Cephalosporin and Aminoglycoside Concentrations in Peritoneal Capsular Fluid in Rabbits

To study the penetration of antibiotics into peritoneal tissue fluid, a subcutaneous tissue capsule model was modified by implanting multiple, perforated spherical capsules in the peritoneal cavity of rabbits. Capsules became vascularized, encased in connective tissue, and filled with fluid having a mean protein concentration of 3.6 g/100 ml. Capsular fluid was obtained by percutaneous needle aspiration and assayed for antibiotic by the disk plate bioassay technique. Cephalosporins were administered intramuscularly at a dose of 30 mg/kg. Mean peak concentrations of cephaloridine and cefazolin were significantly higher than cephalothin and cephapirin in capsular fluids, but the percent penetration (ratio of capsular mean peak to serum mean peak) ranged from 8.7 to 16.9% and was not significantly different among the cephalosporins. At 24 h the capsular concentration of cefazolin was significantly greater than for the other cephalosporins (P < 0.001). Lower rabbit serum protein binding observed at high in vivo concentrations may have enabled cefazolin to penetrate capsular fluid, but in vitro protein binding studies did not confirm a decrease in serum protein binding at high concentrations within the clinical range. Kanamycin and amikacin showed comparable capsular fluid peak concentrations as did gentamicin and tobramycin. The percent penetration ranged from 15.2 to 34.5% for the aminoglycosides. The only statistical difference was that amikacin penetration was significantly higher than that for tobramycin. Mean capsular concentrations of amikacin, cefazolin, and cephaloridine compared most favorably with the minimum inhibitory concentration of gram-negative bacilli at the dosages used in this study.     

Effect of Probenecid on Cerebrospinal Fluid Concentrations of Penicillin and Cephalosporin Derivatives

Probenecid may elevate the cerebrospinal fluid (CSF) concentration of penicillin G by inhibiting the excretion of organic acids from CSF. We have studied this phenomenon with various penicillin and cephalosporin derivatives. Penicillin concentrations were determined in rabbits under steady-state conditions before and after intravenous probenecid administration. With both low-dose and high-dose probenecid, CSF penicillin levels increased two to three times as did CSF concentration as a percentage of serum level. The same probenecid effect was consistently demonstrated in animals with experimental pneumococcal meningitis. Probenecid likewise increased the CSF concentration of ampicillin, carbenicillin, nafcillin, cephacatrile, and cefazolin. Probenecid may prove useful in certain bacterial infections where high CSF antibiotic levels are necessary.     

Serum Protein Binding of the Aminoglycoside Antibiotics

The binding of four aminoglycoside antibiotics by human serum was investigated under controlled conditions of physiological pH and temperature, by means of an ultrafiltration technique. No serum binding was demonstrable for gentamicin, tobramycin, or kanamycin, whereas streptomycin was 35% bound. Previous conflicting studies are discussed, and some of the pharmacological implications are considered.     

Antibiotic Penetrance of Ascitic Fluid in Dogs

Antibiotic concentrations in ascitic fluid after parenteral therapy may be important in the treatment of peritonitis. We have created ascites in dogs by partial ligation of the inferior vena cava. Ascitic fluid volume was measured at the time each antibiotic was administered. Nine antibiotics were studied in the same three dogs. Antibiotic concentration in ascitic fluid was found to vary inversely with ascites volume. Percentage of penetration (ratio of ascites peak to serum peak ×100) ranged from 5.8 to 65% among the drugs studied. Only metronidazole showed a statistically significant higher percentage of penetration than other antimicrobials. Concentrations in ascitic fluid after single doses of cephalothin (15 mg/kg) and the aminoglycosides (2 mg/kg, gentamicin and tobramycin; 7.5 mg/kg, amikacin and kanamycin) did not exceed the minimum inhibitory concentration of many gram-negative rods and may justify the use of higher than usual initial parenteral doses, or possibly initial intraperitoneal administration in seriously ill patients.     

