Improved column liquid chromatographic method for the determination of moricizine in plasma or serum.
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Chromatography, Liquid↗
Biomedical subjects
K Chan
Publications and source records attributed to K Chan.
Multiple sequential periods of DNA synthesis and quiescence in primary hepatocyte cultures maintained on the DMSO-EGF on/off protocol.
Repeated periods of DNA synthesis activity (each period consisting of two to three cycles) separated by intervals of quiescence in primary rat hepatocytes can be stimulated by sequential addition and removal of 2% dimethyl sulfoxide (DMSO) in the presence of epidermal growth factor (EGF). Hepatocytes can be kept in nonproliferating cultures for 7 days in media supplemented with 2% DMSO and EGF. If DMSO is removed while EGF is maintained, rat and human hepatocytes enter a 3 to 4 day period of DNA synthesis that declines rapidly by days 4 and 5. If DMSO is reintroduced into cultures at that point, kept on for 3 more days and removed again, hepatocytes reenter into proliferation with another self-limited response of 3 to 4 days. Similar phenomena can seen with hepatocytes maintained in the presence of 3 mM phenobarbital. These protocols demonstrate that loss of responsiveness to mitogens in primary hepatocyte cultures is not an irreversible process. They also raise the possibility that signals for termination of DNA synthesis in hepatocytes emanate from hepatocytes themselves. These studies also suggest for the first time the possibility of designing in vitro systems that will allow clonal expansion of differential hepatocytes.
Animals↗
The simultaneous determination of active ingredients in cough-cold mixtures by isocratic reversed-phase ion-pair high-performance liquid chromatography.
A simple, rapid and accurate method for the simultaneous determination of active ingredients in cough-cold mixtures using isocratic reversed-phase ion-pair high-performance liquid chromatography has been developed. It involves the use of an octadecylsilane column as the stationary phase with methanol, water, tetrahydrofuran, phosphoric acid mixtures as mobile phase including sodium dioctylsulphosuccinate as the ion-pair agent. The pH of the mobile phase was adjusted to 4.6 by means of phosphoric acid and ammonium hydroxide solutions. The proposed method involves the simple dilution of the samples with the mobile phase and the addition of metoclopramide hydrochloride as the internal standard. The active ingredients under investigation were chlorpheniramine, codeine, diphenhydramine, ephedrine, ethylmorphine, phenylephrine, phenylpropanolamine and pholcodine, which exist as various combinations in cough-cold mixtures. The optimum composition of the mobile phase and the optimum flow rate were determined and are reported. The method was applied to the determination of active ingredients in seven commercially available cough-cold mixtures.
Antitussive Agents↗
Gastrointestinal transit of a solid indigestible capsule as measured by radiotelemetry and dual gamma scintigraphy.
The objectives of the present study were to evaluate gastric and small bowel transit times of an indigestible solid matrix and to characterize the specific changes in intraluminal pH as a function of transit time through the gastrointestinal tract. Particular attention was paid to the lag time at the ileocecal junction. A Heidelberg capsule (HC), labeled with 10 microCi Indium-111, was given orally to six healthy male subjects 15 min after oral ingestion of 100 microCi of 99mTc-sulfur colloid as a liquid fatty meal (4 ml/kg). Intraluminal pH was monitored continuously via the HC. Gastric and small bowel transit of the radionuclides was monitored via external scintigraphy at 0.5-hr intervals. Gastric residence times (GRT) of the HC ranged from 2.8 to 4.8 hr. with a mean (+/- SD) of 3.6 +/- 0.8 hr. These values were independent of the individual's weight, height, or body surface area. Small bowel transit times of the HC ranged from 2.8 to greater than 5.5 hr. which were consistent with the reported values of 3 to 5 hr. The lag times of the HC at ileocecal junction ranged from 0.8 to greater than 2.5 hr. The presence of the lag times at the ileocecal junction in all subjects confirmed that it acts as a valve or sphincter. Mouth-to-cecum transit times of the HC occurred within 9.0 hr in 50% of the subjects. In general, following a sharp rise upon pyloric passage of HC the pH dropped slightly but then increased linearly throughout the small intestine.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
In vitro activities of a dual-action antibacterial agent, Ro 23-9424, and comparative agents.
