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Biomedical subjects

B Rambeck

Publications and source records attributed to B Rambeck.

48 records · Page 3Linked to original sources
PubMed1981

Quantitative simultaneous determination of eight common antiepileptic drugs and metabolites by liquid chromatography.

Specific antiepileptic drug (AED) concentrations in serum are believed to cause therapeutic effects in individual patients. Communication between the clinician and the laboratory performing the drug level determinations is therefore essential for safe and effective medication. The now common practice of multiple drug therapy preferably requires simultaneous separation and quantitation of the various drugs and their metabolites. The advantages and disadvantages of current AED analysis methods are discussed. Liquid chromatography (LC) was found to be the most versatile technique for routine and research analysis and can be applied to the determination of common, less common and new AED and metabolites. Carbamazepine and its metabolite, carbamazepine-10,11-epoxide, were determined with high accuracy. The sample preparation procedures, the internal standards, and mode of LC separation used for the analysis are given. The chromatographic parameters for optimized resolution and analysis are given. The chromatographic parameters for optimized resolution and analysis time of eight AEDs and metabolites were devised with special consideration for the influence of the oven temperature on resolution. About 300 patient serum samples were analyzed by automatic unattended operation. By this method some 50 samples per day can be extracted and analysed. Quantitative results achieved by LC and gas liquid chromatography (GLC) on the same patient samples are reported and chromatograms discussed. Peak scanning was used to demonstrate the presence of compounds which could eventually interfere with the detection of phenylethylmalonamide. The overall accuracy of the employed LC method, the repeatability of retention times on three different columns, and the measured ranges of AED concentrations are reported.

Anticonvulsants↗
PubMed1980

Gas chromatographic methods for the determination of antiepileptic drugs: a systematic review.

Despite the availability of a variety of methods for determining the concentrations of antiepileptic drugs in body fluids--including thin-layer chromatography, high pressure liquid chromatography, radioimmunoassay, etc.--gas chromatography remains perhaps the routinely used tool for therapeutic drug monitoring in this area. As a result of the need to improve precision and reproducibility, as well as to reduce costs, among other factors, there has been a continuous technical improvement in the technique. And in the last 10 years, more than 100 papers have described gas chromatography for the determination of antiepileptic drugs. Needless to say, only a small percentage of these publications described methods of a significantly new character. In order to facilitate the task, of comparing methods for the purpose of choosing a technique suitable to a specific need, we have reviewed the analytic parameters described in the 114 publications of the last decade. These parameters include the following: (1) drugs determined, (2) internal standard, (3) amount of sample, (4) extraction procedure, (5) preparation of derivatives, (6) sample injection, (7) detection, (8) column support and temperature, and (9) stationary phase. We present these data in a comprehensive tabular form together with a number of comments concerning specific techniques.

Anticonvulsants↗
PubMed1979

Predicting phenytoin dose - a revised nomogram.

The nomogram devised by Richens and Dunlop for predicting phenytoin dose has been tested in 127 residential epileptic patients, and the data obtained were used to prepare a revised version of the nomogram. In a further 78 patients, this new version was found to be superior to the original. The mean Km value was found to be 23.8 mumoles/liter. Km was independent of age and body surface area, but Dmax correlated positively with the latter two variables.

Adolescent↗
PubMed1979

Pharmacological interactions of mesuximide with phenobarbital and phenytoin in hospitalized epileptic patients.

In order to study the pharmacological interactions of the anticonvulsant drugs mesuximide (MSM), phenobarbital (PB), and phenytoin (PHT), serum concentrations of N-desmethyl-mesuximide (N-DESM-MSM, the main metabolite of MSM), PB, and PHT were determined in 94 hospitalized patients suffering from petit mal epilepsy. When MSM was administered to patients on stable PB or primidone therapy, the mean concentrations of PB increased by statistically significant amounts of 38 and 40%, respectively. Similarly, the additional administration of MSM caused the mean concentration of PHT to rise by 78%. The data also indicate that patients with PB and/or PHT comedication have higher N-DESM-MSM serum concentrations than patients without comedication. The pharmacological reasons for these interactions are discussed. These studies demonstrate that the disturbing side effects of MSM are often due to the co-medication. A carefully planned therapeutical dose procedure with regular serum level determinations is proposed to avoid or at least reduce the adverse effects of MSM.

