dextrorphan and norlevorphanol

Dextromethorphan, a clinically available N-methyl-D-aspartic acid (NMDA) receptor antagonist, has an analgesic effect in patients with diabetic neuropathy. The aim of this study was to evaluate the analgesic and adverse effects of a single high dose of dextromethorphan on spontaneous pain in patients suffering long-term neuropathic pain of traumatic origin.. Fifteen patients with post-traumatic neuropathic pain participated in this placebo-controlled, double-blind, randomized crossover study. On two separate occasions, the participants received 270 mg of dextromethorphan hydrobromide or placebo. Pain intensity, adverse effects and serum concentrations of dextromethorphan and metabolites were registered.. Dextromethorphan had a statistically significant analgesic effect compared with placebo, but the effect varied markedly among the patients. Light-headedness was the most important adverse effect reported. Extensive metabolizers of dextromethorphan had an apparently better analgesic effect than poor metabolizers.. This report indicates that a single high dose of dextromethorphan has an analgesic effect in patients with neuropathic pain of traumatic origin. The main metabolite dextrorphan seems to be important for the analgesic effect. At the relatively high dose studied, the clinical usefulness of dextromethorphan is limited to that portion of the patient population experiencing analgesia without an unacceptable level of adverse effects.

Topics: Adult; Aged; Analgesics; Chronic Disease; Cross-Over Studies; Dextromethorphan; Dextrorphan; Dizziness; Double-Blind Method; Female; Humans; Male; Middle Aged; Neuralgia; Pain Measurement; Placebos; Receptors, N-Methyl-D-Aspartate; Sleep Stages; Wounds and Injuries

The plasma concentration and cumulative urinary excretion over 34 h of dextromethorphan, free and conjugated dextrorphan, and 3-hydroxymorphinan were determined in seven healthy Japanese subjects after oral administration of 30 mg dextromethorphan hydrobromide. Conjugated metabolites were extensively present, whereas no detectable dextromethorphan or free metabolites were observed in the plasma of any subject. On average, 72% of the dose was excreted in urine within 34 h. This was detected mainly as conjugated metabolites with only slight traces of dextromethorphan and free metabolites. From the time-courses of the metabolic ratio (the ratio of urinary output of dextromethorphan to dextrorphan), the metabolic ratios seemed to become constant 7.5 h after oral administration. Phenotyping was performed using metabolic ratios in 75 unrelated healthy Japanese subjects (43 males and 32 females). The logarithmic metabolic ratio was bimodally distributed and one subject (1.3%) was identified as a poor metabolizer.

Topics: Administration, Oral; Adult; Antitussive Agents; Chromatography, High Pressure Liquid; Cytochrome P-450 CYP2D6; Dextromethorphan; Dextrorphan; Female; Humans; Japan; Male; Oxidation-Reduction; Phenotype; Polymorphism, Genetic; Reference Standards

1. The interindividual differences in serum concentrations of dextromethorphan (DM) and its metabolites were studied in 29 healthy subjects given 120 mg orally. They were also phenotyped according to the urinary ratio of debrisoquine and 4-hydroxy-debrisoquine. 2. Four (14%) subjects were found to be poor metabolizers (PM) with a dextromethorphan/dextrorphan metabolite ratio in plasma of 3.6 or more compared with extensive metabolizers (EM) with a ratio of 0.11 or less. Significant levels of 3-hydroxymorphinan were measurable in all individuals except two, both of whom were PMs. This subdivision corresponded to the phenotype determined by the metabolic ratio of debrisoquine (r = 0.92). 3. Twelve of the 29 subjects reported adverse drug reactions after dextromethorphan administration compared with none after placebo.

