Rapid high-performance liquid chromatographic measurement of buspirone in human plasma after overdose.

For toxicological purposes, a rapid reversed-phase high-performance liquid chromatographic method was developed for the determination of the anxiolytic drug, buspirone, in human plasma. A liquid-liquid procedure was used to extract this compound from plasma in the presence of an internal standard, quinupramine. The analysis was performed on a Spherisorb S5 C8 analytical column with UV detection at 240 nm. No endogenous compounds were found to interfere. A linear response was observed over the concentration range 5-100 ng/mL. A good accuracy (bias < or =7.9%) was achieved for all quality controls, with intra-day and inter-day variation coefficients equal or less than 7.6%. The limit of quantification was 5 ng/mL. Stability of buspirone in plasma stored at different temperatures was checked. This rapid method (run time <12 min) was used to manage an acute poisoning involving buspirone.

Direct injection HPLC micro method for the determination of voriconazole in plasma using an internal surface reversed-phase column.

A direct plasma injection liquid chromatographic method has been developed for the determination of a new triazole antifungal agent, voriconazole, using an internal surface reversed phase column. Therapeutic drug monitoring of voriconazole is relevant for patient management, especially in the case of drug-drug interaction. The method is easy to perform and requires 10 microL of a plasma sample. The chromatographic run time is less than 9 min using a mobile phase of 17:83 v/v acetonitrile-potassium dihydrogen phosphate buffer, 100 mM, pH 6.0 and UV detection at 255 nm. The fl ow rate was 1 microL/min. A linear response was observed over the concentration range 0.5-10 microg/mL (r2 = 0.977). A good accuracy (bias < or = 7.5%) was achieved for all quality controls, with intra-day and inter-day variation coefficients inferior to 6.7%. The lower limit of quantitation was 0.2 microg/mL, without interference of endogenous components. The stability of voriconazole in plasma stored at different temperatures was checked. Finally, the possibility of direct injection of plasma samples into the column permits a reduction in reagent consumption and in analytical steps, and hence in analytical error.

HPLC microdetermination of flurbiprofen enantiomers in plasma with a glycopeptide-type chiral stationary phase column.

A rapid and stereospecific HPLC micromethod to quantify flurbiprofen enantiomers was developed. Both flurbiprofen enantiomers and indomethacin, used as internal standard, were extracted with methylene chloride from 100 microL of acidified plasma. The resolution of the R- and S-forms was performed on a bonded vancomycin chiral stationary phase (Chirobiotic V) with 20% of tetrahydrofuran in ammonium nitrate (100 mM, pH 5) as mobile phase. Calibration curves were linear in the range 0.5-10 microg/mL for both enantiomers. A good accuracy (< or = 5%) was obtained for all quality controls, with intra-day and inter-day variation coefficients equal or less than 7.7%. Recovery of both enantiomers was found in the range 77.4-86.3%. The lower limit of quantitation was 0.25 microg/mL for both enantiomers, without interference of endogenous components. This validated micromethod has been successfully applied for quantifying R- flurbiprofen and S- flurbiprofen in rat plasma.

[Pharmacokinetics in the elderly]. / Pharmacocinétique chez le sujet âgé.

Physiological changes that occur in the aging process may directly affect drug pharmacokinetics. In the absence of disease or other pathologic conditions, age-related changes in pharmacokinetics principally affect drug absorption, distribution, metabolism or elimination. One factor that does change consistently with age is renal clearance, consequently a common pharmacokinetic change is reduced drug clearance, especially for drugs excreted largely unchanged by the kidneys. Alteration of the pharmacokinetics of drugs in the elderly may necessitate adjustment of dosages to prevent toxicity or inadequate therapy. As a broad generalization, dosage should be reduced in elderly patients, reflecting the general decline in body function with age.

Simultaneous determination of four antipsychotic drugs in plasma by high-performance liquid chromatography. Application to management of acute intoxications.

