Sensor Noise in LISA Pathfinder: In-Flight Performance of the Optical Test Mass Readout.

We report on the first subpicometer interferometer flown in space. It was part of ESA's Laser Interferometer Space Antenna (LISA) Pathfinder mission and performed the fundamental measurement of the positional and angular motion of two free-falling test masses. The interferometer worked immediately, stably, and reliably from switch on until the end of the mission with exceptionally low residual noise of 32.0_{-1.7}^{+2.4} fm/sqrt[Hz], significantly better than required. We present an upper limit for the sensor performance at millihertz frequencies and a model for the measured sensitivity above 200 mHz.

LISA Pathfinder Performance Confirmed in an Open-Loop Configuration: Results from the Free-Fall Actuation Mode.

We report on the results of the LISA Pathfinder (LPF) free-fall mode experiment, in which the control force needed to compensate the quasistatic differential force acting on two test masses is applied intermittently as a series of "impulse" forces lasting a few seconds and separated by roughly 350 s periods of true free fall. This represents an alternative to the normal LPF mode of operation in which this balancing force is applied continuously, with the advantage that the acceleration noise during free fall is measured in the absence of the actuation force, thus eliminating associated noise and force calibration errors. The differential acceleration noise measurement presented here with the free-fall mode agrees with noise measured with the continuous actuation scheme, representing an important and independent confirmation of the LPF result. An additional measurement with larger actuation forces also shows that the technique can be used to eliminate actuation noise when this is a dominant factor.

Beyond the Required LISA Free-Fall Performance: New LISA Pathfinder Results down to 20 µHz.

In the months since the publication of the first results, the noise performance of LISA Pathfinder has improved because of reduced Brownian noise due to the continued decrease in pressure around the test masses, from a better correction of noninertial effects, and from a better calibration of the electrostatic force actuation. In addition, the availability of numerous long noise measurement runs, during which no perturbation is purposely applied to the test masses, has allowed the measurement of noise with good statistics down to 20 µHz. The Letter presents the measured differential acceleration noise figure, which is at (1.74±0.05) fm s^{-2}/sqrt[Hz] above 2 mHz and (6±1)×10 fm s^{-2}/sqrt[Hz] at 20 µHz, and discusses the physical sources for the measured noise. This performance provides an experimental benchmark demonstrating the ability to realize the low-frequency science potential of the LISA mission, recently selected by the European Space Agency.

Charge-Induced Force Noise on Free-Falling Test Masses: Results from LISA Pathfinder.

We report on electrostatic measurements made on board the European Space Agency mission LISA Pathfinder. Detailed measurements of the charge-induced electrostatic forces exerted on free-falling test masses (TMs) inside the capacitive gravitational reference sensor are the first made in a relevant environment for a space-based gravitational wave detector. Employing a combination of charge control and electric-field compensation, we show that the level of charge-induced acceleration noise on a single TM can be maintained at a level close to 1.0 fm s^{-2} Hz^{-1/2} across the 0.1-100 mHz frequency band that is crucial to an observatory such as the Laser Interferometer Space Antenna (LISA). Using dedicated measurements that detect these effects in the differential acceleration between the two test masses, we resolve the stochastic nature of the TM charge buildup due to interplanetary cosmic rays and the TM charge-to-force coupling through stray electric fields in the sensor. All our measurements are in good agreement with predictions based on a relatively simple electrostatic model of the LISA Pathfinder instrument.

Sub-Femto-g Free Fall for Space-Based Gravitational Wave Observatories: LISA Pathfinder Results.

We report the first results of the LISA Pathfinder in-flight experiment. The results demonstrate that two free-falling reference test masses, such as those needed for a space-based gravitational wave observatory like LISA, can be put in free fall with a relative acceleration noise with a square root of the power spectral density of 5.2±0.1 fm s^{-2}/sqrt[Hz], or (0.54±0.01)×10^{-15} g/sqrt[Hz], with g the standard gravity, for frequencies between 0.7 and 20 mHz. This value is lower than the LISA Pathfinder requirement by more than a factor 5 and within a factor 1.25 of the requirement for the LISA mission, and is compatible with Brownian noise from viscous damping due to the residual gas surrounding the test masses. Above 60 mHz the acceleration noise is dominated by interferometer displacement readout noise at a level of (34.8±0.3) fm/sqrt[Hz], about 2 orders of magnitude better than requirements. At f≤0.5 mHz we observe a low-frequency tail that stays below 12 fm s^{-2}/sqrt[Hz] down to 0.1 mHz. This performance would allow for a space-based gravitational wave observatory with a sensitivity close to what was originally foreseen for LISA.