Assessment of Oritavancin Serum Protein Binding across Species

Biophysical methods to study the binding of oritavancin, a lipoglycopeptide, to serum protein are confounded by nonspecific drug adsorption to labware surfaces. We assessed oritavancin binding to serum from mouse, rat, dog, and human by a microbiological growth-based method under conditions that allow near-quantitative drug recovery. Protein binding was similar across species, ranging from 81.9% in human serum to 87.1% in dog serum. These estimates support the translation of oritavancin exposure from nonclinical studies to humans.Estimates of serum protein binding are essential to translate drug exposure from nonclinical species to humans during assessments of toxicology, pharmacokinetics, and pharmacodynamics since the free fraction dictates drug activity (3, 7, 17, 18). Recent evidence supports the concept of an “active fraction” that offers insight into the pharmacodynamic behavior of highly protein-bound drugs, such as daptomycin (20).Oritavancin is a late-stage investigational lipoglycopeptide under study for treatment of serious Gram-positive infections (6). Nonspecific binding of oritavancin to labware surfaces (1, 2) and to dialysis membranes has called into question the accuracy of previous oritavancin human serum binding estimates (85.7% to 89.9% [16]). We therefore used conditions that minimize nonspecific oritavancin binding (4, 5) to estimate its binding to serum by a single in vitro methodology for three nonclinical species (mouse, rat, and dog) and humans. Protein binding estimates were derived from serum-induced increases in oritavancin MICs (9, 10, 21). To control for any impact of serum components on bacterial growth and antibiotic activity, oritavancin activity in serum was compared to its activity in serum ultrafiltrate, which is devoid of albumin, the protein responsible for the majority of oritavancin serum binding (23). The method was benchmarked using daptomycin and ceftriaxone (8, 18, 22). (Part of this work was previously presented at the 19th European Congress of Clinical Microbiology and Infectious Diseases as a poster [12].)Pooled serum from humans, mice, and rats was from Equitech-Bio (Kerrville, TX); pooled serum from beagle dogs was from Bioreclamation (Liverpool, NY). Serum ultrafiltrate was prepared using Centricon Plus-50 ultrafilters (Millipore, Billerica, MA), whose molecular mass cutoff (50 kDa) excludes albumin. MICs against Staphylococcus aureus ATCC 29213 were determined by broth microdilution (4) using arithmetic drug dilutions in 95% serum or 95% serum ultrafiltrate, each supplemented with 5% cation-adjusted Mueller-Hinton broth (CAMHB). Serum protein binding for each drug was calculated using the following formula: % bound = (1 − [mean MIC in serum ultrafiltrate/mean MIC in serum]) × 100.The MICs for each condition, serum source, and test agent were precise (Table ​(Table1),1), with a mean coefficient of variation of 17%. MICs as determined under CLSI M7-A8 conditions (Table ​(Table1)1) (4) were within the quality control ranges (5).

TABLE 1.

Oritavancin, ceftriaxone, and daptomycin MICs against S. aureus ATCC 29213 in cation-adjusted Mueller-Hinton broth and 95% serum ultrafiltrate and 95% serum from human, mouse, rat, and dog

Rate of Binding of Antibiotics to Canine Serum Protein

The time rates of binding of three antibiotics of similar chemical structure, each with differing degrees of protein binding, were determined. Cephaloridine, which is 10% bound by serum proteins, was bound at a more rapid rate than cephalothin, which is 40% bound by serum protein. Cefazolin, bound 80%, required for longest time period for maximum binding to occur. The rate of protein binding appears directly related to the total percentage bound. The data from this study indicate that prolonged rates of binding of highly protein-bound drugs may influence pharmacological studies.     

