Simultaneous determination of dihydrocodeine and its metabolites in dog plasma by high-performance liquid chromatography with electrochemical and ultraviolet detection

Development of a Sensitive and Rapid HPLC-MS Method for Dihydrocodeine and Dihydromorphine: Application to Bioequivalence Studies

A ultraperformance liquid chromatography-tandem mass spectrometry method has been developed to determine dihydrocodeine (DHC) and dihydromorphine (DHM) in human plasma using dihydrocodeine-d6 and desomorphine as internal standards (IS). Acetonitrile-water-ammonium format was used as the mobile phase, in gradient elution on a C18 column. The concentration of DHC and DHM was determined in the positive ionization mode of mass spectrometry. The total chromatogram run time was 3.2 min, and the linear ranges of DHC and DHM were 1.000-400.0 ng/mL and 0.050-20.00 ng/mL, respectively. The method was fully validated concerning precision, accuracy, selectivity, linearity, recovery, stability and matrix effect. The method had been successfully applied to the bioequivalence test. In addition, we found that a high-fat diet impacts the Tmax and t1/2 of DHC.

Rapid detection of dihydrocodeine by thermospray mass spectrometry

Rapid assay of dihydrocodeine (DHC) by thermospray mass spectrometry is explored. Liquid-liquid extractions of blood, urine and gastric contents were injected into a thermospray mass spectrometer, to which there was no column connected, and DHC was assayed by the flow injection method. The mass spectra of DHC under thermospray ionization and filament-on ionization modes consist of the MH+ ion of mlz 302 alone, which was clearly detected in the samples. Although DHC should be quantitated by gas chromatography-mass spectrometry, this method is applicable for rapid identification of DHC in biological materials.

Glucuronidation of dihydrocodeine by human liver microsomes and the effect of inhibitors

1. Glucuronidation is the major route of metabolism of dihydrocodeine (DHC) and accounts for 25-30% of an oral dose in urine. The kinetics of DHC-6-glucuronide formation in liver microsomes from five human donors and the effect of a number of potential inhibitor drugs were examined using a newly developed and validated HPLC assay. 2. The formation of DHC-6-glucuronide exhibited atypical kinetics that conformed to the Hill equation. The mean intrinsic dissociation constant (Ks) and maximum velocity (Vmax) values were 1566 micromol/L and 0.043 micromol/min per g, respectively. The Ks and Vmax values varied 1.5- and 3.5-fold, respectively. 3. Seven drugs were tested for inhibitory effects on DHC glucuronidation at low (50 micromol/L) and high (500 micromol/L) concentrations. At 50 micromol/L, only diclofenac produced greater than 50% inhibition, while at concentrations of 500 micromol/L inhibition was greater than 35% for diclofenac, amitriptyline, oxazepam, naproxen, chloramphenicol and probenecid, but not paracetamol. 4. The present study found little interindividual variation in the activity of human liver microsomes for glucuronidation of DHC. Comparison of the results from the inhibition studies with those reported previously for codeine and morphine suggest that the UDP-glucuronosyltransferase isoform UGT2B7 is involved in the glucuronidation of DHC.

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.

Determination of the dihydrocodeine metabolites, dihydromorphine and nordihydrocodeine, in hepatic microsomal incubations by high-performance liquid chromatography

A high-performance liquid chromatographic assay for the oxidative metabolites of dihydrocodeine, nordihydrocodeine and dihydromorphine, formed in human liver microsomal incubations, is described. A simple solvent extraction followed by reversed-phase high-performance liquid chromatography with UV detection allows quantification of both metabolites in a single assay. Standard curve concentration ranges for dihydromorphine and nordihydrocodeine were 0.05-5 and 0.2-20 microM, respectively. Assay performance was assessed by intra- and inter-day accuracy and precision of quality control (QC) samples. The difference between the calculated and the actual concentration and the relative standard deviation were less than 15% at low QC concentrations and less than 10% at medium and high QC concentrations for both analytes. The method provides good precision, accuracy and sensitivity for use in kinetic studies of the oxidative metabolism of dihydrocodeine in human liver microsomes.

Exploration of the metabolism of dihydrocodeine via determination of its metabolites in human urine using micellar electrokinetic capillary chromatography

After single-dose administration of 40 or 60 mg of dihydrocodeine (DHC, in a slow-release tablet) to four healthy individuals known to be extensive metabolizers of debrisoquine, the urinary excretion of DHC and its four major metabolites, dihydrocodeine-6-glucuronide, nordihydrocodeine, dihydromorphine and nordihydromorphine, was assessed using micellar electrokinetic capillary chromatography (MECC). DHC and two of its metabolites (dihydrocodeine-6-glucuronide and nordihydrocodeine) could be analyzed by direct urine injection, whereas the metabolic pattern was obtained by copolymeric bonded-phase extraction of the solutes from both plain and hydrolyzed urine specimens prior to analysis. The total DHC equivalents excreted within 8 and 24 h were determined to be 30.4 +/- 7.7% (n = 5) and 63.8 +/- 6.1% (n = 2), respectively, and only about 4% of the excreted DHC equivalents were identified as morphinoids. Furthermore, almost no morphinoid metabolites of DHC could be found after administration of quinidine (200 mg of quinidine sulfate) 2 h prior to DHC intake.

Metabolism and pharmacokinetics of dihydrocodeine in dog

1. The metabolism and pharmacokinetics of dihydrocodeine have been studied in dog. Urinary metabolites after oral administration of dihydrocodeine were identified using hplc with diode-array and ms. 2. In urine, dihydronorcodeine, dihydromorphine and dihydrocodeine glucuronide were identified in comparison with their authentic standards, and dihydronorcodeine 6-glucuronide also appeared to be excreted as a metabolite. 3. The major urinary metabolite was dihydrocodeine glucuronide, recovered as 49% of the dose, and other metabolites were found to be 0.1-3%, 24 h after 3 mg/kg oral administration of dihydrocodeine. Plasma concentrations of unchanged dihydrocodeine were significantly lower after oral rather than intramuscular administration; the maximum concentrations were 40 and 549 ng/ml after oral and intramuscular administration, respectively. This suggests that dihydrocodeine was metabolized via a hepatic first-pass effect after oral administration. 4. Overall, our results indicate that the metabolic pathways of dihydrocodeine in dog were similar to that of codeine metabolism in animals and man.