Prescription Opioids. V. Metabolism and Excretion of Oxymorphone in Urine Following Controlled Single Dose Administration

Oxymorphone (OM), a prescription opioid and metabolite of oxycodone, was included in the recently published proposed revisions to the Mandatory Guidelines for Federal Workplace Drug Testing Programs. To facilitate toxicological interpretation, this study characterized the time course of OM and its metabolite, noroxymorphone (NOM), in hydrolyzed and non-hydrolyzed urine specimens. Twelve healthy subjects were administered a single 10 mg controlled-release OM dose, followed by a periodic collection of pooled urine specimens for 54 h following administration. Analysis for free and total OM and NOM was conducted by liquid chromatography tandem mass spectrometry (LC-MS-MS), at a 50 ng/mL limit of quantitation (LOQ). Following enzymatic hydrolysis, OM and NOM were detected in 89.9% and 13.5% specimens, respectively. Without hydrolysis, OM was detected in 8.1% specimens, and NOM was not detected. The mean ratio of hydrolyzed OM to NOM was 41.6. OM was frequently detected in the first pooled collection 0-2 h post-dose, appearing at a mean of 2.4 h. NOM appeared at a mean of 8.3 h. The period of detection at the 50 ng/mL threshold averaged 50.7 h for OM and 11.0 h for NOM. These data support that OM analysis conducted using a 50 ng/mL threshold should include hydrolysis or optimize sensitivity for conjugated OM.

[Determination of dimemorfan in human plasma and urine with HPLC-MS/MS]

OBJECTIVE

To develop a sensitive and reproducible HPLC-MS/MS method for analyzing dimemorfan in human plasma and urine.

METHODS

Dimemorfan was extracted from plasma and urine by redistilled ether, with lidocaine serving as the internal standard (IS). The analysis was performed on a column of ultimate C18 (50 mm x 4.6 mm, 5 microm) with the mobile phase consisting of methyl alcohol-water-formic acid = 75:25 : 0.05 at a flow rate of 0. 2 mL/min. Dimemorfan was detected by API 3000 mass spectrometer, with multiple reaction monitoring after protonated with ESI in positive electron ionization mode. The ion pairs being detected were (m/z) 256.4-->155. 3 (dimemorfan) and 235.4-->86.1 (lidocaine), respectively.

RESULTS

The regression equation for dimemorfan showed excellent linearity (r = 0.995 7) from 0. 025 to 5.0 ng/mL of plasma with detecting limitation of 0.025 ng/mL and perfect linearity (r = 0.9983) from 0.1 to 20.0 ng/mL of urine with detecting limitation of 0.1 ng/mL. The method recoveries of dimemorfan in plasma and urine were ranging from 103.38% to 106.88% and 90.05% to 101.40%, respectively. The maximum intra-day and inter-day relative standard deviations (RSD) of concentration of dimemorfan were 5.92% and 5. 70% (for plasma), 10.35% and 8.80% (for urine), respectively.

CONCLUSION

This new method was validated to be accurate and sensitive to determinate the concentration of dimemorfan in plasma and urine samples, and can be applied for pharmacokinetic studies of dimemorfan.

Monitoring oxycodone use in patients with chronic pain: analysis of oxycodone and metabolite excretion in saliva and urine

OBJECTIVE

Saliva is purported to have a close correspondence to plasma concentrations due to a passive diffusion process from plasma to saliva. However, limited data are available characterizing oxycodone and its metabolites in saliva. The purpose of this analysis was to evaluate the use of saliva monitoring in patients prescribed oxycodone and to compare the disposition of oxycodone in saliva and urine.

DESIGN

This retrospective analysis examined deidentified urine and saliva specimens collected from patients with chronic pain. These specimens were received at Millennium Laboratories between March and June 2012 and analyzed using LCMS/MS to quantitate oxycodone, noroxycodone, and oxymorphone concentrations.

RESULTS

The geometric mean metabolic ratio (MR) of noroxycodone to oxycodone in saliva was 0.11, whereas the geometric mean MR in urine was 1.7. The geometric mean oxycodone concentration in saliva was 860 ng/mL (range, 1.5-8,600,000 ng/mL; 95% CI, 770-950 ng/mL), whereas the geometric mean noroxycodone concentration was 98 ng/mL (range, 2.3-8,800 ng/mL; 95% CI, 90-107 ng/mL). Fifty-four of the saliva specimens (6 percent) had oxycodone concentrations between 10,000 and 9,000,000 ng/mL.

