Optimizacion de una tecnica de cromatografia liquida de alta eficacia para la determinacion de lamotrigina en plasma humano / Optimisation of a high-efficiency liquid chromatography technique for measuring lamotrigine in human plasma

Objetivo Optimizar el metodo bioanalitico HPLC-UV empleado hasta el momento en el Hospital Clinico Universitario de Salamanca, para la determinacion de los niveles plasmaticos de la lamotrigina (LTG).Material y métodos La tecnica analitica de HPLC-UV desarrollada y utilizada hasta el momento (..) (AU)

Objective The purpose of this study was to optimise the HPLC-UV bio-analytical method currently used by the Salamanca University Clinical Hospital for determining lamotrigine plasma levels. Material and methods The developed HPLC-UV analytic technique currently in use was shown to be linear, exact and precise, and suitable for use in routine monitoring of lamotrigine levels. The drawback of this method has always been the time required for analysing samples, so our aim was to improve on that elapsed time. That improvement involved using a different chromatographic column from the one used up until now. We replaced the column that was normally used (Kromasil-100C18¨C5¦Ìm-15*0.4cm with a LiChroCART-RP18e¨C3¦Ìm-5.5*0.4cm); in both cases, a liquid-liquid extraction was performed and the same sample extraction protocol was followed. Results Both validation methods showed that the two column types are valid for routine lamotrigine monitoring. Conclusion The decrease in retention time, in addition to a lower quantification limit and better precision and accuracy parameters obtained with the LiChorCART column, suggest that this unit is ideal for use in clinical practice because it enables a large number of determinations to be performed in less time and the greater precision of LTG measurements (AU)

[Optimisation of a high-efficiency liquid chromatography technique for measuring lamotrigine in human plasma]. / Optimización de una técnica de cromatografía líquida de alta eficacia para la determinación de lamotrigina en plasma humano.

OBJECTIVE: The purpose of this study was to optimise the HPLC-UV bio-analytical method currently used by the Salamanca University Clinical Hospital for determining lamotrigine plasma levels. MATERIAL AND METHODS: The developed HPLC-UV analytic technique currently in use was shown to be linear, exact and precise, and suitable for use in routine monitoring of lamotrigine levels. The drawback of this method has always been the time required for analysing samples, so our aim was to improve on that elapsed time. That improvement involved using a different chromatographic column from the one used up until now. We replaced the column that was normally used (Kromasil-100C18-5 microm-15*0.4 cm with a LiChroCART-RP18e-3 microm-5.5*0.4 cm); in both cases, a liquid-liquid extraction was performed and the same sample extraction protocol was followed. RESULTS: Both validation methods showed that the two column types are valid for routine lamotrigine monitoring. CONCLUSION: The decrease in retention time, in addition to a lower quantification limit and better precision and accuracy parameters obtained with the LiChorCART column, suggest that this unit is ideal for use in clinical practice because it enables a large number of determinations to be performed in less time and the greater precision of LTG measurements.

Degradation of tetradecyltrimethylammonium by Pseudomonas putida A ATCC 12633 restricted by accumulation of trimethylamine is alleviated by addition of Al 3+ ions.

AIMS: To establish if tetradecyltrimethylammonium (TDTMA) might be degraded by pure culture of Pseudomonas strains, and how the presence of a Lewis' acid in the medium influences its biodegradability. METHODS AND RESULTS: From different strains of Pseudomonas screened, only Pseudomonas putida A ATCC 12633 grows with 50 mg l(-1) of TDTMA as the sole carbon and nitrogen source. A monooxygenase activity catalyzed the initial step of the biodegradation. The trimethylamine (TMA) produced was used as nitrogen source or accumulated inside the cell. To decrease the intracellular TMA, the culture was divided, and 0.1 mmol l(-1) AlCl(3) added. In this way, the growth and TDTMA consumption increased. The internal concentration of TMA, determined using the fluorochrome Morin, decreased by the formation of Al(3+) : TMA complex. CONCLUSIONS: Pseudomonas putida utilized TDTMA as its sole carbon and nitrogen source. The TMA produced in the initial step of the biodegradation by a monooxygenase activity was used as nitrogen source or accumulated inside the cell, affecting the bacterial growth. This effect was alleviated by the addition of AlCl(3). SIGNIFICANCE AND IMPACT OF THE STUDY: The use of Lewis' acids to sequester intracellular amines offers an alternative to achieve an efficient utilization of TDTMA by Ps. putida.

