Determination of codeine and its metabolites in microsomal incubates by high-performance liquid chromatography

Comparative biotransformation of morphine, codeine and pholcodine in rat hepatocytes: identification of a novel metabolite of pholcodine

1. Pholcodine (3-morpholinoethylmorphine), a semi-synthetic alkaloid, is widely used as an antitussive agent. 2. Norpholcodine [7,8-didehydro-4,5alpha-epoxy-3-(2-morpholinoethoxy)morphinan-6alpha-ol] (NP) and pholcodine-N-oxide [1(9a)-dehydro-(4aR,5S,7aR,9cS,12S)-4a,5,7a,8,9,9a-hexahydro-5-hydroxy-12-methyl-3-morpholinoethoxy-1H-8,9,c-(iminoethano)phenanthro[4,5-bcd] furan-12-oxide] (PNOX) were identified in incubations of pholcodine with freshly isolated rat hepatocytes by liquid chromatography/electrospray-mass spectrometry (LC/ESI-MS). 3. Synthesized NP and PNOX were characterized by mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy. 4. N-oxidation was the major metabolic pathway for pholcodine, producing a previously unreported metabolite. 5. The metabolism of morphine and codeine was also determined using freshly isolated hepatocytes. 6. For morphine, 3-glucuronidation was the major metabolic pathway, whilst for codeine it was dealkylation (O- and N-). 7. Neither morphine nor its metabolites were metabolites of pholcodine. 8. This observation supports the hypothesis that the absence of analgesic activity with pholcodine may be due to less O-dealkylation in vivo. 9. Together with the slow biotransformation of pholcodine (k(met) = 0.021 microM min(-1)) in comparison with morphine (k(met) = 0.057 microM min(-1)) and codeine (k(met) = 0.112 microM min(-1)), the results obtained were consistent with its low addiction potential and suggest that its antitussive efficacy is mediated by the parent drug or one of its metabolites other than morphine.

Fully automated analytical method for codeine quantification in human plasma using on-line solid-phase extraction and high-performance liquid chromatography with ultraviolet detection

A simple, sensitive and fully automated analytical method for the analysis of codeine in human plasma is presented. Samples are added with oxycodone, used as internal standard (I.S.), and directly loaded in the autosampler tray. An on-line sample clean-up system based on solid-phase extraction (SPE) cartridges (Bond-Elut C2, 20 mg) and value switching (Prospekt) is used. Isocratic elution improved reproducibility and allowed the recirculation of the mobile phase. A Hypersil BDS C18, 3 microns, 10 x 0.46 cm column was used and detection was done by UV monitoring at 212 nm. Retention times of norcodeine (codeine metabolite), codeine and oxycodone (I.S.) were 5.5, 6.4 and 9.1 min, respectively. Morphine was left to elute in the chromatographic front. Detection limit for codeine was 0.5 microgram l-1 and inter-assay precision (expressed as relative standard deviation) and accuracy (expressed as relative error) measured at 2 micrograms l-1 were 5.03% and 1.82%. Calibration range was 2-140 micrograms l-1.

Effect of fentanyl on morphine levels in the brain in rats receiving intracerebroventricular injection of TNF-alpha

Fentanyl citrate analgesia attenuates the excess nitrogen excretion in the urine and glucose production induced by trauma. On the other hand, intracerebroventricular injection of morphine stimulates excretion of stress hormones, such as catecholamines and corticosterone. Furthermore, morphine levels in the brain are increased during fasting and sepsis. The aims of this study were to determine whether intracerebroventricular injection of tumor necrosis factor-alpha (TNF-alpha) elevates morphine levels in the rat brain and whether prophylactic administration of fentanyl blocks metabolic responses induced by intracerebroventricular injection of TNF-alpha because of a reduction of morphine levels in the brain. Morphine levels in the brain were increased from 648 to 1,134 fmol/g at 30 min after intracerebroventricular injection of TNF-alpha (P < 0.05 vs. control). This increase was associated with an increase in stress hormones (corticosterone: 416.1 +/- 69.1 ng/ml, P < 0.05 vs. control; epinephrine: 3,778.3 +/- 681.3 pg/ml, P < 0.01 vs. control) and an enhancement of proteolysis (254.2 +/- 45.7 micromol Leu . kg-1 . h-1, P < 0.01 vs. control) and glucose production (7.5 +/- 0. 7 mg . kg-1 . min-1, P < 0.05 vs. control). Fentanyl reduced morphine levels in the brain to 624 fmol/g (not significant vs. control), resulting in a reduction of stress hormone levels in the plasma and blunted metabolic responses. In conclusion, prophylactic administration of fentanyl prevented an increase in morphine levels in the brain induced by intracerebroventricular injection of TNF-alpha, leading to a reduction in stress hormone levels and subsequent metabolic responses.