CONCLUSIONS

Oxycodone is predominant over noroxycodone in saliva (similar to plasma), while the reverse relationship exists in urine. Much greater oxycodone concentrations were found in saliva than are expected in plasma (up to a 1,000-fold difference). Saliva concentrations are lower than urine concentrations but still may not reflect plasma disposition. Possible explanations include medication residue in the mouth (recent medication use or misuse) or active secretion into saliva. Saliva analysis may be used for qualitative drug monitoring of oxycodone, with detection rates similar to urine; however, further characterization is needed for appropriate interpretation.

Three major urinary metabolites of sinomenine in rats

Urinary metabolites of sinomenine were investigated in rats after intragastric administration. Three major metabolites were obtained and characterised as 4-hydroxy-3,7,7-trimethoxy-17-methyl-(9alpha,13alpha,14alpha)-morphinan-6-one (1), 7,8-didehydro-4-hydroxy-3,7-dimethoxy-17-methyl-N-oxide-(9alpha,13alpha,14alpha)-morphinan-6-one (2), and 7,8-didehydro-4-hydroxy-3,7-dimethoxy-(9alpha,13alpha,14alpha)-morphinan-6-one (3). Their structures have been elucidated on the base of spectral analysis, among which 1 and 2 were new compounds.

Analysis of oxycodol and noroxycodol stereoisomers in biological samples by capillary electrophoresis

A capillary electrophoresis (CE) method for the separation of the diastereoisomers of 6-oxycodol (6OCOL) and nor-6-oxycodol (N6OCOL), the 6-keto-reduced metabolites of oxycodone (OCOD) and noroxycodone (NOCOD), respectively, is reported and employed to assess the stereoselectivity of these metabolic steps in vivo, in vitro, and in chemical synthesis. CE in an untreated fused-silica capillary with acidic buffers containing 2-hydroxypropyl-beta-cyclodextrin, randomly sulfated beta-cyclodextrin, or single isomer heptakis(2,3-diacetyl-6-sulfato)-beta-cyclodextrin (HDAS-beta-CD) is shown to permit the simultaneous separation of the stereoisomers of 6OCOL and N6OCOL. A 100 mM phosphate buffer of pH 2.0 containing 2.05% w/v HDAS-beta-CD provides a medium for rapid analysis and unambiguous identification of these stereoisomers in solid-phase extracts of (i) urines stemming from patients under pharmacotherapy with OCOD, (ii) incubations of OCOD and NOCOD with human liver cytosol and the human liver S9 fraction, and (iii) after chemical synthesis from OCOD and NOCOD using NaBH(4). In all cases, alpha-N6OCOL is shown to be the predominant stereoisomer of N6OCOL. For 6OCOL, the same is true for in vitro formation and for chemical synthesis. In urine, however, beta-6OCOL is observed to be excreted in a higher amount than alpha-6OCOL. For the urinary alpha-/beta-isomer ratio of 6OCOL and N6OCOL, there are no differences between the data obtained for nonhydrolyzed and enzymatically hydrolyzed urines. The data document the stereoselectivity of the 6-keto-reduction of OCOD and NOCOD in man.

Tentative Identification of Novel Oxycodone Metabolites in Human Urine

Oxycodone is a semisynthetic codeine derivative that has been used both as an analgesic and antitussive. In the mid 1990s, OxyContin was introduced as a slow-release formulation of oxycodone for use in patients with moderate to severe chronic pain from such ailments as arthritis, vertebral disc disease, and cancer. Doctors wrote 6.9 million prescriptions for OxyContin from May 2000 through May 2001. Thus, it is no surprise that hospitals and medical examiners' offices across the country have seen an increasing number of admissions and deaths resulting from oxycodone abuse and overdose. The laboratory identifies oxycodone as part of its routine abused and therapeutic drug-testing procedures. Routine gas chromatographic analysis of bile or urine in many of these cases revealed unidentified peaks in the region of oxycodone that appeared to be oxycodone metabolites. In humans, the only documented metabolites of oxycodone are oxymorphone and N-desmethyloxycodone (noroxycodone). This study attempts to characterize these compounds as "presumptive" metabolites based on circumstantial evidence from known metabolic pathways of oxycodone in other species, as well as of other opiates and narcotic analgesics.