Topics: Adult; Automobile Driving; Debrisoquin; Dextromethorphan; Dextrorphan; Double-Blind Method; Humans; Levorphanol; Noscapine; Phenotype; Random Allocation

Ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-QToF-MS) analysis of dextromethorphan (DXM) and its metabolites-dextrorphan, 3-methoxymorphinan (3-MEM) and 3-hydroxymorphinan-in skeletal remains of rats exposed to DXM under different dosing patterns is described. Rats (n = 20) received DXM in one of four dosing patterns: acute (ACU1 or ACU2-100 or 200 mg/kg, i.p.; n = 5, respectively) or repeated (REP1 or REP2-3 doses of 25 or 50 mg/kg, i.p., 30 min apart; n = 5, respectively). Drug-free animals (n = 5) served as negative controls. Following euthanasia, the animals decomposed to skeleton outdoors. Bones were sorted by animal and skeletal element (vertebra, femur, pelvis, tibia, rib and skull), washed, air-dried and pulverized prior to dynamic methanolic drug extraction, filtration/pass-through extraction and analysis by UPLC-QToF-MS in positive electrospray ionization mode. Analyte levels (expressed as mass-normalized response ratios, RR/m) differed significantly between ACU1 and ACU2 (Mann-Whitney (MW), P < 0.05) in all skeletal elements for all analytes investigated, and between REP1 and REP2 in most skeletal elements for 3-MEM and 3-HOM, but in all skeletal elements for DXM. Between ACU1 and ACU2, and between REP1 and REP2, analyte level ratios (RRi/RRj) differed significantly (MW, P < 0.05) in 3/6 to 6/6 skeletal elements, depending on the ratios concerned, with no analyte level ratio differing significantly between both ACU1 vs ACU2 and REP1 vs REP2. Kruskal-Wallis (KW) analysis showed skeletal element to be a main effect for all analyte levels and analyte level ratios in all ACU and REP groups examined (P < 0.05). For data pooled only according to exposure pattern, KW analysis showed dose pattern to be a main effect for both analyte levels and analyte level ratios (P < 0.05). These data illustrate a dependence of these measures on dose, dose pattern and skeletal element, suggesting that some exposure patterns may be distinguished by toxicological analysis of bone.

Topics: Animals; Body Remains; Bone and Bones; Chromatography, Liquid; Dextromethorphan; Dextrorphan; Mass Spectrometry; Rats

A rapid and sensitive ultra performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) method has been developed and validated for the simultaneous quantitative determination of dextromethorphan (DM) and its metabolites dextrorphan (DX), 3-methoxymorphinan (3MM) and 3-hydroxymorphinan (3HM), in human lithium heparinized plasma. The extraction involved a simple liquid-liquid extraction with 1 ml n-butylchloride from 200μl aliquots of plasma, after the addition of 20 μl 4% (v/v) ammonium hydroxide and 100 μl stable labeled isotopic internal standards in acetonitrile. Chromatographic separations were achieved on an Aquity UPLC(®) BEH C(18) 1.7 μm 2.1 mm x 100mm column eluted at a flow-rate of 0.250 ml/min on a gradient of acetonitrile. The overall cycle time of the method was 7 min, with elution times of 1.3min for DX and 3HM, 2.8 min for 3MM and 2.9min for DM. The multiple reaction monitoring transitions were set at 272>215 (m/z), at 258>133 (m/z), at 258>213 (m/z) and at 244>157 (m/z) for DM, DX, 3MM and 3HM, respectively. The calibration curves were linear (r²≥0.995) over the range of 0.500-100 nM with the lower limit of quantitation validated at 0.500 nM for all compounds, which is equivalent to 136, 129, 129 and 122 pg/ml for DM, DX, 3MM and 3HM, respectively. Extraction recoveries were constant, but ranged from 39% for DM to 83% for DX. The within-run and between-run precisions were within 11.6%, while the accuracy ranged from 92.7 to 110.6%. The applicability of the bioanalytical method was demonstrated and is currently implemented in a clinical trial to study DM as probe-drug for individualized tamoxifen treatment in breast cancer patients.

