Biomedical subjects
Publications and source records attributed to F Bressolle.
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A procedure is proposed for the quantitative determination of both benzoic and sorbic acids in fruit beverages. This method is carried out by direct ultraviolet spectrophotometric measurements in silica chromatoplates after development with chloroform-methanol-water (65 + 35 + 7) and makes use of an internal standard. Applied to samples spiked with benzoic and sorbic acids, this technique gives accurate and reliable results with good recoveries. The sensitivity (about 1 ppm) is particularly convenient for trace level determination.
Assays are proposed for sulpiride and other benzamides, vincamine and naftazone in plasma (or blood) and urine with direct UV reflectance spectrophotometry on this are applied directly on TLC along with a calibration curve on each plate. Plasma (or total blood) samples are extracted, and an internal standard is added before aplication; slopes of the obtained calibration curves do not change significantly from plate to plate, thus allowing several determinations on the same plate. The sensitivity is 2 microgram in a 1-ml sample (amount applied 30 ng) for sulpiride and related compounds and about the same for vincamine. Naftazone is determined in plasma with simultaneous reflectance and transmittance spectrophotometric measurements at 520 nm on chromatoplates sprayed with lead acetate, the sensitivity reached is 10 ng in a 1-ml sample (amount applied 0.5 ng). For all drugs studied, the proposed techniques are specific, reliable and sensitive enough and can be used to perform pharmacokinetic studies in human or in animal after administration of doses in the therapeutic range.
The relative bioavailability of 100 mg canrenone capsules and the commercial 50 mg capsules has been determined in 12 healthy male subjects. The study was conducted in a cross over design. After the absorption phase canrenone plasma concentrations followed a biexponential decay. The half lives of the three phases observed were respectively 40.7 +/- 21.7 min, 1.94 +/- 0.558 hr and 18.5 +/- 3.93 hr after administration of a 100 mg capsules; they were respectively 31.8 +/- 14 min, 1.64 +/- 0.513 hr and 16.1 +/- 3.09 hr after administration of two 50 mg capsules. These values were similar to those reported in man. Bioequivalence of the two forms tested was ascertained by a two way analysis of variance and by the Westlake symmetrical confidence interval (95%). Peak plasma levels, Cmax, time to reach the peak, tmax, and the rate constant of absorption showed great inter and intra individual variations. In vivo hydrolysis of canrenone into canrenoic acid and subsequent lactonization of the acid are pH-dependent and could give rise to these variations if occurring before absorption.
We retrospectively analyzed amikacin pharmacokinetics in 19 critically ill patients who received amikacin intravenously. Fourteen subjects (577 serum amikacin concentrations, 167 urine measurements) were studied to obtain data for population modeling, while 5 patients (267 serum amikacin concentrations, 68 urine measurements) were studied for the assessment of predictive performance. The population analysis was performed using serum and urine amikacin measurements; the renal clearance of amikacin was expressed as a function of creatinine clearance. A two-compartment model was fitted to the population data by using NONMEM. The population characteristics of the pharmacokinetic parameters (fixed and random effects) were estimated using the FOCE method. The population pharmacokinetic parameters with the interindividual variability (CV%) were as follows: slope (0.254, 126%) and intercept (3 l/h, 59.6%) of the linear model which relate the amikacin renal clearance to the creatinine clearance, initial volume of distribution (17.1 l, 22.2%), intercompartment clearance (5.22 l/h, 104%), steady state volume of distribution (55.2 l, 64.1%) and urinary elimination (67.5%, 36.3%). The Bayesian approach developed in this study accurately predicts amikacin concentrations in serum and urine and allows for the estimation of amikacin pharmacokinetic parameters, minimizing the risk of bias in the prediction.
AIM OF THE STUDY: SFU-dose adaptation optimal schedule using bimonthly LV5FU2 regimen was modulated by previously validated individual pharmacokinetic parameters, in 38 patients with advanced colorectal cancer. METHODS: At the 1st cure, 5F-U pharmacokinetic parameters (particularly the area under curve (AUC) in mg.h/l.m2) were calculated in all patients. In 19 patients (A), 5FU infusion doses were progressively increased from 25 to 50% (at every cycle), according to AUC levels from 2nd to 6th; in 19 consecutive patients (B), 5FU infusion doses were increased, at the same time, at the 2nd cure, according to a protocol taking in account AUC at the 1st cure: increase of 150% it AUC < 5, of 100% if 5 < AUC < 10, of 50% if 10 < AUC < 15, of 25% if 15 < AUC < 20 in case of toxicity < grade 3. RESULTS: a) AUC in all patients, at the beginning of the treatment averaged 9.05 +/- 3.115 (range from 3.9 to 16.41). Large interindividual variability was observed. b) FU infusion doses at the 2nd cure, increased 40% in group A and 82% in group B. Corresponding AUC increased respectively of 42% and 96%. 3-WHO toxicity 23 (per cycle) occurred not very frequently (8% haematological, 6% digestive and 2% cutaneous toxicity) and remained acceptable. CONCLUSION: This feasibility study established a 5FU-dose intensification optimal strategy within the bimonthly LV5FU2 schedule with a control for the risk of toxicity. This study constitutes the basis for a multicentre phase II trial to evaluate the importance of this approach in terms of efficacy and survival.