血清-腹水白蛋白梯度在鉴别门脉高压性与非门脉高压性腹水中的临床意义

目的探讨血清-腹水白蛋白梯度（SAAC；）在腹水鉴别中的临床应用价值。方法选择诊断明确的腹水患者55例，门脉高压41例、非门脉高压14例，测定血清和腹水总蛋白、白蛋白、乳酸脱氢酶、并进行对比。结果门脉高压组SAAG为（17．86±4．66）g／L，非门脉高压组SAAG为（11．05±6．74）g／L，两组比较有显著性差异（P〈0．001）。对门脉高压诊断的准确率SAAG为94．55％，腹水总蛋白为61．82％、腹水血清总蛋白比值83．64％，腹水乳酸脱氢酶为67．27％。此外，SAAG大于11g／L的病人食管静脉曲张的发生率高。结论SAAG对鉴别门脉高压性与非门脉高压性腹水具有重要的临床意义。     

血清-腹水白蛋白梯度在鉴别门脉高压性与非门脉高压性腹水中的临床意义

目的探讨血清-腹水白蛋白梯度(SAAG)在腹水鉴别中的临床应用价值。方法选择诊断明确的腹水患者55例,门脉高压41例、非门脉高压14例,测定血清和腹水总蛋白、白蛋白、乳酸脱氢酶、并进行对比。结果门脉高压组SAAG为(17.86±4.66)g/L,非门脉高压组SAAG为(11.05±6.74)g/L,两组比较有显著性差异(P<0.001)。对门脉高压诊断的准确率SAAG为94.55%,腹水总蛋白为61.82%、腹水血清总蛋白比值83.64%,腹水乳酸脱氢酶为67.27%。此外,SAAG大于11 g/L的病人食管静脉曲张的发生率高。结论SAAG对鉴别门脉高压性与非门脉高压性腹水具有重要的临床意义。     

Analytical and Functional Determination of Polymyxin B Protein Binding in Serum

To enhance our understanding of the pharmacological properties of polymyxin B, serum protein binding for polymyxin B1, B2, and B3 and for isoleucine-polymyxin B1 was evaluated. Using equilibrium dialysis and ultrafiltration, comparable protein binding was found in all 4 components of polymyxin B (92% to 99%). Protein binding in human serum was further assessed using a functional assay, the results of which were in general agreement with previous findings (approximately 90%).     

血清视黄醇结合蛋白4 及骨桥蛋白与绝经后骨质疏松症的相关性研究

目的　探讨绝经后妇女血清视黄醇结合蛋白4（retinol binding protein 4,RBP4）及骨桥蛋白（osteopontin,OPN） 水平与骨密度（bone mineral density,BMD） 的关系, 分析其在绝经后骨质疏松症（postmenopousalosteoporosis,PMOP）中的应用价值。方法　对262 例绝经后妇女进行研究双能X 线骨密度仪测量腰椎1-4（L1-4）和左侧股骨颈（FN）,测定血中RBP4,OPN,I 型原胶原N- 端前肽（PINP）,β- 胶原降解产物（β-CTX）,甲状旁腺素（PTH）,骨钙素（OC）,血钙（Ca）及血磷（P）水平。ROC 曲线分析RBP4 及OPN 诊断PMOP 的价值。结果　骨质疏松组血清 RBP4(μg/ml)（25.13±4.74 , 18.46±4.25 和15.30±3.87）及OPN(ng/ml)（13.58±4.42 , 10.47±3.46 和8.24±3.13）水平均明显高于骨量减少组和正常组,差异有统计学意义（均P ＜ 0.05）。相关分析显示,骨质疏松症组血清RBP4及OPN 水平与β-CTX 呈正相关（r=0.291,0.284,均P ＜ 0.05）,与Ca,L1-4 及左FN 骨密度呈负相关（r = - 0.247,-0.513,-0.486,-0.265,-0.556,-0.574,均P ＜ 0.05）。ROC 曲线显示,血清RBP4 及OPN 水平为21.53μg/ml 和12.27 ng/ml 是诊断PMOP 的最佳截值。结论　血清RBP4 及OPN 水平升高与低BMD 相关,是影响PMOP 发生的关键因子。     

Serum and Cerebrospinal Fluid Pharmacokinetics of Intravenous and Oral Lamivudine in Human Immunodeficiency Virus-Infected Children

