François Jehl

Clinical pharmacokinetics of vinorelbine.

SummaryVinorelbine (5′-noranhydrovinblastine) is a recently developed semisynthetic anticancer drug which belongs to the Catharanthus alkaloid family. Its mechanism of action is only partially known but it is assumed that it acts, like vinblastine and vincristine, as an antimicrotubule agent arresting cell division in mitosis. Clinically, vinorelbine has mainly shown activity in the treatment of advanced non—small-cell lung cancer and the treatment of metastatic breast cancer.Early pharmacokinetic data were obtained with radioactive assays (radio-immunoassay or 3H-labelled vinorelbine), then with more selective high performance liquid Chromatographic techniques. Vinorelbine is usually administered intravenously but there has also been some experimentation with an oral formulation. The bioavailability of a liquid filled gelatin capsule ranges between 12 and 59% with a mean value of 27% [standard deviation (SD) 12%]. Vinorelbine is rapidly absorbed with peak serum concentration reached within 2 hours. In vitro, vinorelbine is mainly distributed into the blood cells, especially platelets (78%) and lymphocytes (4.8%). The unbound blood fraction is around 2%. In lung tissue vinorelbine concentrations are much higher than in serum, by up to 300-fold 3 hours after administration.Little is known about the biotransformation of vinorelbine. Desacetylvinorelbine is considered to be a minor metabolite and is only found in urine fractions, representing 0.25% of the injected dose. Urinary excretion of vinorelbine is low, accounting for less than 20% of the dose. Faecal elimination has been demonstrated in 2 patients who were administered 3H-labelled vinorelbine; the amount of radioactivity recovered in the faeces was 33.9 and 58.4% for the 2 patients, respectively.The pharmacokinetic profile of vinorelbine is often described as a 3-compartment model characterised by a long terminal half-life (t½) that varies between 20 and 40 hours and a large apparent volume of distribution (Vd) of around 70 L/kg. Systemic clearance ranges between 72.54 and 89.46 L/h (1209 and 1491 ml/min) when determined by high performance liquid chromatography and is higher than that reported by radioimmunoassay [46.2 L/h (770 ml/min)]. This could be due to the greater specificity of the Chromatographic method. Vinorelbine has been administered by continuous intravenous infusion over 4 days. Steady-state was reached and the concentrations obtained were above the in vitro IC50 (concentration of drug causing 50% inhibition).The effect of liver disease on vinorelbine pharmacokinetics has been studied in patients with breast cancer. Patients with massive secondary liver disease had a lower systemic clearance than those who have no liver disease or a lesser invasion.In children, vinorelbine seems to display a shorter t½ (14.7 hours) than that found in adults. In addition, the systemic clearance is highly variable [from 12 to 93.96 L/h/m2 (200 to 1566 ml/min/m2)].Vinorelbine is often co-administered with cisplatin in the treatment of advanced non—small-cell lung cancer. The disposition of the alkaloid is not altered by concurrent administration of cisplatin.

High-performance liquid chromatographic assay for meropenem in serum

High-performance liquid chromatographic procedures have been developed for the measurement of meropenem in serum. The separation was performed on an Ultrasphere XL-ODS analytical column (75 x 4.6 min I.D.). The mobile phase consisted of 10.53 mmol/l ammonium acetate-acetonitrile (95:5, v/v) (pH 4). The UV detection was at 298 nm. The quantitation limit both in serum and water was 0.25 micrograms/ml. The method was validated in serum and aqueous solution over the concentration range 0.25-50 micrograms/ml. The extraction recovery from serum spiked with meropenem was 99.7 +/- 3.4%. The intra- and inter-assay coefficients of variation were below 6%. Stored at -80 degrees C for three months at various concentrations in serum and in aqueous solution, meropenem did not reveal any appreciable degradation. After 24 h, it was also stable at 4 degrees C in serum, aqueous solution and supernatant of extraction but not at room temperature. The stability of the drug was also confirmed in serum after repeated freezing-thawing cycles at -80 degrees C on four consecutive days.

High-performance liquid chromatography of antibiotics

High-performance liquid chromatographic (HPLC) monitoring of antimicrobial agents has recently become more widely used, and represents an interesting alternative to other methods. The methodology is characterized by good specificity and accuracy, and it is applicable to almost all antibiotics. This review first describes the successive steps to investigate for the development of an HPLC method for a new antibiotic, and how to make use of it. Particular emphasis is put on the problems related to the standardization of sample preparation and to the development of mobile phases for use with different molecules belonging to the same class. The second part of the review describes one or more HPLC techniques for a representative antibiotic of each major class.

