] mg × h/L, P = .0078) and muscle tissue fC_max (0.15 [0.14-0.19] vs. 0.19 [0.18-0.24] mg/L, P = .0078) were significantly increased by 38% and 24%, respectively. The human endotoxin challenge was associated with increased tissue concentrations of tedizolid, without affecting its plasma concentration-time profile. The human endotoxin challenge combined with microdialysis may be used to investigate the influence of systemic inflammation on tissue pharmacokinetics.

Comparison of pharmacokinetics and stability of generics of cefepime, linezolid and piperacillin/tazobactam with their respective originator drugs: an intravenous bioequivalence study in healthy volunteers

OBJECTIVES

The efficacy and quality of generic antibacterial drug formulations are often questioned by both healthcare specialists and patients. Therefore, the present study investigated the interchangeability of generic drugs with their originators by comparing bioequivalence parameters and stability data of generic cefepime, linezolid and piperacillin/tazobactam with their respective originator drugs.

METHODS

In this open-label, randomized, crossover bioequivalence study, three groups of 12 healthy volunteers each received a single intravenous infusion of either 2 g of cefepime or 4.5 g of piperacillin/tazobactam and two generic formulations, or 600 mg of linezolid and one generic formulation. Plasma sampling was performed, with a 5 day washout period between study days. Stability was tested by storing reconstituted generic and originator products according to their own storage specifications and those of the comparator products. All concentrations were measured by LC-MS.

RESULTS

Similar ratios of generic/originator (90% CI) Cmax were observed for Cefepime-MIP/Maxipime [93.7 (88.4-99.4)], Cefepime Sandoz/Maxipime [95.9 (89.1-103.2)], Linezolid Kabi/Zyvoxid [104.5 (91.1-119.9)], Piperacillin Kabi/Tazobac [95.9 (90.4-101.7)], Piperacillin Aurobindo/Tazobac [99.7 (84.9-104.7)], Tazobactam Kabi/Tazobac [93.4 (87.4-99.8)] and Tazobactam Aurobindo/Tazobac [97.4 (89.7-105.8)]. Accordingly, similar ratios of AUC0-t were observed for Cefepime-MIP/Maxipime [91.1 (87.6-94.8)], Cefepime Sandoz/Maxipime [97.9 (92.5-103.5)], Linezolid Kabi/Zyvoxid [99.7 (93.3-106.6)], Piperacillin Kabi/Tazobac [92.2 (88.3-96.3)], Piperacillin Aurobindo/Tazobac [99.9 (97.0-102.8)], Tazobactam Kabi/Tazobac [91.4 (86.4-96.7)] and Tazobactam Aurobindo/Tazobac [98.8 (94.3-103.6)]. Stable and similar concentrations were measured for all contiguous substances, regardless of storage conditions.

CONCLUSIONS

Compared with their respective originator drugs, generic cefepime, linezolid and piperacillin/tazobactam met the predetermined bioequivalence criteria. All formulations were stable under the storage conditions of their respective comparators.

Diclofenac in vitro microdialysis study comparing different experimental setups to improve quantitative recovery

Several studies investigated diclofenac tissue concentrations using microdialysis (MD). However, thorough evaluations of the optimal MD set‐up for diclofenac are unavailable. Thus, this in vitro MD study aimed to compare different set‐ups to improve quantitative recovery of diclofenac. In forward and reverse in vitro MD experiments with diclofenac at two concentrations (1 and 100 ng/ml), the perfusion solutions physiological saline 0.9% (PS) and human albumin 1% (HSA) were compared using tissue probes (10‐mm membrane) and customized intravenous (iv) probes (30‐mm membrane). Using PS, the mean relative recovery of diclofenac at 1 ng/ml was 1.6% ± 0.04% and 3.12% ± 0.00% with the tissue probe and the iv probe, respectively. The respective mean relative recovery for diclofenac at 100 ng/ml was 0.02% ± 0.01% and 0.21% ± 0.11%. Using HSA, the mean relative recovery was 314% ± 25% (tissue probe) and 1064% ± 97% (iv probe) for diclofenac at 1 ng/ml and 444% ± 91% and 1415% ± 217% for diclofenac at 100 ng/ml. In reverse dialysis using PS, the mean relative loss of diclofenac was 99.2% ± 0.5% (tissue probe) and 95.8% ± 1.7% (iv probe). Using HSA, the mean relative loss was −4.4% ± 7.2% and 0.2% ± 7.5%, respectively. PS and HSA were not suitable perfusion solutions for quantification of absolute diclofenac concentrations. Despite methodological challenges, HSA may be used for comparative experiments or bioequivalence studies.

Protein binding of clindamycin in vivo by means of intravascular microdialysis in healthy volunteers

OBJECTIVES

The efficacy of an anti-infective drug is influenced by its protein binding (PB), since only the free fraction is active. We hypothesized that PB may vary in vitro and in vivo, and used clindamycin, a drug with high and concentration-dependent PB to investigate this hypothesis.

METHODS

Six healthy volunteers received a single intravenous infusion of clindamycin 900 mg. Antibiotic plasma concentrations were obtained by blood sampling and unbound drug concentrations were determined by means of in vivo intravascular microdialysis (MD) or in vitro ultrafiltration (UF) for up to 8 h post dosing. Clindamycin was assayed in plasma and MD fluid using a validated HPLC-UV (ultraviolet) method. Non-linear mixed effects modelling in NONMEM® was used to quantify the PB in vivo and in vitro.

RESULTS

C max was 14.95, 3.39 and 2.32 mg/L and AUC0-8h was 41.78, 5.80 and 6.14 mg·h/L for plasma, ultrafiltrate and microdialysate, respectively. Calculated ratio of AUCunbound/AUCtotal showed values of 13.9%±1.8% and 14.7%±3.1% for UF and microdialysate, respectively. Modelling confirmed non-linear, saturable PB for clindamycin with slightly different median (95% CI) dissociation constants (Kd) for the alpha-1 acid glycoprotein (AAG)-clindamycin complex of 1.16 mg/L (0.91-1.37) in vitro versus 0.85 mg/L (0.58-1.01) in vivo. Moreover, the estimated number of binding sites per AAG molecule was 2.07 (1.79-2.25) in vitro versus 1.66 in vivo (1.41-1.79).

