Pharmacokinetics of ciprofloxacin in eels by high-performance liquid chromatography with fluorescence detection

The plasma kinetics of ciprofloxacin (CF) were investigated in the eels after administration by oral gavage and bath treatment. Plasma concentrations of CF were determined by high-performance liquid chromatography with fluorescence detection. The mean concentration time data after oral gavage of a single dose (10.0 mg/kg CF) and after bath treatment by exposure (10 microg/ml CF) to medicated water for 48 h were both best fitted by a one-compartment model. After oral gavage in eels, the half-time of absorption (T1/2Ka) was 0.10 h, the half-time of elimination (T1/2Ke) was 51.87 h, and the maximum plasma concentration (Cmax) was 0.4552 microg/ml at Tmax 0.88 h. After bath treatment, the (T1/2Ka) was 0.02 h, the (T1/2Ke) was 15.46 h, and the Cmax was 0.1175 microg/mL at Tmax 0.22 h.     

Separation of levofloxacin,ciprofloxacin, gatifloxacin,moxifloxacin, trovafloxacin and cinoxacin by high-performance liquid chromatography: application to levofloxacin determination in human plasma

A selective, sensitive and accurate liquid chromatographic method with UV and fluorescence detection was developed, validated and applied for the determination of fluoroquinolones in human plasma. The effects of mobile phase composition, ion-pair and competing-base reagents, buffers, pH, and acetonitrile concentrations were investigated on the separation of six quinolones (cinoxacin, levofloxacin, ciprofloxacin, gatifloxacin, moxifloxacin and trovafloxacin). Sample preparation was carried out by adding internal standard and displacing agent and processing by ultrafiltration. This method uses ultraviolet and fluorescence detection and separation using a C(18) column. The recovery, selectivity, linearity, precision, and accuracy of the method were evaluated from spiked human plasma samples. The method was successfully applied to patient plasma samples in support of a levofloxacin pharmacokinetic study.     

Determination of free malondialdehyde in human serum by high-performance liquid chromatography

Lipid peroxidation involves the oxidative deterioration of polyunsaturated fatty acids in biomembranes and generates a variety of aldehydic products including malondialdehyde (MDA). To demonstrate the occurrence of lipid peroxidation in biological systems, the production of MDA has been shown to be a relevant indicator. Therefore, we describe a new method for measurement of free malondialdehyde in human serum. A simple, rapid but sensitive method for determination of MDA in human serum was applied to goiter patients and control groups. Patients with goiter had high levels of MDA compared to control groups. Our method is fast and practical for clinical measurements. The detection limit was found to be 1.2 x 10(-8) mol L(-1).     

Simultaneous determination of levofloxacin, gatifloxacin and moxifloxacin in serum by liquid chromatography with column switching

Liquid chromatography with a column-switching technique was developed for simultaneous direct quantification of levofloxacin, gatifloxacin and moxifloxacin in human serum. Serum samples were injected on a LiChroCART 4-4 pre-column (PC) filled with a LiChrospher 100 RP-18, 5 microm where fluoroquinolones (FQs) were purified and concentrated. The FQs were back-flushed from the PC and then separated on a Supelcosil ABZ+ Plus (150 mm x 4.6 mm i.d.) analytical column with a mobile phase containing 10 mM phosphate buffer (pH 2.5), acetonitrile (88:12, v/v) and 2mM tetrabutyl ammonium bromide. The effects of ion-pair reagents, buffer type, pH and acetonitrile concentrations in the mobile phase on the separation of the three FQs were investigated. Fluorescence detection provided sufficient sensitivity to achieve a quantification limit of 125 ng/ml for levofloxacin and moxifloxacin; 162.5 ng/ml for gatifloxacin with a 5 microl sample size. The on-line process of extraction avoids time-consuming treatment of the samples before injection and run time is shortened. The recovery, selectivity, linearity, precision and accuracy of the method are convenient for pharmacokinetic studies or routine assays.     

