Biomedical subjects
Publications and source records attributed to K A Pittman.
Explore the source record for details and available documents.
Buspirone and a buspirone metabolite, 1-(2-pyrimidinyl)piperazine (1-PP), are extracted from matrix using C18 extraction columns. The metabolite and its internal standard (d4-1-PP) are derivatized with pentafluorobenzoyl chloride to the corresponding amides. The 1-PP derivatives, buspirone and the buspirone internal standard (5-fluorobuspirone) are co-chromatographed. Chromatography and detection are performed using capillary gas chromatography with a fused-silica column and selected-ion monitoring-mass spectrometry. Linear range of the standard curves in plasma is 0.1-14 ng/ml for buspirone and 0.2-25 ng/ml for 1-PP with lower limits of quantitation of 0.1 and 0.2 ng/ml, respectively. In urine the linear range of the standard curves is 0.2-14 ng/ml for buspirone and 8-500 ng/ml for 1-PP with lower limits of quantitation of 0.2 and 8.0 ng/ml, respectively. Intra-assay accuracies were within 14% for buspirone and 1-PP in plasma and urine. Intra-assay precision was within 12% for both compounds in both matrices.
A specific and reproducible high-performance liquid chromatographic (HPLC) procedure was developed for the quantitative analysis of carboplatin (JM-8) in dog plasma ultrafiltrate. Plasma ultrafiltrate samples were generated using Amicon Centrifree micropartition systems or Amicon Centriflo cones, and injected onto a microBondapak NH2 column. The mobile phase consisted of acetonitrile:methanol:0.005 M sodium perchlorate, pH 2.4 (77-75:13-15:10, v/v/v); the flow rate was 1.5 mL/min. Detection was performed by monitoring UV absorbance of the column effluent at 229 nm. Carboplatin eluted between 9.5 and 11.0 min. The internal standard, JM-10, eluted between 11.0 and 13.0 min. The peak height ratio of carboplatin:internal standard versus carboplatin concentration was linear over a range of 0.2 to 20.0 micrograms/mL. The limit of quantitation was 0.2 microgram/mL. The intra-assay precision of this method, as measured by percent relative standard deviation (%RSD), was within 12% for the theoretical concentrations 0.5, 5.0, and 50.0 micrograms/mL. Accuracies were within 11%. The results of the validation procedures indicated that this procedure was accurate and specific.
High-performance liquid chromatographic methods for quantification of a novel carbapenem anti-infective agent, I, in plasma and urine have been developed, validated, and applied to clinical samples. The carbapenem is stabilized in the matrix by the addition of a non-nucleophilic buffer, rapid freezing, and storage at -70 degrees C. After addition of another carbapenem, II, as internal standard, plasma proteins are precipitated with acetonitrile, which is subsequently extracted from the sample with methylene chloride. A portion of the aqueous phase is injected onto a reversed-phase phenyl column that is eluted with 4% (v/v) acetonitrile in 15 mM ammonium phosphate (pH 7.4). The urine assay entails addition of the internal standard II to buffered urine, which is subsequently extracted with methylene chloride prior to injection of the aqueous phase onto a cation-exchange column. The urine assay mobile phase is 5% v/v tetrahydrofuran in 100 mM sodium acetate (pH 5.4). The detector response at 313 nm is a linear (r greater than 0.99) function of concentration over the ranges 0.50-100 micrograms/ml and 2.0-200 micrograms/ml for the plasma and urine assays, respectively. Thermal degradation products do not interfere with either assay. These assays have proven to be accurate, precise, reproducible, and rugged during clinical sample analyses.
A simple and sensitive assay for quantitating 9-methyl-3-(1H-tetrazol-5-yl)-4H-pyrido[1,2-a]pyrimidin-4-one (1; BMY 26517) in human plasma was developed using high-performance liquid chromatography with fluorescence detection. The method involves precipitation of protein and reversed-phase chromatography. The method is linear in the range of 4.3-429 ng/mL of 1, and the limit of detection is 0.4 ng/mL. The day-to-day precision values of this method at 25.7 and 386 ng/mL are 2.1 and 2.6%, respectively. The day-to-day accuracy values at these concentrations are 99.7 and 99.8%, respectively. The recovery of 1 is 98.3%.