A specific reversed phase-high pressure liquid chromatography (RP-HPLC) method has been developed for the simultaneous determination of clozapine (CZP), loxapine (LXP), zuclopenthixol (ZPT) and flupenthixol (FPT) in plasma. These four antipsychotic drugs are frequently used for the treatment of schizophrenia and other neuropsychiatric diseases. Carpipramine, a dihydrodibenzazepine, was used as an internal standard (I.S.). A liquid-liquid procedure was used to extract the drugs from human plasma. The analysis was performed on a XTerra MS C18 column with UV detection. Calibration curves were linear in the range 50-1000 microg/l. The limit of quantification (LOQ) was 15 microg/l for clozapine and loxapine and 20 microg/l for zuclopenthixol and flupenthixol. The coefficient of variation (CV) for intra- and inter-day precision was 7.2% or less with accuracies within 10% for the three concentrations.This isocratic and rapid method (run time<10 min) is useful for the management of acute intoxication.

Rapid high-performance liquid chromatographic measurement of amisulpride in human plasma: application to manage acute intoxication.

Amisulpride, a substituted benzamide derivative, is a second-generation (atypical) antipsychotic and is effective as maintenance therapy in patients with schizophrenia. For toxicological purpose, a rapid RP-HPLC assay was developed for the determination of amisulpride in human plasma. A linear response was observed over the concentration range 100-1000 ng/ml. A good accuracy (< or =5%) was achieved for all quality controls, with intra- and inter-day variation coefficients equal or inferior to 4.9%. The lower limit of quantification was 20 ng/ml, without interferences of endogenous components. This rapid method (run time <5 min) was used to monitor eight intoxications involving amisulpride.

High-performance liquid chromatographic method with diode array detection to identify and quantify atypical antipsychotics and haloperidol in plasma after overdose.

For toxicological purposes, an HPLC assay was developed for the simultaneous determination of haloperidol and atypical antipsychotics (risperidone, 9-hydroxyrisperidone, olanzapine, clozapine) in human plasma. After a double-step liquid-liquid extraction, compounds were separated on a C(8) column eluted with a gradient of acetonitrile and phosphate buffer 50 mM pH 3.8. A sequential ultraviolet detection was used (260, 280 and 240 nm). Calibration curves were linear in the range 10-1000 ng/ml. The limits of quantification were 5 ng/ml for all drugs. Average accuracy at four concentrations ranged from 93 to 109%. Both inter- and intra-day variation coefficients were lower than 11% for all drugs. This simple and rapid method (run time<15 min) is currently used for poison management.

Rapid HPLC measurement of buflomedil in plasma in poisoning cases.

A rapid high-performance liquid chromatographic method for the determination of buflomedil in human plasma is described. It requires a single liquid-liquid extraction step from 1 mL of plasma with diethyl ether followed by chromatography on a Nova Pak C(18) reversed-phase column and detection by ultaviolet light. Metoclopramide was used as internal standard. The method is sensitive with a quantification limit at 500 ng/mL. It was used for the determination of buflomedil in biological fluids in poisoning cases.

[Plasmatic dosage of antiretroviral drugs by high performance liquid chromathography ]. / Dosage plasmatique des antirétroviraux par chromatographie liquide haute performance.

A high-performance liquid chromatographic method has been developed for the determination of eight antiretroviral drugs (amprenavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, efavirenz and nevirapine) in a single run. After a liquid-liquid extraction with diethylether, the antiretroviral drugs are separated on a Stability RP18 column eluted with a gradient of acetonitrile and phosphate buffer (50 mM pH 5.65). A sequential ultraviolet detection allowed for simultaneous quantitation of antiretroviral drugs (240, 215, 260 nm). Calibration curves were linear in the range 100-10,000 ng/ml. The limit of quantitation was 50 ng/ml for all drugs except for nevirapine (100 ng/ml). The accuracies ranged from 88.2% to 110.9% and both inter- and intra-day coefficients of variation were lower than 11%. The extraction recoveries were higher than 62%. This method is simple and shows good specificity with respect to commonly coprescribed drugs.

[Pharmacokinetics in the elderly]. / Pharmacocinétique chez le sujet âgé

Physiological changes that occur in the aging process may directly affect drug pharmacokinetics. In the absence of disease or other pathologic conditions, age-related changes in pharmacokinetics principally affect drug absorption, distribution, metabolism or elimination. One factor that does change consistently with age is renal clearance, consequently a common pharmacokinetic change is reduced drug clearance, especially for drugs excreted largely unchanged by the kidneys. Alteration of the pharmacokinetics of drugs in the elderly may necessitate adjustment of dosages to prevent toxicity or inadequate therapy. As a broad generalization, dosage should be reduced in elderly patients, reflecting the general decline in body function with age.

