Green synthesis of hesperidin coated silver nanoparticles for colorimetric detection of gentamicin sulfate in real samples.

Gentamicin sulfate (GEN), a well-known broad-spectrum antibiotic is mostly administered through intramuscular injections and entirely excreted in un-metabolized form through urination from patient's body. Quantitative detection of GEN by direct UV absorption is usually challenging due to lack of chromophores and fluorophores in structure. The current study described the hesperidin coated silver nanoparticles (HSPAgNPs) based novel colorimetric quantitative assay for GEN. HSPAgNPs, based colorimetric detection involved a transition from characteristic yellow colour to blackish brown upon addition of GEN, accompanied by a significant quenching in localized surface plasmon resonance (LSPR) band at λmax 398 nm. Moreover, the synthesized HSPAgNPs were employed to rapid and quantitative detection of GEN in concentration range of 5 to 100 µM. Limit of detection (LOD) and limit of quantification (LOQ) was calculated by standard deviation of the ordinate intercept and slope of the regression line and estimated to be 6.89 µM and 20.88 µM respectively, with a linear correlation factor R2 equal to 0.9990 which strictly followed Beer's law. Furthermore, the utility and effectiveness of HSPAgNPs was also explored for selective recognition of GEN in tap water, serum, human blood plasma and urine.

Population Pharmacokinetic Analysis of Gentamicin in Pediatric Extracorporeal Membrane Oxygenation.

BACKGROUND: Gentamicin pharmacokinetics may be altered in pediatric patients undergoing extracorporeal membrane oxygenation (ECMO). Description of gentamicin pharmacokinetics and relevant variables can improve dosing. METHODS: A retrospective population pharmacokinetic study was designed, and pediatric patients who received gentamicin while undergoing ECMO therapy over a period of 6 1/2 years were included. Data collection included the following: patient demographics, serum creatinine, albumin, hematocrit, gentamicin dosing and serum concentrations, urine output, and ECMO circuit parameters. Descriptive statistics were used to characterize the patient population. Population pharmacokinetic analysis was performed with NONMEM, and simulation was performed to identify empiric doses to achieve therapeutic serum concentrations. RESULTS: A total of 37 patients met study criteria (75.7% male patients), with a median age of 0.17 [interquartile range (IQR) 0.12-0.82] years. Primary indications for ECMO included the following: congenital diaphragmatic hernia (n = 17), persistent pulmonary hypertension (n = 5), and septic shock (n = 4). Patients received a total of 117 gentamicin doses [median 1.8 (IQR 1.4-2.9) mg/kg/dose] and had 125 serum concentrations measured at a median of 22.8 (IQR 15.8-25.5) hours after a dose. Population pharmacokinetic analysis identified a 2-compartment model with additive error as the best fit. Covariates included the following: allometrically scaled fat-free mass on clearance, central and peripheral volume of distribution (VDcentral and VDperipheral), and intercompartmental clearance; serum creatinine on clearance; ultrafiltration rate on central volume of distribution. Simulation identified dosage of 4-5 mg/kg/dose every 24 hours for neonates and infants as an acceptable empiric dosing regimen. Children and adolescents had elevated trough concentrations when dosed according to traditional dosing methods. CONCLUSIONS: Fat-free mass should be used to dose gentamicin in pediatric ECMO patients. Serum creatinine is a marker of gentamicin clearance and should be used to adjust gentamicin dosing in pediatric ECMO patients.

Characterisation of in vivo release of gentamicin from polymethyl methacrylate cement using a novel method.

