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T Tarnowski

Publications and source records attributed to T Tarnowski.

12 recordsLinked to original sources
PubMed1999

An HPLC method for the determination of diastereomeric prodrug RS-79070-004 in human plasma.

Ganciclovir is an antiviral nucleoside analogue approved for treatment and prevention of cytomegalovirus infections in immunocompromised subjects. RS-79070-194, a diastereomeric monovalyl ester of ganciclovir (hydrochloride salt), is under evaluation as a prodrug to increase the bioavailability of ganciclovir. An HPLC method with column switching has been developed and validated for quantification of the corresponding free base RS-79070-004 in human plasma. In the method, proteinaceous material in 0.25 ml of plasma is precipitated by trichloroacetic acid. An aliquot of the supernatant is analyzed by HPLC, with automated column switching to remove late-eluting materials that might interfere with the analyte peaks in subsequent runs. Detection of RS-79070-004 is by UV lambda = 254 nm). The peak areas for each isomer are summed to generate a value for total RS-79070-004. The method has a validated range of 0.0400-4.00 microg/ml and a lower limit of quantification of 0.0400 microg/ml. All intra- and inter-assay %CVs were < 7.5%, and all recoveries (accuracy) were within 6% of nominal values. No interference was observed by ganciclovir, caffeine, acetaminophen, or ibuprofen. Analyte stability in plasma and in the sample extracts is adequate for the specified collection, storage, and analysis conditions. The validated method has been successfully used to analyze clinical study samples.

Antiviral Agents↗
PubMed1999

A rapid, sensitive HPLC method for the determination of ganciclovir in human plasma and serum.

A method for ganciclovir determination in human serum and plasma has been developed and validated. The method has a lower limit of quantification (LLOQ) adequate for sensitive pharmacokinetic studies ( < or = 0.05 microg/ml), has run times of < or = 15 min, and uses aliquot volumes adequate for pediatric studies (0.25 ml). In the method, proteinaceous material in serum or plasma is precipitated by trichloroacetic acid. An aliquot of the supernatant is analyzed by HPLC; automated column switching removes late-eluting materials that might interfere with the analyte peak in subsequent runs. Detection and quantification of ganciclovir is by fluorescence (lambda(ex) = 278 nm; lambda(em) = 380 nm). The method has a validated range of 0.0400-4.00 microg/ml and an LLOQ of 0.0400 microg/ml. All intra- and inter-assay % C.V. values were < 8%; all recoveries (accuracy) were within 7% of nominal values. No interference was observed by mycophenolic acid or its glucuronide metabolite, by AZT, salicylic acid, acetaminophen, ibuprofen, naproxen prednisone, acyclovir, or cyclosporine. Ganciclovir is very stable in the samples and the extract during storage and sample processing. Both serum and plasma methods have been validated for use and have been successfully used to analyze samples from clinical studies.

Antiviral Agents↗
PubMed1998

The pharmacokinetics of a single oral dose of mycophenolate mofetil in patients with varying degrees of renal function.

BACKGROUND: The purpose of this study was to determine the effect of renal function on the elimination and disposition of mycophenolic acid and its glucuronide metabolite (MPAG) after oral administration of the pro-drug mycophenolate mofetil. In addition, this study sought to examine hemodialysis removal of mycophenolic acid and its MPAG. METHODS: Subjects were stratified into five groups on the basis of iohexol clearance. After an overnight fast, all subjects received a single 1 gm dose of mycophenolate mofetil. Plasma concentrations of mycophenolic acid and MPAG were measured from 0 to 96 hours after administration. Mycophenolic acid and MPAG maximum plasma concentration (Cmax) and the time to reach Cmax (tmax) for each group were determined from the mean plasma concentration-time profiles. Area under the plasma concentration-time curve values for mycophenolic acid and MPAG were calculated by the trapezoidal rule. The half-lives of mycophenolic acid and MPAG were calculated from the terminal portions of the concentration-time profiles. RESULTS: Mycophenolic acid clearance was not associated with changes in glomerular filtration rate (GFR). Cmax tended to increase as GFR declined. MPAG clearance correlated well with GFR (r2 = 0.905). Clearance of mycophenolic acid and MPAG were unaffected by hemodialysis. CONCLUSIONS: Clearance of mycophenolic acid after a single 1 gm oral dose of mycophenolate mofetil is unaffected by renal function. Clearance of mycophenolic acid is unaffected by hemodialysis. Diminished renal function should not require preemptive adjustment of 1 gm doses of mycophenolate mofetil; however dosage adjustment may be warranted on the basis of adverse effects or toxicity in individual patients. Mycophenolate mofetil can be administered irrespective of hemodialysis session without effect on mycophenolic acid exposure.

Administration, Oral↗
PubMed1996

High-performance liquid chromatographic method for the determination of mycophenolate mofetil in human plasma.

