Neurologically active plant compounds and peptide hormones: a chirality connection.
The most dramatic, but seldom mentioned, difference between alkaloid and peptide opioids is the change of chirality of the alpha carbon of the tyramine moiety. We propose that the presence of Gly2 or D-Ala2 in the two most common message domains compensates this change by allowing the attainment of unusual conformations. A thorough conformational search of Tyr-D-Ala-Phe-NH-CH3 and of its isomer Tyr-L-Ala-Phe-NH-CH3 backs this view and establishes a solid link between alkaloid and peptide opioids. This finding supports the notion that morphine, like other neurologically active plant compounds, may bind to endogenous receptors in plants to regulate cell-to-cell signaling systems. (+info)
GC-MS confirmation of codeine, morphine, 6-acetylmorphine, hydrocodone, hydromorphone, oxycodone, and oxymorphone in urine.
A procedure for the simultaneous confirmation of codeine, morphine, 6-acetylmorphine, hydrocodone, hydromorphone, oxycodone, and oxymorphone in urine specimens by gas chromatography-mass spectrometry (GC-MS) is described. After the addition of nalorphine and naltrexone as the two internal standards, the urine is hydrolyzed overnight with beta-glucuronidase from E. coli. The urine is adjusted to pH 9 and extracted with 8% trifluoroethanol in methylene dichloride. After evaporating the organic, the residue is sequentially derivatized with 2% methoxyamine in pyridine, then with propionic anhydride. The ketone groups on hydrocodone, hydromorphone, oxycodone, oxymorphone, and naltrexone are converted to their respective methoximes. Available hydroxyl groups on the O3 and O6 positions are converted to propionic esters. After a brief purification step, the extracts are analyzed by GC-MS using full scan electron impact ionization. Nalorphine is used as the internal standard for codeine, morphine, and 6-acetylmorphine; naltrexone is used as the internal standard for the 6-keto-opioids. The method is linear to 2000 ng/mL for the 6-keto-opioids and to 5000 ng/mL for the others. The limit of quantitation is 25 ng/mL in hydrolyzed urine. Day-to-day precision at 300 and 1500 ng/mL ranged between 6 and 10.9%. The coefficients of variation for 6-acetylmorphine were 12% at both 30 and 150 ng/mL. A list of 38 other basic drugs or metabolites detected by this method is tabulated. (+info)
Adaptation of stress-induced mucosal pathophysiology in rat colon involves opioid pathways.
Acute stress increases ion secretion and permeability of rat colonic epithelium. However, it is not known if stress-induced mucosal changes are subject to adaptation. Wistar-Kyoto rats were exposed to either continuous water-avoidance stress (CS) for 60 min or intermittent stress (IS) for three 20-min periods. Distal colonic segments were mounted in Ussing Chambers, and ion-transport [short-circuit current (I(sc))] and permeability [conductance and flux of horseradish peroxidase (HRP)] parameters were measured. CS significantly increased I(sc), conductance, and HRP flux compared with control values. In contrast, in IS rats these variables were similar to those in nonstressed controls. To study the pathways involved in IS-induced adaptation, rats were pretreated intraperitoneally with the opioid antagonists naloxone or methylnaloxone. Opioid antagonists had no effect on values in control or CS rats. However, in the IS group, naloxone and methylnaloxone reversed the adaptive responses, and all variables increased to CS values. We conclude that stress-induced colonic mucosal pathophysiology is subject to rapid adaptation, which involves opioid pathways. (+info)
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. (+info)
Quantitative contribution of CYP2D6 and CYP3A to oxycodone metabolism in human liver and intestinal microsomes.
Oxycodone undergoes N-demethylation to noroxycodone and O-demethylation to oxymorphone. The cytochrome P450 (P450) isoforms capable of mediating the oxidation of oxycodone to oxymorphone and noroxycodone were identified using a panel of recombinant human P450s. CYP3A4 and CYP3A5 displayed the highest activity for oxycodone N-demethylation; intrinsic clearance for CYP3A5 was slightly higher than that for CYP3A4. CYP2D6 had the highest activity for O-demethylation. Multienzyme, Michaelis-Menten kinetics were observed for both oxidative reactions in microsomes prepared from five human livers. Inhibition with ketoconazole showed that CYP3A is the high affinity enzyme for oxycodone N-demethylation; ketoconazole inhibited >90% of noroxycodone formation at low substrate concentrations. CYP3A-mediated noroxycodone formation exhibited a mean K(m) of 600 +/- 119 microM and a V(max) that ranged from 716 to 14523 pmol/mg/min. Contribution from the low affinity enzyme(s) did not exceed 8% of total intrinsic clearance for N-demethylation. Quinidine inhibition showed that CYP2D6 is the high affinity enzyme for O-demethylation with a mean K(m) of 130 +/- 33 microM and a V(max) that ranged from 89 to 356 pmol/mg/min. Activity of the low affinity enzyme(s) accounted for 10 to 26% of total intrinsic clearance for O-demethylation. On average, the total intrinsic clearance for noroxycodone formation was 8 times greater than that for oxymorphone formation across the five liver microsomal preparations (10.5 microl/min/mg versus 1.5 microl/min/mg). Experiments with human intestinal mucosal microsomes indicated lower N-demethylation activity (20-50%) compared with liver microsomes and negligible O-demethylation activity, which predict a minimal contribution of intestinal mucosa in the first-pass oxidative metabolism of oxycodone. (+info)
GC-MS quantitation of codeine, morphine, 6-acetylmorphine, hydrocodone, hydromorphone, oxycodone, and oxymorphone in blood.