[Determination of sinomenine HCl in serum and urine by HPLC and its pharmacokinetics in normal volunteers]

A RP-HPLC method was developed to determine the concentrations of sinomenine HCl in serum and urine and its pharmacokinetics was studied in healthy volunteers. C18H37 column was eluted with the mobile phase of acetonitrile--0.01 mol.L-1 sodium phosphate monobasic--N, N, N', N'-tetramethylenediamine (46:54:0.22 v/v, pH 6.9) and the ultraviolet absorbance was monitored at 263 nm. Triazolan was used as internal standard. The calibration curves were linear in the range of 6-480 ng.ml-1 in serum and 0.06-3 micrograms.ml-1 in urine, with mean recoveries of 75.46% and 91.38% respectively. The lowest detectable limits were 4 ng.ml-1 in serum and 40 ng.ml-1 in urine and the RSD for the intra-day and inter-day were less than 5%. A single oral dose of 80 mg sinomenine HCl tablet was given to 8 healthy male volunteers. The concentrations of sinomenine HCl in serum and urine were determined. The serum concentration--time curve was found to fit a two-compartment open model with first order elimination. The pharmacokinetic parameters were: T1/2 alpha 0.791 +/- 0.491 h, T1/2 beta 9.397 +/- 2.425 h, Tmax 1.040 +/- 0.274 h, Cmax 246.604 +/- 71.165 ng.ml-1, AUC 2651.158 +/- 1039.050 ng.h.ml-1, CL 0.033 +/- 0.010 ng.ml-1.

The pharmacokinetics of oxycodone in uremic patients undergoing renal transplantation

STUDY OBJECTIVE

To determine the pharmacokinetics of oxycodone and the excretion of oxycodone and its metabolites noroxycodone and oxymorphone in uremic patients undergoing renal transplantation.

DESIGN

Open study of the pharmacokinetics and excretion of oxycodone.

SETTING

IV Department of Surgery, Helsinki University Central Hospital.

PATIENTS

10 uremic patients undergoing renal transplantation and 10 ASA status I patients undergoing general surgery.

INTERVENTIONS

Intravenous (IV) oxycodone chloride 0.07 mg/kg was administered 30 minutes before induction of standardized anesthesia. Sampling of blood and urine was conducted for 24 hours.

MEASUREMENTS AND MAIN RESULTS

The concentrations of oxycodone and noroxycodone in plasma and the 24 hour urine recoveries of the conjugated and unconjugated forms of oxycodone, noroxycodone, and oxymorphone were measured. Mean elimination half-life was prolonged in uremic patients due to increased volume of distribution and reduced clearance. Interindividual variation was very great. Plasma concentrations of noroxycodone were higher in uremic patients. Significantly smaller quantities of free oxycodone and noroxycodone and both free and conjugated oxymorphone were excreted in the urine in the uremic than in the control patients.

CONCLUSIONS

Elimination of oxycodone is impaired in end-stage renal failure.

The pharmacokinetics and metabolism of oxycodone after intramuscular and oral administration to healthy subjects

1. The pharmacokinetics and metabolism of oxycodone were studied in nine healthy young volunteers in a cross-over study. Each subject received oxycodone chloride once intramuscularly (0.14 mg kg-1) and twice orally (0.28 mg kg-1) at intervals of 2 weeks. A double-blind randomized pretreatment with amitriptyline (10-50 mg a day) or placebo was given prior to oral oxycodone. 2. The concentrations of oxycodone, noroxycodone and oxymorphone in plasma and the 24 h urine recoveries of their conjugated and unconjugated forms were measured by gas chromatography. 3. No differences were found between treatments in mean Cmax and AUC values of oxycodone which varied from 34 to 38 ng ml-1 and from 208 to 245 ng ml-1 h, respectively. The median tmax of oxycodone was 1 h in all groups. The bioavailability of oral relative to i.m. oxycodone was 60%. The mean renal clearance of oxycodone was 0.07-0.08 l min-1. The kinetics of oxycodone were unaffected by amitriptyline. 4. The mean ratio of the AUC(0.24 h) values of unconjugated noroxycodone to oxycodone was 0.45 after i.m. oxycodone and 0.6-0.8 after oral oxycodone. Plasma oxymorphone concentrations were below the limit of the assay. Eight to 14% of the dose of oxycodone was excreted in the urine as unconjugated and conjugated oxycodone over 24 h. Oxymorphone was excreted mainly as a conjugate whereas noroxycodone was recovered mostly in an unconjugated form.