A method for the quantification of mycophenolate mofetil (MMF, CellCept) in plasma using solid-phase extraction and HPLC is described here. A solution of internal standard is added to a 0.5-ml plasma aliquot. The resulting sample is treated with water and dilute HCl and applied to a C18 solid-phase extraction column. After a water wash, the MMF and internal standard are eluted with methanol-0.1 M citrate-phosphate buffer, pH 2.6 (80:20, v/v). A 20-microliters aliquot of the eluate is injected onto a C18 column (5 microns particle size, 150 x 4.6 mm I.D.) and eluted at ambient temperature with acetonitrile-0.05 M citrate-phosphate buffer, pH 3.6, containing 0.02 M heptanesulfonic acid (41:59, v/v). Quantification is achieved by UV detection at 254 nm. The method is reproducible, accurate and specific for MMF. Using 0.5 ml of plasma for analysis, the quantification limit is 0.400 microgram/ml and the range is 0.400-20 micrograms/ml. Based on the stability profile of MMF in plasma, it is recommended that blood samples collected following intravenous infusion be immediately stored on ice and that plasma be prepared rapidly, immediately stored frozen at -80 degrees C and analyzed within four months of collection.

Chromatography, High Pressure Liquid↗
PubMed1996

Simple reversed-phase high-performance liquid chromatography quantitation of ganciclovir in human serum and urine.

A fast, simple, and cost-effective HPLC method for the quantitation of the antiviral drug ganciclovir is described. The serum samples are extracted with perchloric acid and neutralized with potassium phosphate buffer, and urine samples are diluted with distilled water. A reversed-phase column with isocratic elution by 15 mM potassium phosphate buffer (pH 2.5) containing 0.25% acetonitrile is used to separate ganciclovir; quantitation is by UV absorbance at 254 nm. Total turnaround time is 22 min; more than 3000 samples can be run on a single column without loss of peak quality. The limit of quantitation is 0.05 micrograms/ml. Recoveries varied from 91 to 107% with coefficients of variation ranging from 0.387 to 7.95%.

Antiviral Agents↗
PubMed1996

Manual and automated (robotic) high-performance liquid chromatography methods for the determination of mycophenolic acid and its glucuronide conjugate in human plasma.

A manual and an automated (Zymark PyTechnology robot) HPLC method for simultaneous determination of plasma mycophenolic acid (MPA) and its glucuronide conjugate (MPAG) are described here. Both methods are reproducible and accurate, and both are equivalent in all respects, including quantification limits (MPA, 0.100 microgram/ml; MPAG, 4.00 micrograms/ml), range (using 0.05-0.5 ml of plasma: MPA, 0.0500-20.0 micrograms/aliquot; MPAG, 2.00-200 micrograms/aliquot), precision, and accuracy. MPA and MPAG were stable under the conditions used with both methods. Results from aliquots of paired control samples, analyzed by the manual method over three years at six analytical laboratories, showed excellent agreement in precision and accuracy.

Chromatography, High Pressure Liquid↗
PubMed1996

Chiral kinetics and dynamics of ketorolac.

It has been shown that the analgesic and cyclooxygenase inhibitor activity of ketorolac tromethamine (KT), which is marketed as the racemic mixture of (-)S and (+)R enantiomers, resides primarily with (-)S ketorolac and that the ulcerogenic activity of this agent also resides in (-)S ketorolac. Resolution of individual enantiomers for analysis in plasma samples has been accomplished by two methods: derivatization to form diastereomers that are separated by HPLC, or direct HPLC using a chiral phase column. When mice and rats were given oral solutions of (-)S and (+) KT, it was found that the kinetics and interconversion of the enantiomers were species and dose dependent. Interconversion was higher in mice than in rats; when (-)S KT was administered, 71% of the area under the concentration-time curve (AUC) was due to (+)R ketorolac in mice, compared with 12% in rats. More interconversion was observed at higher doses; the percent of AUC due to (-)S ketorolac when (+)R KT was administered increased from 12% to 25% in mice and from 2% to 8% in rats. In general, more interconversion occurred from (-)S to (+)R ketorolac in the animal studies. Human subjects were given single oral solution doses of racemic KT (30 mg), (-)S KT (15 mg), and (+)R KT (15 mg). The plasma concentrations of (-)S ketorolac were lower than (+)R ketorolac at all sample times after racemic KT (22% of the AUC was due to (-)S ketorolac). When (+)R KT was administered, (-)S ketorolac was not detectable and interconversion was essentially 0%. When (-)S KT was administered, significant levels of (+)R ketorolac were detectable and interconversion was 6.5%. After all doses, plasma half-life was shorter and clearance greater for (-)S ketorolac than for (+)R ketorolac. Thus, in humans very little or no interconversion of (+)R to (-)S was observed, and interconversion of (-)S to (+)R was minimal (6.5%). These data demonstrate that the kinetics and interconversion of the enantiomers of ketorolac is different in animals and humans as well as from most other NSAIDs. This may be due to more rapid excretion or metabolism of (-)S ketorolac and a different mechanism of interconversion.

Animals↗
PubMed1996

An indirect (derivatization) and a direct HPLC method for the determination of the enantiomers of ketorolac in plasma.