Adolescent↗
PubMed1978

Properties of two Clostridia strains acting as catalysts for the preparative stereospecific hydrogenation of 2-enoic acids and 2-alken-1-ols with hydrogen gas.

A Clostridium strain growing on crotonate/hydrogencarbonate, which is able to hydrogenate stereospecifically 2-enoates as well as other unsaturated compounds with hydrogen gas, has been isolated and methods for its propagation elucidated. For this strain and for Clostridium kluyveri DSM 555 grown on ethanol/acetate/hydrogencarbonate, samples of 200-l batches were assayed to determine the hydrogenation activity for (E)-2-methyl-2-butenoate and (E)-2-buten-1-ol as a function of time during the exponential and stationary growth phases. For the strain growing on crotonate/hydrogencarbonate, the hydrogenation rate as a function of substrate concentration, pH and temperature has been measured. Storage conditions for both strains are given.

Clostridium↗
PubMed1977

Bioavailability of three phenytoin preparations in healthy subjects and in epileptics.

Serum phenytoin concentrations have been studied in epileptic patients and healthy subjects taking tablets of phenytoin calcium (Desitin), A, phenytoin acid (Desitin), B, and phenytoin acid (Nordmark), C. Retrospective data and prospective investigation of hospitalized patients on long-term phenytoin treatment showed that significantly higher serum concentrations of phenytoin were produced by the phenytoin acid preparations B and C than by the phenytoin calcium preparation A. In a cross over study six volunteers received 200 mg/day of preparations A, B, and C for three weeks. In this study, too, higher phenytoin serum concentrations were produced by B and C than by A, although the differences were not statistically significant. The reasons for the discrepancies between the studies in healthy and epileptic subjects are discussed.

Adult↗
PubMed1975

[The occurrence of a reductase of delta2-carboxylic acids in Clostridium kluyveri with a stereospecificity different from that of butyryl-CoA dehydrogenase (author's transl)].

A Clostridia strain (R-strain) which hydrogenates tiglinate (1b) and alpha-methylcinnamate (1c) in the presence of hydrogenase gas in 2H2O to (2R, 3S)2-methyl-[2,3-2H]butyrate (5b, H = 2H) and (alphaR, betaR)alpha-methyl[alpha,beta-2H]dihydrocinnamate (5c, H = 2H), respectively, was isolated. The configuration at C-3 was determined by 1H-NMR spectroscopy in the presence of Eu(fod)3. The stereochemistry of this hydrogenation is the mirror image of that which has been determined with intact cells of another strain of Clostridium kluyveri (S-strain). In the presence of hydrogen gas, the R-strain hydrogenates crotonate in 2H2O to butyrate with the following deuterium distribution: C-2, 1.85; C-3, 1.35; and C-4, 0.63 deuterium atoms. Crotonate seems to be the substrate of two reductases with sterically different actions. Tiglinate (1b) and alpha-methylcinnamate, however, are hydrogenated only by that reductase which is different from the butyryl-CoA dehydrogenase.

Butyrates↗
PubMedDate not supplied

Steady-state pharmacokinetics of phenytoin from routinely collected patient data.

Previously reported routine phenytoin clinical pharmacokinetic data from Japan, England, and Germany were analysed to estimate population pharmacokinetic parameters. There were 780 steady-state phenytoin concentrations and associated dosage rates (mg/day) from 322 patients. The patient group spanned paediatric and adult ages, mean age being 18.4 +/- 17.3 (SD) years; 53% were males. The data were analysed using NONMEM, a computer programme designed for population pharmacokinetic analysis. Estimates of the influence of age, gender, data source, height and weight on the maximum elimination rate (Vm) and Michaelis-Menten constant (Km) were obtained. The Vm and Km of a 70 kg adult male European were estimated to be 415 mg/day and 5.7 mg/L, respectively. Vm is not influenced by gender, age or data source. The parameters of a power function of height and weight were estimated to adjust Vm for body size. The best function adjusts Vm in proportion to weight to the 0.6 power; height contains no useful information. Km is not influenced by gender. The Km for patients less than 15 years old is 43% less than that of older patients. The Km of Japanese patients appears to be 23% less than that for European patients. Even after adjustments for age, etc., apparent Vm and Km vary unpredictably among individuals with a coefficient of variation between 10 to 20% and approximately 50% respectively.

Adolescent↗