Capillary electrophoresis with laser-induced fluorescence detection, an adequate alternative to high-performance liquid chromatography, for the determination of ciprofloxacin and its metabolite desethyleneciprofloxacin in human plasma

A method to determine plasma concentrations of ciprofloxacin and its metabolite desethyleneciprofloxacin (M1) by CE with HeCd laser-induced fluorescence detection is described. Following precipitation of proteins and centrifugation supernatant is injected hydrodynamically (10 s, 0.5 p.s.i.) into the capillary. Overall analysis time for the quantification of both analytes was 7 min. The total amount of plasma needed for multiple injections (n>5) was 10–20 μl. Data on accuracy and precision are presented. The assay performance is compared to the specifications of a validated HPLC method, which is routinely used for the quantification of ciprofloxacin and M1 in body fluids. Both methods showed comparable accuracy and precision for both analytes throughout the whole working range (inter-day precision <9%; inter-day accuracy 96–110%). The limit of quantification (LOQ) of 20 μg/l (M1 10 μg/l) for the CE procedure was slightly higher than for the HPLC method, where 10 μg/l (M1 2.5 μg/l) was determined. However, application of the methods to human plasma samples derived from a clinical study proved that comparable results are obtained and that the sensivity of the HPCE method was sufficient to fully describe typical plasma concentration timie profiles of ciprofloxacin and its metabolite M1. Both the adequate sensitivity and the required smaller sample volume compared to HPLC indicate that the method is feasible for clinical studies where sample amounts are limited, e.g., studies to investigate pharmacokinetics in pediatric patients. Preclinical studies form another possible application of this technique.     

Determination of levofloxacin in plasma, bronchoalveolar lavage and bone tissues by high-performance liquid chromatography with ultraviolet detection using a fully automated extraction method

The aim of this study was to develop a specific and sensitive high-performance liquid chromatographic (HPLC) assay for the determination of levofloxacin in human plasma, bronchoalveolar lavage and bone tissues. The sample extraction was based on a fully automated liquid-solid extraction with an OASIS cartridge. The method used ultraviolet detection set at a wavelength of 299 nm and a separation with a Supelcosil ABZ+ column. The assay has been found linear over the concentration range 0.25-25 microg/ml for levofloxacin in plasma, 1-6 microg/ml in bronchoalveolar lavage and 0.5-10 microg/g for bone tissues and it provided good validation data for accuracy and precision. The assay will be applied to determine the penetration of levofloxacin in human bronchoalveolar lavage (BAL) and bone tissues during pharmacokinetic steady state.     

Simultaneous determination of lysophospholipids by high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatography (HPLC) procedure for the separation of choline lysophospholids including 1-acyl-lysophosphatidylcholines and 1-O-alkyl-lysophosphatidyl-cholines, like the lysoform of the platelet activating factor (2-lysoPAF), is described. The lysophospholipids are derivatized at the sn-2 position of the hydroxyl group by 7-diethylaminocoumarin-3-carbonylazide, which converts them into the corresponding carbamoyl derivatives. The derivatized compounds were well separated by reversed-phase HPLC and quantified by fluorimetric detection. This method shows a high sensitivity and allows the separation and quantification of mixtures of lysophospholipids at picomolar level. The method was applied to assay enzyme activities, like phospholipase A₂ and PAF-acetylhydrolase, on single phospholipids or their mixtures.     

Simultaneous determination of aciclovir, ganciclovir, and penciclovir in human plasma by high-performance liquid chromatography with fluorescence detection

A fast, simple and selective HPLC method has been developed for the assay of aciclovir, ganciclovir, and penciclovir in human plasma by coupling HPLC with fluorescence detection. 200 microl plasma, with guanosine 5'-monophosphate as an internal standard, was subjected to protein precipitation with a 7% [v/v] aqueous perchloric acid solution. The 40 microl supernatant was injected into a Diamonsil-5 microm C18 column. Aciclovir, ganciclovir, and penciclovir, with solvents composed of methanol and 0.08% aqueous trifluoroacetic acid solution, were analysed by fluorescence detection at 260 nm (excitation) and 380 nm (emission) using a gradient elution program. The calibration curves of all three analytes were linear between 20 and 2000 ng/ml. The mean absolute recoveries of aciclovir, ganciclovir, and penciclovir were 93.91+/-1.20%, 97.42+/-0.75%, and 99.01+/-3.30%, respectively. The mean inter-day CVs for aciclovir, ganciclovir, and penciclovir, were within 1.29-7.30%, 1.00-5.53%, and 1.19-3.54%, respectively. The intra-day bias for aciclovir, ganciclovir, and penciclovir ranged from -2.01 to 6.33%, 1.81 to 7.37%, and 1.42 to 6.91%, respectively. The method has been validated and applied in pharmacokinetic studies in Chinese adult renal transplant patients.     

