Simultaneous high-performance liquid chromatographic assay of droperidol and flunitrazepam in human plasma: Application to haemodilution blood samples collected during clinical anaesthesia

doi:10.1016/0378-4347(93)80173-2

Journal of Chromatography B: Biomedical Sciences and Applications

Volume 612, Issue 2, 26 February 1993, Pages 269-275

https://doi.org/10.1016/0378-4347(93)80173-2 Get rights and content

Abstract

A simultaneous assay for droperidol and flunitrazepam by high-performance liquid chromatography has been developed and applied to blood samples collected during an acute normovolemic haemodilution under general anaesthesia. Haemodilution blood samples were stored at +4°C to be transfused, if required, to a patient during the post-surgical phase. A C₁₈ Supelclean cartridge was used for solid-phase extraction, and the recoveries were 74% and 89%, respectively, for droperidol and flunitrazepam. Compounds were chromatographed on a C₁₈ Novapak column at 250 nm, with a mobile phase of acetonitrile—10 mM ammonium acetate buffer (pH 6.7) (45:55, v/v). Nitrazepam was used as the internal standard. For both drugs, the assay was linear up to 500 μg/l, and the detection limits were 20 and 10 μg/l for droperidol and flunitrazepam, respectively, and their observed levels in haemodilution samples were 93 ± 82 μg/l and 76 ± 107 μg/l, respectively. Some of the values for flunitrazepam were higher than the minimal efficient concentration, defined as the plasma level observed at the time of the patient wakening from anaesthesia (12 ± 4 μg/l). According to our results, haemodilution sampling can be performed before induction of anaesthesia. When the blood is collected after the anaesthetic induction, it seems necessary to determine levels of the two drugs in haemodilution samples to avoid side-effects.

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A review of methods for the measurement of benzodiazepines in biological specimens published over the last five years is presented. A range of immunoassay procedures using EIA, ELISA, FPIA, agglutination or kinetic interaction of microparticles, or RIA methods are now available. Cross reactivities to benzodiazepines are variable such that no one kit will recognise all benzodiazepines and their relevant metabolites at concentrations likely to be encountered during therapeutic use. Prior hydrolysis of urine to convert glucuronide metabolites to immunoreactive substances improves detection limits for many benzodiazepines. Several radioreceptor assays have now been published and show good sensitivity and specifity to benzodiazepines and offer the advantage (over immunoassay) of being able to detect these drugs with equal sensitivity. Solvent extraction techniques using a variety of solvents were still popular and offer acceptable recoveries and lack of significant interference from other substances. A number of papers describing solid phase extraction procedures were also published. Direct injection of specimens into a HPLC column with back flushing were also successfully described. Seventy two chromatographic methods using HPLC, LC–MS, GC and GC–MS methods were reviewed. HPLC was able to achieve detection limits for many benzodiazepines using UV or DAD detection down to 1–2 ng/ml using 1–2 ml of urine or serum (blood). ECD detectors gave detection limits better than 1 ng/ml from 1 ml of specimen, which was an order of magnitude lower than for NPD. EI-MS offered similar sensitivity, whilst NCI-MS was capable of detection down to 0.1 ng/ml. Methods suitable for the separation of enantiomers of benzodiazepines have been described using HPLC. Electrokinetic micellar chromatography has also been shown to be capable of the analysis of benzodiazepines in urine.
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Simultaneous high-performance liquid chromatographic assay of droperidol and flunitrazepam in human plasma: Application to haemodilution blood samples collected during clinical anaesthesia

Abstract

J. Chromatogr.

J. Chromatogr.

J. Chromatogr.

J. Chromatogr.

J. Chromatogr.

Br. J. Anaesth.

Anaesthesiology

J. Chromatogr.

Pharm. Week bl.

J. Pharm. Pharmacol.