Differential phase-noise properties of a ytterbium-doped fiber amplifier for the Laser Interferometer Space Antenna.

The interferometric gravitational-wave detector Laser Interferometer Space Antenna (LISA) needs to transfer clock information among its three spacecraft in the form of phase-modulation sidebands. For this reason phase noise introduced by the optical chain between the carrier and a sideband must be low. We have measured this differential phase noise for a ytterbium-doped fiber amplifier emitting up to 2 W. For 1 W of output power as required for LISA, the measured differential phase noise was within its requirement. For 2 W output power the amplifier exhibited stimulated Brillouin scattering and showed a differential phase-noise factor of up to 15 higher. Dependencies on operating parameters and optical length noise of the amplifier were also measured.

Analysis of the accuracy of actuation electronics in the laser interferometer space antenna pathfinder.

The Laser Interferometer Space Antenna Pathfinder (LPF) main observable, labeled Δg, is the differential force per unit mass acting on the two test masses under free fall conditions after the contribution of all non-gravitational forces has been compensated. At low frequencies, the differential force is compensated by an applied electrostatic actuation force, which then must be subtracted from the measured acceleration to obtain Δg. Any inaccuracy in the actuation force contaminates the residual acceleration. This study investigates the accuracy of the electrostatic actuation system and its impact on the LPF main observable. It is shown that the inaccuracy is mainly caused by the rounding errors in the waveform processing and also by the random error caused by the analog to digital converter random noise in the control loop. Both errors are one order of magnitude smaller than the resolution of the commanded voltages. We developed a simulator based on the LPF design to compute the close-to-reality actuation voltages and, consequently, the resulting actuation forces. The simulator is applied during post-processing the LPF data.

Amino acid kinetics in patients with sepsis.

BACKGROUND: In patients with sepsis and systemic inflammatory response syndrome, amino acid extraction by the liver is enhanced, resulting in decreased plasma amino acid concentrations. Systematic investigations of the elimination of intravenously infused amino acids have not been performed. OBJECTIVE: The objective of this study was to compare the elimination of 17 amino acids in patients with sepsis and in healthy control subjects. DESIGN: Elimination of amino acids was evaluated in 9 patients with sepsis and in 8 healthy control subjects by using a combined loading and maintenance infusion of 375 mg amino acids/kg body wt for 60 min. Pharmacokinetic variables were analyzed from plasma curves. RESULTS: With the exception of lysine, methionine, glutamate, ornithine, phenylalanine, and tyrosine, plasma concentrations of amino acids were lower in the patients with sepsis than in the control subjects; phenylalanine was the only amino acid whose plasma concentration increased (P < 0.001). In patients with sepsis, whole-body clearance (Cl(tot)) of total amino acids was 74% higher than in control subjects (x +/- SEM: 13,161 +/- 1659 and 7566 +/- 91 mL/min, respectively; P < 0.01), the Cl(tot) of essential amino acids was 64% higher (P < 0.02), that of nonessential amino acids was 82% higher (P < 0.01), and that of both branched-chain amino acids and glucogenic amino acids was 97% higher (P < 0.001). With the exception of phenylalanine, ornithine, proline, and glutamate, the Cl(tot) of all amino acids was elevated. The Cl(tot) of phenylalanine and ornithine decreased slightly (NS). CONCLUSIONS: In patients with sepsis, plasma concentrations of most amino acids are greatly decreased and the elimination of amino acids from the intravascular space during intravenous infusion is greatly enhanced.

Interaction of meloxicam with cimetidine, Maalox, or aspirin.