We studied the pharmacokinetics of intravenously and orally administered lamivudine at six dose levels ranging from 0.5 to 10 mg/kg of body weight in 52 children with human immunodeficiency virus infection. A two-compartment model with first-order elimination from the central compartment was simultaneously fitted to the serum drug concentration-time data obtained after intravenous and oral administration. The maximal concentration at the end of the 1-h intravenous infusion and the area under the concentration-time curve after oral and intravenous administration increased proportionally with the dose. The mean clearance of lamivudine (± standard deviation) in the children was 0.53 ± 0.19 liter/kg/h (229 ± 77 ml/min/m² of body surface area), and the mean half-lives at the distribution and elimination phases were 0.23 ± 0.18 and 2.2 ± 2.1 h, respectively. Clearance was age dependent when normalized to body weight but age independent when normalized to body surface area. Lamivudine was rapidly absorbed after oral administration, and 66% ± 25% of the oral dose was absorbed. Serum lamivudine concentrations were maintained above 1 μM for ≥8 h of 24 h on the twice daily oral dosing schedule with doses of ≥2 mg/kg. The cerebrospinal fluid drug concentration measured 2 to 4 h after the dose was 12% (range, 0 to 46%) of the simultaneously measured serum drug concentration. A limited-sampling strategy was developed to estimate the area under the concentration-time curve for concentrations in serum at 2 and 6 h.     

Protein Binding and Population Pharmacokinetics of Dexmedetomidine after Prolonged Infusions in Adult Critically Ill Patients

PurposeDexmedetomidine (DEX) is a highly selective α₂-adrenoceptor agonist with high protein binding of 94%. Critical illness may affect protein binding and the pharmacokinetic (PK) parameters of many drugs, including DEX. In critically ill patients receiving prolonged infusions of DEX, there is little information documenting the relationship between key pathophysiologic factors and DEX protein binding or PK parameters. The purpose of this study was to characterize the protein binding and PK profile of prolonged DEX infusion in critically ill patients.MethodsCritically ill, adult intensive care unit patients at a university hospital in Hong Kong were studied. The association between the pathophysiologic changes of critical illness and protein binding was evaluated using a generalized estimating equation. A population pharmacokinetic model to establish the PK profile of DEX was developed, and key pathophysiologic covariate effects of severity of illness, organ dysfunction measures, and altered protein binding on DEX PK parameters in this critically ill population were evaluated.FindingsA total of 22 critically ill patients and 1 healthy control were included. Mean protein binding of DEX in the critically ill patients was 90.4% (95% CI, 89.1–91.7), which was 4% lower than that in the healthy control. The PK data were adequately described by a 2-compartment model. The estimated population mean (relative standard error [RSE]) values of systemic clearance (CL), volume of distribution of the central compartment (V2), intercompartmental clearance (Q), and V_d in the peripheral compartment (V3) were 38.6 (11.7) L/h, 32.1 (46.1) L, 114.5 (58.3) L/h and 95.1 (30.6) L, respectively. The corresponding estimated interindividual variability expressed as CV% (RSE) was 52.4 (23.8) for CL, 172.9 (19.3) for V2, 123.7 (33.7) for Q, and 106 (39.9) for V3. No significant explanatory pathophysiologic covariates were identified.ImplicationsAlthough a marginally significant reduction of protein binding in critically ill patients was demonstrated, the magnitude of the difference was unlikely to be of clinical significance. Higher alanine aminotransferase concentration was associated with decreased protein binding. No significant pathophysiologic covariates were associated with the observed PK parameters. The high interindividual variability of PK parameters supports the current practice of dose titration to ensure the desired clinical effects of DEX infusion in the intensive care unit setting.     