Hospital routine analysis of penicillins, third-generation cephalosporins and aztreonam by conventional and high-speed high-performance liquid chromatography

A high-performance liquid chromatographic procedure for the measurement of fifteen beta-lactam antibiotics in body fluids is described, with special reference to high-speed techniques. The procedure involves a unique sample preparation before analysis for all the following fifteen compounds: benzylpenicillin, ampicillin, cloxacillin, ticarcillin, mezlocillin, azlocillin, piperacillin, cefotaxime and its desacetyl metabolite, cefsulodin, cefoperazone, cefmenoxime, ceftazidime, ceftriaxone and the monobactam aztreonam; thus all biological samples arriving at the laboratory can be treated in batch. Of these fifteen antibiotics, eleven can be chromatographed with the same type of mobile phase, which consists of a mixture of ammonium acetate and acetonitrile in various ratios. Three others need ionpairing chromatography because of their polarity, and ticarcillin requires citric acid. High-speed high-performance liquid chromatography seems to be particularly suitable for the routine analysis of beta-lactam antibiotics because columns equilibrate more rapidly, retention times are much shorter, detection limits are lower and the longer lifetime of columns reduces analysis costs.

Determination of vancomycin in human serum by high-pressure liquid chromatography.

A rapid, accurate, reverse-phase high-pressure liquid chromatographic procedure for vancomycin quantitation in human serum, cerebrospinal fluid, and peritoneal fluid was developed. This procedure involves a simple chemical extraction of the antibiotic and is suitable for each of these body fluids. The column and mobile phase used provided a good resolution of the vancomycin peak with a retention time of 6.1 min. The precision of the assay was within the requirement for a daily routine clinical application. Coefficients of variation for within-day reproducibility were 5.80 and 6.28%, respectively, for samples at 50 and 25 micrograms/ml, and for between-day reproducibility they were 11.4 and 11.1%, respectively. No interference was found with respect to beta-lactam and aminoglycoside antibiotics and many other currently used drugs, indicating a good specificity for the procedure. The detection limit of 100 ng/ml has proven to be sufficient for monitoring drug levels in serum obtained after usual dosages. Drug levels in 112 clinical serum specimens assayed by high-pressure liquid chromatography were regressed against the levels obtained for the same samples by radioimmunoassay and fluorescent polarization immunoassay. Correlation coefficients were 0.945 and 0.967, respectively, and were highly significant (alpha less than 0.001).

Molecular pharmacokinetics of catharanthus (vinca) alkaloids

This review focuses on the published data regarding the molecular determinants (enzymes, transporters, orphan nuclear receptors) of Catharanthus (vinca) alkaloids pharmacokinetics in humans. The clinical impact of these determinants (drug disposition, drug‐drug interactions) is also discussed.

Taxonomic study of Corynebacterium group ANF-1 strains : proposal of Corynebacterium afermentans sp. nov. containing the subspecies C. afermentans subsp. afermentans subsp. nov. and C. afermentans subsp. lipophilum subsp. nov.

We have determined the cell wall composition, guanine-plus-cytosine (G+C) contents of the DNA, rRNA gene restriction patterns, and the levels of DNA-DNA relatedness of 11 strains identified biochemically as Centers for Disease Control (CDC) Corynebacterium group absolute nonfermenter 1 (Corynebacterium group ANF-1). For seven of these strains, growth is abundant on 5% sheep blood agar, which differentiates them from the four other strains, whose growth requires a lipid supplement such as Tween 80. Two of the lipid-requiring strains produced mucoid colonies on 1% Tween 80-supplemented sheep blood agar. All strains possess cell wall component type IV, short-chain mycolic acids, and G+C contents of DNA of 66 to 68 mol% as determined by reverse-phase high-performance liquid chromatography. DNA-relatedness experiments by an S1 nuclease procedure showed that nine of these strains, including two of the lipid-requiring strains, constitute a new genomic species less than 40% related to Corynebacterium species and other coryneform groups. The lipid-requiring strain T18502 exhibited 98% DNA relatedness with another lipid-requiring strain, T88593 (difference in thermal denaturation midpoint [delta Tm] = 2 degrees C) and 71 to 77% similarity with the nonlipophilic strains (delta Tm range of from to 5 degrees C). Conversely, the DNA relatedness between strain LCDC 88199 and the six other nonlipophilic strains ranged from 86 to 100% (delta Tm range of from 1 to 3 degrees C) and was only 73 and 76% with the lipophilic strains T18502 and T88593, respectively (delta Tm, 3 and 4 degrees C). These results indicated that these two cultural types of bacteria constitute two subspecies within the new genomic species.(ABSTRACT TRUNCATED AT 250 WORDS)