Simultaneous determination of codeine and its seven metabolites in plasma and urine by high-performance liquid chromatography with ultraviolet and electrochemical detection

A sensitive and selective high-performance liquid chromatography method has been developed for the measurement of codeine and its seven metabolites, norcodeine, morphine, normorphine, codeine-6-glucuronide, morphine-6-glucuronide, morphine-3-glucuronide and norcodeine glucuronide, in plasma and urine. The compounds were recovered from plasma and urine using solid-phase extraction with C18 cartridges and separated on a reversed-phase C8 column with a mobile phase consisting of 77% buffer (5 mM sodium phosphate monobasic and 0.70 mM sodium dodecyl sulfate, pH 2.35) and 23% acetonitrile. Codeine, norcodeine, codeine-6-glucuronide, norcodeine glucuronide and morphine-3-glucuronide were detected by ultraviolet detection at 214 nm, with a detection limit of 0.02 nmol/ml for each compound in plasma. Morphine-6-glucuronide, normorphine and morphine were monitored by electrochemical detection at 350 mV, with a detection limit of 0.003 nmol/ml for each compound in plasma. The assay showed good reproducibility and accuracy using external standardization. The recovery and inter-day variation for all compounds in plasma samples were 63.40-77.90% and 3.49-16.77% (R.S.D.) and while in urine were 64.98-90.13% and 2.93-9.96% (R.S.D.), respectively.

Comparative bioavailability study of codeine and ibuprofen after administration of the two products alone or in association to 24 healthy volunteers

The study objective was to compare the bioavailability of codeine and ibuprofen after oral administration of the two drugs alone or in association. The study was performed in three different periods, each separated by a wash-out of 6 days. Plasma concentrations were measured in 24 healthy volunteers after administration of a single oral dose of codeine phosphate (25 mg) and/or ibuprofen (200 mg). Codeine and ibuprofen assays were performed using two different HPLC methods. The relative bioavailabilities of codeine and ibuprofen (alone or in association) were 106 +/- 24% (mean +/- sd) and 101 +/- 19%, respectively. The results obtained demonstrated that bioavailabilities of codeine and ibuprofen were not modified when the two drugs were administrated alone or in association.

Determination of morphine in urine by solid-phase immunoextraction and high-performance liquid chromatography with electrochemical detection

The analysis of morphine in biological fluids is of vital interest in monitoring opiate abuse and in drug abuse research. Although methods for analysis of morphine and its metabolites are well established, studies are still being carried out to improve sample preparation procedures as well as detection levels of morphine in biological samples. In this study, morphine-specific immunosorbents were developed to concentrate morphine prior to HPLC analysis. Urine (0.1 ml) was diluted 10-fold with phosphate-buffered saline, pH 7.4 (PBS), loaded onto a solid-phase immunoextraction column and washed with 15 ml PBS followed by elution with 2 ml of elution buffer (40% ethanol in PBS, pH 4). The eluted fraction was analysed for morphine by HPLC-electrochemical detection using a cyanopropyl (CN) analytical column with 25% acetonitrile in phosphate buffer-sodium lauryl sulphate, pH 2.4 as the mobile phase. Duration of the extraction procedure was approximately 40 min. Calibration graphs were linear from 100 ng ml-1 to 500 ng ml-1 in urine. The inter-assay R.S.D. was < 10% and the recovery of morphine from urine was > 98%. Immunocolumns demonstrated remarkably high specificity towards morphine showing minimal binding with other opiate metabolites such as codeine, normorphine, norcodeine, morphine-3-glucuronide, morphine-6-glucuronide.