Standardization of a Preparative Ultracentrifuge Method for Quantitative Determination of Protein Binding of Seven Antibiotics

The ability of cefazolin to cross the capillary membranes and its concentrations in the interstitial fluid spaces were studied in normal and osteomyelitic canine bone. The maximum extraction after a single capillary passage and the net extraction after 3 min, determined with triple-tracer indicator-dilution techniques, demonstrated that cefazolin readily traversed the capillaries of normal and osteomyelitic bone. These studies suggest that the altered pathophysiology of osteomyelitic tissue and the complex diffusional characteristics of cefazolin enhanced the ability of this agent to cross the endothelial cells lining the capillaries of osteomyelitic bone. Volume of distribution studies demonstrated that cefazolin was distributed in the plasma and interstitial fluid spaces of normal cortical bone.Although these spaces were increased 330 and 941% in osteomyelitic tissue, the distribution of cefazolin increased proportionally. There was a direct correlation between the calculated concentrations of cefazolin in the interstitial fluid spaces of normal and osteomyelitic cortical bone and the simultaneous serum levels in animals in which a steady-state equilibrium had been achieved. These studies suggest that a physiological barrier or concentration gradient for cefazolin does not exist in normal or osteomyelitic bone. Cefazolin can cross the capillary membranes of bone and achieve bactericidal concentrations in the interstitial fluid space of normal and osteomyelitic tissue.

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Penetration of cefazolin into normal and osteomyelitic canine cortical bone

Daly¹,

Fitzgerald²,

Washington³

1982

“…Serum protein binding of ampicillin, oxacillin, and amikacin was determined by ultracentrifugation with rabbit serum as previously described (13). Gentamicin binding to rabbit serum protein as determined by ultracentrifugation has been previously reported (7).…”

Section: Methodsmentioning

confidence: 99%

Effect of method of administration on extravascular penetration of four antibiotics

Etta¹,

Kravitz²,

Russ³

et al. 1982

The effect of both method of drug administration and serum protein binding on antibiotic penetration into subcutaneous Visking chambers was studied in rabbits. Ampicillin and oxacillin were administered by either repeated intramuscular injection of 30 mg/kg every 4 h or by constant infusion of 7.5 mg/kg per h for 24 h. Gentamicin was given by intramuscular injection of 4 mg/kg every 4 h for 28 h and by constant infusion of 1 mg/kg per h for 24 h. Amikacin was given by intramuscular injection of 8 mg/kg every 4 h for 12 h and by constant intravenous infusion of 2 mg/kg per h for 12 h. Protein binding to rabbit serum was 73% for oxacillin, 9% for ampicillin, 19% for gentamicin, and 0% for amikacin. Chamber concentrations achieved for oxacillin, gentamicin, and amikacin were not significantly different for constant infusion versus intermittent administration. For ampicillin, chamber concentration was slightly higher by constant infusion than by intermittent administration (P less than 0.02). Fluctuations in drug concentration from peak to trough values in the chambers during the intermittent administration studies were markedly dampened when compared with serum fluctuations. This study demonstrates that whereas steady state is reached more rapidly by intermittent administration, the mean steady-state concentration of an antibiotic achieved at an extravascular site is the same or greater by constant infusion than by intermittent dosing. This is true for highly protein bound antibiotics as well as those with low serum protein binding.

“…To determine the free concentration, the samples were ultrafiltered using an Amicon Centrifree YM-30 cartridge (Millipore, Burlington, Mass.) with centrifugation at 1,500 ϫ g for 30 min (18,20). The ultrafiltrate was then mixed 1:1 with stabilizer and frozen at Ϫ80°C.…”

Section: Chemicals and Reagents Mes (2-[n-morpholino]ethanesulfonic mentioning

confidence: 99%

Effect of Ertapenem Protein Binding on Killing of Bacteria

Nix

Matthias

Ferguson

2004

The effect of protein binding on the antimicrobial activity of ertapenem was evaluated using the bacterial kill rate and concentration-response studies. Various proportions of human serum were utilized to determine the total and free-drug concentrations using a validated high-performance liquid chromatography assay. The MICs and kill curves were determined for test isolates of Enterobacter cloacae and Staphylococcus aureus at various percentages of human serum. The killing of bacteria was analyzed in relation to the free and total concentrations of ertapenem at various proportions of human serum. It was determined that unbound ertapenem was responsible for the antimicrobial activity against the test isolates.