A high-pressure liquid chromatographic assay was developed for the quantitative analysis of a new cephalosporin, BMY-28142, in plasma and urine. The plasma method involved protein precipitation with acetonitrile and trichloroacetic acid followed by extraction of the acetonitrile into dichloromethane. After centrifugation, the organic phase was discarded, the aqueous solution was injected into a reverse-phase column, and peaks were detected at 280 nm. The urine method involved dilution of a urine sample with sodium acetate buffer (pH 4.25) and direct injection into the high-pressure liquid chromatography system. The assay validation data indicate that the assays for BMY-28142 in plasma and urine were specific, accurate, and reproducible. The analytical methods were applied to the determination of protein binding in human serum and to a pharmacokinetic study in rats. The results of the protein-binding study indicated that BMY-28142 was 16.3% bound to human serum proteins. In the pharmacokinetic study in rats, the maximum level in plasma of 38.7 micrograms/ml was achieved at 2.33 h after administration of a subcutaneous dose of 100 mg/kg. The levels in the plasma then declined with an elimination half-life of about 0.56 h. The mean values for the steady-state volume of distribution and total body clearance were 0.46 liters/kg and 11.9 ml/min per kg, respectively. The 0- to 24-h excretion of intact BMY-28142 in urine accounted for 88.6% of the dose.
The disposition of the novel cephalosporin cefepime (BMY-28142) was characterized for intravenous administration of single doses to rats and cynomolgus monkeys, the species used most extensively for safety evaluation of the compound. Serial blood samples were collected from individual animals, and plasma was analyzed for intact cefepime by a high-pressure liquid chromatography-UV method. Assay results were evaluated by compartmental and noncompartmental methods to characterize pharmacokinetics for each species and dosage regimen. For intravenous (i.v.) bolus administration of 28 to 386 mg/kg (body weight) to rats, total body clearance (CL; 11.0 ml/min per kg) was essentially invariant with the dose; however, the terminal half-life (t1/2) and the steady-state distribution volume (Vss) increased with increasing dose level. After administration of 87 to 1,502 mg/kg by i.v. infusion, CL (12.5 ml/min per kg) was again similar for all dose groups. Mean t1/2 values (1.3 to 4.6 h) appeared unusually long for a cephalosporin in rats, and inordinately variable. No consistent differences among dose group mean Vss values were found. The maximal concentration of drug in plasma at the end of infusion was not a linear function of dose. For the cynomolgus monkey, kinetic parameters for 5-min i.v. infusions were linearly related to dose over the range of 10 to 600 mg/kg. Mean parameter values were t1/2 = 1.7 h, CL = 1.6 ml/min per kg, and Vss = 0.21 liters/kg. The pharmacokinetic results indicate substantive differences between the two species with respect to their response to toxicologic doses of cefepime.
A high-performance liquid chromatographic method for the analysis of chlorhexidine in human serum and urine was developed. Chlorhexidine and the internal standard, chlorpheniramine, were extracted into chloroform, containing 5% 2-propanol, and back-extracted into dilute sulfuric acid. Chromatographic separation was achieved on a C18 column equilibrated with methanol-water (70:30, v/v), containing 0.005 M sodium heptane-sulfonate. The sensitivity of the assay was 20 ng/ml of biological matrix, using 0.5-ml samples. The application of this method to monitor chlorhexidine levels in burn patients treated topically with a chlorhexidine-containing burn cream was demonstrated.
A quantitative analytical method has been established for the determination of a semi-synthetic epipodophyllotoxin, etoposide, in plasma. The method employs reversed-phase high-performance liquid chromatography and electrochemical detection. Sample preparation consisted of extraction with 1,2-dichloroethane followed by phase separation, evaporation of the organic phase, and reconstitution of the residue. Observed recoveries were 76.8 and 87.5% for 50 and 500 ng/ml, respectively. The method had a linear range of 10-1000 ng/ml. Correlation coefficients of 0.997 or greater were obtained during validation experiments and study sample analysis.