Determination of mirtazapine and its demethyl metabolite in plasma by high-performance liquid chromatography with ultraviolet detection. Application to management of acute intoxication.

Mirtazapine is a new centrally acting noradrenergic and specific serotonin antidepressant, with an active demethyl metabolite. For toxicological purposes, a specific and accurate RP-HPLC assay was developed for the simultaneous plasma determination of these compounds. A linear response was observed over the concentration range 50-500 ng/ml. A good accuracy (bias <10%) was achieved for all quality controls, with intra-day and inter-day variation coefficients less than 8.3%. The lower limit of quantification was 20 ng/ml, without interferences with endogenous or exogenous components. This rapid method (run time <12 min) was used to manage three intoxications involving mirtazapine.

Influence of a polymeric formulation of ketoprofen on its diffusion into cerebrospinal fluid in rats.

Poly(D,L)lactide nanocapsules (NCs) have been proposed as an alternative carrier for many drugs. We investigated the influence of this formulation on the pharmacokinetics of ketoprofen in the plasma and cerebrospinal fluid (CSF). Male Wistar rats were given intraperitoneal dose of ketoprofen (5 mg/kg) in a suspension of NCs or in a carboxymethylcellulose (CMC) solution (reference preparation). Blood and CSF samples were collected at different times up to 24 h after dosing. The unbound fraction of ketoprofen in plasma (f(u)) was determined using ultrafiltration. The total (C(T)) and free (C(F)) concentrations of ketoprofen in plasma and the simultaneous CSF concentrations (C(CSF)) were measured by a HPLC method and the areas under the curve (AUC(T), AUC(F), AUC(CSF)) were calculated. AUC(T) of ketoprofen-loaded NCs in plasma was similar to that of the reference solution, while AUC(F) of the former (5.41 mg/l x h) was higher than that produced by the latter (4.03 mg/l x h). Accordingly, the unbound fraction (f(u)) was higher after administration of NCs than that of the solution (2.5 and 1.8%, respectively). Finally, AUC(CSF) were identical for both formulations. These findings suggest that the binding of ketoprofen to plasma proteins is not the major factor that governs its blood-to-CSF exchanges.

In vitro distribution of ketoprofen enantiomers in articular tissues of osteoarthritic patients.

The distribution of ketoprofen enantiomers in joint tissues was studied as a function of their relative tissular affinities using the multi-chamber distribution dialysis system described by Bickel et al. Selected off-cuts of synovial membrane, joint capsule, cartilage and ligament were obtained from ten patients suffering from osteoarthritis of the knee (n=3) or hip (n=7). Sörensen solution (4 ml) spiked with racemic ketoprofen (2 microg ml(-1)) was dialysed against 1 ml of the four solutions of tissue homogenates (0.4 g ml(-1)). Ketoprofen enantiomers were quantified in buffer and tissue solutions by high-performance liquid chromatography. The distribution of ketoprofen enantiomers in the Bickel's multi-compartment model indicated that there was a non-stereoselective affinity of ketoprofen enantiomers for their potential target tissues. Despite the interindividual variability in articular tissues, the concentrations (+/-S.D.) of R- and S-ketoprofen were significantly higher in synovial membrane (8.69 (4.76) microg g(-1) for S, 9.14 (5.57) microg g(-1) for R), joint capsule (5.71 (2.49) microg g(-1) for S, 5.49 (2.62) microg g(-1) for R) and ligament (6.28 (3.61) microg g(-1) for S, 6.40 (3.64) microg g(-1) for R) than in articular cartilage (3.67 (1.75) microg g(-1) for S, 3.70 (1.67) microg g(-1) for R). There were no significant differences in the distribution of R- and S-ketoprofen between the solutions of joint capsule, synovium and ligament tissues. These data may be related to differences in ketoprofen affinity for the different constituents of joints. This in vitro distribution profile is similar to that reported in vivo for other non-steroidal anti-inflammatory drugs.

Fat distribution in obese women is associated with subtle alterations of the hypothalamic-pituitary-adrenal axis activity and sensitivity to glucocorticoids.