CONCLUSIONS

Concentration-dependent PB was observed for both investigated methods with slightly lower levels of unbound drug fractions in vitro as compared with in vivo.

Phase I Study to Assess Safety of Laser-Assisted Topical Administration of an Anti-TNF Biologic in Patients With Chronic Plaque-Type Psoriasis

Ablative fractional laser treatment facilitates epidermal drug delivery, which might be an interesting option to increase the topical efficacy of biological drugs in a variety of dermatological diseases. This work aims at investigating safety and tolerability of this new treatment approach in patients with plaque-type psoriasis. Eight patients with plaque-type psoriasis were enrolled in this study. All patients received (i) ablative fractional laser microporation (AFL) of a psoriatic lesion with an Er:YAG laser + etanercept (ETA; Enbrel® solution for injection) (AFL-ETA), (ii) ETA alone on another lesion, and, if feasible, (iii) AFL alone on an additional lesion. Overall, all treatment arms showed a favorable safety profile. AFL-ETA improved the lesion-specific TPSS score by 1.75 vs. baseline, whereas ETA or AFL alone showed a TPSS score improvement of 0.75 points, a difference that was not statistically significant and might be attributable to differences in baseline scores. Topical administration of ETA to psoriatic plaques via AFL-generated micropores was generally well-tolerated. No special precautions seem necessary in future studies. Clinical benefit will need assessment in sufficiently powered follow-up studies.

Single-dose pharmacokinetics of temocillin in plasma and soft tissues of healthy volunteers after intravenous and subcutaneous administration: a randomized crossover microdialysis trial

BACKGROUND

The antibiotic temocillin has recently been rediscovered as a promising therapeutic option against MDR Gram-negative bacteria. However, some aspects of the pharmacokinetic (PK) profile of the drug are still to be elucidated: subcutaneous administration of temocillin might be of interest as an alternative to the intravenous route in selected patients. Similarly, information on the penetration of temocillin into human soft tissues is lacking.

OBJECTIVES

To investigate the feasibility and plasma PK of subcutaneous dosing as well as soft tissue PK of temocillin after intravenous administration to healthy volunteers.

METHODS

Eight healthy volunteers received 2 g of temocillin both as intravenous and subcutaneous infusion in a randomized two-period crossover study. Concentration-time profiles of total temocillin in plasma (after both routes) and of unbound temocillin in plasma, muscle and subcutis (only after intravenous dosing) were determined up to 12 h post-dose.

RESULTS

Subcutaneous dosing caused some infusion site discomfort but resulted in sustained drug concentrations over time with only slightly decreased overall exposure compared with intravenous dosing. Plasma protein binding of temocillin showed concentration-dependent behaviour and was higher than previously reported. Still, unbound drug concentrations in muscle and subcutis determined by microdialysis markedly exceeded those in plasma, suggesting good tissue penetration of temocillin.

CONCLUSIONS

The subcutaneous administration of temocillin is a valid and feasible alternative to intravenous dosing. With the description of plasma protein binding and soft tissue PK of temocillin in healthy volunteers, this study provides important information that adds to the ongoing characterization of the PK profile of temocillin and might serve as input for PK/PD considerations.

Plasma and soft tissue pharmacokinetics of ceftolozane/tazobactam in healthy volunteers after single and multiple intravenous infusion: a microdialysis study

OBJECTIVES

To investigate ceftolozane/tazobactam pharmacokinetics (PK) in plasma and interstitial space fluid (ISF) of muscle and subcutaneous tissue and establish a population PK model.

METHODS

Eight healthy volunteers received four IV doses of 1000/500 mg ceftolozane/tazobactam q8h in a prospective, open-labelled PK study. ISF concentration-time profiles were determined via in vivo microdialysis up to 8 h post-dose and efficacy of unbound ceftolozane and tazobactam was estimated using the time above MIC (%ƒT>MIC) and time above threshold concentration (%T>CT), respectively. A population PK model was established by merging derived plasma and soft tissue PK data.

RESULTS

Ceftolozane reached %ƒT>MIC values of 100% in plasma, muscle and subcutaneous ISF for Enterobacteriaceae and 87%, 89% and 87%, respectively, for Pseudomonas aeruginosa. Tazobactam %T>CT was 21%, 22% and 21% in plasma, muscle and subcutaneous ISF, respectively. Plasma protein binding was 6.3% for ceftolozane and 8.0% for tazobactam. Multiple-dose ceftolozane AUC0-8 ISF/plasma ratios were 0.92 ± 0.17 in muscle and 0.88 ± 0.18 in subcutis, and tazobactam ratios were 0.89 ± 0.25 in muscle and 0.87 ± 0.21 in subcutis, suggesting substantial soft tissue penetration.

CONCLUSIONS

Tazobactam %T>CT values were distinctly below proposed target values, indicating that tazobactam might be underdosed in the investigated drug combination. However, ISF/unbound plasma ratios of ceftolozane and tazobactam support their use in soft tissue infections. A plasma and soft tissue PK model adds important information on the PK profile of ceftolozane/tazobactam. Further investigations in patients suffering from wound infections are needed to confirm these findings.

Lack of dermal penetration of topically applied gentamicin as pharmacokinetic evidence indicating insufficient efficacy

Background

Treatment of skin and superficial soft tissue infections with topically applied antibiotics is a controversial topic, because only few clinical studies exist and target site concentrations after topical treatment are widely unknown.

Objectives

This study aimed to investigate the target site concentration of topically applied gentamicin as a potential cause of therapeutic failure and to explore if microporation by laser might be used to improve penetration of gentamicin through the skin barrier.

Methods

Six healthy volunteers were included in this cross-over Phase 1 study. On two study days, separated by a washout period, microdialysate and plasma sampling was performed for 6 h after administration of 500 mg of gentamicin cream on a predefined area. On one of the study days the skin was microporated before drug application using the P.L.E.A.S.E. Professional laser system.

