Comparison of fluorescence polarization immunoassay and bioassay of vancomycin

An Overview of Analytical Methodologies for Determination of Vancomycin in Human Plasma

Vancomycin is regarded as the last resort of defense for a wide range of infections due to drug resistance and toxicity. The detection of vancomycin in plasma has always aroused particular concern because the performance of the assay affects the clinical treatment outcome. This article reviews various methods for vancomycin detection in human plasma and analyzes the advantages and disadvantages of each technique. Immunoassay has been the first choice for vancomycin concentration monitoring due to its simplicity and practicality, occasionally interfered with by other substances. Chromatographic methods have mainly been used for scientific research due to operational complexity and the particular requirement of the instrument. However, the advantages of a small amount of sample needed, high sensitivity, and specificity makes chromatography irreplaceable. Other methods are less commonly used in clinical applications because of the operational feasibility, clinical application, contamination, etc. Simplicity, good performance, economy, and environmental friendliness have been points of laboratory methodological concern. Unfortunately, no one method has met all of the elements so far.

Use of vancomycin in high-flux hemodialysis: experience with 130 courses of therapy

Vancomycin is often administered to hemodialysis patients at long dosage intervals because its removal by hemodialysis is considered to be negligible. We and others, however, have demonstrated significant removal of vancomycin by high-flux hemodialysis. This report describes our experience with 89 courses of vancomycin using a revised regimen with a loading dose followed by 500 mg doses after each dialysis treatment, and compares results with 41 courses using single weekly dosing. All patients were dialyzed with high-flux membranes using volumetric ultrafiltration and bicarbonate dialysate. Serum vancomycin levels were obtained two hours after completion of infusion (peak) and immediately prior to dialysis (trough) and were measured by Abbot TDx fluorescence polarization immunoassay. Duration of multiple-dose therapy was 11 +/- 8 days, with mean total dose 3.6 +/- 1.8 g. Initial doses of 20 mg/kg rapidly and reliably established therapeutic pre-dialysis serum levels (10 to 25 micrograms/ml). In patients treated with multiple dosing 431 pre-dialysis levels were obtained. The mean level was 15.9 +/- 5.7 micrograms/ml; 55 levels (13%) were less than 10 micrograms/ml and 22 (5%) were above 25 micrograms/ml. In patients treated once weekly, 77% of levels were below 10 micrograms/ml by five days after administration, and 84% at one week. No patient developed demonstrable ototoxicity. Twenty-five patients were treated for > or = two weeks, five for > or = four weeks, and two for > five weeks, with no evidence of toxic accumulation. Mean peak level was 20.1 +/- 4.6 micrograms/ml, with a mean difference from preceding pre-dialysis level of 7.2 +/- 2.2 micrograms/ml. We conclude that in high-flux hemodialysis, a 20 mg/kg loading dose of vancomycin followed by 500 mg doses after each dialysis treatment achieves predictable, adequate and safe therapeutic levels, does not lead to unacceptably high peaks, and does not accumulate during long treatment courses. By contrast, once-weekly vancomycin dosing resulted in subtherapeutic serum levels after five to seven days, and should be abandoned in the high-flux setting.

Vancomycin kinetics in plasma and synovial fluid following intravenous administration in horses

Vancomycin hydrochloride was infused intravenously (i.v.) over a 30-min period in five horses at doses of 6.6, 11.0 and 15.4 mg/kg. Vancomycin concentration in plasma and synovial fluid samples was measured using a polarization immunoassay. A pharmacokinetic model was developed to accommodate the special features of the present study. The data were described by a two compartment open model with synovial fluid as an additional compartment in exchange with plasma. Minimum inhibitory concentration (MIC) and minimum bacterial concentration (MBC) were measured for Staphylococcus aureus and Enterococcus sp. using isolates from hospital patients. Based on the pharmacokinetic model and MIC/MBC data, a practical therapeutic protocol for vancomycin administration was established at doses of 4.3-7.5 mg/kg given as a 1-h infusion every 8 h.

Clinical pharmacokinetics of vancomycin

Vancomycin utilisation has increased dramatically in the last 10 years due to the increasing clinical significance of infections with methicillin-resistant staphylococci. Recent studies have focused on characterising the disposition of vancomycin in patients and assessing the relationship between serum concentrations and therapeutic as well as adverse effects. Although vancomycin is not appreciably absorbed from the intact gastrointestinal tract, several recent case reports have documented the attainment of therapeutic and potentially toxic vancomycin serum concentrations following oral administration to patients with pseudomembranous colitis. The disposition of parenterally administered vancomycin has been best characterised by a triexponential model. The half-life of the initial phase (t1/2 pi) is approximately 7 minutes, that of the second phase (t1/2 alpha) is approximately 0.5 to 1 hour, while the terminal elimination half-life (t1/2 beta) ranges from 3 to 9 hours in subjects with normal renal function. The volume of the central compartment (Vc) in adults is approximately 0.15 L/kg while the steady-state volume of distribution (Vdss) ranges from 0.39 to 0.97 L/kg. More than 80% of a vancomycin dose is excreted unchanged in the urine within 24 hours after administration, and the concentration of vancomycin in liver tissue and bile has been reported to be at or below detection limits. Vancomycin renal clearance approximates 0.5 to 0.8 of simultaneously determined creatinine or 125I-iothalamate clearances, suggesting that the primary route of renal excretion is glomerular filtration. Recently, non-renal factors such as hepatic conjugation have been proposed as an important route of vancomycin elimination. However, these data are difficult to reconcile with other studies showing minimal non-renal clearance of vancomycin in subjects with end-stage renal disease. As yet, the disposition of vancomycin in patients with hepatic disease has not been adequately defined. Only limited data are available regarding the concentrations of vancomycin in biological fluids other than plasma. The penetration of vancomycin into cerebrospinal fluid (CSF) in patients with and without meningitis has been quite variable. Although early studies suggested that adequate CSF concentrations may not be achieved in subjects with uninflamed meninges, more recent investigations have reported contradictory results. Therapeutic concentrations of vancomycin, i.e. greater than 2.5 mg/L, have, however, been reported in ascitic, pericardial, pleural and synovial fluids. Tissue concentrations of vancomycin have exceeded simultaneous serum concentrations in heart, kidney, liver and lung sp

Vancomycin: an update

Vancomycin is a narrow-spectrum glycopeptide antibiotic with potent antistaphylococcal activity. It is primarily active against gram-positive organisms. Bacterial resistance rarely develops due to its numerous modes of action. The toxic potential of vancomycin is less significant than previously thought. "Red neck syndrome" seems to be the most common side effect and appears to be caused by rapid intravenous infusion. It is characterized by erythema at the base of the neck and the upper back; hypotensive episodes may also occur. Nephrotoxicity and ototoxicity are rare. Relationships between toxicities and serum concentrations have not been established. The disposition of vancomycin after intravenous administration proceeds biphasically--rapid distribution followed by elimination. The drug is excreted primarily unchanged in the urine by glomerular filtration. Vancomycin clearance is reduced and elimination half-life is prolonged in patients with renal insufficiency. Various methods have been published to aid in dosing the drug in these patients. Vancomycin is the drug of choice in the treatment of methicillin-resistant staphylococcal infections. It is also useful in the treatment of gram-positive endocarditis and has been used as alternative therapy in the treatment of prophylaxis of gram-positive infections in penicillin-allergic patients. Oral vancomycin is the preferred therapy in antibiotic-associated colitis.