A diffusion chamber technique for measuring concentrations of antibiotics in interstitial fluid

A diffusion chamber technique for testing of antifungal drugs against Sporothrix schenckii in vivo

Growth of the yeast form of Sporothrix schenckii (ATCC 14804) was determined in diffusion chambers with 0.45 and 3.0 micron pore size over a period of 24 to 192 h after subcutaneous implantation into mice. Numbers of S. schenckii in 0.45 micron chambers increased significantly by 192 h when inocula of 10(3) and 10(5) colony forming units were implanted. In chambers with a pore size of 3.0 microns, only a slight decrease of fungal growth occurred, although host cells readily passed the filter membrane and phagocytosed yeast-form cells. The activities of amphotericin B, ketoconazole, itraconazole, ICI 153.066, vibunazole and potassium iodide against S. schenckii in implanted chambers were determined in terms of their effects on S. schenckii. ICI 153.066, ketoconazole, itraconazole and amphotericin B significantly reduced the numbers of reisolated S. schenckii in both types of chambers. There was a slight activity with vibunazole but none with potassium iodide.

Pharmacokinetics of cephalosporins in normal and septicemic rabbits

The differences in the pharmacokinetics of cefotaxime, moxalactam, and CPW 86-363, a new expanded-spectrum cephalosporin, were studied in healthy rabbits and in rabbits infected intravenously with Streptococcus pneumoniae. The pharmacokinetic analysis of concentration-time courses in the sera of infected animals according to a two compartment-model evidenced a clear decrease of drug fractions in the central compartment but enhanced drug fractions in the peripheral compartment. The shift was more pronounced in animals which received CPW 86-363 (60%; P less than 0.05) than in those which received cefotaxime (20%) or moxalactam (5%). Corresponding increases in drug concentration were observed in soft tissue interstitial fluid; therefore, the areas under the curve and mean residence times in the soft tissue interstitial fluid of infected rabbits were prolonged. The shift of drug fractions from the central compartment to other body fluid compartments during infection was thought to be due to cardiovascular changes associated with fever. No changes in serum binding of the three drugs were found during the course of the infection. The quantitative differences in the extent of altered distribution properties of the drugs might be due to variations in the physicochemical properties of the drugs.

Distribution of ceftazidime in ascitic fluid

The pharmacokinetics of ceftazidime were investigated in eight normal subjects and eight patients with ascites after intravenous administration of 1 g of the drug. Samples of blood and ascitic fluid were collected for 6 h after dosage, and urine samples were collected for 24 h. Pharmacokinetic data were calculated by using a one-compartment model. The apparent volume of distribution and half-life of elimination (t1/2 beta) in patients with ascites were approximately three times those in normal subjects. In contrast, renal clearance was greater in the normal subjects. With respect to ascites, the mean area under the concentration-time curve was 95.3 +/- 38.3 micrograms X h/ml. The mean ratio of the area under the concentration-time curve for ascitic fluid to that for plasma was 69.9% (+/- 38.2). These data show that ceftazidime rapidly diffuses into the peritoneal space, in which concentrations greater than 10 micrograms/ml were present for at least 6 h.

Absorption of doxorubicin-hydrochloride and mitomycin-C after instillation into noninfected and infected bladders of dogs

The described investigations were carried out in order to determine the degree of absorption of doxorubicin, and mitomycin-C after intravesical instillation into noninfected or Staphylococcus aureus-infected bladders in beagle dogs. The drug concentrations in the bladder wall were determined using diffusion chambers with permeable membranes. Two hours after end of instillation of 10 mg. doxorubicin, a concentration of 1.4 ng. per ml. was measured in the bladder wall of noninfected animals, and 3.75 ng. per ml. in that of infected animals (p less than 0.05). The simultaneously measured serum concentration reached mean peak levels after 30 minutes. The concentrations in infected animals were 3 times higher (1.9 ng. per ml.) than in noninfected animals (0.6 ng. per ml.) (p less than 0.05). After instillation of 1 mg. per kg. bw. mitomycin-C the concentration in both groups of animals was below 0.06 micrograms per ml. Doxorubicin concentrations were determined with a radioimmunoassay and mitomycin-C with a micro-agar diffusion method.