Results

In intact skin, Cmax and AUC values were 3.3 ± 5.64 ng/mL and 5.4 ± 10.4 ng·h/mL, respectively; thereby far under the threshold needed to treat common pathogens. With a Cmax of 474.2 ± 555.3 ng/mL laser application showed a significant increase in tissue penetration and decrease in pharmacokinetic variability; however, even after microporation no therapeutically active concentrations were achieved as indicated by Cmax/epidemiological cut-off ratios of 0.237 and 0.059 for Staphylococcus aureus and Pseudomonas aeruginosa, respectively. Solely after administration on microporated skin, plasma concentrations of gentamicin were quantifiable (lower limit of quantification 10 pg/mL).

Conclusions

This study confirmed that after topical administration gentamicin penetration through the dermal barrier is insufficient, providing pharmacokinetic evidence that topical gentamicin in its current form might be inappropriate to treat skin infections.

High voriconazole target-site exposure after approved sequence dosing due to nonlinear pharmacokinetics assessed by long-term microdialysis

Voriconazole, a broad-spectrum antifungal drug used to prevent and treat invasive fungal infections, shows complex pharmacokinetics and is primarily metabolised by various CYP enzymes. An adequate unbound antibiotic concentration-time profile at the target-site of an infection is crucial for effective prophylaxis or therapy success. Therefore, the aim was to evaluate the pharmacokinetics of voriconazole after the approved sequence dosing in healthy volunteers in interstitial space fluid, assessed by microdialysis, and in plasma. Moreover, potential pharmacogenetic influences of CYP2C19 polymorphisms on pharmacokinetics were investigated. The prospective, open-labelled, uncontrolled long-term microdialysis study included 9 healthy male individuals receiving the approved sequence dosing regimen for voriconazole. Unbound voriconazole concentrations were sampled over 84 h in interstitial space fluid of subcutaneous adipose tissue and in plasma and subsequently quantified via high-performance liquid chromatography. For pharmacokinetic data analysis, non-compartmental analysis was used. High interindividual variability in voriconazole concentration-time profiles was detected although dosing was adapted to body weight for the first intravenous administrations. Due to nonlinear pharmacokinetics, target-site exposure of voriconazole in healthy volunteers was found to be highly comparable to plasma exposure, particularly after multiple dosing. Regarding the CYP2C19 genotype-predicted phenotype, the individuals revealed a broad spectrum, ranging from poor to rapid metaboliser status. A strong relation between CYP2C19 genotype-predicted phenotype and voriconazole clearance was identified.

Pharmacokinetics of doripenem in plasma and epithelial lining fluid (ELF): comparison of two dosage regimens

Purpose

In 2014, FDA released a warning for prescription of doripenem for ventilator-associated bacterial pneumonia due to unsatisfactory clinical cure rates. The present study explores if the observed lack of efficacy might be explained by insufficient target site pharmacokinetics in intensive care patients after two different infusion schemes.

Methods

Plasma and bronchoalveolar lavage sampling was performed in 16 intubated patients with pneumonia receiving doripenem either as 1-h or as 4-h infusion. Doripenem concentrations were measured at steady state in plasma over 8 h, bronchoalvoelar lavage was performed in each patient once either after 0 h, 2 h, 4 h or 6 h.

Results

In plasma, mean values of C_max, T_max and AUC_0–8 were 16.87 mg/L, 0.69 h and 52.98 mg/L^×h after 1 h of infusion, and 12.94 mg/L, 3.21 h and 70.64 mg/L^×h after 4 h of infusion, respectively. While the later t_max in plasma was with delay mirrored in the lung, for ELF, much lower concentrations were observed (C_max, T_max and AUC_0–8 after 1-h infusion of 4.6 mg/L, 2 h and 15.3 mg/L^×h and after 4-h infusion 6.9 mg/L, 4 h and 14.8 mg/L^×h).

Conclusion

The difference in plasma pharmacokinetics after 1-h and 4-h infusion reflects in the concentration versus time profile in the lung, but concentration at the target site was not only considerably lower but also subject to high inter-individual variability. We hypothesise that insufficient concentrations at the target site might have contributed to the previously described lack of clinical efficacy and confirmed the demand for assessment of target site pharmacokinetics in larger patient collectives.

Colistin Reduces LPS-Triggered Inflammation in a Human Sepsis Model In Vivo: A Randomized Controlled Trial

The previously described anti-endotoxin effect of colistin has not been investigated in humans yet. We performed a randomized, double-blind, placebo-controlled crossover trial to determine the degree of colistin-driven modulation of inflammatory response in blood of lipopolysaccharide (LPS)-challenged healthy volunteers in a human endotoxemia model. After a single intravenous dose of 2.5 million IU colistin methanesulfonate, interleukin (IL)-6, IL-8, tumor necrosis factor alpha (TNF-α), and IL-1β concentrations as well as other biomarkers of inflammation such as C-reactive protein, differential leukocyte counts, and body temperature were measured up to 24 h postdose. Colistin significantly decreased the inflammatory cytokine response to LPS in blood of healthy volunteers. This effect was most evident for IL-6, IL-8, and TNF-α. This study is the first to confirm the anti-endotoxin effect of colistin in humans in vivo. Further studies might increase our knowledge on the interaction between colistin and the effectors of the immune system.

Single- and Repeated-Dose Pharmacokinetics of Ceftaroline in Plasma and Soft Tissues of Healthy Volunteers for Two Different Dosing Regimens of Ceftaroline Fosamil

Ceftaroline fosamil (CPT-F) is currently approved for use for the treatment of complicated skin and soft tissue infections and community-acquired pneumonia at 600 mg twice daily (q12h), but other dosing regimens are under evaluation. To date, very limited data on the soft tissue pharmacokinetics (PK) of the active compound, ceftaroline (CPT), are available. CPT concentrations in the plasma, muscle, and subcutis of 12 male healthy volunteers were measured by microdialysis after single and repeated intravenous administration of 600 mg CPT-F q12h or three times daily (q8h) in two groups of 6 subjects each. Relevant PK and PK/pharmacodynamic (PD) parameters were calculated and compared between groups. In plasma, the area under the concentration-time curve (AUC) from 0 to 24 h for total CPT and the cumulative percentage of the dosing interval during which the free drug concentrations exceeded the MIC (fTMIC) for unbound CPT for the currently established threshold of 1 mg/liter were significantly higher in the group receiving CPT-F q8h. Exposure to free drug in soft tissues was higher in the group receiving CPT-F q8h, but high interindividual variability in relevant PK parameters was observed. The mean ratios of the AUC from time zero to the end of the dosing interval (AUC0-τ) for free CPT in soft tissues and the AUC0-τ for the calculated free fraction in plasma at steady state ranged from 0.66 to 0.75. Administration of CPT-F q8h led to higher levels of drug exposure in all investigated compartments. When MIC values above 1 mg/liter were assumed, the calculated fTMIC after dosing q12h was markedly lower than that after dosing q8h. The clinical implications of these differences are discussed in light of recently completed clinical phase III and PK/PD studies.

