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The pharmacokinetics of rufloxacin, after repeated doses, was evaluated in 12 elderly patients with lower respiratory tract infections. Patients were given a single loading dose of 400 mg on the first day of treatment and single daily maintenance doses of 200 mg for the next 6-9 days. Serum concentrations of the drug were determined by high-performance liquid chromatography (HPLC) at regular intervals during treatment and fitted to a one-compartment open model for repeated doses. The maximum serum concentration after the first dose was 6.46 +/- 1.06 (mean +/- SEM) micrograms/ml and was reached in 4.3 +/- 0.8 h after the first administration. The elimination half-life was 28.7 +/- 4.1 h. The area under the serum levels-time curve from 0 to 24 h was 103 +/- 14 micrograms/h/ml after the first dose. On the last day of observation it increased to 155 +/- 28 micrograms/h/ml, with a mean extent of accumulation of 2.3 +/- 0.3 times. The elimination half-life was comparable to those in other studies in healthy young subjects, while plasma levels were about 80% higher. These results suggest that in elderly patients elevated drug concentrations may be reached in the serum. Although no untoward reactions related either to the drug concentration in serum or the dose have been noted with rufloxacin, this patient population should nevertheless be monitored carefully for adverse effects.
Ther Drug Monit 1992 Feb
PMID:Steady-state pharmacokinetics of rufloxacin in elderly patients with lower respiratory tract infections. 131 63

The problem of accurate identification of alarm sounds in the operating room, recovery room, and intensive care environment has persisted for many years. Monitors made by different companies may have different alarm sounds for the same monitored variable, and similar alarm sounds for different variables. In an effort to illustrate universal alarms sounds, a system of six musical alarm tones was designed with musical themes from popular songs used for oxygenation, ventilation, cardiovascular monitoring, temperature monitoring, artificial perfusion, and drug administration systems. These melodies were played for a group of anesthesiologists and others, who were initially asked to guess the organ system for each melody. The answers were then given to the participants, and after a short delay the melodies were played again in a different order. Seventy-nine response sheets were collected. The expected random score was 1.0 +/- 1.0 SEM correct. The observed score on the first hearing was 1.5 +/- 1.6 SEM, p = 0.01 compared with the random score. The observed score on the second testing was 4.3 +/- 2.2 SEM, p = 0.001 compared with the first hearing. Indeed, 42 of 79 (53%) respondents got all six answers correct on the second testing, versus three respondents for the first testing. The implications of these findings are discussed in the context of integrated alarm systems used in complex medical environments such as the operating room.
J Clin Monit 1992 Oct
PMID:Evaluation of users' abilities to recognize musical alarm tones. 145 88

Epinephrine is routinely used as a marker for intravascular injection during administration of regional anesthesia. The cardiovascular response of patients on beta-blockers to such a test dose has been reported to be unpredictable. We investigated this interaction by administering 15 micrograms of epinephrine intravenously to 6 healthy volunteers 39 to 48 years old before and after beta-blockade, accomplished by intravenous injection of propranolol, 0.04 mg/kg. Epinephrine administration caused a 20 +/- 4% (mean +/- SEM) increase in heart rate before beta-blockade but a 38 +/- 3% reduction after beta-blockade. The lowest heart rate recorded was 28 beats/min. We conclude that, in middle-aged beta-blocked men, intravenous injection of a standard epinephrine-containing test dose will predictably cause significant hypertension followed by marked bradycardia.
J Clin Monit 1991 Jul
PMID:Epinephrine-containing test dose during beta-blockade. 167 42

The impact of a new monitoring strategy on whole blood concentrations of cyclosporine measured by a specific monoclonal radioimmunoassay was investigated in a group of 37 renal transplant patients. Before transplantation, the patients received a standard intravenous (i.v.) and oral (p.o.) test dose of cyclosporine to calculate their individual i.v. and p.o. starting dose rates to achieve a certain target steady-state cyclosporine concentration. After transplantation, the designated i.v. dose rate was continuously infused for 2 days, at which time the steady-state concentration was measured. Then, the designated oral dose for 24 h was administered while the infusion was continued at an unaltered rate. The oral absorption of cyclosporine was documented by blood samples over the following 8 h. If necessary, this overlap of i.v. and p.o. dosing was repeated until blood concentrations of cyclosporine rose at least 700 ng/ml over the steady-state concentration. By that time, the infusion was stopped and oral dosing continued. Individualized infusions led to steady-state concentrations within a range that did not exceed 1.1 times the median concentration of 472 ng/ml. Standard infusion rates in the past produced a much wider range of steady-state concentrations (9.6 times the median). Individualized infusions reached the target steady-state concentration with a significant positive bias of 17% (SEM = +/- 32%, range of -36 to +105%). Individualized oral doses reached the target average steady-state concentration (calculated by dividing the area under the concentration-time curve by the dosing interval) with an inferior precision (median = 2.6%, range of -54 to +130%) but without a positive or negative bias.(ABSTRACT TRUNCATED AT 250 WORDS)
Ther Drug Monit 1991 Mar
PMID:Area under the curve monitoring of cyclosporine therapy: the early posttransplant period. 205 29