The in vitro activity of the dual-action antibacterial agent Ro 23-9424 was compared with those of cefotaxime, ceftazidime, ciprofloxacin, fleroxacin, imipenem, and amikacin against 358 aerobes and anaerobes. The MIC ranges, MICs for 50 and 90% of the strains (MIC50s and MIC90s), and percentage of strains susceptible for each agent at the recommended susceptible MIC breakpoint were determined for each genus. The MIC90s (micrograms per milliliter) of the agents against members of the family Enterobacteriaceae were as follows: ciprofloxacin, 0.063; Ro 23-9424, fleroxacin, and imipenem, 0.5; ceftazidime, 2; amikacin, 4; and cefotaxime, 16. The MIC90s (micrograms per milliliter) against Pseudomonas and Acinetobacter spp. were as follows: ciprofloxacin, 2; ceftazidime and imipenem, 8; Ro 23-9424, 16; fleroxacin, 32; amikacin, 64; and cefotaxime, 128. Against gram-positive bacteria, excluding the enterococci, the MIC90s (micrograms per milliliter) were as follows: ciprofloxacin, 1; imipenem, 4; Ro 23-9424 and fleroxacin, 8; amikacin, 64; and ceftazidime and cefotaxime, greater than 128. Against gram-positive bacteria, including the enterococci, the MIC90s changed only for the following agents: Ro 23-9424, 16 micrograms/ml; and amikacin, 128 micrograms/ml. Strains of Branhamella catarrhalis, Haemophilus influenzae, and Neisseria gonorrhoeae were 100% susceptible to Ro 23-9424, cefotaxime, ciprofloxacin, and fleroxacin, while the other three agents showed somewhat less activity only against N. gonorrhoeae. Against anaerobes, imipenem was the most effective agent, while the activities of the other six agents were variable.
Anti-Bacterial Agents↗
A PCR artifact: generation of heteroduplexes.
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Animals↗
Potential problem with fluorescence polarization immunoassay cross-reactivity to vancomycin degradation product CDP-1: its detection in sera of renally impaired patients.
During the development of a homogeneous immunoassay for the antibiotic vancomycin, we observed in certain patient samples a quantitation difference between the enzyme multiplied immunoassay technique (EMIT) method and the comparison method, fluorescence polarization immunoassay (FPIA). This prompted us to evaluate the integrity of vancomycin in samples from renally impaired patients. Since it has been reported in the scientific literature that vancomycin degrades into an antibiotically inactive crystalline degradation product (CDP-1) in vitro, we developed high-performance liquid chromatography (HPLC) and liquid chromatography/mass spectrometry (LC/MS) methods to determine whether CDP-1 is present in patient sera. HPLC and LC/MS analysis on samples from renally impaired patients positively identified CDP-1 in fresh samples. Next, we tested the cross-reactivity of three currently available vancomycin immunoassays, radioimmunoassay (RIA) FPIA, and EMIT, to CDP-1 prepared in our laboratory. Our data suggest that CDP-1 is recognized by FPIA and RIA, both polyclonal antibody-based methods, but not by EMIT, which uses a monoclonal antibody.
Chromatography, High Pressure Liquid↗
Predicting plasma concentrations of bupivacaine after epidural administration in obstetric analgesia.
The elimination half-life and plasma concentrations of bupivacaine were predicted after its epidural administration in six pregnant women at term for elective Caesarean section using a repeated one-point method. There was a direct correlation between predicted concentrations and observed concentrations of bupivacaine using this simple method (r = 0.9947). The assay of bupivacaine in a 0.5-ml plasma by gas chromatography with nitrogen sensitive detection can be achieved in a short time (rapid extraction and chromatographic analysis required 20 min and 10 min, respectively) to cope with emergency. It is suggested that the repeated one-point method may be useful to obtain early prediction of kinetic parameters in patients who required prolonged epidural anesthesia with bupivacaine in order to minimize adverse effects.
Adult↗
Pharmacokinetic and phase I evaluation of esorubicin (4'-deoxydoxorubicin) by continuous infusion over forty-eight hours in patients with leukemia.