The objective of this study was to determine the pharmacokinetic profile of total platinum administered by hyperthermic peritoneal perfusion (HPP) in 16 patients with ovarian cancer. The patients had a performance status of lIIalpha/b/c on the FIGO scale. They received 60, 80 or 100 mg of cisplatin. The percent of cisplatin remaining in the body after the peritoneum was emptied averaged 65% (41.7-85.4%). The average ratio between peritoneal drug concentrations and plasma concentrations was 73. A Bayesian estimation of individual phamacokinetic parameters was carried out using the non-linear mixed-effect modeling approach as implemented in the NONMEM computer program. A two-compartment model with an additional peritoneal cavity compartment was used to fit the data. Large interindividual variability of the pharmacokinetic parameters occurred The maximum platinum concentration in plasma was reached between 1 and 1.5 hours after the beginning of administration; it ranged from 0.37 to 1.7 microg/ml (1.9 to 8.72 microM). The elimination half-life was 80 hours (48-152 hours and the area under the plasma concentration time curve normalized to a 100 mg cisplatin dose was 79 mg/liter x hours. The simultaneous fit of perfusate and plasma concentrations allowed us to estimate the percent of cisplatin that reached the systemic circulation at about 20%. At time infinity, the urinary cisplatin recovery accounted for only 20% of the administered dose. The results in this study showed that a high proportion of the cisplatin dose was absorbed by target tumor cells. In spite of the advanced disease of patients at the time of HPP, 37.5% of them were still alive three years after HPP (ie., 3-6 years after cancer diagnosis) and 12.5%, 7 years after HPP (i.e., 8 years after cancer diagnosis).
The metabolism of the main beta-adrenoceptor stimulants which are not catechol derivatives involves conjugation with glucuronic or sulphuric acids in several animal species and conjugation with sulphuric acid in man. These drugs are not metabolized by MAO like isoproterenol or by COMT like the catechol derivatives: isoproterenol, trimetoquinol, hexoprenaline and rimiterol. Sulphate conjugation, in man, increases with the number of hydroxy groups. For salbutamol, pirbuterol, terbutaline and fenoterol, about 30%, 30%, 15% and 10% are respectively present in plasma as the unchanged active compound. Clenbuterol, a new specific beta 2-adrenoceptor stimulant, is a 4-amino-3,5 dichloro-benzene derivative and cannot be conjugated. It is cleared from the body mainly by the renal route (43% of the administered dose) and has eight minor metabolites, identical in several animal species and in man. Tulobuterol with no hydroxy substitute does not undergo conjugation, but is metabolized to 4-hydroxy tulobuterol. This metabolite is shown to be eight times more potent than tulobuterol. Metabolism depends greatly upon the route of administration: intravenous, subcutaneous, oral, by aerosol or instillation into the bronchial tree. Conjugation or COMT inactivation can take place in the gut wall (terbutaline), in lungs (isoproterenol, terbutaline, rimiterol) or by hepatic first-pass. These processes decrease the amount of drug reaching the blood and the receptor sites. Metabolism in the lung is important for ibuterol (terbutaline diisobutyrate), which is more lipophilic than terbutaline and spreads throughout tissues where it is hydrolyzed to active terbutaline. Biotransformations are determined by environmental or genetic factors and by the associated therapy and can change dramatically from one patient to another (interindividual variability) or for the same patient by multiple dosing (intra-individual variability). These differences in the rates of the metabolism can explain, partly, the differences observed in the response to beta-adrenoceptor stimulants by responder or non-responder patients. Decision about a therapeutic dosage regiment involves the choice of the drug, of the route of administration and of the dose. This choice is made on the basis of the dose/response relationship. In the kinetic approach, pharmacokinetic data obtained after a single dose facilitate the development of an appropriate dosage regimen.
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OBJECTIVE: To determine the correlation between the pharmacokinetic (PK) parameters of methotrexate (MTX), clinical status and laboratory test results in rheumatoid arthritis (RA) patients. METHODS: 22 patients (4 M/18F, mean age: 50 +/- 12 years, mean duration of RA: 8.5 +/- 6.5 years, mean duration on MTX: 8 +/- 10 months) were included in a prospective study. The mean dose of MTX administered was 6 +/- 0.7 mg/m2 of body area/week. No patient received any nonsteroidal antiinflammatory drug (NSAID). Blood and urine samples were collected over 24 hours (9 blood samples). The MTX concentrations were assayed by fluorescence polarization immunoassay. Clinical parameters (Ritchie articular index, morning stiffness, joint pain count, joint swelling count), hematological, liver and renal function tests, and ESR were recorded. Correlations between the patients' PK parameters, laboratory tests and clinical status were carried out using Pearson's correlation coefficient test. RESULTS: A significant correlation was observed between the Ritchie articular index, morning stiffness and the area under the curve (p = 0.009 and p = 0.026, respectively). No correlation was found with the other parameters. CONCLUSION: These results suggest that when the patient's disease activity is higher, the AUC becomes more important, reflecting a greater body exposure to MTX.