GC/MS confirmatory method for etorphine in horse urine

A highly sensitive procedure for GC/MS determination of etorphine in horse urine is described. This assay provides both specificity and reliability and is particularly well suited for the confirmation of radioimmunoassay screening procedures usually used for etorphine. After solvent extraction and purifications, the etorphine is characterized as a pentafluoroacetic derivative (PFAA) by using mass fragmentography. The detection limit is 0.1 ng/mL in urine; the coefficient of variation of the estimations is 10.9%. The procedure has been validated after on-field administration of 5 to 90 micrograms of etorphine to five thoroughbred horses (10 to 180 ng/kg).

Determination of dextromethorphan metabolizer phenotype in healthy volunteers

The dextromethorphan metabolizer phenotype in 450 healthy volunteers (299 men, 151 women) was determined after oral administration of a 15 mg dose. In 8 h-postdose urine samples the ratio of dextrorphan (DOP) to dextromethorphan (DMP) was measured by HPLC. Urinary excretion of DMP and DOP within 8 h after the dose varied greatly between individuals, ranging from 0-11% and 0.04-100% of dose, respectively. In 143 test subjects the fraction of the dose of DMP in urine was below the detection limit. In the remaining 307 volunteers the metabolic ratio (MR) of DOP to DMP varied from 0.07 to 2906. In 404 test subjects the MR was greater than 10 and they were classified as extensive metabolizers (90% of the entire group). Of the entire group 5% had MRs of 1-10 and less than 1, respectively. Depending on the limit for classification of poor metabolizers, their frequency was 5-10% in the Caucasian population studied. The present data are in agreement with previous findings that the oxidative metabolic polymorphisms of debrisoquin and DMP co-segregate; the frequency of the PM phenotype of dextromethorphan in Caucasian populations varies between 5 and 10%.

Radioimmunoassay screening for etorphine in racing horses

A commercially available radioimmunoassay kit was used to screen for the presence of etorphine in post-race urines from horses racing in Kentucky. Most horse urines contained small amounts of materials which reacted positively in this immunoassay. These materials are apparently endogenous to the horse and were called apparent etorphine equivalents. The levels of these apparent etorphine equivalents in post-race urines from 70 horses were estimated. Their modal level averaged 0.1 ng/ml, the population distribution was log normal, and individual horses showed levels of up to 0.8 ng/ml.

Polymorphic dextromethorphan metabolism: co-segregation of oxidative O-demethylation with debrisoquin hydroxylation

Dextromethorphan hydrobromide, 25 mg po, was given to 268 unrelated Swiss subjects to study urinary drug and metabolite profiles. Rates of O-demethylation yielding the main metabolite dextrorphan were expressed by the urinary dextromethorphan/dextrorphan metabolic ratio. We found a bimodal distribution of this parameter in our population study, which indicates that there are two phenotypes for dextromethorphan O-demethylation. The antimode at a metabolic ratio of 0.3 separated the poor metabolizer (PM; n = 23; prevalence of 9%) from extensive metabolizer (EM) phenotypes. Urinary output of dextrorphan was less than 6% of the dose in all PMs and was 50% in the 245 EMs. Pedigree analysis of 14 family studies revealed an autosomal-recessive transmission of deficient dextromethorphan O-demethylation. In these families, 37 heterozygous genotypes could be identified; however, through use of the urinary drug and metabolite analysis it was not possible to identify the heterozygous genotypes within the EM phenotype group. Co-segregation of dextromethorphan O-demethylation with debrisoquin 4-hydroxylation was also studied. Complete concordance of the two phenotypic assignments was obtained, with a Spearman rank correlation coefficient of rs = 0.78 (n = 62; P less than 0.0001) for dextromethorphan and debrisoquin metabolic ratios. Presumably the two drug oxidation polymorphisms are under the same genetic control. Thus the innocuousness and ubiquitous availability of dextromethorphan render it attractive for worldwide pharmacogenetic investigations in man.