PURPOSE: The purpose of this study was to investigate the in vivo elution kinetics of gentamicin from bone cement by assessing antibiotic levels in the urine. METHODS: Urinary samples of 35 patients who had undergone primary total hip arthroplasty were collected post-operatively. Gentamicin concentrations were analysed using the fluorescence polarisation immunoassay technique. RESULTS: The mean duration of urinary gentamicin release in all cases was 43 days (range 13-95). There was still detectable gentamicin at the final collection in 20% (7/35) of cases, and in these cases, the mean gentamicin release was 71 days. CONCLUSIONS: From the assessment of urinary gentamicin, we were able to demonstrate the biphasic gentamicin elution from bone cement. In addition, there were detectable concentrations of the antibiotic from the urinary samples for prolonged periods of up to two to six months. Our study indicates that the assessment of urinary antibiotics can offer a non-invasive method of monitoring the in vivo release kinetics of antibiotics from bone cement.

A rat model of early sepsis: relationships between gentamicin pharmacokinetics and systemic and renal effects of bacterial lipopolysaccharide combined with interleukin-2.

A rat model of early sepsis induced by lipopolysaccharide (LPS) combined with interleukin-2 (IL-2) was developed. The primary aim was to assess the pharmacokinetics of gentamicin and sepsis-induced pathophysiological changes. Moreover, the effects on the glomerular filtration rate and tubular function were studied in septic and control rats. First, an intravenous (i.v.) bolus of LPSIL-2 (1 mg/kg-Pseudomonas aeruginosa, 15 µg/kg IL-2) or saline (controls, C) was administred. The Wistar rats were treated 30 min after LPSIL-2 with gentamicin as a 3 mg/kg i.v. bolus followed 10 min later by an i.v. 170-min infusion (GE, 0.09 mg/kg·min(-1)). The monitoring of vital functions, biochemistry and GE concentrations was performed. Creatinine clearance was 2-3 times lower and fractional urea excretion was 3-4 times less in septic rats as compared to controls(p<0.05), although urine flow was comparable. Capillary leakage caused a 55% elevation in the volume of distribution (V(c)) in the LPSIL+GE group vs. C+GE (p<0.05). The renal CL(ge) was less (2.2±0.59 vs. 3.8±0.53 mL/min·kg(-1), p<0.05), while the total CL(ge) was comparable (5.9±1.5 vs. 6.7±1.1 mL/min·kg(-1); p=0.30). In the LPSIL+GE group relative to C+GE, the half-life (t(1/2)) was 79% higher (p<0.05) and GE concentrations detected at the end of the study in the plasma and kidney were elevated 2.5-fold (p=0.09) and 2.2-fold (p<0.05), respectively. The model reproduced several consequences of early sepsis like in patients such as capillary leak, a decreased glomerular filtration rate (GFR) and the changes in pharmacokinetics of GE (increased values of V(c) and t(1/2) and a drop in renal CL(ge) proportional to that of CL(cr)). Nonrenal routes which, for the most part, compensate the reduced renal CL(ge) in septic rats deserve further study.

A comparative study on several models of experimental renal calcium oxalate stones formation in rats.

In order to compare the effects of several experimental renal calcium oxalate stones formation models in rats and to find a simple and convenient model with significant effect of calcium oxalate crystals deposition in the kidney, several rat models of renal calcium oxalate stones formation were induced by some crystal-inducing drugs (CID) including ethylene glycol (EG), ammonium chloride (AC), vitamin D(3)[1alpha(OH)VitD(3), alfacalcidol], calcium gluconate, ammonium oxalate, gentamicin sulfate, L-hydroxyproline. The rats were fed with drugs given singly or unitedly. At the end of experiment, 24-h urines were collected and the serum creatinine (Cr), blood urea nitrogen (BUN), the extents of calcium oxalate crystal deposition in the renal tissue, urinary calcium and oxalate excretion were measured. The serum Cr levels in the stone-forming groups were significantly higher than those in the control group except for the group EG+L-hydroxyproline, group calcium gluconate and group oxalate. Blood BUN concentration was significantly higher in rats fed with CID than that in control group except for group EG+L-hydroxyproline and group ammonium oxalate plus calcium gluconate. In the group of rats administered with EG plus Vitamin D(3), the deposition of calcium oxalate crystal in the renal tissue and urinary calcium excretion were significantly greater than other model groups. The effect of the model induced by EG plus AC was similar to that in the group induced by EG plus Vitamin D(3). EG plus Vitamin D(3) or EG plus AC could stably and significantly induced the rat model of renal calcium oxalate stones formation.