Topics: Chromatography, Liquid; Dextromethorphan; Dextrorphan; Humans; Mass Spectrometry; Reference Standards; Reproducibility of Results; Sensitivity and Specificity; Time Factors

Cytochrome P450 2D6 (CYP2D6) mediated formation of dextrorphan (DOR) from dextromethorphan (DEX) is widely used as a marker to assess the activity of this enzyme both in vitro and in vivo. The sequential metabolism of DOR during in vitro studies, particularly using recombinant systems (rCYPs) expressing human CYP2D6, is assumed to be negligible. The extent of metabolism was investigated for a range of DEX and DOR concentrations in microsomal preparations from three different rCYPs expressing human CYP2D6 (yeast, Supersomes and Bactosomes) containing 10 pmol of the enzyme. Bactosomes and Supersomes, but not yeast rCYP microsomes, were capable of metabolising DOR to 3-hydroxymorphinan (HYM). Two novel CYP2D6 related metabolites were identified in Bactosomes, and assigned as single hydroxylations in the phenyl rings of DOR and HYM using ion-trap mass spectrometry. Therefore, in rCYP systems with high turn over rate (e.g. Bactosomes) DOR may not be considered as an end product particularly at low concentrations of DEX; leading to an underestimation of true metabolic rate. The results also put further emphasis on the necessity of optimising study conditions when switching between rCYP sources.

Topics: Bacteria; Biotransformation; Cloning, Molecular; Cytochrome P-450 CYP2D6; Dextromethorphan; Dextrorphan; Humans; Hydroxylation; Kinetics; Mass Spectrometry; Microsomes; Recombinant Proteins; Saccharomyces cerevisiae; Substrate Specificity

Dextromethorphan is used as a probe drug for assessing CYP2D6 and CYP3A4 activity in vivo and in vitro. A SIM GC/MS method without derivatization for the simultaneous determination of dextromethorphan and its metabolites, dextrorphan, 3-methoxymorphinan and 3-hydroxymorphinan, in human plasma, urine and in vitro incubation matrix was developed and validated. Calibration curves indicated good linearity with a coefficient of variation (r) better than 0.995. The lower limit of quantitation was found to be 10 ng/mL for all analytes in all matrices. Intra-day and inter-day precision for dextromethorphan and its metabolites was better than 9.02 and 9.91%, respectively and accuracy ranged between 91.76 and 106.27%. Recovery for dextromethorphan, its metabolites and internal standard levallorphan was greater than 72.68%. The method has been successfully applied for the in vitro inhibition of metabolism of dextromethorphan by CYP2D6 and CYP3A4 using known inhibitors of CYPs such as quinidine and verapamil.

Topics: Antitussive Agents; Calibration; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP2D6 Inhibitors; Cytochrome P-450 CYP3A; Cytochrome P-450 CYP3A Inhibitors; Dextromethorphan; Dextrorphan; Gas Chromatography-Mass Spectrometry; Humans; Reproducibility of Results; Sensitivity and Specificity

A simple and improved HPLC method with fluorometric detection for simultaneous determination of dextromethorphan (DM) and its three metabolites (dextrorphan (DX), 3-methoxymorphinan (MM), 3-hydroxymorphinan (HM)) in human plasma was developed and validated. The method involved a simple and efficient extraction protocol using an n-heptane/ethyl acetate (1:1) solvent mixture that achieved recoveries of 70-90% with an insignificant interference from the plasma matrix. The analysis was performed on a phenyl column with isocratic elution, a mobile phase composed of 20% methanol, 30% acetonitrile, and 50% KH2PO4 buffer (10mM, with adding 0.02% of TEA; adjusted with phosphoric acid to pH 3.5), and a run time of only 15 min. Linear calibration curves were constructed in the concentration range of 1-200 nM for DM and its three metabolites. The lower limit of quantitation (LLOQ) in human plasma was 1 nM for each compound. The coefficient of variation and RSE% of the intraday and interday analyses for DM and its three metabolites all complied with USFDA requirements. This analytical method was preliminarily applied to determine the polymorphic functions of CYP2D6 and CYP3A4 in the metabolic pathway of DM to DX and then to HM.