Quantitation of etorphine in urine by selective ion monitoring using tritiated etorphine as an internal standard

Selective ion monitoring combined with GLC was used for the assay of etorphine in urine. Commercially available tritiated etorphine was added as an internal standard. The advantage of the methodology using this internal standard is higher sensitivity by a factor of about 20 when compared with ordinary GLC.

General procedure for the isolation and identification of 6-alpha- and 6-beta-hydroxy metabolites of narcotic agonists and antagonists with a hydromorphone structure

In order to aid in the elucidation of the metabolism of drugs containing the hydromorphone structure, a method is described for isolation from urine, separation and identification of the 6-alpha- and 6-beta-hydroxy metabolites. The samples were acid-hydrolyzed, extracted, and separated by thin-layer chromatography. The zone containing the hydroxy metabolites was removed and the compounds were re-extracted and analyzed by gas-liquid chromatography (GLC). Silylation of the extract was necessary in most cases for optimum GLC resolution of the alpha- and beta-hydroxy epimers. To demonstrate application of this method, the urine of guinea-pigs and rats which had received a single 40-mg dose of naloxone subcutaneously was analyzed. Analysis indicated a alpha/beta ratio of 0.41 for the guinea-pig. In contrast, the amount of 6-alpha-naloxol found in the urine of the rat was negligible in comparison with the 6-beta-hydroxy metabolite, indicating a species difference in the stereospecificity of the drug-metabolizing enzyme.

GLC determination of l-2-hydroxy-N-cyclopropylmethylmorphinan in plasma and urine

A specific method was developed for the determination of l-2-hydroxy-N-cyclopropylmethylmorphinan in plasma and urine by GLC, using flame-ionization detection. The method involves the extraction of the compound into ether from plasma or urine at pH 7.4, followed by back-extraction into 1 N HCl. The acid phase is ether washed and made alkaline, and the compound is reextracted into ether. The ether is evaporated to dryness, the residue is dissolved in methanol, and an aliquot is analyzed by GLC. The same method is applicalble to plasma and urine samples following deconjugation of the compound with glucuronidase-sulfatase. The overall recovery is 93.1 +/- 9.4% SD) in the concentration range of 0.020-2.0 microgram/ml. The method was successfully applied to plasma and urine specimens obtained after administering single 25-mg oral doses to humans.

Etrophine in man. II. Detectability in urine by common screening methods

A single highly euphorogenic dose of etorphine, 100 mug, was administered subcutaneously to 7 nontolerant subjects, and all urine samples were collected for 1 day prior to and 3 days following drug administration. Samples were analyzed for the presence of opiates by radioimmunoassay (Abuscreen) and homogeneous enzyme immunoassay (EMIT), with cutoffs for "ositives" of 40 and 500 ng/ml, respectively. Samples were analyzed for etorphine by thin-layer chromatography (TLC) with iodoplatinate preceded by XAD-2 resin extraction (sensitivity = 0.2 mug etorphine/ml of urine) and by gas-liquid chromatography (GLC) preceded by organic solvent extraction and trimethylsilyl derivatization (sensitivity = 0.1 mug etorphine/ml of urine). The last pre-drug and first two post-drug samples were also analyzed after acid hydrolysis by TLC and after glucuronidase hydrolysis by TLC and GLC. No sample gave a "positive" opiate result in either immunoassay, and no etorphine was detected in the TLC and GLC analyses of any urine sample. Thus, it is unlikely that the abuse of etorphine could be diagnosed by urinalysis using the common screening methods of radioimmunoassay, EMIT, TLC preceded by XAD-2 resin extraction, or GLC preceded by organic solvent extraction and trimethylsilyl derivatization.

Some aspects of the metabolism of morphine-N-oxide

After administration of morphine-N-oxide (MNO) to rats the opiates appearing in the urine were morphine (61%) and MNO (39%). After administration of morphine, the urinary opiates were morphine (80%) and normorphine (20%). When tacrine was given with morphine the urine also contained MNO (46% of total urinary opiates) and the amount of normorphine was much decreased (to 1%), the remainder being morphine (53%). Tacrine and amiphenazole inhibited demethylation of morphine and codeine by a rat liver fraction in vitro. MNO had weak inhibitory activity. Neither MNO nor codeine-N-oxide were demethylated in vitro.