Search PubMed⌕ Search

Biomedical subjects

R J Ptachcinski

Publications and source records attributed to R J Ptachcinski.

At least 19 recordsLinked to original sources
PubMed1992

Stability and sorption of FK 506 in 5% dextrose injection and 0.9% sodium chloride injection in glass, polyvinyl chloride, and polyolefin containers.

The effects of the diluent, the storage container, light, and infusion through various types of tubing on the stability and sorption of FK 506 were studied. Solutions of FK 506 in 0.9% sodium chloride injection or 5% dextrose injection were stored at room temperature (24 +/- 2 degrees C) in glass i.v. bottles, polyvinyl chloride (PVC) minibags, and polyolefin containers. FK 506 solution in 0.9% sodium chloride injection was stored in plastic syringes at room temperature and either exposed to normal room light or stored in the dark. FK 506 solution in 5% dextrose injection was placed in plastic syringes and infused through PVC anesthesia extension tubing, PVC i.v. administration set tubing, and fat emulsion tubing over a two-hour period. The infused samples and samples collected from the containers and syringes at intervals up to 48 hours were analyzed for FK 506 concentration by high-performance liquid chromatography. FK 506 concentrations remained greater than 90% of initial concentration for admixtures in 5% dextrose injection stored in glass bottles for 48 hours and for admixtures in 5% dextrose injection or 0.9% sodium chloride injection stored in polyolefin containers for 48 hours. No change in concentration was measured for admixtures in 0.9% sodium chloride injection stored in plastic syringes, and exposure to light did not affect the stability of FK 506 solution. No substantial change in concentration occurred in FK 506 solution in 5% dextrose injection infused through PVC anesthesia extension tubing, PVC i.v. administration set tubing, or fat emulsion tubing. FK 506 admixtures prepared with 5% dextrose injection or 0.9% sodium chloride injection should be stored in polyolefin containers. If polyolefin containers are not available, solutions should be prepared with 5% dextrose injection and stored in glass bottles.

Adsorption↗
PubMed1991

In-vitro interaction of a novel immunosuppressant, FK 506, and antacids.

The effect of selected antacids on the amount of FK 506 in solution in simulated gastric juice has been studied. FK 506 (2.5 mg) was incubated in 100 mL simulated gastric fluid (SGF) with the equivalent of 500 mg of various antacids. The addition of Mylanta and Tums resulted in 14 and 30% loss of FK 506, respectively, in 24 h; 98% loss was observed in 12 h in the presence of Mag-Ox; 100% loss was observed in the presence of magnesium oxide powder in 2 h. The loss of FK 506 from these solutions appears to be due to a pH mediated degradation of FK 506. The addition of aluminium hydroxide gel USP (Roxane) to the FK 506 solution resulted in a 35% loss within 2 min but no further loss was noted for 24 h, indicative of adsorption of FK 506. These results suggest that until additional in-vivo studies are carried out, it is prudent not to dose FK 506 and antacids at the same time to avoid potential interactions.

Antacids↗
PubMed1989

Clinical pharmacokinetics in organ transplant patients.

Diseases of the liver, kidney and heart influence the pharmacokinetics of several drugs. Organ transplantation is an accepted therapeutic option for the treatment of several disease states associated with these organs. Recently, there has been an increase in both graft and patient survival after transplantation of the liver, heart, kidney and bone marrow. Such patients normally receive a wide range of drugs, and optimisation of drug therapy requires a thorough understanding of the pharmacokinetics and pharmacodynamics of these drugs in transplant patients. However, only limited studies have been carried out to characterise drug kinetics in these situations. Available information indicates that drug kinetics cannot be considered normal in transplant patients. Drug absorption generally appears to be similar to that in healthy subjects. The plasma protein binding of drugs that primarily bind to albumin increases after transplantation, but remains lower than that observed in healthy subjects. While the binding of certain basic drugs may increase after transplantation due to an increase in the concentration of alpha 1-acid glycoprotein, a lower albumin concentration may mask this effect. Oxidative and conjugative metabolism as measured by the kinetics of antipyrine (phenazone) and paracetamol (acetaminophen) is normal, while the metabolism of steroids may be impaired. Serum creatinine does not appear to be a good indicator of the functional status of the kidney in transplant patients. It is also important to realise that there will be time-dependent changes in several kinetic parameters of drugs due to improvement in the physiological function from that associated with the disease state to that of the normal state. Individualisation and close monitoring of drug therapy is necessary in transplant patients.

Azathioprine↗
PubMed1989

Pharmacokinetics of the cyclosporine-ketoconazole interaction in dogs.

Numerous clinical reports have documented an increase in trough blood concentrations of cyclosporine in transplant recipients treated concomitantly with ketoconazole. The objective of this study was to elucidate the mechanism(s) underlying the cyclosporine-ketoconazole interaction using a choledochoureterostomy dog model. Five male beagle dogs received a 4 mg/kg, i.v. bolus dose of cyclosporine either alone or on day seven of a 10-day, 13 mg/kg/day, oral dosing regimen of ketoconazole. Blood samples were collected prior to and at predetermined times for 60 hrs after the cyclosporine dose, while the bile/urine mixture was collected quantitatively for 96 hours after the cyclosporine dose. Ketoconazole decreased the systemic clearance of cyclosporine from 7.0 ml/min/kg to 2.5 ml/min/kg. The terminal disposition rate constant was also decreased significantly from 0.0794 to 0.0354 hrs-1. Ketoconazole caused no significant changes in cyclosporine steady state volume of distribution, or plasma unbound fraction. Ketoconazole did not significantly alter the excretion of cyclosporine and various cyclosporine metabolites in the bile/urine mixture. Inhibition of hepatic drug metabolizing enzymes appears to be the primary reason for the ketoconazole induced elevation in cyclosporine concentration.