We tested the hypothesis that amino acids in a parenteral nutrition (PN) solution would result in the decreased metabolism of a model compound, lidocaine. One bolus infusion of lidocaine HCl (1 mg/kg) was administered to seven healthy subjects in association with each of three nutrient regimens: (a) a standard PN solution, (b) 10% dextrose water (D10W), and (c) a meal (control) containing similar fluid volume and caloric, protein, and sodium content as the PN solution. Intravenous nutrients were infused consecutively in a random order at 1 L/12 h. Intravenous and control studies were performed 28 days apart. There was no significant difference in the means (+/- SEM) of total body clearance [7.70 +/- 0.70 (PN) versus 6.78 +/- 0.79 (D10W) versus 7.86 +/- 0.93 (control) ml/min kg], half-life [74.0 +/- 12.2 (PN) versus 89.6 +/- 4.35 (D10W) versus 79.2 +/- 7.22 (control) min], volume of distribution [0.82 +/- 0.15 (PN) versus 0.88 +/- 0.13 (D10W) versus 0.78 +/- 0.13 (control) L/kg], and the fraction of unbound lidocaine in the serum [0.34 +/- 0.025 (PN) versus 0.36 +/- 0.019 (D10W) versus 0.33 +/- 0.020 (control)] among the three nutrient regimens. The concentration-time course of the active metabolite, N-ethylglycyl-2,6-xylidide, did not differ significantly regardless of the nutritional regimen used. Our study indicates that amino acids used for PN do not have any acute effect on lidocaine pharmacokinetics in healthy subjects.
Ther Drug Monit 1990 Mar
PMID:Lack of acute effect on lidocaine pharmacokinetics from parenteral nutrition. 210 8

Determination of plasma methadone is essential in connection with dose adjustments for patients participating in methadone maintenance programs. We successfully adapted the existing fluorescence polarization immunoassay (FPIA) kit intended for urinary methadone to plasma assays. A concentration interval of 50-900 ng/ml could be covered. The coefficient of variation was less than 7%, and the limit of detection below 50 ng/ml. The intercorrelation between the immunoassay and a specific gas chromatographic-mass spectrometric (GC-MS) method was studied in samples from 19 heroin addicts in methadone maintenance treatment. A total number of 97 plasma samples with a concentration range of 31-842 ng/ml were used. The slope and intercept of the regression line (CFPIA = 0.93 X CGC-MS + 15) was in good agreement with the theoretical relation (CFPIA = CGC-MS), with a coefficient of correlation of 0.978. The mean ratio, in quantitative result, between the techniques (CFPIA/CGC-MS) was 1.03 +/- 0.01 (SEM). We conclude that the immunoassay proposed in this study can be safely used in patients participating in methadone maintenance programs.
Ther Drug Monit 1990 Sep
PMID:Monitoring of plasma methadone: intercorrelation between immunoassay and gas chromatography-mass spectrometry. 229 10

The pharmacokinetics of a 500-mg dose of i.v. vancomycin were studied in six Chinese patients with end-stage renal failure. Serum vancomycin concentrations were determined by high-performance liquid chromatography. Observed peak and trough (at 168 h postinfusion) concentrations were in the range of 14.2-35.0 micrograms/ml and 2.8-5.5 micrograms/ml, respectively. The data were analyzed using the PCNONLIN. In all six patients, the data could be fitted well by both the biexponential and triexponential models, but in three patients the latter model provided a better fit. Two-compartment pharmacokinetic parameters obtained from the six patients were t 1/2 alpha 1.13 +/- 0.25 h (mean +/- SEM), t 1/2 beta 121.3 +/- 8.2 h, Vc 0.45 +/- 0.09 L/kg, Vss 1.00 +/- 0.12 L/kg, ClT 5.90 +/- 0.69 ml/kg/h, and the calculated Cmax 25.0 +/- 6.1 micrograms/ml. The mean vancomycin serum protein binding was 18.5 +/- 12.0% as compared with a mean of 46.0% in pooled serum from normal controls. Hemodialysis had no significant effect on vancomycin protein binding or clearance. On the basis of our kinetic study, 500 mg of vancomycin given every seven days is probably adequate treatment for methicillin resistant Staphylococcus aureus infection in end-stage renal failure patients, but further clinical studies are necessary to confirm this.
Ther Drug Monit 1990 Jan
PMID:Pharmacokinetics of intravenous vancomycin in patients with end-stage renal failure. 230 18