A simple, sensitive, and reproducible high-performance liquid chromatographic (HPLC) procedure was developed for the quantitative analysis of megestrol acetate in human plasma. An internal standard, 2,3-diphenyl-1-indenone, was added to 0.5 mL of plasma followed by extraction with hexane. The residue remaining after evaporation of hexane was reconstituted in methanol and injected onto a mu-Bondapak C18 column. The column was eluted with acetonitrile:methanol:water:acetic acid (41:23:36:1), and the eluant was monitored at 280 nm. Megestrol acetate and the internal standard eluted at 6-7 and 12-14 min, respectively. The peak height ratio (megestrol acetate/internal standard) versus plasma concentration was linear over a range of 10-600 ng of megestrol acetate/mL of plasma, and the limit of detection was 5 ng/mL. The mean intra- and interassay accuracies were within 3% of the actual values. The mean intra- and interassay precision, as estimated by RSD, were 4 and 6%, respectively. Constituents in human plasma and megestrol, a possible degradation product, did not interfere in the assay. The procedure was applied to the analysis of plasma samples from subjects receiving 40 mg of Megace q.i.d.
The bioequivalence of two new investigational 160 mg tablets, one containing the regular form and the other a micronized form of megestrol acetate, was determined relative to a commercially available 40 mg tablet. The tablets were administered to 24 male subjects in a three-way crossover study, balanced for sequence, with 1 week between administrations. The 40 mg tablets were administered qid at 8 AM, 12 PM, 6 PM, and 10 PM, while the 160 mg tablets were administered once at 8 AM. Plasma samples were collected at appropriate times up to 96 hours after administration and were analyzed for megestrol acetate with a validated high-performance liquid chromatographic procedure. Based on the times to maximum plasma concentrations (2.5 to 2.8 h) the rate of absorption was the same for each of the tablets. Relative to the 40 mg qid dose, the 160 mg regular and the 160 mg micronized tablets had mean relative bioavailabilities of 97% and 118%, respectively.
A single oral solution dose (40 mg/m2) of 14C-prednimustine was administered to each of four cancer patients. Plasma, urine, and feces were collected at appropriate times and analyzed for total radioactivity. Plasma samples were analyzed for prednimustine. Peak plasma levels of radioactivity (1-3 micrograms 14C-prednimustine equivalents) occurred at 1.5-3 h in three patients and at 5-6 h in one patient. No intact prednimustine was detected in the plasma; this means that if present, it would be at a concentration of 0.02 micrograms/ml or less and would account for less than 1% of the total drug-related material at the time of peak plasma levels. Solvent-extractable metabolites had a plasma half-life of about 8 h or less. By 24 h essentially all the plasma radioactivity appeared to be covalently bound, and it was eliminated slowly with an estimated terminal elimination half-life of about 10 days. Rapid urinary excretion occurred in the first 24 h, and 40%-60% of the dose was recovered in the urine in 72 h. Although prednimustine was well absorbed, the ester was subject to extensive presystemic metabolism and was not present in the systemic circulation after oral administration.
The gastric antisecretory activity of etintidine, a new histamine H2-receptor antagonist, was evaluated in 5 patients with quiescent duodenal ulcer disease. Meal-stimulated acid secretion was measured after 100 and 300 mg oral doses of etintidine, 100 and 300 mg oral doses of cimetidine, and placebo. Reductions from placebo in four-hour gastric acid secretion were 49, 65, 80, and 94%, with 100 mg cimetidine, 100 mg etintidine, 300 mg cimetidine, and 300 mg etintidine, respectively. Drug concentrations in plasma were determined by HPLC. The pharmacokinetics of the 2 drugs were similar. We analyzed sigmoid-shaped concentration-response curves to both agents; the concentrations causing 50% inhibition of meal-stimulated gastric acid secretion were 0.44 +/- 0.04 and 0.15 +/- 0.04 micrograms/ml for cimetidine and etintidine, respectively. However, characteristics of these curves were such that the potency difference diminished at higher concentrations.
A method is given for the determination of carminomycin (CMM) and a major metabolite carminomycinol (CMMOH) in serum from cancer patients after intravenous administration of carminomycin as the free drug. CMM and CMMOH are extracted from serum with chloroform, the extract evaporated and the residue dissolved in methanol. High performance liquid chromatography analysis utilized a C18 microBondapak reversed-phase column eluted with 0.1 mol/l acetate buffer (pH 4)-acetonitrile (60:40, v/v) with fluorescence detection. The assay is linear, reproducible, and precise with a limit of detection of 2 ng/ml. Representative serum levels of CMM and CMMOH in a cancer patients are presented.