Psychological predictors of admission and discharge global assessment of functioning scale scores for geropsychiatric inpatients.

This study examined psychological predictors of Global Assessment of Functioning Scale scores (GAF) at intake and at discharge for geropsychiatric inpatients. A total of 301 predominantly male geropsychiatric inpatients were recruited from the Houston Veterans Affairs Medical Center. Path analysis was used to test a model proposing causal paths of psychological predictors (cognitive status, depression, agitation, general psychiatric status) to GAF scores on admission and discharge. At admission, all four psychological predictors had positive paths to the admission GAF scale scores but at discharge, only two (i.e., cognitive status and general psychiatric status) of the four psychological predictors had positive paths to the discharge GAF scale scores. The admission GAF scale scores also had a positive path to the discharge GAF scale scores. The overall functioning level of geropsychiatric inpatients may be predicted by measures which assess overall cognitive status and general psychiatric functioning during hospitalization. Results prompt consideration of a modified global scale specifically reflecting an older adult's activities during this period of life.

Lamotrigine analysis in blood and brain by high-performance liquid chromatography.

A reversed-phase high-performance liquid chromatography assay was developed and validated to determine plasma and brain lamotrigine concentrations allowing pharmacokinetic-pharmacodynamic studies of this new antiepileptic drug in patients and laboratory animals. Lamotrigine and its internal standard were extracted, under alkaline conditions, from plasma and brain homogenate, into ethyl acetate; brain proteins were previously precipitated with trichloroacetic acid. The method was linear between 0.1 and 15.0 mg/l for plasma, with a detection limit of 0.008 mg/l, and between 0.1 and 5.0 mg/l for brain homogenate, with a detection limit of 0.023 mg/l. The method proved to be simple, useful and appropriate, not only for clinical and experimental research, but also for routine monitoring of lamotrigine concentrations in patients.

A review of the isolated kidney as an experimental model for pharmacokinetic studies.

Traditional distribution studies have been based on methods affording steady-state partition coefficient or sparsely defined tissue profiles. Isolation organ techniques provide a methodology for complete description of drug disposition at any particular tissue; the kidney constitutes a case for importance for those drugs eliminated by renal excretion of those whose toxicological or pharmacological target space is located at this level. The aim of the present review is to analyze the use of the isolated perfused kidney in pharmacokinetic studies and its potential in this field.

Influence of verapamil and digoxin on the in vitro binding of doxorubicin to the rat heart.

A study has been carried out to characterize the binding of doxorubicin to heart homogenates and subcellular fractions. The technique chosen to perform the study was equilibrium dialysis and the levels of anthracycline in the samples obtained from the dialysis were assessed using HPLC. Doxorubicin has high affinity to heart homogenates and subcellular fractions such as nuclear, mitochondrial and microsomal. The binding was saturable and dose-dependent. Doxorubicin binding is decreased in the presence of digoxin and especially verapamil.

Pharmacokinetic parameters of netilmicin and protective effect of piperacillin regarding nephrotoxicity caused by netilmicin.

The pharmacokinetic interaction of Netilmicin and Piperacillin has been studied as well as the potential protective effect that Piperacillin exert on nephrotoxicity caused by Netilmicin, when both antibiotics are administered to rabbits by single and multiple dosage regimens. Netilmicin was administered at a dose of 7 mg/kg and 12 h interval, which allometrically correspond to 5 mg/kg at 24 h interval for men. Piperacillin was administered at a dose of 280 mg/kg at 12 h interval (the total number of doses of both antibiotics was 20). After single and multiple dose regimens plasma level curves of Netilmicin and renal concentration were determined using an HPLC technique. Besides that, an histologic study was carried out by electronic microscopy to determine the renal damage. A significant variation of some pharmacokinetic parameters of Netilmicin such as Vc and t(1/2) was observed when Netilmicin is administered together with Piperacillin; a similar modification in the renal accumulation and renal damage caused by Netilmicin was shown.