Therapeutic implications of gentamicin accumulation in severly diseased kidneys.

We evaluated the influence of severe disease in human kidneys (12 patients) on gentamicin sulfate accumulation characteristics in such tissue and compared the results with intrarenal tissue concentration data derived from the study of healthy dogs (54 kidneys) during variation in hydration and urinary pH. Our results indicate that, in the management of pyelonephritis complicating preexisting renal disease, if the minimal inhibitory gentamicin concentration for an infecting organism is greater than the usual therapeutic an nontoxic serum levels of the compound, then it may be appropriate to use alternate antibiotics that demonstrate lesser reduction in tissue drug accumulation in diseased kidneys.

Renal clearance and tissue accumulation of gentamicin.

Multiple-dose studies of gentamicin pharmacokinetics were performed in 2 treated patients. After the final dose, serum and urine concentration declined in biphasic fashion with beta half-lives of 87 and 173 hr. Recovery of the total dose administered required urine collection for at least 10 to 20 days after the last dose. A two-compartment model was used to describe the biphasic decline in serum concentrations, to simulate all measured concentrations during treatment, and to predict the amount of gentamicin in the tissue compartment. Analysis of autopsy tissues yielded the predicted amount of drug. A linear two-compartment model adequately quantitates gentamicin disposition until about 4 days after cessation of therapy when gentamicin renal clearance begins to decline because of tubular reabsorption.

Factors affecting aminoglycoside disposition: effects of circadian rhythm and dietary protein intake on gentamicin pharmacokinetics.

The effects of dietary protein loading and circadian cycle on the pharmacokinetics of gentamicin were studied in healthy adult men. Ten subjects fasted overnight, and at 8 AM the next morning they received gentamicin, 1.5 mg/kg. Serum and urine samples were obtained over a 6-hour period. In two additional clearance studies with 2-week washout periods in between, 10 subjects were given the same dose of gentamicin at 8 PM in the fasted state and six subjects were also studied in a protein-supplemented (90 gm) state. Pharmacokinetic analysis revealed no significant effect of circadian cycle on gentamicin pharmacokinetic parameters at each of the two fasted periods. In contrast, dietary protein loading resulted in a significant decrease in the elimination t1/2 (P less than 0.05) and an increase in total body clearance compared with the fasted 8 PM study. Urinary excretion of gentamicin was also found to increase significantly (P = 0.03) as a result of protein intake compared with the fasted evening study period. Our study demonstrates the importance of dietary controls in chronopharmacokinetic studies of drugs eliminated predominantly by renal mechanisms.

Treatment of chronic urinary tract infections with gentamicin.

Gentamicin was of value in the treatment of chronic urinary tract infections caused by multiresistant bacterial strains for which no atoxic antibiotic was available. The treatment was carried out after alkalinization of the patient's urine. With the dosage given, gentamicin gave a low serum and a relatively high urine concentration. Excretion of active gentamicin in the urine was high even in patients with impaired renal function. The results of treatment of complicated chronic urinary tract infections with initial gentamicin and following long-term therapy showed negative urinary cultures in 12 out of 24 patients within one to 14 months of follow-up time. To reduce the risk of toxic side effects the dosage was adjusted according to the patient's kidney function. No development of resistance was demonstrated in the bacteria.

Gentamicin distribution from a collagen carrier.