Topics: Chromatography, High Pressure Liquid; Dextromethorphan; Dextrorphan; Humans; Reproducibility of Results; Sensitivity and Specificity; Spectrometry, Fluorescence; Time Factors

A rapid, sensitive and selective liquid chromatography-mass spectrometry (LC-MS) method was developed for the simultaneous assay of dextromethorphan and its metabolites in tissue culture medium and its intestinal metabolism studied with the rat everted gut sac model. The method was validated in the concentration range of 0.1-2.5 microM (27.1 ng/mL-0.677 microg/mL) for dextromethorphan and 0.005-0.5 microM for dextrorphan and 3-methoxymorphinan (1.28 ng/mL-0.128 microg/mL) and 3-hydroxymorphinan (1.22 ng/mL-0.122 microg/mL). The limits of quantification (LOQ) were 0.0025 microM (12.5 fmoles, 3.4 pg, 5 microL injected) for dextromethorphan; 0.0025 microM for dextrorphan, 3-methoxymorphinan (24.9 fmoles, 6.4 pg injected), and 3-hydroxymorphinan (25.1 fmoles, 6.1 pg injected) with 10 microL injected. The detection of dextrorphan and 3-methoxymorphinan showed that both the P450 isoforms CYP3A and 2D were active in the intestinal mucosa and metabolised dextromethorphan during its passage across the mucosa.

Topics: Animals; Aryl Hydrocarbon Hydroxylases; Chromatography, Liquid; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP3A; Dextromethorphan; Dextrorphan; In Vitro Techniques; Intestinal Mucosa; Intestine, Small; Male; Mass Spectrometry; Oxidoreductases, N-Demethylating; Rats; Rats, Sprague-Dawley; Reproducibility of Results; Sensitivity and Specificity

An HPLC method has been developed and validated for the determination of dextromethorphan, dextrorphan, 3-methoxymorphinan and 3-hydroxymorphinan in urine samples. Deconjugated compounds were extracted on silica cartridges using dichloromethane/hexane (95:05, v/v) as an eluent. Chromatographic separation was accomplished on a Phenyl analytical column serially connected with a Nitrile analytical column. The mobile phase consisted of a mixture of an aqueous solution, containing 1.5% acetic acid and 0.1% triethylamine, and acetonitrile (75:25, v/v). Compounds were monitored using a fluorescence detector. Calibration curves were linear over the range investigated (0.2-8.0 microM) with correlation coefficients >0.999. The method was reproducible and precise. Coefficients of variation and deviations from nominal values were both below 10%. For all the analytes, recoveries exceeded 77% and the limits of detection were 0.01 microM. The validated assay proved to be suitable for the determination of DEM metabolic indexes reported to reflect the enzymatic activity of the cytochrome P450s, CYP2D6 and CYP3A, both in vivo, when applied to urine samples from patients, and in vitro, when applied to samples from the incubation of liver microsomes with dextromethorphan.

Topics: Aryl Hydrocarbon Hydroxylases; Chromatography, High Pressure Liquid; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP3A; Cytochrome P-450 Enzyme System; Dextromethorphan; Dextrorphan; HIV Infections; Humans; Malaria; Microsomes, Liver; Models, Chemical; Oxidoreductases, N-Demethylating; Reproducibility of Results; Sensitivity and Specificity