Meloxicam is a new enol carboxamide nonsteroidal antiinflammatory drug (NSAID). Preclinical studies have indicated that it possesses a high antiinflammatory potency and a low ulcerogenic potency. This open, randomized, crossover study was conducted to examine the effects of aspirin, the antacid Maalox (Rhone-Poulenc Rorer, Cologne, Germany), and cimetidine on the pharmacokinetics and bioavailability of a single oral dose of meloxicam 30 mg in healthy male volunteers. Plasma concentrations of meloxicam were determined and subjected to noncompartmental pharmacokinetic analysis. Meloxicam was well tolerated, and concomitant treatment with cimetidine or Maalox had little or no effect on the plasma concentration-time curves, maximum plasma concentration (Cmax), or the area under the plasma concentration-time curve (AUC0-infinity) of meloxicam. Concurrent treatment with aspirin increased plasma concentrations of meloxicam, increasing Cmax by approximately 25% and AUC0-infinity by 10%. These differences were not considered to be clinically relevant, and no adjustments of meloxicam dose should be required with coadministration of aspirin, Maalox, or cimetidine.

Integrated pharmacokinetics and pharmacodynamics of atropine in healthy humans. II: Pharmacodynamics.

This study determined the kinetics of the effects of atropine on heart rate and saliva flow in three healthy male volunteers after intravenous administration of 1.35 and 2.15 mg of the drug. The pharmacokinetics of atropine and its primary metabolite, tropine, were determined simultaneously. Both the pharmacokinetic and effect data were fitted to an integrated kinetic-dynamic model. The maximum heart rate and minimum saliva flow occurred with a significant delay of 7-8 min after drug administration. Both effects were nonlinearly related to the amount of drug in the peripheral compartment. Maximum heart rates of 192 and 217% of the control values were observed at the lower and higher dose levels, respectively. Minimum saliva flows of 8 and 3% of the control values were measured after the lower and higher doses of atropine, respectively. The time durations of the positive chronotropic effect of the drug were 170 and 250 min at the lower and higher dose levels, respectively; the corresponding values for the length of the antisialogogue effect of the drug were 230 and 340 min, respectively.

Zatebradine: pharmacokinetics of a novel heart-rate-lowering agent after intravenous infusion and oral administration to healthy subjects.

Zatebradine (1; UL-FS 49 CL; 1,3,4,5-[tetrahydro-7,8-dimethoxy-3-[3-[ [2-(3,4-dimethoxyphenyl)ethyl]methylamino]propyl]-2H-3-benzazepin- 2-on- hydrochloride) is the proposed INN name for a nonchiral, novel, specific heart-rate-lowering drug that is suitable for the treatment of stable angina pectoris. The pharmacokinetics of 1 and of total radioactivity in healthy volunteers (n = 6) were determined after intravenous infusion and oral administration of an experimental drug solution containing 7.5 mg (1.85 MBq) of 14C-labeled drug. Concentrations in plasma and urine were measured by a specific, sensitive, reversed-phase automated high-performance liquid chromatography system with fluorimetric detection at 285 nm Ex, 315 nm Em and by liquid scintillation counting. Recovery of total radioactivity was 89.8 +/- 2.3% (infusion) and 92.2 +/- 3.0% (oral). Renal elimination of total radioactivity was 62.5 +/- 2.0% (infusion) and 48.8 +/- 3.1% (oral). After intravenous infusion and oral administration, 27.3 +/- 2.4 and 43.4 +/- 3.9%, respectively, of the administered dose was eliminated in the feces. Absorption, based on renal excretion of total radioactivity following oral and intravenous dosing, was 79.2 +/- 15.3% (mean +/- standard deviation). Unchanged parent drug contributed 28.4 +/- 5.8% (infusion) and 12.4 +/- 3.7% (oral) of the dose to renal excretion. Zero to three minutes after cessation of the 20-min infusion, the maximum concentration of parent drug in plasma was 161.9 +/- 70.9 ng/mL. After oral administration, a mean peak concentration in plasma of 24.3 +/- 6.7 ng/mL (0.5-3 h postadministration) was reached. Data regarding levels of 1 in plasma could be adequately fitted with an open, two-compartment model.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetic-pharmacodynamic and metabolite modeling with TopFit.