Pilot investigation on long-term subcutaneous microdialysis: proof of principle in humans

Reliable drug concentration measurements at the target site are increasingly demanded and can be achieved by microdialysis. The aim of this pilot study was to demonstrate the proof of principle of long-term subcutaneous microdialysis in humans. For long-term microdialysis, a special setting implementing both concentric and linear catheters has been developed ensuring good clinical practice compliance, tolerability, and convenience for participants and personnel. As a model compound, moderately lipophilic voriconazole was selected as a well-characterized drug in in vitro microdialysis experiments. Multiple in vivo relative recovery (RR) determinations for microdialysis were performed by retrodialysis during the entire study (n = 48 samples). Continuous microdialysis was successfully applied and well tolerated over 87 h in three adults for the first time. RR revealed low intra-individual (coefficient of variation (CV) = 4.4-12.5%) and inter-individual variability (CV = 4.3-12.5%) across all samples and catheters. Lower RR values were consistently determined for linear catheters. One catheter leakage was managed without an impact on the reliability of the RR values. Overall, RR values were calculated to be 73.3% (linear: CV = 18.5%, n = 23) and 84.9% (concentric: CV = 5.6%, n = 23). Long-term microdialysis application over almost 4 days was feasible by reliable multiple RR (proof of principle), well tolerated, and reduced the burden in humans avoiding several catheter insertions, thereby allowing to monitor concentration-time courses continuously. Moreover, a moderately lipophilic drug has been proven suitable for in vivo microdialysis, as previously suggested by in vitro microdialysis.

A new topical formulation enhances relative diclofenac bioavailability in healthy male subjects

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT

• Therapy with topical non-steroidal anti-inflammatory drugs (NSAIDs) relies on the ability of the active drug to penetrate the skin in sufficiently high amounts to exert a clinical effect, which is linked to the specific galenic properties of the formulation.

WHAT THIS STUDY ADDS

• This phase 1 study characterizes the transdermal penetration and plasma exposure of different dose levels with galenic differences of a novel topical diclofenac formulation under development and indicates greater diclofenac penetration through the skin when compared with a commercially available formulation.

AIMS

To evaluate the relative plasma and tissue availability of diclofenac after repeated topical administration of a novel diclofenac acid-based delivery system under development (DCF100C).

METHODS

This was a single-centre, open-label, three-period, crossover clinical trial of five discrete diclofenac formulations. Test preparations comprised two concentrations (1.0% and 2.5%) of DCF100C, with and without menthol and eucalyptus oil (total daily doses of 5 mg and 12.5 mg). Voltaren Emulgel gel (1.0%) was the commercially available comparator (total daily dose of 40 mg). Topical application was performed onto the thigh of 20 male healthy subjects for 3 days. Applying a Youden square design, each drug was evaluated in 12 subjects, with each subject receiving three test preparations. Blood sampling and in vivo microdialysis in subcutaneous adipose and skeletal muscle tissues were performed for 10 h after additional final doses on the morning of day 4.

RESULTS

All four DCF100C formulations demonstrated a three- to fivefold, dose-dependent increase in systemic diclofenac availability compared with Voltaren Emulgel and were approximately 30-40 times more effective at facilitating diclofenac penetration through the skin, taking different dose levels into account. Tissue concentrations were low and highly variable. The 2.5% DCF100C formulation without sensory excipients reached the highest tissue concentrations. AUC(0,10 h) was 2.71 times greater than for Voltaren Emulgel (90% CI 99.27, 737.46%). Mild erythema at the application site was the most frequent adverse event associated with DCF100C. There were no local symptoms after treatment with the reference formulation.

CONCLUSION

DCF100C formulations were safe and facilitated greater diclofenac penetration through the skin compared with the commercial comparator. DCF100C represents a promising alternative to oral and topical diclofenac treatments that warrants further development.

Disposition and metabolism of ralfinamide, a novel Na-channel blocker, in healthy male volunteers

Ralfinamide is an α-aminoamide derivative with ion channel blocking properties, acting both peripherally and centrally through different molecular targets important in pain control. Absorption, blood and plasma time courses, and urinary and faecal excretion of total radioactivity were assessed in 6 male healthy volunteers administered a single oral dose of 320 mg ¹⁴C-(S)-ralfinamide. Pharmacokinetics of the parent drug were investigated over 120 h, urinary and plasma metabolites up to 192 h post-dose. ¹⁴C-(S)-ralfinamide was rapidly and completely absorbed. Ralfinamide and the dealkylated ralfinamide metabolite (NW-1716) represented the majority of plasma radioactivity. Plasma elimination of the parent compound occurred mono-exponentially (half-life approx. 15 h). ¹⁴C-radioactivity was eliminated in a bi-phasic manner (terminal half-life of 60 and 24 h for plasma and whole blood, respectively). Plasma-concentrations of unchanged ralfinamide were significantly lower than radioactivity concentrations, indicating metabolism of the parent compound. At 192 h post-dose the total balance of radioactivity was almost complete (95%). The main route of excretion was via the kidneys (94% of the dose). Major metabolites identified in urine and plasma were the N-dealkylated acid of ralfinamide and deaminated ralfinamide acid (NW-1799). Other metabolites, in particular the product of glucuronide conjugation N-dealkylated-β-glucuronide, were identified.

Minimal local anaesthetic volumes for sciatic nerve block: evaluation of ED 99 in volunteers

BACKGROUND

This randomized, double-blinded volunteer study was designed to evaluate the ED(99) volume of local anaesthetic for sciatic nerve blocks using a step-up/step-down methodology.