Determination of bestatin in serum by high-performance liquid chromatography with fluorescence detection

A simple method for the determination of bestatin and its major metabolite in man, p-hydroxybestatin, in human serum was investigated; the method employs high-performance liquid chromatography with fluorescence detection. Bestatin and p-hydroxybestatin are oxidized to phenylacetaldehyde and p-hydroxyphenylacetaldehyde, respectively, with periodate, which are then converted into fluorescent compounds with 4,5-dimethoxy-1,2-diaminobenzene. The compounds are separated by reversed-phase chromatography on LiChrosorb RP-18. The detection limits of bestatin and p-hydroxybestatin are 0.2 and 0.4 μg/ml serum, respectively. This method permits the precise determination of bestatin in serum (20 μl) from patients administered bestatin. p-Hydroxybestatin in serum can not be measured by this method because of its low concentration (less than the detection limit).     

Simultaneous measurement of blood and brain microdialysates of granisetron in rat by high-performance liquid chromatography with fluorescence detection

Simultaneous microdialysis probes in the blood and brain and sensitive high-performance liquid chromatography with fluorescence detection were used to examine the granisetron concentration in the jugular vein and frontal cortex of rats after drug administration. Two microdialysis probes were inserted into the right jugular vein and frontal cortex of male Sprague–Dawley rats to which granisetron (6 mg/kg, i.v.) had been administered. Dialysates were automatically collected using a microfraction collector. Samples were eluted with a mobile phase containing 25 mM acetate buffer (pH 4.8)–acetonitrile (72:28, v/v). Excitation and emission wavelengths were set at 305 and 360 nm, respectively, on a scanning fluorescence detector. The limit of quantification for granisetron was 0.5 ng/ml. The in vitro recovery of granisetron was 29.7±1.2% (n=6) for the jugular vein microdialysis probe and 6.1±0.5% (n=6) for the frontal cortex microdialysis probe. The increasing brain/blood concentration ratio of granisetron suggests that granisetron penetrates the blood–brain barrier.     

Measurement of homocysteine thiolactone hydrolase activity using high-performance liquid chromatography with fluorescence detection and polymorphisms of paraoxonase in normal human serum

We developed a non-radioactive and sensitive assay method for measurement of the HTL hydrolase (HTLase) activity in biological samples, using OPA as a fluorescent post-labeling agent, l-homocysteine thiolactone (L-HTL) as the substrate, and HPLC to achieve rapid and selective separation of the substrate and product. The method was applied to measure the activity of HTLase in human, rabbit, rat and mouse serum samples. In addition, the correlation between the serum HTLase activity and PON1 polymorphisms in Japanese subjects was also investigated. The serum HTLase activity in humans, as determined by measurement of the enzyme activity in 22 subjects, was found to be in the range of 0.89-2.06 nmol/min mg protein, with a mean activity of 1.44 nmol/min mg protein.     

Simultaneous determination of theophylline, enoxacin and ciprofloxacin in human plasma and saliva by high-performance liquid chromatography

A simple reversed-phase high-performance liquid chromatographic method has been developed for the simultaneous determination of theophylline, ciprofloxacin and enoxacin in plasma and saliva. The biological fluid samples were extracted with methylene chloride-isopropyl alcohol prior to isocratic chromatography on a Waters C₁₈ μBondapak column. Ultraviolet detection was carried out at 268 nm. The assay in linear for ciprofloxacin and enoxacin (0.05–10 μg/ml), and theophylline (0.1–20 μ/ml). The assay can be used to investigate the interaction of these two fluoroquinolones with theophylline.     

Determination of amlodipine in human plasma by high-performance liquid chromatography with fluorescence detection

A sensitive and specific HPLC method has been developed for the assay of amlodipine in human plasma. The assay involves derivatization with 4-chloro-7-nitrobenzofurazan (NBD-Cl), solid-phase extraction on a silica column and isocratic reversed-phase chromatography with fluorescence detection. Nortriptyline hydrochloride was used as an internal standard. The assay was linear over the concentration range of 0.25–18.00 ng/ml. Both of the within-day and day-to-day reproducibility and accuracy were less than 11.80% and 12.00%, respectively. The plasma profile following a single administration of 10 mg amlodipine to a healthy volunteer was presented.     

Determination of polyamines in human prostate by high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method for the determination of polyamines in human prostate has been developed. This method is based on pre-column derivatization with dansyl chloride (Dns-Cl). The derivatives were separated on a μBondapak C₁₈ column (250×4.6 mm I.D.; 10 μm), and eluted with methanol and distilled water using a one-step linear gradient. The column eluate was monitored by fluorescence detection (excitation, 370 nm; emission, 506 nm). The within-assay precision of the study (C.V.) was as follows: putrescine (PUT) 2.88%, spermidine (SPD) 2.94% and spermine (SP) 1.17%. The between-assay precision (C.V.) was: PUT 2.66%, SPD 3.06%, SP 2.79%. The recovery was greater than 97%. The detection limit for PUT, SPD and SP were 0.05, 0.08 and 0.06 nmol/ml, respectively. In contrast to other studies, sample or polyamine derivatives did not require extraction with an organic solvent such as ethanol, evaporation under vacuum or other condensation procedures. This is a simple, rapid and sensitive method that can be applied to the determination of polyamines in nearly all biological tissues and body fluids, such as urine and serum.     