Two examples illustrating the ease of use and powerful data fitting and simulation techniques provided by the validated program TopFit 2.0 for the PC are presented. In the first, kinetics of parent compound and metabolite for (+) and (-) enantiomers of a racemic compound X were determined during a Phase III clinical study. Four data sets were fitted simultaneously for each patient. The model could be defined by the user without programming differential equations. The fit results indicated enantiomer specific kinetics for the metabolite but not for parent compound. In the second example, a model with nonlinear elimination and an Emax-effect function was used to simultaneously fit data from six doses of compound Y in a Phase I study. The fitted parameters predicted the feasibility of a twice-daily dose regimen despite a very short plasma half-life of the compound. In conclusion, TopFit provides rapid and cost-effective support in analysis and design of clinical trials.

PK/PD simulations as a tool for rational design of clinical dosage regimens: an example with Fradafiban.

In clinical studies, pharmacodynamic effects should be achieved, e.g. maintenance of certain effects with reversibly acting drugs. Available data base for early phase II studies is frequently kinetics in healthy volunteers from phase I studies and pharmacodynamic effects from in vivo or ex vivo data. Using the fibrinogen receptor antagonist Fradafiban as an example, a procedure to achieve rational dosage regimens is described. Applied methods were: curve fitting of plasma concentrations obtained in phase I studies, correlation of fibrinogen receptor occupancy (FRO) to plasma concentrations using a sigmoid Emax model with Hill coefficient for PK/PD correlation, simulation of time course of FRO for various dosage regimens, using estimates for variability from PK and PD data in order to estimate not only mean values but also expected range of FRO. In a phase II study with Fradafiban administered intravenously, therapeutically active plasma levels had to be achieved rapidly and maintained over 24 hours employing a simple infusion regimen in 20 patients and 3 dose groups. For the target dose, a FRO of 80% should be achieved in most patients. Using the tools mentioned above, a rapid initial infusion rate of 10 mg over 30 minutes, followed by a maintenance infusion of 30 mg for the remaining 23.5 hours for the target dose resulted in a median predicted FRO of 82%. For the lower dose, a 5/15 mg infusion over 0.5/23.5 hours, achieving a predicted FRO of 68% was used and the upper dose (15/45 mg) resulted in 87% FRO. Median experimental results were 84% FRO for the target dose and 73% and 88%, respectively, for the lower and upper dose. As these results fit reasonably well to the predictions, it can be concluded that kinetics in the mostly elderly patients is similar to kinetics in healthy young volunteers. Furthermore, FRO in patients is nearly identical to that in spiked human plasma. Taken together, it could be proven that PK/PD methods are a useful tool for design of clinical studies of Fradafiban.

Comparative cardiac toxicity of the i.v. administered benzimidazole pyridazinon derivative Pimobendan and its enantiomers in female Beagle dogs.

The new positive-inotropic and vasodilatating drug Pimobendan (racemate), 4,5-dihydro-6-[2-(4-methoxyphenyl)-1H-benzimidazole-5-yl]-5-methyl-3 (2-H)-pyridazinone, and its enantiomers were investigated with regard to their cardiotoxicity in young adult female Chbb: Beagle dogs. The racemate and the (-)-isomer (eutomer) were intravenously injected once daily for 4 consecutive weeks at doses of 0.25, 0.75 and 2.25 mg/kg, and the (+)-isomer (distomer) at doses of 0.75, 2.25 and 6.75 mg/kg, respectively. Clinical signs, hematological, clinico-chemical, ophthalmologic and electrophysiological parameters were monitored. Plasma concentration-time profiles of the parent compound and the major metabolite UD-CG 212 were established on day 1 and in week 4 using an HPLC assay. Partial areas under the curves from 0.08 h to 1 h (AUC0.08-1 h) as well as the plasma concentration at time point 0.5 h/C0.5 h) were used for statistical calculations. Necropsy and histopathologic examination were performed after completion of the treatment period. Reduction of the blood pressure occurred already at low dosages of the racemate and the eutomer, but only in high dose distomer-treated animals. A tendency to tachycardia developed only in high dose females receiving the racemate. Consequently, with respect to the pharmacological effects and the adverse events, the racemate is equivalent to the eutomer. Plasma concentrations of parent compound and metabolite were dose-linear for racemate, eutomer and distomer within the dose range 0.25-2.25 mg/kg.d at both time points. There were no significant effects of form or repeated administration. A moderate increase of AUC0.08 1 h and C0.5 h could be seen on day 23 for the distomer indicating a stereoselektive metabolism of the latter. Histologic changes of the valvular and parietal endocardium being termed jet lesion were observed after administration of the racemate (> or = 0.75 mg/kg.d) and the eutomer (> or = 0.25 mg/kg.d) at distinctly lower doses than after the distomer (> or = 2.25 mg/kg.d). Furthermore, extent and severity of the morphologic lesions were found to be higher in dogs exposed to the racemate or the eutomer than in those receiving the distomer. The results gave evidence that the so-called cardiotoxicity by Pimobendan in dogs resulted from the exaggerated pharmacodynamic effect but not from the chemical nature of the compound per se. They corroborate also the previously raised assumption that the exaggerated pharmacodynamic activity of cardiotonic compounds in the broadest sense accounts for their morphologic adverse effects in experimental animals.