METHODS

A maximum of 20 volunteers were included to receive an ultrasound-guided sciatic nerve block with mepivacaine 1.5% and a starting volume of 0.2 ml mm(-2) cross-sectional nerve area. In cases of a complete sensory block, the volume was reduced by 0.02 ml mm(-2) cross-sectional nerve area until the first block failed. Thereafter, the volume of local anaesthetic was increased by 0.02 ml mm(-2) cross-sectional nerve area. After three cycles of successful/failed blocks, the ED(99) volume of local anaesthetic could be calculated by a probability function. The influence of the volumes of local anaesthetics on sensory onset times and duration of sensory block was evaluated by linear regression.

RESULTS

The ED(99) volume of local anaesthetic for sciatic nerve block was calculated with 0.10 ml mm(-2) cross-sectional nerve area. The correlation between the volume of local anaesthetic and the sensory onset time was weak (r=0.14), whereas the correlation between the volume of local anaesthetic and the duration of sensory block was moderate (r=0.65).

CONCLUSIONS

This is the first study where an ED(99) volume of local anaesthetic for sciatic nerve block has been evaluated. The resulting local anaesthetic volume of 0.10 ml mm(-2) cross-sectional nerve area seems to have no impact on sensory onset time, whereas the duration of sensory block is shorter.

Targeting of Hsp32 in solid tumors and leukemias: a novel approach to optimize anticancer therapy

Heat shock protein 32 (Hsp32), also known as heme oxygenase-1 (HO-1), is a stress-related anti-apoptotic molecule, that has been implicated in enhanced survival of neoplastic cells and in drug-resistance. We here show that Hsp32 is expressed in most solid tumors and hematopoietic neoplasms and may be employed as a new therapeutic target as evidenced by experiments using specific siRNA and a Hsp32-targeting pharmacologic inhibitor. This Hsp-32 targeting drug, SMA-ZnPP, was found to inhibit the proliferation of neoplastic cells with IC(50) values ranging between 1 and 50 microM. In addition, SMA-ZnPP induced apoptosis in all neoplastic cells examined. Furthermore, SMA-ZnPP was found to synergize with other targeted and conventional drugs in producing growth-inhibition. Resulting synergistic effects were observed in all tumor and leukemia cells examined. Interestingly, several of the drug partners, when applied as single agents, induced the expression of Hsp32 in neoplastic cells, suggesting that synergistic effects resulted from SMA-ZnPP-induced ablation of a Hsp32-mediated survival-pathway that is otherwise used by tumor cells to escape drug-induced apoptosis. Together, Hsp32 is an important survival factor and target in solid tumors and hematopoietic neoplasms, and may be used to optimize anticancer therapy by combining conventional or targeted drugs with Hsp32-inhibitors. Based on these data, it seems desirable to explore the value of Hsp32-targeting drugs as anti-cancer agents in clinical trials.

Effects of olanzapine and ziprasidone on glucose tolerance in healthy volunteers

Atypical antipsychotics have been linked to a higher risk for glucose intolerance, and consequentially the development of type 2 diabetes mellitus (DM2). We have therefore set out to investigate the acute effects of oral administration of olanzapine and ziprasidone on whole body insulin sensitivity in healthy subjects. Using the standardized hyperinsulinemic euglycemic clamp technique we compared whole body insulin sensitivity of 29 healthy male volunteers after oral intake of either olanzapine 10 mg/day (n = 14) or ziprasidone 80 mg/day (n = 15) for 10 days. A significant decrease (p<0.001) in whole body insulin sensitivity from 5.7 ml/h/kg ( = mean, SM = 0.4 ml/h/kg) at baseline to 4.7 ml/h/kg ( = mean, SM = 0.3 ml/h/kg) after oral intake of olanzapine (10 mg/day) for 10 days was observed. The ziprasidone (80 mg/day) group did not show any significant difference (5.2+/-0.3 ml/h/kg baseline vs 5.1+/-0.3 ml/h/kg) after 10 days of oral intake. Our main finding demonstrates that oral administration of olanzapine but not ziprasidone leads to a decrease in whole body insulin sensitivity in response to a hyperinsulinemic euglycemic challenge. Our finding is suggestive that not all atypical antipsychotics cause acute direct effects on glucose disposal and that accurate determination of side effect profile should be performed when choosing an atypical antipsychotic.

The Hsp32/HO-1-targeted drug SMA-ZnPP counteracts the proliferation and viability of neoplastic cells in solid tumors and hematologic neoplasms

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Background: Heat shock protein 32 (Hsp32) is a stress-related survival factor that is overexpressed in various neoplastic cells. Recently, specific Hsp32- targeting drugs such as styrene maleic acid encapsulated zinc protoporphyrin (SMA-ZnPP) have been developed. Methods: We examined the effects of SMA-ZnPP on proliferation and survival of various tumor cell-lines, including U97MG (glioblastoma), A549 (lung cancer), MDA-MB-231 (breast cancer), BxPC-3 (pancreatic), HepG2 (hepatocellular), Colo201, Colo320DM, DLD-1 (colon), OvCar3 (ovarian carcinoma), KG1, U937, HL60, K562 (myeloid leukemias), RAJI, NALM-6 (lymphatic leukemias), RPMI 8226, U266 (multiple myeloma) as well as on primary neoplastic cells. Moreover, Ba/F3 cells with doxycycline-inducible expression of oncoproteins (RAS-G12V, BCR/ABL, KIT-D816V) were analyzed. Expression of Hsp32 mRNA was examined by RT-PCR and Northern blotting, and expression of the Hsp32 protein by Western blotting. To silence Hsp32 in neoplastic cells, we used specific siRNA as well as SMA-ZnPP. Proliferation was analyzed by 3H-thymidine uptake and apoptosis by light microscopy. Results: All neoplastic cells tested were found to express Hsp32 mRNA and the Hsp32 protein in a constitutive manner. In Ba/F3 cells, induction of RAS-G12V, BCR/ABL, or KIT D816V enhanced the expression of Hsp32. The Hsp32 siRNA was found to lead to a reduced viability and induction of apoptosis. Treatment of malignant cells with SMA-ZnPP resulted in a significant decrease in proliferation and induction of apoptosis. The effects of SMA- ZnPP on primary neoplastic cells and cell lines were dose-dependent and occurred at pharmacologic concentrations (IC50 1–30 μM). Moreover, SMA-ZnPP was found to synergize with various anti-neoplastic drugs (cisplatin, cytarabine, tyrosine kinase inhibitors, bortezomib) in producing growth-inhibition in neoplastic cells. Conclusions: The Hsp32-targeting drug SMA-ZnPP counteracts malignant cell growth and sensitizes neoplastic cells against various other targeted or conventional antineoplastic drugs. Hsp32-targeting drugs may represent an interesting new aproach to inhibit malignant cell growth in solid tumors and leukemias.