Determination of appropriate theophylline maintenance doses in preterm infants is confounded by interpatient variability. This study evaluated the performance of an IBM PC computer program applying Bayesian regression before and during steady state in 37 preterm infants. Prior population estimates of clearance and distribution volume in preterm infants and Bayesian estimates of clearance and distribution volume based on one to three theophylline plasma concentrations were used to predict subsequent concentrations (drawn 1-17 days later). We assessed the accuracy and precision of the predictive performance of the Bayesian program with the mean prediction error and the mean absolute prediction error. The absolute prediction error (mean absolute error +/- SEM) significantly decreased with increasing feedback concentrations from 3.54 +/- 0.45 micrograms/ml (population estimates) to 2.74 +/- 0.42 (one feedback) and 2.02 +/- 0.35 micrograms/ml (two feedback concentrations). Mean prediction errors (+/- SEM) based on one to three feedbacks (-1.5 +/- 0.40 micrograms/ml) were significant improvements over population predictions (-2.63 +/- 0.72 micrograms/ml, p less than 0.05), although a small but significant average overprediction remained. Absolute prediction error was correlated with postconceptional and postnatal age when zero or one but not two feedback concentrations were available. Computer program predictions based on one measured feedback concentration were more accurate and precise than population-based predictions. Refinement of population parameters or two feedback concentrations further improved performance.
Ther Drug Monit 1990 Jan
PMID:An evaluation of Bayesian microcomputer predictions of theophylline concentrations in newborn infants. 230 21

We developed a two-compartment model to simulate neuromuscular function and heart rate following the administration of four nondepolarizing neuromuscular blocking agents (atracurium, vecuronium, pancuronium, and d-tubocurarine), three neuromuscular block reversal agents (edrophonium, neostigmine, and pyridostigmine), and two anticholinergic agents (atropine and glycopyrrolate). Twitch depression, train-of-four ratio, and heart rate were modeled during fentanyl, halothane, enflurane, or isoflurane anesthesia, optionally supplemented with nitrous oxide. Simulation results, compared with published values for each drug, fell within the clinical accuracy range (onset time 6.1 +/- 3.9% [mean +/- SEM]; duration, 1.7 +/- 3.5%, 50% effective dose, 0.5 +/- 5.7%; and 95% effective dose, 2.1 +/- 1.1%). The simulation graphically demonstrates the pharmacokinetics, pharmacodynamics, and interactions between neuromuscular blocking agents, reversal agents, and anticholinergic agents. During a simulation, the need for frequent monitoring and repeated delivery of a neuromuscular blocking agent to keep neuromuscular blockade stable becomes apparent, especially with the intermediate-acting neuromuscular blocking agents. When inhalational agents are given concomitantly, the task becomes even more difficult, since potentiation changes with anesthetic uptake. Recurarization, tachycardia, or bradycardia may be seen with the simulation if an improper drug regimen is followed. Concurrent simulation of two identical patients allows comparison of different modes of administration, choice of anesthetic agents, and drug doses.
J Clin Monit 1990 Jan
PMID:A simulation of neuromuscular function and heart rate during induction, maintenance, and reversal of neuromuscular blockade. 240 85

A multiple-center study was performed to determine the relationship between lower esophageal contractility, clinical signs, and anesthetic concentration as expressed by minimum alveolar concentration (MAC). One hundred four American Society of Anesthesiologists Class I through III patients were exposed to isoflurane (with and without nitrous oxide) or halothane in concentrations of 0.5, 1.0, and 1.5 MAC. Heart rate and systolic blood pressure were continuously monitored. Both the amplitude and frequency of spontaneous and provoked lower esophageal contractions were measured in situ by using a 24-F probe equipped with provoking and measuring balloons. Combined results demonstrated statistically significant correlations (P less than 0.001) between lower esophageal contractility and MAC. Spontaneous lower esophageal contractions decreased from 1.10 +/- 0.12 (SEM) contractions per minute (0.5 MAC) to 0.42 +/- 0.05 (1 MAC) to 0.18 +/- 0.05 (1.5 MAC). Provoked lower esophageal contractility values decreased from 45 +/- 4 mm Hg (0.5 MAC) to 29 +/- 3 (1 MAC) to 19 +/- 2 (1.5 MAC). Heart rate changes did not correlate with MAC, and systolic blood pressure correlated in only one of three centers. Intracenter and intercenter analyses failed to demonstrate a significant relationship between lower esophageal contractility and heart rate or systolic blood pressure. No intracenter differences in either amplitude or frequency of lower esophageal contractions were observed, despite differences in volatile agents, induction techniques and agents, patient populations, and durations of anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)
J Clin Monit 1988 Oct
PMID:Response of lower esophageal contractility to changing concentrations of halothane or isoflurane: a multicenter study. 305 20


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