Precision of measurement of tissue concentrations by RLG.

Existing investigations about the precision of radioluminography (RLG) are restricted to descriptive analysis of the tissue samples. The aim of the present experiments was to obtain a general prospective statement about the precision that the RLG method can achieve. Several pharmaceutical companies in Europe participated in the experiments. Albino rats of various strains were dosed with various (14)C-labeled compounds. Whole-body sections were produced, and blood calibration scales were set up with standard radioactivity sources of dog or rat blood. Photostimulated luminescence was detected using Fuji imaging plate BAS-III. For each organ separately, variability was investigated on each of the levels: rat, section of rat, region within section, and residual, with the help of variance components. The producing company was seen as a fixed factor and adjusted for. A mixed linear model was fitted to the log-transformed data. The variance component (SD estimate) for the residual term gave the desired prospective statement about the achievable precision of the RLG method. Exponential back transformation from the logarithmic to the natural scale transformed the SD estimates to multiplication factors. In total, 29 organs were investigated. The RLG method was comparable in precision to the dissection/combustion method.

The effect of cholestyramine on the pharmacokinetics of meloxicam, a new non-steroidal anti-inflammatory drug (NSAID), in man.

The influence of multiple oral doses of cholestyramine on the single dose pharmacokinetics of meloxicam has been studied in 12 healthy male volunteers. Each subject received on two occasions a single IV injection of meloxicam 30 mg. The cholestyramine group received the material suspended in water 3 times a day. Compared to controls, cholestyramine accelerated the elimination of meloxicam. The mean terminal phase elimination half-life was reduced from 19.5 h to 12.7 h due to an increase in clearance of the drug (0.426 vs 0.636 l.h-1). Also, as a consequence of increased clearance in the presence of cholestyramine, the mean residence time of the drug in the body was significantly decreased (39%) P < 0.01. However, the volume of distribution for meloxicam was largely unaffected by cholestyramine which suggests that meloxicam undergoes gut recirculation. These changes are of the same magnitude as those previously reported for the structurally related piroxicam and are much smaller than those observed for tenoxicam.

Steady-state pharmacokinetics of lithium in healthy volunteers receiving concomitant meloxicam.

AIMS: This open, controlled study investigated the effect of concomitant 15 mg oral meloxicam on the pharmacokinetics of lithium in healthy male volunteers. METHODS: On days 1-14 lithium was coadministered with meloxicam to 16 volunteers; on days 10-14 lithium was administered in individualized dosage regimes to achieve stable lithium plasma concentrations in the lower therapeutic range of 0.3-0.7 mmol l(-1). A 12 h steady-state concentration profile for lithium was obtained at day 14, after which meloxicam was withdrawn. The lithium dose remained unchanged from day 15 to day 22, at which time a second lithium concentration profile was determined. RESULTS: Lithium and meloxicam were well tolerated throughout the study and all 16 volunteers completed the study. Lithium predose concentrations (Cpre,ss) and area under the curve (AUCss) values both increased by 21% (paired t-test P = 0.0002; 90% confidence intervals for test/reference ratios: 113-130% and 115-128%, respectively) when lithium was coadministered with meloxicam compared with values obtained for lithium alone. The geometric mean lithium Cpre,ss was 0.65 mmol l(-1) when coadministered with meloxicam and 0.54 mmol l(-1) for lithium alone. Lithium Cmax,ss values were increased by 16% by coadministration of meloxicam, from 0.97 mmol l(-1) to 1.12 mmol l(-1). The total plasma clearance of lithium was lower with concomitant meloxicam administration (82.5% of value for lithium alone). CONCLUSIONS: Meloxicam (15 mg) moderately increased the plasma concentration of lithium in healthy volunteers, but by a magnitude thought to be of low clinical relevance. Nevertheless, lithium plasma concentrations should be closely monitored in patients receiving concomitant meloxicam and lithium therapy.