A method is described for the simultaneous analysis of seven opiates, codeine, morphine, 6-acetylmorphine, hydrocodone, hydromorphone, oxycodone, and oxymorphone, in blood samples by gas chromatography-mass spectrometry (GC-MS). One milliliter of blood is combined with an internal standard mixture containing 200 ng of each of the seven deuterated opiates. Two milliliters of acetonitrile is added to precipitate the proteins and cellular material. After centrifugation, the clear supernatant is removed, and the acetonitrile is evaporated. The remaining aqueous portion is adjusted to pH 9 with sodium bicarbonate buffer, and the drugs are extracted into chloroform/ trifluoroethanol (10:1). The organic extractant is transferred and dried under nitrogen. The residue is reconstituted in dilute hydrochloric acid and washed consecutively with hexane and chloroform. The purified aqueous portion is adjusted to pH 9 with bicarbonate buffer, and the drugs are again extracted into chloroform/trifluoroethanol (10:1). The organic portion is removed from the aqueous fraction and dried under nitrogen. The residue is consecutively derivatized with methoxyamine and propionic anhydride using pyridine as a catalyst. The ketone groups on hydrocodone, hydromorphone, oxycodone, and oxymorphone are converted to methoximes. Hydroxyl groups present at the O(3) and O(6) positions of codeine, morphine, 6-acetylmorphine, hydromorphone, and oxymorphone are converted to their respective propionyl esters. After a post-derivatization purification step, the extracts are analyzed by full scan GC-MS using electron impact ionization. The method is linear to at least 2000 ng/mL. Day-to-day precision (N = 15) at 500 ng/mL and 75 ng/mL were less than 10% for all seven targeted opiates. Extraction efficiencies at these two concentrations ranged from 50% to 68%. For each opiate, the limit of quantitation was 10 ng/mL, and the limit of detection was 2 ng/mL. (+info)
Evaluation of the DRI oxycodone immunoassay for the detection of oxycodone in urine.
We evaluated the performance of the DRI Oxycodone (DRI-Oxy) enzyme immunoassay for the detection of oxycodone and its primary metabolite, oxymorphone, in urine, by testing 1523 consecutive urine specimens collected from pain management patients. All 1523 specimens were tested with the DRI-Oxy assay at a cut-off of 100 ng/mL and then analyzed by gas chromatography-mass spectrometry (GC-MS) for opiates, including oxycodone and oxymorphone. Approximately 29% (435) of the 1523 specimens yielded positive results by the DRI-Oxy assay. Of these 435 specimens, GC-MS confirmed the presence of oxycodone and/or oxymorphone at >100 ng/mL in 433 specimens, an agreement of 99.5%. In addition to oxycodone and/or oxymorphone, 189 of the 433 positive specimens contained other opiates including codeine, hydrocodone, hydromorphone, and morphine. These other opiates were also present in 54% (590/1084) of the oxycodone negative specimens. The DRI-Oxy assay demonstrated no cross-reactivity, yielding negative results, with specimens containing concentrations of codeine, >75,000 ng/mL; hydrocodone, >75,000 ng/mL; hydromorphone, >12,000 ng/mL; and morphine, >163,000 ng/mL. From the presented study, the sensitivity of the DRI-Oxy was 0.991 and the selectivity 0.998. The DRI-Oxy assay provided a highly reliable method for the detection of oxycodone and/or oxymorphone in urine specimens. (+info)
Antinociception by spinal and systemic oxycodone: why does the route make a difference? In vitro and in vivo studies in rats.
BACKGROUND: The pharmacology of oxycodone is poorly understood despite its growing clinical use. The discrepancy between its good clinical effectiveness after systemic administration and the loss of potency after spinal administration led the authors to study the pharmacodynamic effects of oxycodone and its metabolites using in vivo and in vitro models in rats. METHODS: Male Sprague-Dawley rats were used in hot-plate, tail-flick, and paw-pressure tests to study the antinociceptive properties of morphine, oxycodone, and its metabolites oxymorphone and noroxycodone. Mu-opioid receptor agonist-stimulated GTPgamma[S] autoradiography was used to study G-protein activation induced by morphine, oxycodone, and oxymorphone in the rat brain and spinal cord. Spontaneous locomotor activity was measured to assess possible sedation or motor dysfunction. Naloxone and the selective kappa-opioid receptor antagonist nor-binaltorphimine were used to study the opioid receptor selectivity of the drugs. RESULTS: Oxycodone showed lower efficacy and potency to stimulate GTPgamma[S] binding in the spinal cord and periaqueductal gray compared with morphine and oxymorphone. This could relate to the fact that oxycodone produced only weak naloxone-reversible antinociception after intrathecal administration. It also suggests that the metabolites may have a role in oxycodone-induced analgesia in rats. Intrathecal oxymorphone produced strong long-lasting antinociception, whereas noroxycodone produced antinociception with very high doses only. Subcutaneous administration of oxycodone and oxymorphone produced thermal and mechanical antinociception that was reversed by naloxone but not by nor-binaltorphimine. Oxymorphone was more potent than oxycodone, particularly in the hot-plate and paw-pressure tests. CONCLUSIONS: The low intrathecal potency of oxycodone in rats seems be related to its low efficacy and potency to stimulate mu-opioid receptor activation in the spinal cord. (+info)