Local delivery of antibiotics by a degradable carrier has the potential for high local antibiotic levels and avoids systemic toxicity. Intravenous access, renal function monitoring, and subsequent surgical removal may not be required when degradable local delivery modalities are used. This study examined the in vivo elution of gentamicin from processed bovine collagen (type I) in 66 adult White rabbits. Collagen impregnated with gentamicin (3 mg/kg) was implanted into the vastus lateralis, and data were collected from 15 minutes to 28 days after implantation. Local tissue biopsies were taken a minimum of 2 mm from the implantation site. The gentamicin was released into the local tissue and averaged more than 3,800 micrograms/ml during the initial 4 hours after implantation. Local levels fell to 6.90 +/- 5.22 micrograms/ml at 24 hours and subsequently were 2.70 +/- 1.75 micrograms/ml or more through day 28. Serum levels reached an average peak of 4.04 +/- 1.75 micrograms/ml at 5 hours after implantation, decreased after the initial 24 hours, and subsequently were less than 0.41 +/- 0.20 microgram/ml through day 28. Collagen impregnated with gentamicin proved to be an effective degradable carrier of gentamicin in the healthy rabbit; it provided local tissue concentrations above the minimum inhibitory concentration and serum concentrations below levels associated with systemic toxicity for 28 days after implantation.

Interaction between the renal excretion rates of beta 2-microglobulin and tobramycin in man.

The renal excretion rate of beta 2-microglobulin in man is 127 +/- 98 ng/min at alkaline urine pH (pH 7). Tobramycin, up to intravenous doses of 160 mg (2 mg/kg) does not increase the renal excretion rate of beta 2-microglobulin. Tobramycin must have less affinity than gentamicin for the tubular system for active reabsorption of amino groups containing organic compounds. Due to this reduced affinity tobramycin will be absorbed less by the proximal tubular cells, which may be one of the reasons for tobramycin being less toxic than gentamicin. beta 2-Microglobulin excretion can be used as a parameter for the relative binding affinity of aminoglycosides.

A comparison of the effects of cisplatin and N-methyliminodiacetato-(1,2-diaminocyclohexane)-platinum(II) on renal function and gentamicin excretion in rats.

N-methyliminodiacetato(1,2-diaminocyclohexane)-platinum(II) (MIDP) is a new third-generation water-soluble antitumor platinum complex. This study compares the effects of MIDP (3 injections of 25 mg/kg each on days 1, 5 and 9) on renal structure and function and the urinary excretion of gentamicin (GENT) with those of a single 6 mg/kg dose of cisplatin (DDP) in F-344 (Fischer) rats. GENT was given as a single dose of 30 mg/kg 7 days after DDP injection or the last MIDP injection. Rats given DDP and GENT had significantly different plasma urea nitrogen (BUN) levels (315 +/- 79 mg/dl) and creatinine clearance (0.40 +/- 0.24 ml/[min.kg]) than did the control group that was given only GENT (15 +/- 1 mg/dl and 5.5 +/- 0.6 ml/[min.kg]). MIDP did not affect renal function (BUN, 16 +/- 3 mg/dl; creatinine clearance, 6.1 +/- 1.0 ml/[min.kg]). Light microscopic examination of renal tissue from MIDP-treated rats did not reveal any evidence of cell degeneration or necrosis. Rats given GENT alone excreted 72 +/- 4% of the dose in 24 h and had plasma gentamicin levels of 19 +/- 2 ng/ml 24 h after injection. The group pretreated with DDP had lower urinary GENT excretion (31 +/- 10%) and higher plasma GENT levels (7491 +/- 3750 ng/ml). MIDP pretreatment had no effect on GENT excretion (72 +/- 8%) or plasma GENT levels (16 +/- 2 ng/ml). Thus, MIDP did not cause any measureable decrease in renal function or GENT excretion in our study. Since nephrotoxicity is a significant problem with DDP administration, further studies with MIDP are warranted.

Determination of gentamicin in urine samples after inhalation by reversed-phase high-performance liquid chromatography using pre-column derivatisation with o-phthalaldehyde.

