Analysis of chlorodesmethyldiazepam and its metabolites in plasma and urine

A fast and sensitive liquid chromatographic-tandem mass spectrometric method for assay of lorazepam and application to pharmacokinetic analysis

A fast and sensitive method of coupled high-performance liquid chromatography-electrospray tandem mass spectrometry for the assay of lorazepam in human plasma was developed. Plasma samples were simply treated with acetonitrile to precipitate and remove proteins and the isolated supernatants were directly injected into the HPLC/MS/MS system. Chromatographic separation was performed on a Zorbax C(18) (100 x 2.1 mm I.D.) column with a 65:35 (v/v) mixed solution of acetonitrile and 10mM aqueous formic acid being used as mobile phase. With diazepam as an internal standard, quantification was performed by selected reaction ion monitoring of the transitions of m/z 321--> m/z 275 for lorazepam and m/z 285--> m/z 193 for the internal standard. The assay was validated in the concentration range of 0.71-71.3 ng/ml in human plasma. A detection limit of 0.10 ng/ml for lorazepam was achieved, and inter- and intra-run precisions of better than 4.4% (R.S.D.) were observed. The developed method has been successfully applied for pharmacokinetic study of the drug in man.

Effects of liver disease on the pharmacokinetics of intravenous and oral chlordesmethyldiazepam

We studied the pharmacokinetics of a single 0.5-mg i.v. dose of chlordesmethyldiazepam in 8 patients with liver disease and in 12 age-matched healthy controls. The kinetics were also studied of a single 1-mg oral dose in the patients with liver disease. After i.v. administration the kinetics of total chlordesmethyldiazepam in patients with liver disease differed from those in controls: elimination half-life was almost twice that in controls (395 and 204 h), as a consequence of a marked reduction in total clearance (0.13 and 0.25 ng.ml-1.h-1), whereas the apparent volume of distribution was similar in patients and controls (4.7 and 3.9 l/kg-1). The free fraction of the drug in patients was higher (5.5%) than in controls (2.9%). Correction for differences in protein binding revealed clearance in the patients was one-fifth (1.8 and 10.5 ng ml-1.kg-1) and volume of distribution one-half (65.0 and 118.4 l.kg-1) that in controls. The systemic availability of oral chlordesmethyldiazepam was high (110%) in spite of a relatively slow absorption rate. These results indicate a need for caution in the administration of chlordesmethyldiazepam to patients with liver disease.

Pharmacokinetics of intravenous and oral chlordesmethyldiazepam in patients on regular haemodialysis

The pharmacokinetics of a single 2 mg IV dose of chlordesmethyldiazepam has been studied in 11 patients with renal failure on regular haemodialysis and in 11 age-matched healthy controls. The kinetics was also examined after a single 2 mg oral dose in 6 of the 11 renal failure patients. After intravenous administration the kinetics of total chlordesmethyldiazepam in renal patients and controls were the same. The unbound fraction of the drug in renal patients was higher (5.5%) than in controls (2.9%). Correction for differences in protein binding revealed a reduced apparent volume of distribution (47 vs. 140 l.kg-1) and a reduced clearance (5.0 vs. 10.5 ml.min-1.kg-1) in the patients. The systemic availability of oral chlordesmethyldiazepam was good (82%) despite a relatively slow absorption rate.

Chromatography of benzodiazepines

An overview of methods for the determination of benzodiazepines in biological media, based on the application of chromatographic techniques, is presented. A general discussion of the techniques in terms of stability, selectivity, validation, standardization, detection and sensitivity is given. No single technique can be claimed as the method of choice for benzodiazepines. Gas chromatography with electron-capture detection has some strong claims and shows generally good sensitivity and reproducibility. High-performance liquid chromatographic equipment is readily available in most laboratories. The ultimate choice of an assay method for benzodiazepines will be determined by the clinical application (routine monitoring, pharmacokinetics, overdose, forensic medicine) and by the characteristics of the benzodiazepine, the expertise of the analyst, the equipment available, the desired sensitivity and specificity and the time involved in method development or adaptation and validation.

Pharmacokinetics and bioavailability of intravenous and oral chlordesmethyldiazepam in humans

Six healthy, fasting volunteers were given single doses of chlordesmethyldiazepam by 1 mg i.v., or as drops or tablets. Chlordesmethyldiazepam and its metabolite, lorazepam, in multiple plasma samples and in urine collected for 120 h after each dose were determined by electron-capture GLC. Mean kinetic variables for intravenous chlordesmethyldiazepam were: volume of distribution, 1.71 l.kg-1; elimination half-life, 113 h; total clearance, 0.21 ml.min-1.kg-1; cumulative excretion of lorazepam glucuronide 24.2% of the dose. Following a lag time of 15.5 min (tablets) and 4.2 min (drops), which were significantly different, the absorption of oral chlordesmethyldiazepam was a first order process, with apparent absorption half-life values averaging 1.5 h (tablets) and 1.1 h (drops). Bioavailability was 77% for tablets and 79% for drops.