Dextromethorphan (DXM) is a widely used probe drug for human CYP2D6 activity both in vitro and in vivo. In humans, DXM is metabolized to dextrorphan (DXO), as well as 3-methoxymorphinan (MEM) and 3-hydroxymorphinan (HYM). The formation of MEM has been attributed primarily to CYP3A4, and the use of DXM has been debated as a simultaneous probe for CYP3A4 and CYP2D6 activities. Recently, we found that highly purified CYP2D6 has significant DXM N-demethylase activity in addition to its well known DXM O-demethylase activity. Therefore, we desired to further compare the contribution to DXM metabolism by individual human cDNA-expressed cytochromes P450, including 2C8, 2C9, 2C18, 2C19, 2D6, 2B6, and 3A4. Metabolites were quantified following separation by high-pressure liquid chromatography and apparent Michaelis-Menten constants determined for the appearance of DXO and MEM. Intrinsic clearance values were estimated for each P450 and normalized using the average percentage content and relative activity factor approaches for comparison. Simplified kinetic models (when [S] << K(m), V(max)/K(m) = V(o)/[S]) were used at fixed DXM concentrations of 20 (for DXM N-demethylation) and 0.2 microM (for DXM O-demethylation), as well as 2 microM to mimic plasma DXM concentrations in human extensive metabolizers. The results confirm that CYP2D6 contributes at least 80% to the formation of DXO, and CYP3A4 contributes more than 90% to the formation of MEM. All of our in vitro results are consistent and indicate that DXM as a marker for monitoring both CYP2D6 and CYP3A activities is practical in an average human or human liver microsomal preparation.

Topics: Antitussive Agents; Aryl Hydrocarbon Hydroxylases; Chromatography, High Pressure Liquid; Cytochrome P-450 CYP2D6; Cytochrome P-450 CYP3A; Cytochrome P-450 Enzyme System; Dextromethorphan; Dextrorphan; Humans; Isoenzymes; Microsomes, Liver; Oxidoreductases, N-Demethylating

A sensitive capillary electrophoretic method was developed and validated for the simultaneous determination of dextromethorphan and its metabolites, dextrorphan, 3-hydroxymorphinan, and 3-methoxymorphinan, in human plasma. After cleavage of conjugates by enzymatic hydrolysis with beta-glucuronidase, dextromethorphan and its metabolites were extracted from 1.5 ml of plasma by a liquid liquid extraction procedure using heptane-ethylacetate (50:50, v/v) and re-extracted to aqueous phase. The compounds were separated within 8 min on a fused silica capillary, 75 microm internal diameter using sodium borate (pH 9.4; 50 mM) as running buffer, and measured by UV-detection at 195 nm using a detection cell with a path length of 1.2 mm. The method was accurate and precise. Linear relationships were observed between the peak response and the concentration in the range of 1-400 ng ml(-1) plasma with correlation coefficients above 0.998. The limit of detection was 0.5-1 ng ml(-1) plasma for all compounds. The method was used for determination of plasma levels of dextromethorphan and its metabolites after transdermal and oral administration of dextromethorphan.

Topics: Administration, Cutaneous; Administration, Oral; Dextromethorphan; Dextrorphan; Electrophoresis, Capillary; Excitatory Amino Acid Antagonists; Humans; Models, Chemical; Reproducibility of Results; Sensitivity and Specificity; Spectrophotometry, Ultraviolet

1. The enzyme kinetics of dextromethorphan O-demethylation in liver microsomes from three extensive metabolisers (EM) with respect to CYP2D6 indicated high (Km1 2.2-9.4 microM) and low (Km2 55.5-307.3 microM) affinity sites whereas microsomes from two poor metabolisers (PM) indicated a single site (Km 560 and 157 microM). Similar differences were shown for 3-methoxymorphinan O-demethylation to 3-hydroxymorphinan (Km 6.9-9.6 microM in EM subjects; Km 307 and 213 microM in PM subjects). 2. Dextromethorphan O-demethylation was inhibited competitively by quinidine (Ki 0.1 microM), rac-perhexiline (Ki 0.4 microM), dextropropoxyphene (Ki 6 microM), rac-methadone (Ki 8 microM), and 3-methoxymorphinan (Ki 15 microM). These compounds were also potent inhibitors of 3-methoxymorphinan O-demethylation with IC50 values ranging from 0.02-12 microM. Anti-LKM1 serum inhibited both dextromethorphan and 3-methoxymorphinan O-demethylations in a titre-dependent manner. 3. The Michaelis-Menten constant for dextromethorphan N-demethylation to 3-methoxymorphinan (Km 632-977 microM) and dextrorphan N-demethylation to 3-hydroxymorphinan (Km 1571-4286 microM) did not differ between EM and PM microsomes. These N-demethylation reactions were not inhibited by quinidine and rac-methadone or LKM1 antibodies. 4. Dextromethorphan and 3-methoxymorphinan are metabolised by the same P450 isoform, CYP2D6, whereas the N-demethylation reactions are not carried out by CYP2D6.