Gentamicin and netilmicin (internal standard) were extracted from urine using C18 solid-phase extraction cartridges (94.3% recovery) and then derivatised with o-phthalaldehyde and 3-mercaptopropionic acid. The derivative was stable for >6 h. The mobile phase methanol-glacial acetic acid-water (800:20:180, v/v), contained 0.02 M sodium heptanesulfonic acid, pH 3.4, and was passed at 1.0 ml min(-1) through a C18 column with fluorescence detection (excitation 340 nm, emission 418 nm). The four main components of gentamicin (C1, C1a, C2, C2a) and netilmicin, the internal standard, were separated. Using the C1a gentamicin peak, linearity was demonstrated from 0.5 to 10 microg ml(-1) and the limit of detection was 75 microg l(-1). Following 80-mg oral, 40-mg intravenous and 80-mg nebulised administration, the mean (SD) gentamicin urinary excretion was zero, 38.27 (0.96) and 1.93 (0.28) mg, respectively. Despite the relatively low lung deposition following inhalation of gentamicin the assay developed can be used to quantify the low urinary concentrations. Using this assay it should be possible to carry out urinary pharmacokinetic studies to identify the relative lung deposition of gentamicin following different methods of inhalation.

Effect of alkylxanthines on gentamicin-induced acute renal failure in the rat.

Adenosine antagonists have been previously shown to be of benefit in some ischaemic and nephrotoxic models of acute renal failure (ARF). In the present study, the effects of three alkylxanthines with different potencies as adenosine antagonists 8-phenyltheophylline, theophylline and enprofylline, were examined in rats developing acute renal failure after 4 daily injections of gentamicin (200 mg kg-1). Renal function was assessed by biochemical (plasma urea and creatinine), functional (urine analysis and [3H]inulin and [14C]p-aminohippuric acid clearances) and morphological (degree of necrosis) indices. The various drug treatments produced improvements in some, but not all, measurements of renal function. However, any improvement produced by drug treatment was largely a result of a beneficial effect exerted by its vehicle (polyethylene glycol and NaOH). The lack of any consistent protective effect noted with the alkylxanthines tested in the present study indicates that adenosine plays little, if any, pathophysiological role in gentamicin-induced ARF.

Gentamicin concentrations in urine, cortex and medulla in an acutely obstructed kidney animal model.

Gentamicin was administered intraperitoneally, three times in 12 h to Hartley type guinea-pigs which had undergone complete unilateral ureteral obstruction with normal contralateral ureteral function for either 24 hours, 7 days or 21 days. Two hours after the last drug dose urine samples were collected from urinary bladder and obstructed ureter. Healthy and obstructed kidneys were then surgically removed from all sacrificed animals. Gentamicin concentration in urine of healthy kidney was 112-266 microg/ml, and in obstructed kidney 18-53 microg/ml, with a tendency of linear decrease over a 3-week obstruction period. The gentamicin concentration in obstructed renal cortex never exceeded one-third of the gentamicin concentration in unobstructed renal cortex. The maximum gentamicin concentration in obstructed renal medulla was 75% of the gentamicin concentration in unobstructed renal medulla.

The effect of calcium on the antibacterial activity of gentamicin in urine.

the influence of various concentrations of calcium on the antibacterial activity of gentamicin in urine on 10 strains of E. coli and 10 strains of P. aeruginosa was studied in vitro. It was found that calcium has a strong antagonistic effect on gentamicin activity, particularly with regard to P. aeruginosa. This effect is greatly reduced when gentamicin concentrations are increased to levels higher than those obtained in urine under conventional treatment schedules.

Pharmacokinetics and urinary excretion of gentamicin in Bubalus bubalis calves following intramuscular administration.