OBJECTIVES: Obesity with abdominal body fat distribution (A-BFD) and hypothalamic-pituitary-adrenal (HPA) axis activity are somehow linked, but the exact interactions still need clarification. Obese subjects display normal circulating plasma cortisol concentrations with normal circadian rhythms. However, when the HPA axis is pharmacologically challenged, body fat distribution matters and then A-BFD obese women differ from those with subcutaneous body fat distribution (P-BFD). We hypothesized that lower dose provocative and suppressive tests than those used to diagnose hypercortisolism of tumour origin or adrenal insufficiency would shed some light on the characteristics of the HPA axis activity in relation with body fat distribution. PATIENTS AND METHODS: Fifty premenopausal obese women were grouped according to their body fat mass distribution. Their plasma cortisol responses to (i) two low doses of dexamethasone (0.25 and 0.5 mg) with (ii) low dose of the ACTH analogue tetracosactrin (1 microg) were assessed. Salivary cortisol was also determined during the ACTH test. RESULTS: A-BFD differed from P-BFD women in terms of HPA axis responsiveness. They had comparatively: (i) increased nocturnal cortisol excretion (9.38 +/- 2.2 vs. 6.82 +/- 0.91 nmol/micromol creatinine, A-BFD vs. P-BFD, respectively, P = 0.03); (ii) increased salivary cortisol response to ACTH stimulation (1 microg) [salivary cortisol peak: 33.4 (14.1-129) vs. 28.5 (13.2-42.8) nmol/l; salivary AUC: 825 (235-44738) vs. 537 (69-1420) nmol/min/l; A-BFD vs. P-BFD, P = 0.04 for both]; and (iii) increased pituitary sensitivity to dexamethasone testing [postdexamethasone (0.25 mg) plasma cortisol levels: 163 (26-472) vs. 318 (26-652) nmol/l and postdexamethasone (0.5 mg) plasma cortisol levels: 26 (26-79) vs. 33 (26-402) nmol/l; A-BFD vs. P-BFD, P = 0.01 for both). CONCLUSIONS: These data demonstrate differences in the HPA axis activity and sensitivity to glucocorticoids between obese women differing in their body fat distribution, with both enhanced negative and positive feedback in those with abdominal obesity. Several mechanisms may explain these differences: central vs. peripheral hypotheses. Thus, abdominal obesity does not appear to be linked solely to one pathophysiological hypothesis.

Rapid high-performance liquid chromatographic measurement of venlafaxine and O-desmethylvenlafaxine in human plasma. Application to management of acute intoxications.

Venlafaxine, a second-generation antidepressant, acts by inhibition of the reuptake of presynaptic noradrenaline and serotonin. The main metabolite, O-desmethylvenlafaxine was found biologically active. For toxicological purpose, a rapid specific and accurate RP-HPLC assay was developed for the simultaneous determination of venlafaxine and O-desmethylvenlafaxine in human plasma. A linear response was observed over the concentration range 0.2-4 microg/ml. A good accuracy (<8%) was achieved for all quality controls, with intra-day and inter-day variation coefficient less than 10%. Finally, no interference was observed with other psychotic drugs encountered in acute poisoning. This rapid method (run time <10 min) was used to manage four voluntary intoxications involving venlafaxine.

Comparison of patient questionnaires, medical records, and plasma assays in assessing exposure to benzodiazepines in elderly subjects.

OBJECTIVE: Exposure in pharmacoepidemiologic studies can rely on various sources such as medical records, patient questionnaires, or plasma samples, which do not always concur. This study endeavored to compare sources of information on current exposure to benzodiazepines in elderly subjects. METHODS: In a study in a hospital admissions department, 1136 elderly subjects included in a case-control study each completed a structured questionnaire. In addition, an inspection of the medical records of each subject was performed, as well as screening of a plasma sample (high-pressure liquid chromatography--diode array detector) for current exposure to benzodiazepines. RESULTS: Benzodiazepines were found in the plasma of 33% of 1013 patients, in the records of 31% of patients, and in the questionnaires of 36% of 797 respondents. With use of the plasma results as a standard, questionnaires had 11% false positives and 28% false negatives; medical records had 14% false positives and 23% false negatives. The kappa for concordance between questionnaires and records was 0.63. Most of the errors were related to the unexpected presence in plasma of clorazepate, commonly used as a hypnotic agent. CONCLUSIONS: Patient recall and medical records are not reliable measures of current exposure to benzodiazepines in elderly persons, although this unreliability may be more marked with certain drugs used as hypnotic agents.