No significant financial relationships to disclose.

5-aminosalicylic acid release from a new controlled-release mesalazine formulation during gastrointestinal transit in healthy volunteers

BACKGROUND

Mesalazine (5-aminosalicylic acid, 5-ASA) containing formulations represent a cornerstone in the treatment of inflammatory bowel diseases. A novel formulation with an Eudragit L/S mixture coating has been developed to provide selective release of 5-ASA to the ileo-caecal region and the colon.

AIM

To determine the release of 5-ASA during the gastrointestinal transit.

METHODS

A single oral dose of mesalazine EC 500 mg gastroresistant tablets (Asamax) was administered to eight healthy male volunteers. Gastrointestinal transit and tablet disintegration were monitored by scintigraphy. 5-ASA release was verified by assessing plasma pharmacokinetics.

RESULTS

Initial tablet disintegration was observed 5.65 +/- 0.86 h after dosing, corresponding to the detection of 5-ASA in plasma. This occurred in the ileo-caecal region in three subjects and the ascending colon in the remaining five. The relative percentage of 5-ASA absorption was more pronounced in the ascending colon (41 +/- 27.4%) than the ileo-caecal region (6.6 +/- 9.2%).

CONCLUSION

This mesalazine EC gastroresistant tablets release locally active 5-ASA specifically in the ileo-caecal region and the ascending colon.

The ability of statins to protect low density lipoprotein from oxidation in hypercholesterolemic patients

OBJECTIVE

It is unclear at the present time whether hydroxy-methylglutaryl coenzyme A reductase inhibitors (HMG-CoA reductase inhibitors; statins) exert a protective effect on low-density lipoproteins (LDL) oxidation in vivo. In addition, it is speculated that pharmacological differences between statins may account for differences in their antioxidative capacities. This is of clinical relevance, because there is strong evidence that oxidized LDL initiates the atherosclerosis process.

MATERIAL AND METHODS

In a controlled, randomized, double-blind study we compared the effects of three different statins (simvastatin, pravastatin and atorvastatin) on the ability to protect LDL from oxidation in 70 hypercholesterolemic but otherwise healthy subjects. Statins were administered in doses which were nearly equi-effective in lowering LDL-cholesterol. Changes in LDL oxidation were measured using diene conjugation (DIENES) and thiobarbituric acid reactive substances (TBARS) at entry and three months after beginning therapy with the statins.

RESULTS

Levels of DIENES, usually generated during the early phases of lipid peroxidation, were significantly reduced by 10.2 +/- 5.5% (mean +/- SEM; p < 0.03), 6.0 +/- 2.0% (p < 0.005) versus baseline in the case of pravastatin and atorvastatin but simvastatin had no significant effect with a mean reduction of 5.5 +/- 6.4% (p > 0.23). Levels of TBARS, reflecting late phases of LDL oxidation, showed no significant changes against baseline (p > 0.34). Pooled data (n = 70) indicated that statins reduce DIENES levels by approximately 9% versus baseline (p < 0.005) but had no significant effect on TBARS levels (p > 0.29) after three months of therapy.

CONCLUSION

This study showed that atorvastatin and pravastatin were capable of protecting LDL from oxidation in vivo in the early treatment phase. Pooled data levels of DIENES were significantly affected by statin therapy over a period of 3 months. No protective effect appeared to be present in the late phases of oxidation evaluated using measurement of TBARS but it should be noted that the clinical impact of such observations are currently discussed controversially in the literature.

Combined PET and microdialysis for in vivo assessment of intracellular drug pharmacokinetics in humans

Because many drugs possess an intracellular site of action, the knowledge of intracellular concentration-time profiles is desirable. In the present study, PET, which measures total (i.e., intracellular, extracellular, and intravascular) concentrations of radiolabeled drugs in tissue, and microdialysis, which determines unbound drug concentrations in the extracellular space fluid of tissue, were combined to describe the intracellular pharmacokinetics of a model compound--that is, the (18)F-labeled antibiotic (18)F-ciprofloxacin--in vivo in humans.

METHODS

Ten healthy male volunteers received a mixture of 687 +/- 50 MBq of (18)F-ciprofloxacin and 200 mg of unlabeled ciprofloxacin as an intravenous bolus infusion over 10 min. The pharmacokinetics of ciprofloxacin in skeletal muscle tissue were assessed by means of combined PET and in vivo microdialysis for 5 h after drug administration. A 3-compartment pharmacokinetic model was fitted to the tissue concentration-time profiles of ciprofloxacin measured by PET to estimate the rate constants of ciprofloxacin uptake and transport.

RESULTS

In muscle tissue, mean total and extracellular peak concentration (C(max)) values of ciprofloxacin of 1.8 +/- 0.4 microg/mL and 0.7 +/- 0.2 microg/mL were attained at 95 +/- 34 min and 48 +/- 20 min after drug administration, respectively. The extracellular-to-intracellular exchange appeared to be very fast, with an estimated rate constant k(3) of 1.69 +/- 0.25 min(-1). An intracellular-to-extracellular concentration ratio (C(intra)/C(extra)) of 3.2 +/- 0.8 was reached at 110 min after injection and followed by sustained intracellular retention of the antibiotic for the remainder of the experiment. The predicted extracellular concentration-time profiles from the compartmental modeling were in good agreement with the measured microdialysis data.

CONCLUSION

The results obtained in the present study were in accordance with previous in vitro data describing cellular ciprofloxacin uptake and retention. The presently used PET/microdialysis combination might be useful during research and development of new drugs, for which knowledge of intracellular concentrations is of interest.