The pharmacokinetics and urinary excretion of gentamicin was studied in buffalo calves after a single intramuscular administration (10 mg kg-1). Kinetic determinants were calculated by using a two compartment open model. The absorption (t1/2Ka) and biological half lives (t1/2 beta) were calculated to be 0.43 +/- 0.08 and 3.79 +/- 0.23 h, respectively. The value of the apparent volume of distribution (VdB) was found to be 0.38 +/- 0.07 litre kg-1. The satisfactory intramuscular dosage regimen of gentamicin for buffalo calves would be 3.23 mg kg-1 as priming dose and 2.88 mg kg-1 as maintenance dose to be repeated at 12 hour intervals to achieve and maintain the therapeutic plasma levels within safe limits. Urinary excretion of gentamicin was very rapid during the first 12 hours as 48.07 +/- 1.39 per cent of the total administered dose was excreted unchanged during this period.

Differential toxicity expression of gentamicine in five-sixths nephrectomized rats assigned to three progressive stages of renal dysfunction--establishment of a new screening approach.

Progressive renal dysfunction in 5/6 nephrectomized (NX) rats can be physiologically divided into three stages, coinciding with morphological stages, after definition of physiological parameters for identification of stage. Now, for the establishment of a toxicity screening approach using 5/6 NX rats, our concept, "Differential toxicity synchronized with renal dysfunction process could be identified using 5/6 NX rats" was examined by dosing gentamicin. Firstly, electrophoretic fractional changes of urinary proteins during gentamicin treatment were clarified with determination of amino acid sequences and the three differential features were proven, revealing the unpredictable depression of urinary albumin with progression of the stages in NX rats. Secondly, marked elevation of urinary lactate dehydrogenase (LDH) and glucose (GLU) was evident, indicating the intensified hypoxic conditions and glycolysis in tubular cells synchronized with increased tubular damage. Thirdly, these transit metabolic changes were proven as intensive cause for the advancement of renal dysfunction by the reduction of FRelectrolytes and water at the end of each dosing period. These results indicate that toxicity studies of newly developed drugs using 5/6 NX rats have potentiality prior to clinical dosing to the patients.

Effects of halothane anesthesia on the clearance of gentamicin sulfate in horses.

Inhalation anesthetics decrease the clearance of some drugs that are eliminated by renal excretion. The purpose of the study reported here was to investigate the effects of halothane anesthesia on the pharmacokinetics and urinary excretion of gentamicin sulfate, using the horse as a model. Using a crossover design, pharmacokinetic values after a single IV dose of gentamicin (4 mg/kg) were compared in halothane-anesthetized and unanesthetized horses. Compared with unanesthetized horses, the anesthetized horses had significant decreases in total body clearance (P less than 0.01) and apparent volume of distribution (P less than 0.05), and a significant increase in half-life (P less than 0.05) of gentamicin.

Therapeutic use of gentamicin in horses: concentrations in serum, urine, and synovial fluid and evaluation of renal function.

Serum, synovial fluid, and urine concentrations of gentamicin were measured in normal mature horses which had been given a single dose of the drug. Mean peak serum concentration (16.8 microgram/ml) occurred in horses 30 minutes after they were given a single intramuscular dose of 4.4 mg of gentamicin/kg of body weight. In horses given a smaller dose of gentamicin (1.7 mg/kg), mean peak serum concentrations of gentamicin (10.2 microgram/ml) appeared at 1 hour. Synovial fluid concentration was maximum at 2 hours for both doses; in horses given the larger dose, mean peak concentration was 6.4 microgram/ml, and in those given the smaller dose (1.7 mg/kg), 3.4 microgram/ml. Measurable concentrations of gentamicin in serum and synovial fluid persisted 8 hours. During the first 8 hours, percentages of gentamicin excreted in the urine were between 3.9 and 32.8% of the larger dose and between 3.3 and 13.4% of the smaller dose. Serum creatinine concentrations were serially measured in 10 hospitalized horses intramuscularly given 1.7 to 4.4 mg of gentamicin/kg 4 times a day' significant increase in creatinine concentration was not found.