Animals↗
PubMed1988

Effect of bile on cyclosporin absorption in liver transplant patients.

1. We quantitated the effect of biliary diversion on cyclosporin (CyA) absorption in liver transplant patients. Multiple blood samples were obtained over one dosing interval following oral CyA administration in eight liver transplant patients before and after T-tube clamping. 2. Cyclosporin concentrations were measured by a high pressure liquid chromatographic method. 3. The mean (+/- s.d.) dose-normalized area under the blood concentration vs time curve (AUC) over a dosing interval was 5.23 (+/- 3.22) ng ml-1 h during the pre clamping period and 15.79 +/- 7.92 ng ml-1 h during the post clamping period. A significant (P less than 0.05) increase (276%) in the dose normalized AUC was observed following the T-tube clamping. 4. Analysis of bile revealed less than 1 mg (less than 1% of dose) of unchanged CyA to be eliminated in bile over 12 h. Therefore the increased CyA AUC/dose following T-tube ligation cannot be explained by enterohepatic recirculation. 5. Increased bile flow secondary to clamping of the T-tube most likely increased the absorption of CyA. Increase in CyA absorption may be due to a bile mediated increase in CyA solubility or gastrointestinal membrane permeability, or increased residence time at the site of absorption. 6. Independent of the mechanism involved, our results indicate that adjustments in CyA dosage must be made whenever external bile diversion is instituted or discontinued.

Adult↗
PubMed1987

Blood protein binding of cyclosporine in transplant patients.

The objective of this study was to compare the binding of cyclosporine to blood proteins between four healthy subjects and five liver and eight renal transplant patients. Fresh heparinized blood was obtained, to which sufficient quantities of tritium-labelled cyclosporine and unlabelled cyclosporine were added to blood samples or red blood cell (RBC) suspensions. Concentrations of cyclosporine in whole blood, plasma, RBC suspension, and phosphate buffer were estimated by liquid scintigraphy. The blood:plasma ratio of cyclosporine in transplant patients was significantly lower (P less than .05) than that in healthy volunteers. The RBC:buffer ratio, a measure of affinity of RBCs for cyclosporine, was highest in those with liver transplants and lowest in those with kidney transplants. The unbound fraction of cyclosporine in plasma was less in transplant patients than in healthy volunteers. The results of this study indicate that there are differences in blood protein binding of cyclosporine between transplant patients that may contribute to the differences in the pharmacokinetics and pharmacodynamics of this drug.

Blood Proteins↗
PubMed1987

Cyclosporine kinetics in healthy volunteers.

The pharmacokinetics of cyclosporine was studied in five healthy male volunteers following intravenous administration. The subjects received 2.1 mg/kg of cyclosporine as a two-hour intravenous infusion. Blood samples were collected over the subsequent 48 hours. Cyclosporine was extracted from whole blood and analyzed by high-performance liquid chromatography (HPLC) and radioimmunoassay (RIA). Following the intravenous infusion of cyclosporine, the drug exhibited multicompartmental behavior. The harmonic mean distribution half-life based on HPLC data was 0.45 hours, and the harmonic mean terminal disposition half-life was 6.2 hours. The clearance of cyclosporine based on HPLC cyclosporine concentrations was 3.9 mL/min/kg, and the volume of distribution at steady state of cyclosporine was 1.23 L/kg. Cyclosporine has a shorter half-life, lower clearance, and smaller Vss in healthy persons as compared to patient populations. The differences observed in the pharmacokinetics of cyclosporine in healthy persons as compared to patient populations may be due to differences in hematocrit, lipoprotein profiles, and/or concurrent drug therapy between the groups. Cyclosporine concentrations determined by RIA were consistently higher than those determined by HPLC, resulting in a significantly higher area under the blood concentration versus time curve and lower clearance rate for cyclosporine. We conclude that: (1) kinetic parameter estimates for cyclosporine are different in healthy individuals as compared with organ-transplant recipients, and (2) the kinetic parameters for cyclosporine are different, depending on the assay technique used.

Adult↗
PubMed1987

Impaired clearance of ceftizoxime and cefotaxime after orthotopic liver transplantation.

The pharmacokinetics of ceftizoxime (CZX) and of cefotaxime (CTX) were studied in five children and five adults after orthotopic liver transplantation (OLT). Delayed clearance of CZX (clearance of 0.21 to 1.26 ml/min per kg [body weight]) and CTX (clearance of 0.40 to 1.49 ml/min per kg) occurred in 7 of the 10 OLT patients. We conclude that abnormal CZX and CTX clearance is common after OLT and may be associated with minimal change in serum creatinine.

Adult↗