Simultaneous Determination of Tramadol and its Metabolite in Human Plasma by GC/MS.

A simple and sensitive GC/MS method for the determination of tramadol and its metabolite (O-desmethyltramadol) in human plasma was developed and validated. Medazepam was used as an internal standard. The calibration curves were linear (r=0.999) over tramadol and O-desmethyltramadol concentrations ranging from 10 to 200 ng/mL and 7.5 to 300 ng/mL, respectively. The method had an accuracy of >95% and intra- and interday precision (RSD%) of ≤4.83% and ≤4.68% for tramadol and O-desmethyltramadol, respectively. The extraction recoveries were 97.6±1.21% and 96.3±1.66% for tramadol and O-desmethyltramadol, respectively. The LOQ using 0.5 mL human plasma was 10 ng/mL for tramadol and 7.5 ng/mL for O-desmethyltramadol. Stability studies showed that tramadol and O-desmethyltramadol were stable in human plasma after 8 h incubation at room temperature or after 1 week storage at -20°C with three freeze-thaw cycles. Also, this method was successfully applied to six patients who had been given an intravenous formulation of 100 mg tramadol with Cmax results of 2018.1±687.8 and 96.1±22.7 ng/mL for tramadol and O-desmethyltramadol, respectively.

Introduction to the pharmacokinetics and pharmacodynamics of benzodiazepines.

The contributions of pharmacokinetics and pharmacodynamics to the generation and maintenance of drug responses are reviewed from the literature. Potential pharmacokinetic determinants of duration of drug action are dose, lipid solubility and elimination half-life. Certain paradoxes are inherent in the view that clinical differences among benzodiazepines are due primarily to their elimination half-lives. It is concluded that the respective roles of pharmacokinetics and pharmacodynamics in the generation and maintenance of clinical responses to benzodiazepines require clarification.

Automated on-line dialysis for sample preparation for gas chromatography: determination of benzodiazepines in human plasma.

An on-line dialysis-solid-phase extraction-gas chromatographic (GC) approach has been developed for the determination of drugs in plasma, using some benzodiazepines as model compounds. Clean-up is based on performing the dialysis of 100 microliters samples for 7 min using water as acceptor phase and trapping the diffused analytes on a PLRP-S copolymer precolumn. After drying of the precolumn with nitrogen for 15 min, the analytes are desorbed with ethyl acetate (275 microliters) and injected on-line into the GC system via a loop-type interface. The system provides a very efficient clean-up, and offers the possibility of adding chemical agents which can help to reduce drug-protein binding and, thus, increase sensitivity. To demonstrate the potential of the described approach, the determination of benzodiazepines in plasma at their therapeutical levels is used as an example with flame ionization, thermionic and mass-selective detection.

Plasma concentrations of benzodiazepines.

1. Twenty anxious patients were treated with medazepam, diazepam, chlordiazepoxide, amylobarbitone and placebo, each given in flexible dosage for 2-4 weeks. 2. At the end of each treatment, a series of clinical, physiological and behavioural variables were measured and plasma samples were taken for estimation of the appropriate drug and metabolite concentrations. 3. Nordiazepam was shown to be an important metabolite of both medazepam and diazepam: the ratio of medazepam to noradiazepam was 0.14 and the ratio of diazepam to nordiazepam following diazepam administration was 0.72. 4. No significant correlations were found between the plasma concentrations of any of the treatments and the clinical ratings or behavioural measures. 5. Some relationship was shown between levels of medazepam and its physiological effects.

Analytical toxicology: Applications of element-selective electrolytic conductivity detection for gas chromatography.

We applied a commercially available microelectrolytic conductivity detector to toxicological problems of qualitative and quantitative analysis by gas chromatography. The detector can be used for the sensitive and selective detection of halogen-, nitrogen-, and sulfur-containing compounds. Relative response in different element-selective detector variables such as reaction gas, reaction catalyst, and furnace temperature can be used to further improve qualitative identification by gas chromatography.

Plasma concentrations of medazepam and its metabolites after oral administration.

The plasma concentrations of medazepam and its metabolites, diazepam and desmethyldiazepam, were determined in volunteer subjects following the oral administration of medazepam 10 mg. The results indicated that medazepam was absorbed rapidly, that low concentrations of metabolites were present during the 1st h, and that the build-up in the circulation of the major metabolite, desmethyldiazepam, was prolonged and variable. As many of the clinical effects and possible adverse reactions of medazepam appear to be associated with the presence of this major metabolite, the metabolic and pharmacokinetic characteristics of the drug should be considered when using medazepam as an anxiolytic before dentistry or surgery.

Analysis of medazepam, diazepam, and metabolites in plasma by gas-liquid chromatography with electrolytic conductivity detection.

An improved electrolytic conductivity detector allowed the gas-liquid chromatographic analysis of medazepam, diazepam, and major metabolites in 2 ml plasma at concentrations of 20 microgram/l. The detector had a sensitivity limit of less than 1 ng (or 100 pg nitrogen) when operated in the nitrogen-selective mode and a nitrogen/carbon elemental selectivity ratio of greater than 100,000 compared to octadecane and cholesterol. Detector response when operated in various element-selective chemical modes was investigated, and its application to the analysis of the title compounds was compared to electron capture and flame ionization detection systems.

Serum medazepam, diazepam, and N-desmethyldiazepam levels after single and multiple oral doses of medazepam.

20 mg of medazepam were taken by mouth by 9 healthy volunteers in an acute absorption study. About a 10-fold variation was found during the first 6 hours after the drug in individual serum medazepam, diazepam, and N-desmethyldiazepam levels. In a subacute study 10 mg of medazepam t.i.d. was given to 10 institutionalized mentally subnormal adults with emotional disorders. After 14 days' treatment serum N-desmethyldiazepam levels were generally above 800 ng/ml, 7 to 8 times higher than the serum medazepam or diazepam levels measured 12 hours after the last dose. No correlation was observed between the serum concentration and efficacy of medazepam.

[Analysis of benzodiazepine derivative mixture by gas-liquid chromatography]. / Benzodiazepino dariniu misinio analize duju ir skysciu chromatografijos metodu.

The analysis of mixture of benzodiazepine derivates (chlordiazepoxide, flunitrazepam, medazepam, nitrazepam, oxazepam and tetrazepam) by gas--liquid chromatography (GLC) in purpose to separate and identify these psychotropic drugs in mixture is presented in this article. The experiment was carried out in vitro, accommodating this method for identification and separation of drugs, isolated from biological objects (blood and urine). Referring to data of annual reports of chemical investigations (1) above-mentioned psychotropic drugs are very frequent among drug intoxication. In most cases they are detected in the mixture of the same or different pharmacological group, and this causes difficulty for separation and identification. The analysis of the mixture was carried out by GLC, which is widely used in practice of forensic-chemical examination. Adsorbents and stationery phases were changed; the conditions and parameters of chromatography were modified, in purpose totally separate preparations in the mixture. For the separation and identification of all three preparation the column packed with Inerton Super with stationary phase 3% OV-17 is suitable. The column temperature-290 degrees C. The mixture of these drugs was excreted from body fluids (blood and urine) in vitro and investigated by GLC under these conditions. The results of investigation were similar.