Sixteen patients with previously treated acute nonlymphocytic leukemia or chronic myelogenous leukemia in blast crisis were given one to three courses of esorubicin by continuous infusion over 48 h. Dosage levels extended from 35 to 85 mg/m2. Four patients showed partial responses of short duration. Nonhematological toxicity observed at dosages of 55 to 85 mg/m2 were mucositis, diarrhea, skin rash, transaminitis, nausea, vomiting, and cardiac dysfunction. One patient receiving 85 mg/m2 developed acute florid congestive heart failure within hours of administration of the drug. Pharmacokinetic analysis revealed large interpatient variation in plasma drug levels. At the end of infusion, plasma decay of esorubicin was rapid initially but slow thereafter, with a terminal half-life of 20 to 54 h. The metabolite 4'-deoxy-13-hydroxydoxorubicin reached significant plasma levels. Total body clearance, renal clearance, volume of distribution at steady state, and mean residence time show little variation during dose escalation for both esorubicin and 4'-deoxy-13-hydroxydoxorubicin. Urinary excretion of esorubicin and 4'-deoxy-13-hydroxydoxorubicin accounted for 10.5 and 1.5%, respectively, of the administered dose.
Doxorubicin↗
Direct and simultaneous high-performance liquid chromatographic assay for the determination of p-aminobenzoic acid and its conjugates in human urine.
Procedures based on high-performance liquid chromatography (HPLC) were developed for identifying and measuring p-aminobenzoic acid (PABA) and its conjugate metabolites in human urine after oral doses of PABA. p-Aminohippuric acid (PAH), PABA, p-acetamidohippuric acid (PAHA) and p-acetamidobenzoic acid (PADB) in urine were resolved and determined by HPLC simultaneously and directly without extraction. A mobile phase consisting of 3% (v/v) acetonitrile in distilled water containing 0.005 M 1-heptanesulphonic acid in glacial acetic acid (PIC-B7) at pH 3.3 was eluted at 1 ml/min through a C18 Spherisorb column, followed by UV detection at 280 nm. After hydrolysis of urine samples at 37 degrees C for 3 h with beta-glucuronidase, the amounts of PABA-glucuronide and PADB-glucuronide were also determined. The retention times of PAH, a dominant peak which disappeared after hydrolysis, PABA, DABA (3,5-diaminobenzoic acid, as the internal standard), PAHA and PADB were 11.8, 14, 15, 18, 24 and 46 min, respectively. The 24-h urinary recoveries of PAH, PAHA, PADB, PADB-glucuronide, PABA and PABA-glucuronide after separate oral doses of 200 and 800 mg of PABA in one healthy subject were 43.4 and 48.1, 7 and 29.1, 11.2 and 11.8, 34.8 and 6.6, 0.2 and 0.3, and 1.0 and 2.4%, respectively. It is interesting that at high dose (800 mg) saturation of glucuronidation of PADB (N-acetylated PABA) appeared to occur, which resulted in an increase in the formation of PAHA, the glycine conjugate of PADB. Over 90% of the oral dose was accounted for by 8 h after administration.
4-Aminobenzoic Acid↗
Comparison of gas chromatographic and high-performance liquid chromatographic assays for the determination of debrisoquine and its 4-hydroxy metabolite in human fluids.
A comparison of an established gas chromatographic assay for 4-hydroxydebrisoquine and debrisoquine and a modified high-performance liquid chromatographic assay was made. Both assays used guanoxan as the internal standard and required derivatization of all three compounds with acetylacetone at 96 degrees C for 2.5 h and subsequent ethereal extraction and cleaning steps before chromatographic analysis. For detailed pharmacokinetic studies the gas chromatographic assay was more sensitive in the measurement of low concentrations in plasma, but the liquid chromatographic assay was adequate for phenotyping the 4-hydroxylation of debrisoquine in a population. In the latter assay a mobile phase consisting of 70% methanol in water at pH 3.5 (adjusted with orthophosphoric acid containing 10 mM 1-pentanesulphonic acid was employed (flow-rate 1.5 ml/min) with a pre-column (C8) linked to a reversed-phase muBondapak C18 cartridge in a Z-module. The eluate was detected at 248 nm. With this assay it was observed that the buccal absorption of debrisoquine and 4-hydroxy-debrisoquine was affected by the pH of the buccal medium. This indicates that urinary pH may influence the excretion of both substances at high pH. The debrisoquine-to-4-hydroxydebrisoquine ratio may be dose-dependent.