Study on pharmacokinetics and nephrotoxicity of netilmicin in rabbits using a new dosage regimen.

The potential nephrotoxicity and pharmacokinetic parameters of netilmicin were investigated in rabbits after single and multiple dosage regimens (7 mg/kg/12 h) allometrically equivalent to a once-daily regimen of 5 mg/kg/24 h in man. Netilmicin was determined in plasma and renal tissue by a high-performance liquid chromatography (HPLC) technique with fluorescence detection and precolumn derivatization. The renal toxicity was determined by electron microscopy. Statistical comparison between animals that received a single dose and those that received a multiple dosage regimen showed that the only parameter significantly different was the elimination constant K10. The histological study revealed a high interindividual variability in the nephrotoxicity induced by prolonged treatment with netilmicin: 50% of the animals experienced tubular necrosis and the remaining did not. Although plasma concentration time curves did not show significant differences between both groups of animals, the concentrations of netilmicin in renal cortex were higher in the group with tubular necrosis. In conclusion, even though netilmicin was administered in a dosage regimen equivalent to once-daily administration in man, it induced tubular necrosis which was probably related to the duration of treatment. The results also showed that there was no correlation between plasma concentrations of the drug and its potential nephrotoxicity.

Irrational beliefs and depressive symptoms among younger and older adults: a cross-sectional comparison.

The present study explored age differences in the expression of depression. Such differences were quite apparent. Among 118 young adults and 107 community-residing elderly individuals, it was found that in the young adult groups, cognitive belief factors labeled "externality/control" and "dependency/emotionality" were associated with both affective and cognitive aspects of depression, but not somatic depressive symptoms over and above the influence of sociodemographic factors. In contrast, among older adults, a cognitive belief factor labeled "cognitive-emotional rigidity/dependency" was uniquely associated with both affective and somatic depressive symptoms. Additionally, a second cognitive factor, labeled "adaptation/internal control" defined in terms of the absence of irrational thinking about adaptation and control, was negatively related to somatic depressive symptoms. For each sample, poorer health was associated with greater depressive symptomatology. While these findings generally tend to support a cognitive view of depression in adulthood, they also underscore the importance of cognitions that may be adaptive which mitigate distress among older persons.

Hopelessness in community-residing aged persons: a viable construct?

Previous work with the Geriatric Hopelessness Scale (GHS; Fry, 1984, 1986) suggests that it may be a useful measure of pessimism for a variety of domains among elderly persons. One hundred seven community-residing aged persons were individually administered the GHS and a variety of personality and cognitive functioning measures in an effort to further refine and validate the GHS. Results suggest very modest internal consistency and a poorly defined factor structure for the GHS, in contrast to earlier findings. Although the GHS failed to differentiate elderly persons by age, it was nonetheless related to self-esteem, depression, self-rated health, internality, morale, and life satisfaction. Taken together, these data indicate that the research and clinical utility of the GHS with community-residing aged persons may be more limited than previously believed.

Open-loop feedback control of serum bentazepam concentrations and Bayesian estimation in multiple dosage regimens in patients.

The time course of serum levels of bentazepam was studied in 10 patients receiving anxiolytic agent orally at a dose of 25 mg on multiple dosage regimens with dosage intervals of 8 and 12 h. Using the methods of "open-loop feedback control", no linear regression programs and Bayesian estimation, it was possible to establish the best estimates of the pharmacokinetic parameters corresponding to the single-compartment model for each patient from all their data relating to the serum levels obtained after the first dose and after multiple dosing with different regimens. The application of the Kruskal Wallis test showed that there were only statistical differences for the absorption constant, determined with and without Bayesian estimation. However, no statistically significant differences were found on comparing the experimentally obtained serum levels with the corresponding theoretical values calculated independently for each patient from the parameters established with and without Bayesian estimation. As population pharmacokinetic parameters of bentazepam, the following were established: Ka = 2.330 +/- 0.665 l/h; Vd = 1.209 +/- 0.546 l/Kg and Ke = 0.160 +/- 0.118 l/h, corresponding to a mean value for the elimination half-life of 4.33 h.