Influence of Assay Methodology on the Measurement of Free Serum Ceftriaxone Concentrations

The influence of assay methodology on the measurement of the active free fraction of ceftriaxone in plasma was determined. The free fraction was measured by three methods: agar diffusion bioassay, precipitation of plasma protein with methanol followed by high-performance liquid chromatography (HPLC) of the supernatant, and ultrafiltration of plasma followed by HPLC of the filtrate. In human serum, the free ceftriaxone levels were significantly lower (P = 0.03) when measured on ultrafiltrates compared to the other two methods. This difference disappeared when dolphin serum was studied. After ultrafiltration, human serum was shown, by Scatchard plot analysis, to have two ceftriaxone binding sites. Species differences were also demonstrated. Hence, in humans, determination of free plasma ceftriaxone varies with the assay method employed.     

Amiodarone: Individualizing Dosage with Serum Concentrations

The purpose of the present report is to review the available pharmacokinetic informaation on amiodarone with an emphasis on our own experience in monitoring serum amiodarone concentrations. We have found that 400 mg should be the maximal maintenance dose; if that treatment fails, careful addition of other antiarrhythmic agents is preferable over an increase in amiodarone dosage. Serum concentrations below 2.5 mg/L will significantly improve amiodarone's benefit-to-risk ratio.     

Amiodarone: Individualizing Dosage with Serum Concentrations

The purpose of the present report is to review the available pharmacokinetic informaation on amiodarone with an emphasis on our own experience in monitoring serum amiodarone concentrations. We have found that 400 mg should be the maximal maintenance dose; if that treatment fails, careful addition of other antiarrhythmic agents is preferable over an increase in amiodarone dosage. Serum concentrations below 2.5 mg/L will significantly improve amiodarone's benefit-to-risk ratio.     

Methyprylon Overdose: Interpretation of Serum Drug Concentrations

Abstract

The effect of two forms of Prussian blue, soluble K₃ Fe[Fe(CN)₆] and insoluble Fe₄[Fe(CN)₆]₃, and of ammonium iron hexacyanoferrate (II) (NH₄Fe[Fe(CN)₆] on intestinal radiocesium absorption was investigated in rats, pigs, and humans. In rats 5?mg of antidote administered 2 min before ¹³⁴Cs tracer reduced radiocesium absorption to 2.4 - 6.3% of the oral dose. In pigs fed with Chernobyl-contaminated whey under normal feeding conditions for a 27 day period, radiocesium activity concentration was reduced from 360 Bq/kg in control animals to 10 - 30 Bq/kg by 5?g antidote/d. In man 1?g of oral Prussian blue diminished the cesium absorption from a ¹³⁴Cs-labelled test meal to 5.6 -6.4% of the controls. The inhibitory effects of colloidally soluble K₃ Fe[Fe(CN₆) and of (NH₄Fe[Fe(CN)₆] were similar with slightly less inhibition by the insoluble Fe₄[Fe(CN)₆]₃.     

Pharmacokinetics and Inflammatory Fluid Penetration of Clinafloxacin

A single 200-mg dose of clinafloxacin was given orally to each of nine healthy male volunteers, and the concentrations of the drug were measured in plasma, cantharidin-induced inflammatory fluid, and urine over the following 24 h (48 h in the case of urine). The mean maximum concentration in plasma was 1.34 μg/ml at a mean time of 1.8 h postdose. The mean maximum concentration in the inflammatory fluid was 1.3 μg/ml at 3.8 h postdose. The mean elimination half-life of clinafloxacin in plasma was 5.65 h. The overall penetration into the inflammatory fluid was 93.1%, as assessed by determining the ratio of area under the concentration-time curves. Recovery of clinafloxacin in urine was 58.8% by 24 h and 71.8% by 48 h postdose.     