Determination of dihydroergotamine in human plasma by high-performance liquid chromatography with fluorescence detection

Dihydroergotamine, a 5-hydroxytryptamine antagonist, is used for the treatment of vascular headaches. A high-performance liquid chromatography assay with fluorescence detection is described for the determination of dihydroergotamine in plasma. The assay was validated over the concentration range 0.1–10 ng/ml plasma and applied to the analysis of plasma samples from subjects treated intramuscularly and intranasally with 2 mg of dihydroergotamine.     

Determination of polyamines in human saliva by high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic method for the determination of polyamines (spermine, spermidine and putrescine) in human saliva was developed. This method is based on pre-column derivatization with o-phthaldialdehyde (OPA). The derivatives were separated on a Nucleosil ODS column (250×4.6 mm I.D.; 5 μm). The gradient elution was performed with two mobile phases A (water) and B (methanol) at a flow rate of 0.8 ml/min. The column eluate was monitored by fluorescence detection (excitation, 360 nm; emission, 510 nm). The within- and between-assay coefficients of variation for all the compounds were below 5%. The detection limits for spermine, spermidine and putrescine were 0.04, 0.05 and 0.06 nmol/ml, respectively. The recovery was greater than 90%. Our analytical technique requires neither preliminary extraction with an organic solvent, nor long multi-step procedures. For saliva samples, this is a simple, rapid and highly reproducible method that can be easily applied to the routine determination of salivary polyamines, whose levels increase early in several pathological conditions.     

Simultaneous determination of uric and ascorbic acids in human serum by reversed-phase high-performance liquid chromatography with electrochemical detection

A rapid, easy, and accurate method for the determination of uric acid and ascorbic acid in human serum by reversed-phase high-performance liquid chromatography with electrochemical detection has been developed. Human serum (0.5 ml) was mixed with 1.5 ml of an aqueous solution containing 2.0% metaphosphoric acid and the mixture was centrifuged at 3000g for 30 min. The supernatant was passed through a membrane filter to remove the particulate matter. Ten microliters of the filtrate was injected into the chromatographic system employed in this study. Complete separation of uric acid and ascorbic acid was achieved in about 2 min. The assay limit for quantitation was about 10 pg for uric acid and ascorbic acid under the present chromatographic conditions. The analytical recoveries of uric acid and ascorbic acid in human serum samples were found to be almost 100%.     

Determination of ciprofloxacin levels in chinchilla middle ear effusion and plasma by high-performance liquid chromatography with fluorescence detection

An isocratic high-performance liquid chromatographic method has been developed to determine ciprofloxacin levels in chinchilla plasma and middle ear fluid. Ciprofloxacin and the internal standard, difloxacin, were separated on a Keystone ODS column (100 × 2.1 mm I.D., 5 μm Hypersil) using a mobile phase of 30 mM phosphate buffer (pH 3), 20 mM triethylamine, 20 mM sodium dodecyl sulphate—acetonitrile (60:40, v/v). The retention times were 3.0 min for ciprofloxacin and 5.2 min for difloxacin. This fast, efficient protein precipitation procedure together with fluorescence detection allows a quantification limit of 25 ng/ml with a 50 μl sample size. The detection limit is 5 ng/ml with a signal-to-noise ratio of 5:1. Recoveries (mean ± S.D., n = 5) at 100 ng/ml in plasma and middle ear fluid were 89.4 ± 1.2% and 91.4 ± 1.6%, respectively. The method was evaluated with biological samples taken from chinchillas with middle ear infections after administering ciprofloxacin.     

Assay for etoposide in human serum using solid-phase extraction and high-performance liquid chromatography with fluorescence detection

An HPLC assay for etoposide in human serum was developed. Serum, spiked with podophyllotoxin (internal standard), was treated with sodium dodecyl sulphate prior to solid phase extraction. Analysis was performed on a 300×3.9 mm Bondclone 10 C18 column coupled with a fluorometric detector (λ_ex 230 nm, λ_em 330 nm). The retention times for etoposide and podophyllotoxin were 14 and 28 min respectively. The range of assay was 0.5 to 20 μg/ml with a detection limit of 0.2 μg/ml. This assay is suitable for use in clinical studies with etoposide.