Adaptive and bayesian control of digoxin in geriatric patients.

The study was carried out in a total of 22 patients classified in two groups: Group "A" (n = 12) was constituted by geriatric patients with cardiac failure diagnostic and with digoxin treatment previously to start our study. Group "B" (n = 10) was also constituted by geriatric patients, but with arteriosclerosis diagnostic and without prior digoxin treatment. Doses of 0.25 mg of digoxin was administered by oral route in a multiple dosage regimen with dosification at times of 0, 24, 48, 72 and 96 h. Samples of blood were obtained at 0, 0.5, 1.75, 7, 24, 49.75, 72 and 168 h after the first administration. The classics one and two-open kinetic model were considered. The elimination constant (Ke) was estimated in function of creatinine clearance (Clcr) according to the following expression: Ke = Kslope * Clcr. The mean value of kinetic parameters established were: For one-compartment kinetic model: Ka = 15.2 and 15.7 h-1, Vd = 5.4 and 4.5 l/Kg and Kslope 0.0006 and 0.0001 min/ml * h for groups "A" and "B", respectively. For two-compartment kinetic model: Ka = 11.5 and 3.6 h-1, K12 = 0.7 and 0.8 h-1, k21 = 0.2 and 0.2 h-1, Vc = 2.7 and 1.9 l/Kg and Kslope 0.0002 and 0.0002 min/ml * h for groups "A" and "B", respectively.

Growth of rural and urban children in the valley of Oaxaca, Mexico.

Weight, stature, arm circumference, and the triceps skinfold were measured in 1,410 school children, 6 through 14 years of age, from two urban colonies in the city of Oaxaca de Juarez (n = 479), and from two rural Ladino (n = 467) and two rural Zapotec (n = 464) communities in the Valley of Oaxaca in southern Mexico. Children from rural Ladino communities and urban colonies are significantly taller, heavier, and more muscular than children in rural Zapotec communities. The differences between rural Ladino and urban colonia children favor the former, particularly for weight and stature. These observations thus suggest 1) that children in the rural, indigenous communities in the Valley of Oaxaca are relatively undernourished compared to children in Ladinoized and urban communities, and 2) that rural-to-urban migration does not necessarily result in improved growth status.

Growth of rural and urban children in the valley of Oaxaca, Mexico.

Weight, stature, arm circumference, and the triceps skinfold were measured in 1,410 school children, 6 through 14 years of age, from two urban colonias in the city of Oaxaca de Juarez (n = 479), and from two rural Ladino (n = 467) and two rural Zapotec (n = 464) communities in the Valley of Oaxaca in southern Mexico. Children from rural Ladino communities and urban colonias are significantly taller, heavier, and more muscular than children in rural Zapotec communities. The differences between rural Ladino and urban colonia children favor the former, particularly for weight and stature. These observations thus suggest 1) that children in the rural, indigenous communities in the Valley of Oaxaca are relatively undernourished compared to children in Ladinoized and urban communities, and 2) that rural-to-urban migration does not necessarily result in improved growth status.

Age of menarche in Oaxaca, Mexico, schoolgirls, with comparative data for other areas of Mexico.

Status quo menarcheal information was collected for a mixed urban colonia and rural sample of 315 girls in the Valley of Oaxaca, Mexico. Comparative status quo data for girls from four major urban centres in Mexico, and for a rural sample were also analysed. Median age at menarche (estimated by probit analysis) for Oaxaca girls was 14.27 +/- 0.20 years, about 0.5 year later than that for the rural sample from Tampico-Altamira, Tamaulipas (13.79 +/- 0.20 years), and approximately 1.5 years later than that for girls from the four urban centres in Mexico (12.55 +/- 0.10, 12.61 +/- 0.08, 12.75 +/- 0.10, 12.76 +/- 0.07 years). The timing of menarche in Oaxaca girls is similar to that for rural Mayans in Guatemala. Ages at menarche for urban Mexican girls are somewhat lower than those for girls of North-west European ancestry and of North American girls of European ancestry.