A single dose of 14C-anagrelide (6,7-dichloro-1,5-dihydroimidazo [2,1-b] quinazoline-2(3H)-one monohydrochloride) equivalent to 1 mg free base and containing 100 muCi radioactivity, was taken by five healthy, fasting men. Blood, plasma, urine, and feces were analyzed for total radioactivity. Plasma and urine concentrations of anagrelide were determined, and the urinary metabolite profile was established by high-performance liquid chromatography (HPLC). The drug was rapidly absorbed with peak plasma levels of radioactivity equivalent to 50 ng anagrelide per milliliter at about 1 hr. These levels decreased to less than 10% of peak in 24 hr. Plasma levels of anagrelide peaked at 5 ng/ml at about 1 hr, decreased rapidly during the first 6 to 8 hr, and then declined more slowly, with an estimated terminal elimination half-life of about 3 days. No significant quantities of radioactivity were associated with the cellular elements of blood. Anagrelide was extensively metabolized before elimination in urine. Means of 68% and 72% of the dose were excreted in urine as metabolites in 24 and 144 hr, and 10% of the dose recovered in the feces. Several urinary metabolites were detected by HPLC.
The perinatal distribution of butorphanol was demonstrated in relation to maternal-neonatal transfer and colostrum/milk excretion in obstetric patients. Parenteral butorphanol passed the placental barrier and was found in neonatal cord serum. The mean neonatal serum concentration of butorphanol was not different from the mean maternal serum concentration of butorphanol, following a 1 or 2 mg intramuscular dose. Butorphanol was detected in the milk of lactating women following oral and intramuscular administration. Serum and milk concentrations appeared to be parallel with time. This observation was confirmed by the constancy of the mean milk-to-serum concentration ratio (0.7 intramuscular, 1.9 oral). We calculated that 4 micrograms would be the maximum amount of butorphanol, which would be expected to be present in the full daily milk output (1 L) following administration four times a day of 2 mg intramuscular or of 8 mg oral doses. An oral dose of 4 micrograms to an infant weighing 4 kg corresponds to the negligible oral dose of 0.7 mg to a 70 kg adult. The demonstrated safety and efficacy of butorphanol as an obstetric analgesic and the characteristics of the maternal-neonatal transfer and milk excretion are indicative of the potential excellence of this agent for obstetric use.
A radioimmunassay was developed for the analysis of butorphanol in human serum. The procedure involves extraction of serum with hexane containing 2% isoamyl alcohol, followed by evaporative solvent removal and radioimmunoassay of the reconstituted residue. The antibody significantly cross-reacts with unidentified butorphanol metabolites but not with two known metabolites, hydroxybutorphanol and norbutorphanol. Extraction eliminated interference from the butorphanol metabolites normally present in serum. The antibody also cross-reacts with pentazocine and cyclazocine but not with morphine, hydromorphone, oxymorphine, codeine, methadone, and meperidine. Butorphanol tartrate was administered intravenously (2 mg) to normal male volunteers. Serum butorphanol levels declined biexponentially with an average terminal half-life of 2.7 hr. Enzymatic serum hydrolysis prior to extraction yielded additional butorphanol, indicating the presence of butorphanol conjugates. The specificity of the assay for butorphanol was confirmed by GLC--mass fragmentography.
Butorphanol tartrate was administered intramuscularly and subcutaneously to adult male and female dogs at a dose of 0.25 mg/kg. No significant absorption lag time and no significant difference bwtween peak intramuscular and subcutaneous serum concentrations were observed. The mean peak serum concentration was 29 ng/ml at mean times of 28 min after subcutaneous administration and 40 min after intramuscular administration. There were no significant differences in the pharmacokinetics of butorphanol in dogs with either route. The serum half-life was 1.62 hr, and the serum clearance was 3.45 liters/kg/hr. The apparent volume of distribution of butorphanol was 7.96 liters/kg. Although considerable inter- and intraanimal variation in Cmax and AUC was observed, there was no significant difference in the area under the serum concentration versus time curves, and the two administration routes were considered bioequivalent.