Absorption↗
Effect of tetrahydrouridine on the clinical pharmacology of 1-beta-D-arabinofuranosylcytosine when both drugs are coinfused over three hours.
When 1-beta-D-arabinofuranosylcytosine (ara-C), 25 mg/m2, is infused over 3 h together with tetrahydrouridine (THU) at 10 to 350 mg/m2 to heavily pretreated patients with solid tumors, Michaelis-Menten type kinetic values are observed with leveling off of delta area under the curve, delta ara-C levels at 3 h, and delta total body clearance after 150 mg/m2 of THU. When the ara-C dose was increased to 50, 75, and 100 mg/m2 coinfusion of 250 or 350 mg/m2 of THU significantly increased plasma ara-C at peak and area under the curve. In contrast, total body clearance and volume of distribution decreased significantly. At 100 mg/m2 of ara-C coinfused with high doses of THU, i.e., at 350 mg/m2, the pharmacokinetics of plasma ara-C was changed from a biphasic decay of plasma ara-C at peaks (control) to a curve similar or identical to a monophasic curve, indicating that THU not only inhibits deamination but also changes the distribution of ara-C. This combination provides plasma ara-C levels (greater than or equal to 10 microM) comparable to high dose ara-C at 1 g/m2. Such plasma ara-C levels are considered to be sufficient for saturation of the kinases catalyzing the production of 1-beta-D-arabinofuranosylcytosine 5'-triphosphate. This reduced ara-C dose necessary to achieve saturation of kinases also reduces plasma 1-beta-D-arabinofuranosyluracil levels substantially. Toxicity of this combination was predominantly confined to bone marrow and gastrointestinal toxicity.
Adult↗
A comparison of alfentanil requirements in European and Asian patients during general anaesthesia.
Alfentanil requirements were compared in thirty-six Asian and forty-three European patients during general anaesthesia with muscle relaxants. Alfentanil infusion at 5 micrograms/kg/min was started immediately after induction with thiopentone and alcuronium. The infusion rate was reduced to 0.5 microgram/kg/min after ten minutes. An incremental dose of 5 micrograms/kg/min for five minutes was given on each occasion when anaesthesia was clinically judged to be inadequate. Recovery parameters were recorded. Pharmacokinetics were also studied in five Europeans, four Chinese and four Nepalese. The dosage of alfentanil required was comparable in both Asian and European patients, but recovery was slower in the Asian patients. The elimination half-life in the Chinese and the Nepalese were both significantly shorter than that of the Europeans (P less than 0.05), but at the time of recovery of spontaneous ventilation, the mean plasma concentrations were not significantly different.
Adolescent↗
Determination of warfarin in human plasma by high performance liquid chromatography.
A simple procedure for the determination of warfarin in plasma samples is described. The assay involves a single ethereal extraction of warfarin and its internal standard, propyl paraben, from an acidified sample. The extract is evaporated to dryness at 45 degrees C and the residue is redissolved in methanol (50 microliters). A 25-microliters aliquot is injected into the liquid chromatograph and eluted with acetonitrile - 10 mM phosphate buffer at pH 3.5 (48:52, v/v) on a C8 pre-column linked to a 5-microns C8 reversed-phase column. The flow rate was set at 1.5 ml min-1 and UV detector at 215 nm. The method has been used to determine plasma concentrations of warfarin in Chinese patients with recent atrial fibrillation scheduled for electrocardioversion.
Administration, Oral↗
Pyrazinamide and rifampicin regimens for patients on maintenance dialysis.