Clinical pharmacology of mitoxantrone.

A pharmacokinetic study on mitoxantrone was performed within the framework of a phase II clinical trial. Serum concentrations and urinary excretion were measured using a high-performance liquid chromatography method. Four metabolites were separated in urine and three in serum. The two major metabolites cochromatographed with the synthesized monocarboxylic and dicarboxylic acids of mitoxantrone. Within 48 hours, 4.4% of the administered dose was excreted in urine as mitoxantrone, 0.5% as Metabolite 1, and 0.3% as Metabolite 2. The pharmacokinetic parameters are adequately described by a three-compartment model with a terminal half-life of 214.8 hours and a volume of distribution of 2248 L/m2. The total-body clearance was 217 ml/min/m2 and the renal clearance was 15 ml/min/m2. These results suggest that mitoxantrone is sequestered in a deep tissue compartment and only slowly released.

Pharmacokinetics and biological activity in subcutaneous long-term administration of recombinant interferon-gamma in cancer patients.

We have investigated the pharmacokinetics, tolerance, and biological activity of recombinant human interferon-gamma (rHuIFN gamma) administered subcutaneously to cancer patients. Twenty-one patients with lymphoma and metastatic cancer received rHuIFN gamma (in doses of 0.1, 0.25, or 0.5 mg/m2) in two or three injections per week for up to 180 days. The most common adverse effects encountered were flu-like symptoms, fever and fatigue. The increase in body temperature after each administration ranged from 0 to 4 degrees C depending on the individual patient, but was unrelated to the rHuIFN gamma dose or its plasma concentration. The pharmacokinetic response of the patients after the two treatments showed a low intra-individual variability with respect to the plasma concentration/time profiles. However, as observed for the fever side-effect, the interindividual variation (CV greater than 50%) was high for the parameters area under the data points (AUC0-t) and maximum plasma concentration (cmax). Despite this high interindividual variability, the mean values obtained for AUC0-t and cmax after s.c. injection of rHuIFN gamma were approximately proportional to the dose administered: the injection of 0.1, 0.25 or 0.5 mg/m2 rHuIFN gamma resulted in AUC0-t values of 15.4, 31.5 or 69.6 ng h/ml, respectively and cmax was found to be 1.0, 2.4 and 4.9 ng/ml, respectively. With this s.c. administration protocol, objective antitumour responses were observed in two patients, but there was no partial or complete remission.

Clinical pharmacokinetics of meloxicam.

Meloxicam (CAS 71125-38-7, UH-AC 62 XX) is a new non-steroidal anti-inflammatory drug (NSAID) which was developed for the treatment of osteoarthritis and rheumatoid arthritis. The basic clinical pharmacokinetics of meloxicam (7.5-30 mg) have been investigated in 78 healthy male volunteers after single and multiple dosing via oral, intravenous and rectal routes. Plasma concentrations of meloxicam were determined by validated high performance liquid chromatography (HPLC) methods. The pharmaco-kinetic profile of meloxicam is characterized by almost complete absorption over a prolonged phase-avoiding high initial drug concentrations- and is bound to plasma proteins by more than 99.5%. Meloxicam is metabolized to four biologically inactive metabolites and excreted in urine and faeces with an elimination half-life (t1/2) of around 20 h. This is reflected in a total plasma clearance of 7 to 8 ml/min. Steady state is achieved within 3 to 5 days. In addition, the pharmacokinetic parameters are linear over the entire dose range, there are no changes with multiple dosing and bioequivalence was shown for a number of different formulations. The results indicate that meloxicam is suitable for once-daily administration and that a switch from one formulation to another is easily possible if necessary or convenient for the patient.