An indirect and a direct HPLC method for the quantification of the (R) and (S) enantiomers of ketorolac are described here. The indirect method employs the chiral amine (+)-R-1-(1-naphthyl)ethylamine to form disastereomeric amides; separation of the disastereomeric derivates is achieved by normal-phase HPLC with a mobile phase of ethyl acetate-hexane. The direct method uses a C18 solid-phase extraction column to extract ketorolac enantiomers from plasma; the reconstituted extract is then injected onto an alpha 1-acid glycoprotein chiral column using a mobile phase of isopropanol-phosphate buffer (0.05 M; pH 5.5). Both methods are reproducible, accurate, and stereospecific, and both have equivalent quantification limits (0.02 microgram ml-1 of plasma for each enantiomer), ranges (0.02-2.0 micrograms per aliquot of plasma), precision (% relative standard deviations of < or = 10.5% and < or = 10.8% for (R)- and (S)-ketorolac respectively), and accuracy (mean recoveries of 88.4-110% and 90.1-110% for (R)- and (S)-ketorolac respectively). Results of analyses of clinical samples by the two methods showed excellent agreement (slope near 1.0 and coefficients of correlation between 0.9740 and 0.9864 for both enantiomers).

Analgesics, Non-Narcotic↗
PubMed1993

Radioimmunoassay of ganirelix in plasma or serum.

A procedure for the radioimmunoassay (RIA) of ganirelix in plasma or serum at concentrations as low as 0.050 ng/ml is described. Antiserum was produced by coupling the N-terminus glycyl analog of ganirelix to BSA by a carbodiimide reaction and immunizing rabbits with this conjugate. The antiserum did not crossreact with LHRH or with various ganirelix peptide fragments. For RIA, 125I labeled ganirelix was used as the tracer and a double antibody procedure was used to separate the free and bound fractions. No purification of the analyte was required prior to RIA. Accuracy of the method was assessed by adding known quantities of ganirelix to ganirelix-free plasma and determining the ratio of measured to added analyte. Linear regression analysis for the concentration range 0.050-50.0 ng/ml yielded a regression equation of y = 0.97x + 0.18, r = 0.999, where x is the amount added and y is the amount measured. Additional validation was obtained from an in vivo study in which [3H]-ganirelix was administered to monkeys and plasma clearance profiles were determined by RIA and an HPLC-radiochemical method. The results were in agreement within experimental error of the two methods. Linear regression analysis of the comparative data gave the equation y = 0.92x + 33.7, r = 0.980, where x is the amount measured by RIA and y is the amount measured by HPLC-radiochemical analysis.

Amino Acid Sequence↗
PubMed1987

Use of liposome encapsulation in a combined single-liquid reagent for homogeneous enzyme immunoassay.

A technique has been developed to permit mutually reactive macromolecular reagents used in immunoassays to be combined without premature reaction. A conjugate of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and theophylline has been encapsulated in 0.2-micron-diameter bi-lamellar liposomes. Suspensions of these liposomes had excellent stability. Whereas the enzyme activity of the free conjugate is rapidly inhibited by anti-theophylline antibody, a suspension of the encapsulated conjugate in a solution of the antibody and NAD+ (6.0 mmol/L) retained greater than 92% of the initial enzyme activity after standing for one year at 4 degrees C. At higher NAD+ concentrations the liposomes aggregated, and enzyme activity was inhibited by leakage of the NAD+ hydrolysis product, adenosine diphosphoryl 5-ribose (ADP-ribose), into the liposomes. Inhibition by ADP-ribose could be blocked and partly reversed by adding semicarbazide. The liposomes were efficiently lysed by Triton X-100, deoxycholate, or octyl glucoside, the kinetics and extent of lysis being affected by liposome size and correlating with the acid strength of various cholate derivatives. Addition of a serum sample and a solution of buffer, substrate, and detergent to a single reagent containing the liposomes and anti-theophylline antibody provided assay results equivalent to those obtained by conventional two-reagent EMIT homogeneous enzyme immunoassay for theophylline.

Adenosine Diphosphate Ribose↗
PubMed1985

Improved sensitivity in homogeneous enzyme immunoassays using a fluorogenic macromolecular substrate: an assay for serum ferritin.

A new highly sensitive nonseparation enzyme immunoassay for human serum ferritin is described. Reagents include a beta-galactosidase-ferritin conjugate, sheep anti-ferritin, anti-sheep IgG, and dextran-linked beta-galactosylumbelliferone as enzyme substrate. The method is based on inhibition of enzyme activity when anti-ferritin binds to the enzyme-ferritin conjugate. Ferritin in the sample and enzyme-labeled ferritin compete for a limited quantity of anti-ferritin. The enzyme activity of the reaction mixture is directly related to the ferritin content of the sample. Some patients' samples caused strong interference in the assay due to the presence of antibody to beta-galactosidase. Several ways of eliminating the interference are presented. When measures were adopted to suppress sample interference, the assay results correlated well with those of other immunoassay methods.

Antibody Affinity↗