Concentrations of doxorubicin in renal interstitial fluid after peripheral intravenous and intrarenal artery infusion in dogs

Concentrations of doxorubicin-hydrochloride in renal interstitial fluid were compared following peripheral and intrarenal artery infusion of 2 milligrams per kilogram body weight using a diffusion chamber model. After intra-arterial application, the mean peak concentration in renal interstitial fluid was approximately 30 times higher than that after intravenous infusion (66.49 and 2.38 nanograms per milliliter respectively). After peripheral application, the concentrations in serum and renal interstitial fluid, as well as the cumulative urinary excretion, were measured until day 7 of the experiment, and the pharmacokinetic parameters were calculated. The diffusion chamber model used proved itself to be suitable for simultaneous and continuous measurement of cytostatic drug concentrations in serum and renal interstitial fluid.

Evaluation of cytostatic drug concentrations in the kidney, bladder wall, and prostate by means of the diffusion chamber technique in dogs

The usefulness of a diffusion chamber model for measurement of concentrations of cytostatics in the interstitial fluid of tissues was tested. Chambers (pore size of the membranes: 0.45 mcm) were implanted in the kidney, bladder wall, and prostate of dogs. The concentrations after application of Doxorubicin-hydrochloride (2 mg/kg body wt.) and high doses of Methotrexate (100 mg/kg body wt.) were measured simultaneously and continuously in serum and in the above organs. The investigations showed that knowledge of the plasma level alone does not permit a prediction of the concentrations in the organs to be made. The diffusion chamber technique proved itself to be relatively simple to perform, economical, and it provides reproducible values.

Comparison of skin blisters and implanted cotton threads for the evaluation of antibiotic tissue concentrations

The skin blister technique and a new technique using subcutaneously implanted cotton threads for the evaluation of antibiotic tissue concentrations were compared. Six volunteers received 2 g ampicillin and, after at least one week, 1 g of cloxacillin intravenously. Samples of serum, blister fluid and thread fluid were analysed by an agar well diffusion technique. The half-life of ampicillin and cloxacillin was prolonged in blister fluid compared to serum and thread fluid. Our conclusions are that the thread technique might reflect the kinetics of antibiotics in extracellular fluid where the penetration mostly depends on serum protein binding of the drug. The blister technique on the other hand might resemble the conditions in different subcutaneously implanted cages, fibrin clots and even abscesses where factors such as time and volume of the extracellular compartments also strongly influence the distribution of antibiotics.

Influence of serum protein binding and mode of administration on penetration of five cephalosporins into subcutaneous tissue fluid in humans

The penetration of five cephalosporins into interstitial fluid was investigated by a new method employing cotton threads implanted subcutaneously. Penetration after short bolus injections, calculated as area under interstitial fluid level curve divided by area under serum level curve x 100, was 47.0% for cephradine, 30.6% for cefuroxime, 26.7% for cefotaxime, 24.6% for cefoxitin, and 9.6% for cefoperazone. There was an inverse correlation between the degree of penetration and serum protein binding with r = -0.97. The area under interstitial fluid level curves was the same whether the drugs were administered as short bolus injections or short time infusions.

Tissue distribution of ampicillin: assays in muscle tissue and subcutaneous tissue cage fluid from normal and nephrectomized rabbits

Tissue distribution of ampicillin following a single intravenous injection was studied in normal and functionally nephrectomized rabbits. Serum concentrations of ampicillin were compared with those obtained in subcutaneous tissue cage fluid, muscle (measured by a direct agar diffusion method) and muscle tissue fluid (obtained from implanted cotton threads). Considerable differences were found. Penetration of ampicillin into rabbit muscle was rapid and the elimination half-life was similar to that of serum. Concentrations in tissue cage fluid were low as compared with muscle tissue fluid levels, and penetration and elimination was slower. Results from experiments in functionally nephrectomized rabbits showed that a steady state between serum and muscle seemed to be attained after 15-30 min. These results were used to estimate the degree of protein binding of ampicillin in muscle tissue fluid.

Composition of fluids from diffusion chambers implanted in the soft tissue and kidneys of rabbits

The fluids from diffusion chambers implanted in soft tissue and kidneys of rabbits were analysed for total protein, albumin, enzymes, ions, glucose, creatinine, urea, uric acid, bilirubin and cholesterol. These date were compared with the corresponding values in plasma. Our data for chamber fluid are in good agreement with data reported for interstitial fluids. The composition of the kidney chamber fluid is nearly constant from three to ten weeks after implantation. The low urea, uric acid and creatinine concentrations indicate that the chamber is not located in the urine collecting area of the kidney. Three days after subcutaneous implantation of chambers, the fluid contains less protein than plasma but has an equal concentration of ions, thus meeting the principal requirements for interstitial fluid. There are indications that the healing process lasts up to ten days after the surgical implantation. In order to examine the permeability of the diffusion chambers, the equilibration half-life times of antibiotics and substances of high and low molecular weights were determined in vitro.