Chlordiazepoxide Overdose: Interpretation of Serum Drug Concentrations

Abstract

Prussian blue salts are used in clinical practice as an antidote for the treatment of humans contaminated with radioactive cesium. A decomposition product of these Prussian blue salts may be the highly toxic cyanide. A method to simulate gastrointestinal cyanide-release was applied to four different Prussian blue salts: K₃Fe[Fe(CN)₆], Fe₄[Fe(CN)₆]₃, NH₄Fe[Fe(CN)₆] (pur. and unpur.). Cyanide-release was higher in artificial gastric juice than in water and artificial intestinal juice. Under all conditions cyanide-release from Fe₄[Fe(CN)₆]₃ was the lowest. Since Fe₄[Fe(CN)₆]₃ also binds more cesium, it appears to be the most suitable Prussian blue salt for use as an antidote after radiocesium contamination in humans.     

In Vitro Activity and Pharmacokinetics in Patients of Cefamandole, a New Cephalosporin Antibiotic

Cefamandole nafate, a new cephalosporin for parenteral use, was evaluated in vitro against 231 recent clinical isolates and in 12 patients. Cefamandole had activity equivalent to cefazolin against Staphylococcus aureus, Escherichia coli, and Klebsiella pneumoniae. Cefamandole was more active than cephalothin or cefazolin against Proteus mirabilis. Both cefamandole and cefazolin were as active as cephalothin against S. aureus, were slightly more active against K. pneumoniae, and were considerably more active against E. coli. All strains of indole-positive Proteus sp. were inhibited by 6.3 mug of cefamandole per ml but only 20% were inhibited by 25 mug of cefazolin or cephalothin per ml. Eighty-eight percent of Enterobacter sp. was inhibited by 25 mug of cefamandole per ml, but only 20 and 5% were inhibited by the same concentration of cefazolin and cephalothin, respectively. Peak levels of cefamandole ranged from 6.0 to 110 mug/ml in serum and levels ranged from 440 to 16,800 mug/ml in a 4- to 6-h collection of urine after a 500-mg or 1-g intramuscular dose (6.1 to 17.3 mg/kg) in patients with endogenous creatinine clearances of >/=31 ml/min. These levels were done after the first dose, at mid-therapy, and at the end of therapy. There was no evidence of accumulation with the 500-mg or 1-g dose given every 4 to 6 h. The percentage of the dose excreted in the urine within the first 4 to 6 h after administration of cefamandole was >/=43%. The half-life of cefamandole in serum was 49 to 126 min.     

Developmental Pattern of a Serum Binding Protein for Multiplication Stimulating Activity in the Rat

The concentration of multiplication stimulating activity (MSA), an insulinlike growth factor (IGF), is high in fetal rat serum. We now report that MSA is exclusively associated wth an albumin-size binding protein in fetal rat serum; the growth hormone-dependent, gamma globulin-size binding protein, which predominates in the older animal, is absent from fetal rat serum. When ¹²⁵I-MSA was incubated with fetal rat serum and then gel filtered on Sephadex G-200, specific radioactivity eluted in the void volume (peak I) and the albumin region (peak III); by contrast, specific radioactivity eluted mainly in the gamma globulin region (peak II) in adult rat serum. Pools of the Sephadex G-200 fractions were chromatographed on Sephadex G-50, in 1 M acetic acid, to separate the binding protein from IGF activity. Analysis of IGF activity by chick embryo fibroblast bioassay, competitive protein binding assay, and MSA by radioimmunoassay revealed that all the IGF activity and MSA in fetal rat serum resided in peak III. Measurement of MSA binding capacity of the stripped binding protein by Scatchard analysis demonstrated that the majority of binding capacity also was found in peak III in fetal rat serum; most of MSA binding capacity was in peak II in adult rat serum. In fetal rat sera, in addition to the peak III binding protein, which is the major carrier of endogenous MSA, there is a component in peak I capable of specifically binding ¹²⁵I-MSA. This component elutes as a single species from a Sepharose-6B column. As MSA associated with peak III gradually declined in early neonatal life, peak II-associated IGF activity measured by chick embryo fibroblast bioassay showed a rise of activity with a peak at 5 d of neonatal life, a nadir at 20 d, with an increase again to attain adult levels. These studies demonstrate that the MSA binding protein in the fetus is different from the growth hormone-dependent binding protein in adult life.