Chiral resolution of flurbiprofen and ketoprofen enantiomers by HPLC on a glycopeptide-type column chiral stationary phase.

Vancomycin is an amphoteric, glycopeptide, macrocyclic antibiotic. When attached to 5 microspherical silica gel, vancomycin proved to be an effective chromatographic chiral stationary phase that could be used in the reversed-phase mode. In this study, a bonded vancomycin chiral stationary phase (Chirobiotic Vtrade mark) was investigated for the chiral liquid chromatography analysis of ketoprofen and flurbiprofen. The selectivity factor (alpha) and the chiral resolution factor (RS) of Chirobiotic Vtrade mark were evaluated first as a function of the buffer pH and molarity, and second as a function of organic modifier type and composition of the mobile phase. Four organic modifiers (tetrahydrofuran, 2-propanol, 1,4-dioxane and methanol) have been tested for their selectivity. Optimized conditions using 20% of tetrahydrofuran in ammonium nitrate (100 mM, pH 5) were selected for the enantioseparation of flurbiprofen and ketoprofen from their racemic forms. At pH 5, these acidic compounds are almost negatively charged, while the chiral selector possesses a positive charge allowing it to interact electrostatistically with the analytes. Using these chromatographic conditions, the column stability was excellent over several months of experiments.

Benzodiazepines and hip fractures in elderly people: case-control study.

OBJECTIVE: To determine whether benzodiazepines are associated with an increased risk of hip fracture. DESIGN: Case-control study. PARTICIPANTS: All incident cases of hip fracture not related to traffic accidents or cancer in patients over 65 years of age. 245 cases were matched to 817 controls. SETTING: Emergency department of a university hospital. MAIN OUTCOME MEASURES: Exposure to benzodiazepines and other potential risk or protective factors or lifestyle items. RESULTS: The use of benzodiazepines as determined from questionnaires, medical records, or plasma samples at admission to hospital was not associated with an increased risk of hip fracture (odds ratio 0.9, 95% confidence interval 0.5 to 1.5). Hip fracture was, however, associated with the use of two or more benzodiazepines, as determined from questionnaires or medical records but not from plasma samples. Of the individual drugs, only lorazepam was significantly associated with an increased risk of hip fracture (1.8, 1.1 to 3.1). CONCLUSION: Except for lorazepam, the presence of benzodiazepines in plasma was not associated with an increased risk of hip fracture. The method used to ascertain exposure could influence the results of case-control studies.

Decreased pituitary sensitivity to glucocorticoids in endurance-trained men.

OBJECTIVE: Muscular exercise induces hypothalamo-pituitary-adrenal (HPA) axis activation and when regularly repeated, as in endurance training, leads to HPA axis adaptation. To assess whether non-professional endurance-trained (ET) men with a substantial training load and no clinical or biological features of HPA axis overactivity can present subtle alterations of HPA axis sensitivity to glucocorticoid negative feedback, nine ET men were subjected to HPA axis testing using the dexamethasone-corticotrophin-releasing hormone (CRH) test. DESIGN: Nine endurance-trained men and eight healthy age-matched sedentary men were studied. Morning plasma cortisol and 24 h urinary free cortisol (UFC) were determined and a low dose dexamethasone suppression test (LDDST) was performed followed by CRH stimulation (dexamethasone-CRH test). RESULTS: After a day without physical exercise, at 0800 h, plasma ACTH and cortisol concentrations, and the 24 h UFC and UFC/urinary creatinine (UC) ratio were similar in ET and sedentary men. By contrast, clear differences between the groups were seen in cortisol and ACTH responses to the dexamethasone-CRH test. In eight ET subjects, after LDDST, basal ACTH and cortisol levels were similar to those of sedentary men, whereas one ET subject displayed a poor suppression of cortisol level (131 nmol/l). After injection of CRH, however, three of nine ET men's cortisol levels were not suppressed by dexamethasone but instead displayed significant CRH-induced increase (peak cortisol: 88, 125 and 362 nmol/l). No sedentary subject exhibited any increase in cortisol levels. CONCLUSION: Three of nine ET men with a mean maximum rate of O2 uptake (VO2, max) of 61 ml/kg per min, running 50-70 km per week, were resistant to glucocorticoid suppression during the combined dexamethasone-CRH test.