Although medications continue to be used extensively in the hospitalized paediatric patient, our knowledge regarding many of these agents remains limited. To date, apart from anecdotal case reports or studies involving a very limited number of patients, few data regarding the dosing and usage of medications in neonates and paediatric patients are available in the literature. This work has been conducted in order to provide sources of information on the intravenous administration of medication to these patients. All recommendations should be individualised in accordance with the clinical situation.
The pharmacokinetics of melphalan following high-dose (140 mg/m2) i.v. administration were determined in 20 patients with advanced malignancies undergoing peripheral blood hematopoietic progenitor-cell transplantation. Melphalan was assayed in plasma by a specific HPLC method with UV detection. Plasma levels of melphalan declined in a biexponential fashion with a mean terminal half-life of 83 minutes (range 52-168 minutes). Estimated peak plasma concentrations ranged from 1.65 to 14.5 micrograms/ml. Plasma levels were lower than the limit of quantitation of the method used (20 ng/ml) 24 hours after drug administration. The average volume of distribution and total clearance were 317 ml/min/m2 (range 127-797 ml/min/m2) and 37.9 l/m2 (range 15.4-108 l/m2), respectively. These parameters are similar to those reported in the literature. A weak correlation was found between total clearance of melphalan and creatinine clearance (p < 0.05). No relationship between the pharmacokinetics of melphalan and myelosuppression and non-hematologic toxicities was recovered. This pharmacokinetic study indicates that on the assumption that there is no more circulating melphalan after seven elimination half-lives, it may be possible to reinfuse autologous PBPC 10-20 hours after melphalan administration.
Mycobacterium avium complex (MAC) infections are the most frequent opportunistic infections in AIDS. Since progress in antiretroviral drugs enables AIDS patients to survive longer, these infections involve an increasing number of sick people. Few controlled assays have evaluated the efficiency of several antibiotics. When used in monotherapy, clarithromycin (one gram twice a day) appeared as the most efficient drug while the effectiveness of azithromycin, clofazimine, rifampin and liposomal encapsulated gentamicin have not been truly proved. Due to its bacteriologic and clinical effects, the most interesting polytherapeutic scheme is the association of clarithromycin (1 g twice a day), ethambutol (15 mg per kg and per day) and rifabutin (600 mg per day).
The pharmacokinetics of 5-fluorouracil (5-FUra) were investigated in 16 patients with metastatic colorectal cancer receiving high-dose folinic acid (LV 200 mg/m2) followed by 5-FUra bolus (400 mg/m2) and continuous infusion (600 mg/m2) on days 1 and 2. Quantitation of unchanged drug was assessed by a highly specific high-performance liquid chromatographic method. The concentrations of 5-FUra at the end of the loading dose averaged 30.7 +/- 13.2 micrograms/ml (i.e., 236 microM). The steady-state plasma concentration averaged 0.31 +/- 0.11 microgram/ml (i.e., 2.4 microM). 5-FUra plasma levels declined rapidly after the end of infusion with an apparent elimination half-life of 7.08 +/- 3.21 minutes. Clearance ranged from 776 to 3023 ml/min/m2. Large patient-to-patient variations in plasma 5-FUra concentrations were observed. No toxicity greater than WHO grade 2 was seen. One patient experienced grade 1 stomatitis and two others experienced grade 1 and 2 myelosuppression. One patient developed diarrhoea and another suffered asthenia. Nausea and vomiting were observed in 5 patients.
The purpose of this work was to determine the role of methyl-beta-cyclodextrin (MEBCD) in combination with doxorubicin (DOX) on DOX intracellular accumulation and efflux, in comparison to verapamil in a sensitive parental and multidrug-resistant human cancer cell line (HL-60 S and HL-60 R). Moreover, cell membrane and nuclear modifications induced by MEBCD were investigated. At concentration of 10 mumol for 10(6) cells, MEBCD combined with doxorubicin (DOX), was able to significantly enhance the intracellular concentration of DOX in HL-60 S and HL-60 R cell lines during the period of exposure. In the resistant subline, MEBCD activity was higher than that of verapamil. Moreover, treatment of cells with MEBCD resulted in a modification in cell membrane integrity and cell morphology, but had no own activity in the distribution of the cells within cell cycle.