Topics: Autoantibodies; Binding, Competitive; Cytochrome P-450 CYP2D6; Cytochrome P-450 Enzyme System; Dextromethorphan; Dextropropoxyphene; Dextrorphan; Humans; In Vitro Techniques; Methadone; Methylation; Microsomes, Liver; Mixed Function Oxygenases; Oxidation-Reduction; Perhexiline; Phenotype; Quinidine

A simple, sensitive, and reproducible high-performance liquid chromatrography assay is described for the simultaneous determination of dextromethophan, dextrorphan, 3-hydroxymorphinan, and 3-methoxymorphinan in plasma and urine. A conventional solvent-solvent extraction procedure was used for the isolation of the analytes from plasma and urine samples. The compounds were separated on a cyano column (150 x 4.6 mm, 5-micron particle size) using a mobile phase of acetonitrile/triethylamine/distilled water (17:0.06:82.94, vol/vol), pH 3.0, and then were measured by fluorescence detection. Calibration curves in the range 2-200 ng/ml for plasma and 0.05-10 micrograms/ml for urine were linear and passed through the origin. The precision and accuracy were greater than 90% and the lowest detectable concentrations were 0.5 ng/ml for 3-hydroxymorphinan and 3-methoxymorphinan and 1 ng/ml for dextromethorphan and dextrophan in plasma. The utility of this method is demonstrated in a preliminary study of dextromethorphan metabolism and pharmacokinetics in man.

Topics: Chromatography, High Pressure Liquid; Dextromethorphan; Dextrorphan; Glucuronidase; Humans; Levorphanol

Polymorphic differences in dextromethorphan metabolism were observed in three studies conducted in a total of 44 subjects (of Dutch origin) administered 60 mg dextromethorphan hydrobromide as an OROS tablet. Mean plasma dextromethorphan (DM) concentrations after a single dose and at steady state were 4-75 times higher in the poor metabolizers (PM) relative to the extensive metabolizers (EM). Following a single dose, the mean areas under the plasma concentration-time curve (AUC, 0-24 hr) of DM, total dextrorphan (DR), and total 3-hydroxymorphinan (HM) were 6.9-fold higher, 17.4-fold lower, and 11-fold lower, respectively, for the PM than for the EM. Correspondingly, steady-state AUC values were 52.8 times higher, 6.7 times lower, and 3.3 times lower for DM, total DR, and total HM, respectively, for the PM relative to the EM. Drug/metabolite ratios (DMR) for amounts excreted in the urine of DR and HM indicated polymorphism in O-demethylation of DM since DMR for PM was 352 and 338 times higher than that for EM for DR and HM, respectively. However, polymorphism in N-demethylation was not observed. Ratios of conjugated/free dextrorphan and 3-hydroxymorphinan excreted in the urine suggest also a lack of conjugative capacity in the PM, relative to the EM. The overall incidence of PM was 9.1% in this population.

Topics: Administration, Oral; Dextromethorphan; Dextrorphan; Humans; Levorphanol; Phenotype

Topics: Chromatography, High Pressure Liquid; Dextromethorphan; Dextrorphan; Humans; Hydrolysis; Levorphanol; Morphinans