Concentrations of gemifloxacin at the target site in healthy volunteers after a single oral dose

Free gemifloxacin concentrations in the interstitial space fluid of skeletal muscle and subcutaneous adipose tissue were measured by means of in vivo microdialysis to characterize the ability of gemifloxacin to penetrate human soft tissues. Twelve healthy volunteers received a single oral dose of 320 mg of gemifloxacin. The mean areas under the concentration-time curves from 0 to 10 h (AUC(0-10)) were significantly higher for soft tissue than for unbound gemifloxacin in plasma (P < 0.05). The ratios of the mean AUC(0-10) for tissue to the AUC(0-10) for free gemifloxacin in plasma were 1.7 +/- 0.7 (mean +/- standard deviation) for skeletal muscle and 2.4 +/- 1.0 for adipose tissue. The AUC(0-24) ratios for free gemifloxacin in tissues to the MIC at which 90% of frequently isolated bacteria are inhibited were close to or higher than 100 h. Therefore, based on pharmacokinetic and pharmacodynamic calculations, we conclude that gemifloxacin might be a useful therapeutic option for the treatment of soft tissue infections.

In vitro and in vivo evaluation of [18F]ciprofloxacin for the imaging of bacterial infections with PET

PURPOSE

The suitability of the 18F-labelled fluoroquinolone antibiotic ciprofloxacin ([18F]ciprofloxacin) for imaging of bacterial infections with positron emission tomography (PET) was assessed in vitro and in vivo.

METHODS

For the in vitro experiments, suspensions of various E. coli strains were incubated with different concentrations of [18F]ciprofloxacin (0.01-5.0 microg/ml) and radioactivity retention was measured in a gamma counter. For the in vivo experiments, 725 +/- 9 MBq [18F]ciprofloxacin was injected intravenously into four patients with microbiologically proven bacterial soft tissue infections of the lower extremities and time-radioactivity curves were recorded in infected and uninfected tissue for 5 h after tracer injection.

RESULTS

Binding of [18F]ciprofloxacin to bacterial cells was rapid, non-saturable and readily reversible. Moreover, bacterial binding of the agent was similar in ciprofloxacin-resistant and ciprofloxacin-susceptible clinical isolates. These findings suggest that non-specific binding rather than specific binding to bacterial type II topoisomerase enzymes is the predominant mechanism of bacterial retention of the radiotracer. PET studies in the four patients with microbiologically proven bacterial soft tissue infections demonstrated locally increased radioactivity uptake in infected tissue, with peak ratios between infected and uninfected tissue ranging from 1.8 to 5.5. Radioactivity was not retained in infected tissue and appeared to wash out with a similar elimination half-life as in uninfected tissue, suggesting that the kinetics of [18F]ciprofloxacin in infected tissue are governed by increased blood flow and vascular permeability due to local infection rather than by a binding process.

CONCLUSION

Taken together, our results indicate that [18F]ciprofloxacin is not suited as a bacteria-specific infection imaging agent for PET.

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.

Transcapillary insulin transfer in human skeletal muscle

BACKGROUND

Transcapillary insulin transfer is considered a rate-limiting step in insulin action at supraphysiological insulin concentrations. However, it remains unclear whether this concept also applies for physiological conditions.

MATERIALS AND METHODS

In the present study we set out to characterize transcapillary insulin transfer by measuring insulin concentrations in plasma and interstitial space fluid of skeletal muscle during an oral glucose tolerance test and euglycaemic hyperinsulinaemic clamp conditions, respectively. For this purpose we employed in vivo microdialysis of skeletal muscle in conjunction with an ultrasensitive insulin assay in eight healthy lean male volunteers (aged 25 +/- 1 years).

RESULTS

Insulin concentrations at baseline were 48 +/- 8 pmol x L(-1) in plasma and 19 +/- 4 pmol x L(-1) in the interstitium (P = 0.002). The mean interstitium to plasma ratio at baseline was 0.48 +/- 0.09 pmol x L(-1). During the oral glucose tolerance test the interstitium to plasma ratio remained unchanged (0.43 +/- 0.12, P = NS vs. baseline), but was significantly reduced during euglycaemic hyperinsulinaemic clamp conditions at steady-state hyperinsulinaemia (0.12 +/- 0.01, P = 0.01 vs. baseline).

CONCLUSION

In summary there is a substantial transcapillary insulin gradient in healthy human skeletal muscle under baseline and glucose-stimulated conditions. Our findings support the hypothesis of a saturable transcapillary insulin transport representing a partly rate-limiting step for insulin action.

Closed-chest microdialysis to measure antibiotic penetration into human lung tissue

The majority of bacterial lung infections are localized to the interstitial space fluid, which is therefore an important target site for antimicrobial chemotherapy. Direct measurement of interstitial concentrations of antimicrobial agents in human lung tissue would allow for a more informed approach to appropriate dosing of antimicrobial agents, but until now this was beyond technical reach. In this exploratory pharmacokinetic study, we measured the time versus concentration profile of cefpirome after a single intravenous dose administration of 2 g in the lung interstitial fluid by flexible microdialysis catheters, which were implanted during lung surgery for pulmonary tumors in five patients. Cefpirome concentrations in lung interstitial fluid were 66% of corresponding plasma values within the first 240 min, and exceeded minimal inhibitory concentrations of most relevant bacteria. The experimental procedure was well tolerated by the patients and no adverse events were observed. The present study provides evidence for the first time that closed chest microdialysis of the human lung is a feasible and safe method to measure lung concentrations in patients in vivo. The present data also corroborate the use of cefpirome as a valuable agent in the treatment of lung infections with most extracellular bacteria.

Angioplasty increases target site concentrations of ciprofloxacin in patients with peripheral arterial occlusive disease

OBJECTIVE

Patients with peripheral arterial occlusive disease are prone to soft tissue infections and frequently require antibiotics. To date, however, it is not known whether improvement of arterial blood flow by angioplasty of stenosis increases antibiotic concentrations in ischemic lesions.

PATIENTS AND METHODS

All patients were scheduled to undergo elective percutaneous transluminal angioplasty (n = 10). Following a single, 400-mg dose of ciprofloxacin, drug concentrations in plasma, ischemic and healthy soft tissue; arterial peak systolic velocity; and ankle-brachial pressure index were assessed before and after angioplasty. Unbound ciprofloxacin concentrations were measured at the site of infection with use of in vivo microdialysis.