High-performance liquid chromatographic assay for cefepime in serum

A simple, rapid, specific and sensitive high-performance liquid chromatographic method was developed for the determination of cefepime 1-[[(6R, 7R)-7-[2-(2-amino-4-thiazolyl) glyoxylamido]-2-carboxy-8-oxo-5-thia-1-azabicyclo- [4.2.0]oct-2-en-3-yl]methyl]-1-methylpyrrolidinium hydroxide, inner salt, 7(2)-(Z)-(O-methyloxime) in human serum. Separation was achieved on a reversed-phase Ultrasphere XL-ODS column (75 x 4.6 mm I.D.). The mobile phase was 7% acetonitrile in 20 mM ammonium acetate (pH 4). Cefepime eluted in the range of 1.8-2.2 min. Detection was by UV absorbance at 254 nm. The lower limit of quantitation of cefepime in plasma was 0.5 microgram/ml. The average absolute recovery was 106.2 +/- 2.1%. The linear range was from 0.1 to 50 micrograms/ml, with a correlation coefficient greater than 0.999. The within-day C.V.s for human samples were 4.9 and 2.3% for 1 and 50 micrograms/ml, respectively. The between-day C.V.s for human serum samples were 14.5, 7.4 and 6.7 for 1, 25 and 50 micrograms/ml, respectively. Cefepime was found to be unstable in serum at room temperature. For delayed assay, samples must be stored at -80 degrees C.

Antibiotic-impregnated plaster of Paris beads. Trials with teicoplanin.

Teicoplanin-impregnated plaster of Paris beads were made and in vitro release properties were studied. Teicoplanin was released in an initial massive dose, with a rapid decline during the first three days, followed by a slowly declining prolonged release up to 30 days. The release tested by diffusion in gelose and high-performance liquid chromatography was found to be 21.4% and 28.2%, respectively, of the amount theoretically present in the beads. Plaster of Paris is a resorbable, nontoxic biomaterial that has already been used to fill dead spaces in bone and deliver antibiotics in the treatment of chronic osteomyelitis. The addition of teicoplanin, a new antistaphylococcal agent with low known bacterial resistance, is a promising alternative. Follow-up tests in vivo, simulating local conditions of the osteomyelitic bone, are necessary to prove efficacy.

Moxifloxacin Efficacy and Vitreous Penetration in a Rabbit Model of Staphylococcus aureus Endophthalmitis and Effect on Gene Expression of Leucotoxins and Virulence Regulator Factors

ABSTRACT Bacterial endophthalmitis is a serious complication of ocular surgery and of eye trauma; the leading causative organisms are Staphylococcus aureus strains. Tissue damage is due both to the host inflammatory response and to toxin synthesis by bacteria. Systemic treatment remains difficult because most antibiotics show poor ocular penetration. Moxifloxacin (MXF), a novel fluoroquinolone, was evaluated for its penetration into the vitreous of normal rabbit eyes and of eyes of rabbits infected for 24 h with methicillin-susceptible and methicillin-resistant S. aureus (MSSA and MRSA) following a single intravenous administration of 5 or 20 mg/kg. MXF penetration was rapid and efficient regardless of the dose, ranging from 28 to 52%. An inflammatory state of the vitreous significantly increased penetration after the 20-mg/kg dose, with penetration reaching 52%. Concentrations determined in the vitreous cavity following a 20-mg/kg administration showed a 3.5-fold decrease of the bacterial density within 5 h for MSSA (MIC, 0.125 μg/ml) and a 1.6-fold decrease for MRSA (MIC, 4 μg/ml) strains, respectively. By using a semiquantitative reverse transcription-PCR method, the expression of luk-PV and hlgCB, but not hlgA, encoding staphylococcal leukotoxins, was detected in the vitreous without MXF treatment. A slight decrease in the expression of leucotoxins and sarA, agr, and sigB virulence regulatory factors was observed 1 h following the administration of 5 mg of MXF per kg.