Ion-pair extraction and liquid chromatographic analysis of morphine in rat brain and plasma

Increased brain uptake and brain to blood efflux transport of 14C-GABA in spontaneously hypertensive rats

The brain uptake and brain to blood efflux transport of (14)C-GABA were studied in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto (WKY) rats using 20 min bilateral in situ brain perfusion in rats anesthetized using urethane. The volume of distribution (Vd) of (14)C-GABA into cerebrospinal fluid (CSF) and brain regions (cortex, diencephalon, cerebellum, and brain stem) was significantly greater in SHR than in the corresponding regions in WKY rats (p<0.05). The estimated Vd value of (14)C-GABA in CSF of SHR was 3.4 fold greater than that in WKY. Also compared to WKY, the Vd of (14)C-GABA into cerebellum and cortex of SHR was 15.3 fold and 19.4 fold greater, respectively. Although the study of blood-brain barrier (BBB) integrity using (3)H-mannitol revealed increased paracellular permeability at the brain capillaries of SHR when compared to WKY rats, this was found to be only partially responsible for the increased (14)C-GABA uptake. The study of brain to blood efflux transport of (14)C-GABA (after loading of brain with (14)C-GABA by vascular perfusion) revealed that the half-time of elimination was significantly shorter in SHR (5.35+/-0.66 min) than in WKY rats (14.83+/-1.94 min), (p<0.001). HPLC analysis revealed that GABA concentrations in brain extracts and CSF of SHR were similar to those in WKY rats (p>0.05). The faster efflux in SHR might be, at least partially, responsible to compensate for increased uptake of this neurotransmitter and to preserve the protective function of BBB towards GABA. The protective function of the BCSFB towards GABA appears to be also preserved, since systemic infusion of GABA within a wide range of administered doses (0.004-5.00 mg/kg) produced an increase in GABA CSF concentration from around 0.5 microM to only 11 microM, and the obtained pattern of CSF GABA concentrations under these conditions did not differ between SHR and WKY rats, as revealed by HPLC.

High-performance liquid chromatographic assay for morphine in small plasma samples: Application to pharmacokinetic studies in rats

In order to perform a reliable pharmacokinetic study of morphine during subchronic treatment in rats, an easy, rapid, sensitive and selective analytical method was proposed and validated. The analyte and internal standard (naloxone) were extracted from plasma samples (100 microL) by a single solid-phase extraction method prior to reverse-phase high performance liquid chromatography (HPLC) along with electrochemical detection (ED). Standard calibration graphs were linear within a range of 3.5-1,000 ng/mL (r=0.999). The intra-day coefficients of variation (CV) were in the range of 5.8-8.5% at eight concentration levels (7-1,000 ng/mL) and the inter-day coefficient of variation ranged from 7.4 to 8.8%. The intra-day assay accuracy was in the range of -5-10% and the inter-day assay accuracy ranged from 3.0 to 9.3% of relative error (RE). The limit of quantification was 3.5 ng/mL using a plasma sample of 100 microL (15.8% of CV and 12.8% of RE). Plasma samples were stable for 2 months at -20 degrees C. This method was found to be suitable for pharmacokinetic studies in rats, after subcutaneous administration of morphine (5.6 mg/kg per day) in subchronic treatment for 6 and 12 days.

Comparison of phenyl-type columns in the development of a fast liquid chromatographic system for eighteen opiates commonly found in forensic toxicology

We report a precise and reliable method for the detection of 18 of the most commonly found opiates on the Belgian legal and illicit market, by ion-exchange, reversed-phase high-performance liquid chromatography, using a conventional phenyl-type analytical column (150x4.6 mm I.D., particle size 5 microm) and diode-array detection. We also describe a performance (efficiency and sensitivity) comparison of this column to a recently developed "high-speed" column (53x7.0 mm I.D., particle size 3 microm) packed with the same stationary phase, and used under slightly adjusted flow and gradient conditions. The final method, using the "high-speed" column, showed a significant reduction (55%) in analysis time without loss of resolution and sensitivity.

Rapid and highly automated determination of morphine and morphine glucuronides in plasma by on-line solid-phase extraction and column liquid chromatography

A high-performance liquid chromatography (HPLC) method has been developed for the determination of morphine and its main metabolites, morphine-6-glucuronide (M-6-G) and morphine-3-glucuronide (M-3-G), in plasma or cerebrospinal fluid. Samples were extracted using on-line solid-phase extraction followed by reversed-phase HPLC with fluorescence detection. Recoveries of 20 ng morphine and morphine glucuronides in plasma were over 95%. The limit of detection using 400 microliters of a biological matrix was 0.85, 3.4 and 1.0 ng/ml of M-3-G, M-6-G and morphine, respectively. Inter- and intra-day assay precision was better than 10%. The main advantages of the present described method are increased recoveries (> 95%) and a high degree of automation allowing a high speed in routine analysis. The time required for the fully automated analysis of one sample was less than 26 min.