RESULTS

Angioplasty increased peak systolic velocity and ankle-brachial pressure index compared with baseline (P <.002). Before angioplasty area under concentration-time curve (AUC(0-300)) values for ciprofloxacin were lower in ischemic tissue than in healthy tissue, with median values of 7.1 mg.h/L (range, 3.5-13.0) and 11.3 mg.h/L (range, 3.4-19.0), respectively (P =.03). After angioplasty AUC(0-300) values were identical in ischemic and healthy adipose tissue; median AUC(0-300) values were 8.0 mg.h/L (range, 4.0-20.7) and 8.5 mg.h/L (range, 4.4-22.9), respectively (P =.7). A combined in vivo pharmacokinetic/in vitro pharmacodynamic simulation based on tissue concentration data indicates that this difference in pharmacokinetics is also reflected in antimicrobial effect.

CONCLUSION

Antibiotic concentrations are reduced significantly in ischemic lesions compared to those of healthy adipose tissue in patients with peripheral arterial occlusive disease. From the present data it might be speculated that improvement of arterial blood flow at the affected extremity is associated with increased cure rates of soft tissue infections in these patients.

Pharmacokinetics of emedastine difumarate, a new anti-histaminic agent in patients with renal impairment

OBJECTIVE

Emedastine difumarate is a new H1 receptor antagonist with well defined pharmacokinetic and pharmacodynamic profiles in healthy volunteers. However, to date it is not known whether impaired renal function in patients with chronic renal insufficiency affects its pharmacokinetics and probably also its tolerability. Therefore, we here set out to compare the pharmacokinetics of emedastine difumarate in patients suffering from different degrees of renal failure with a control group of healthy volunteers.

METHODS AND RESULTS

For this purpose we conducted an open, single-centre, comparative parallel group study in patients and healthy volunteers. Emedastine difumarate 2 mg was administered orally to the study population in single and seven repetitive doses twice daily (b.i.d.). Pharmacokinetics differed markedly between volunteers (n = 6) and patients (n = 17). The maximum serum concentration of emedastine (Cmax), area under the serum concentration-time curve, mean residence time and terminal disposition half-life were significantly higher in patients (P < 0.05), while time to reach Cmax and apparent volume of disposition were not statistically different after single and repeated (steady-state) oral administrations. Blood pressure and heart rate were also not affected by the study medication.

CONCLUSION

The present study shows that impaired renal function alters the pharmacokinetics of emedastine in plasma. Thus, dose adjustment of emedastine difumarate is advisable in patients with impaired renal function.

Effects of erythropoietin on platelet reactivity and thrombopoiesis in humans

A recent study in dogs suggested that erythropoietin (EPO) not only promotes the synthesis of increased numbers of reticulated platelets but that these newly produced platelets are hyperreactive compared with controls. Because of the increasing use of EPO in the perioperative setting, we characterized the effects of EPO on platelet reactivity in healthy human volunteers. In a randomized, controlled trial, we studied the effects of EPO on platelet reactivity, thrombopoiesis, and endothelial activation in circumstances similar to those of autologous blood donation. Thirty healthy male volunteers received placebo or EPO (100 or 500 U/kg of body weight given intravenously) three times a week for 2 weeks and underwent phlebotomy on days 8 and 15. Thrombin receptor-activating peptide induced expression of P-selectin, and CD63 increased 2- to 3-fold during EPO treatment. The enhanced platelet reactivity was also reflected by a 50% increase in soluble P-selectin in plasma. Plasma E-selectin levels increased in a dose-dependent fashion by more than 100% during EPO treatment, indicating substantial activation of endothelial cells. A 10% to 20% increase in platelet counts was observed in both EPO groups on day 5. In the placebo group, platelets increased only several days after the first phlebotomy. The increase in platelet counts was not reflected by changes in the amounts of reticulated platelets or circulating progenitor cells. In summary, we found that EPO markedly enhances endothelial activation and platelet reactivity, which may adversely affect patients at cardiovascular risk. However, the increased platelet reactivity could be exploited in patients with platelet dysfunction. (Blood. 2000;95:2983-2989)

Penetration of moxifloxacin into peripheral compartments in humans

To characterize the penetration of moxifloxacin (BAY 12-8039) into peripheral target sites, the present study aimed at measuring unbound moxifloxacin concentrations in the interstitial space fluid by means of microdialysis, an innovative clinical sampling technique. In addition, moxifloxacin concentrations were measured in cantharides-induced skin blisters, saliva, and capillary plasma and compared to total- and free-drug concentrations in venous plasma. For this purpose, 12 healthy volunteers received moxifloxacin in an open randomized crossover fashion either as a single oral dose of 400 mg or as a single intravenous infusion of 400 mg over 60 min. An almost-complete equilibration of the free unbound plasma fraction of moxifloxacin with the interstitial space fluid was observed, with mean area under the concentration-time curve (AUC)(interstitial fluid)/AUC(total-plasma) ratios ranging from 0.38 to 0.55 and mean AUC(interstitial fluid)/AUC(free-plasma) ratios ranging from 0.81 to 0.86. The skin blister concentration/plasma concentration ratio reached values above 1.5 after 24 h, indicating a preferential penetration of moxifloxacin into inflamed lesions. The moxifloxacin concentrations in saliva and capillary blood were similar to the corresponding levels in plasma. Our data show that moxifloxacin concentrations attained in the interstitial space fluid in humans and in skin blister fluid following single doses of 400 mg exceed the values for the MIC at which 90% of isolates are inhibited for most clinically relevant bacterial strains, notably including penicillin-resistant Streptococcus pneumoniae. These findings support the use of moxifloxacin for the treatment of soft tissue and respiratory tract infections in humans.

Distribution and antimicrobial activity of ciprofloxacin in human soft tissues

Interstitial ciprofloxacin concentrations in soft tissues were measured by microdialysis following intravenous administration of 200 mg to each of eight healthy volunteers. Interstitial ciprofloxacin concentrations were significantly lower than corresponding total serum drug concentrations; the interstitium-to-serum concentration ratios ranged from 0.55 to 0.73. An in vitro simulation based on interstitial pharmacokinetics showed a substantially lower antimicrobial activity than did the simulation based on serum pharmacokinetics. Thus, ciprofloxacin concentrations at the site of effect may be subinhibitory although effective concentrations are attained in serum.