We measured pyrazinamide and rifampicin plasma concentrations in five patients with pulmonary tuberculosis and end stage renal failure treated by haemodialysis or continuous ambulatory peritoneal dialysis. Using conventional daily doses of oral pyrazinamide and rifampicin, we found that the drugs were removed efficiently by both dialysis methods, so that plasma levels were sub-optimal for maximal bactericidal action. These findings suggest that in patients with tuberculosis on maintenance dialysis, treatment should be either with higher doses of these two drugs, or with additional replacement doses given after each dialysis. Further detailed pharmacokinetic studies on larger numbers of patients are indicated.
Adolescent↗
Liquid chromatographic assay for the simultaneous determination of pyrazinamide and rifampicin in serum samples from patients with tuberculous meningitis.
A simple high-performance liquid chromatographic assay for the simultaneous determination of pyrazinamide and rifampicin in serum from patients with tuberculous meningitis is presented. The drugs and internal standard, p-acetamidobenzoic acid, were extracted from the acidified sample containing 2% ascorbic acid at pH 4.2 into dichloromethane-diethyl ether (2:3). The solvent extract was evaporated to dryness with the aid of nitrogen and the residue redissolved in methanol (75 microliters). The concentrate was analysed by a liquid chromatograph using a reversed-phase 30-microns C8 pre-column linked to a 5-microns C8 analytical column with a gradient solvent programme, which delivered 6% to 48% (v/v) acetonitrile in phosphate buffer (10 mM potassium dihydrogenphosphate, pH 3.5) in 10 min at 1.5 ml/min. The eluate was detected at 215 nm. Twelve patients with tuberculous meningitis were given daily chemotherapy, and their serum samples were assayed for pyrazinamide and rifampicin.
Calibration↗
Molecular isolation and sequence determination of the cDNA for the mouse sperm-specific lactate dehydrogenase-X gene.
Several cDNA clones for the mouse lactate dehydrogenase-X (LDH-X), a sperm-specific glycolytic enzyme, were isolated from mouse testicular cDNA libraries constructed in the bacteriophage vectors, lambda gt11 and gt10. The largest cDNA clone contains an insert of 1135 base pairs in length and an open reading frame that encodes a 332 amino acid polypeptide with a molecular weight of 35.89 kD. The deduced amino acid sequence of this protein is in close agreement with the published sequence of mouse LDH-X obtained by direct protein sequencing. Northern analysis of RNA isolated from different tissues detected a single size mRNA of 1.5 kilobases in mouse testis but not in brain or liver. The Ldh-x structural gene was estimated to be about 12 kb in size as demonstrated by Southern hybridization analysis of mouse genomic DNA using the full-length cDNA as a probe.
Amino Acid Sequence↗
Pharmacokinetics of low-dose intravenous pethidine in patients with renal dysfunction.
The kinetics and elimination of pethidine (meperidine) after intravenous administration (150 micrograms/kg) to ten healthy volunteer subjects were compared with those obtained from 18 patients who suffered from varying degrees of renal dysfunction. In both groups of subjects, pethidine was eliminated triexponentially from plasma. However, plasma concentrations in the patients (who were subdivided into patients with severe dysfunction, moderate dysfunction, and mild dysfunction) were consistently higher. The mean +/- SEM elimination half-life (t1/2) of pethidine was significantly longer in the three groups of renal patients: 7.9 +/- 1.1, 20.2 +/- 13.6, 16.6 +/- 5.4, and 14.3 +/- 3.1 hr, respectively, for healthy volunteers, patients with severe, moderate, and mild dysfunction; their mean +/- SEM creatinine clearances were 97.3 +/- 7.5, less than 9.5, 30.0 (3.7), and 63.3 +/- 8.5 mL/min respectively. The mean plasma clearance of the drug was higher in healthy subjects (342.7 +/- 62.5 mL/min) than various groups of renal patients (99.9 +/- 11.6, 120.9 +/- 45.8, and 123.8 +/- 34.1, respectively, for patients with severe, moderate, and mild dysfunction). Impairment of renal function also reduced total plasma protein binding: 58.2 +/- 5.0% in healthy subjects and 31.8 +/- 3.9%, 44.5 +/- 5.0%, and 42.5 +/- 5.6%, respectively, for the three renal patient groups. The percentage of pethidine recovered in the urine was significantly lower in the severe dysfunction group while norpethidine recovery was significantly lower in all three groups of renal patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