Pain management in chronic kidney disease: the pharmacokinetics and pharmacodynamics of hydromorphone and hydromorphone-3-glucuronide in hemodialysis patients

OBJECTIVE

To describe the pharmacokinetics of hydromorphone (HM) and its primary metabolite hydromorphone-3-glucuronide (H3G) both on and off dialysis in relation to the pharmacodynamic measurements of pain.

DESIGN

Prospective, open-label, observational study.

SETTING

Canadian, university-based renal program.

PARTICIPANTS

Twelve anuric hemodialysis patients with chronic pain, established on immediate-release HM.

MAIN OUTCOME MEASURES

HM and H3G plasma concentrations were measured during and between hemodialysis treatments using a reverse-phase high-performance liquid chromatography assay with liquid chromatography/mass spectrometer/mass spectrometer detection. The McGill Pain Questionnaire (MPQ) and a Visual Analogue Scale (VAS) were used to measure pain. Noncompartmental analyses were conducted. Adverse effects were recorded.

RESULTS

HM did not substantially accumulate (accumulation factor R = 2.7 (1.6)), most likely due to the rapid conversion to H3G. Conversely, H3G accumulated between dialysis treatments (R = 12.5 (12.1)) but appeared to be effectively removed during hemodialysis (1.8 (0.7), p = 0.03). HM resulted in > 65 percent reduction in pain over dosing intervals. Mean MPQ pain scores decreased from 39.8 (18.2) to 12.3 (16.2) on dialysis and from 35.0 (18.5) to 15.5 (13.6) between dialysis treatments. Mean VAS pain scores decreased from 7.5 (2.5) to 3.0 (1.5) on dialysis and from 5.9 (3.2) to 4.4 (1.6) between dialysis treatments. No clinically significant opioid toxicity was observed. The accumulation of H3G between hemodialysis treatments was associated with greater sensory-type pain (r = 0.76, p < 0.0001) and reduced duration of analgesia.

CONCLUSIONS

HM may be a safe and effective opioid for use in selected hemodialysis patients.

Induction of non-apoptotic cell death by morphinone in human promyelocytic leukemia HL-60 cells

As previously suggested, codeinone (oxidation product of codeine) induces non-apoptotic cell death, characterized by marginal caspase activation and the lack of DNA fragmentation in HL-60 human promyelocytic leukemia cells, which was inhibited by N-acetyl-L-cysteine. Whether, morphinone, an oxidative metabolite of morphine, also induced a similar type of cell death in HL-60 cells was investigated. Morphinone showed slightly higher cytotoxic activity against human tumor cell lines (oral squamous cell carcinoma HSC-2, HSC-3, HSC-4, NA, Ca9-22, promyelocytic leukemia HL-60, cervical carcinoma HeLa) than against normal oral human cells (gingival fibroblast HGF, pulp cells HPC, periodontal ligament fibroblast HPLF). Morphinone also induced an almost undetectable level of internucleosomal DNA fragmentation in the HL-60 cells. Morphinone did not activate caspase-8 or -9 in these cells. Morphinone dose-dependently activated caspase-3 in both HL-60 and HSC-2 cell lines, but to a much lesser extent than actinomycin D. Electron microscopy demonstrated that morphinone induced mitochondrial shrinkage, vacuolization and production of autophagosome and the loss of cell surface microvilli, without destruction of cell surface and nuclear membranes in the HL-60 cells. The autophagy inhibitor 3-methyladenine (0.3-10 mM) slightly inhibited the morphinone-induced cytotoxicity, when corrected for its own cytotoxicity. These data suggest that morphinone induces non-apoptotic cell death in HL-60 cells.

Decoration of the Aromatic Ring of Dihydrocodeinone (Hydrocodone) and 14-Hydroxydihydrocodeinone (Oxycodone)

Improved protocols for the preparation of 1-bromodihydrocodeinone (1-bromohydrocodone) and 1-bromo-14-hydroxydihydrocodeinone (1-bromooxycodone) and synthesis of the corresponding 1-chloro and 1-iodo derivatives have been achieved using the corresponding N-halosuccinimides in acidic milieu. The corresponding 1-carboethoxy derivative of 14-hydroxydihydrocodeinone (1-carboethoxyoxycodone) has been prepared by Pd-catalyzed reaction with carbon monoxide in ethanol. The ester was hydrolyzed to the corresponding zwitterionic amino acid.

Bioactivation of Morphine in Human Liver: Isolation and Identification of Morphinone, a Toxic Metabolite

Morphinone, identified in the bile of guinea pigs and rats given morphine, is a reactive electrophile and has the ability to bind to glutathione (GSH) and tissue macromolecules, leading to GSH depletion and cell damage. We previously demonstrated that the livers of various animal species are capable of forming morphinone from morphine. In this study, we examined whether the human liver can produce morphinone from morphine. HPLC analysis revealed that the incubation of morphine with the 9000xg supernatant of human liver in the presence of NAD(P) and 2-mercaptoethanol (ME) gave a peak corresponding to the synthetic morphinone-ME adduct (MO-ME), which is readily formed by a nonenzymatic reaction of morphinone with ME. The reaction product was isolated and was unambiguously identified as MO-ME using FAB-MS and NMR analyses in comparison with synthetic MO-ME. The conversion of morphine to morphinone required NAD(P), and NAD was a preferred cofactor over NADP. All the 9000xg supernatants from six human livers could produce morphinone at different rates, ranging from 30 to 120 nmol/g liver/30 min with NAD at pH 7.4. The enzyme activity responsible for the formation of morphinone from morphine was mainly localized in the microsomes. The microsomal enzyme activity was inhibited by steroids, lithocholic acid and indomethacin. Among these compounds, steroids with a 17beta-hydroxyl group almost completely depressed morphinone formation. In conclusion, the metabolic pathway of morphine to morphinone, a toxic metabolite, in human was shown for the first time in in vitro experiments.

Identification and synthesis of norhydromorphone, and determination of antinociceptive activities in the rat formalin test

The main objective of this paper is to report the identification and synthesis of norhydromorphone, a novel metabolite of hydromorphone, and its antinociceptive activities when tested in the formalin test as compared to other known analgesics. In addition, we are reporting for the first time the lack of antinociceptive activities of hydromorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide in the rat formalin test. Norhydromorphone was isolated and identified as a metabolite of hydromorphone in a cancer patient's urine. An authentic standard of norhydromorphone was synthesized. The identity of norhydromorphone in the urine sample was confirmed by comparing the LC retention time and MS ion fragmentation with the synthetic standard using a liquid chromatographic-mass spectrometric-mass spectrometric (LC-MS-MS) assay. Norhydromorphone was found to be a minor metabolite of hydromorphone in the urine. Additionally, the antinociceptive activities of norhydromorphone, hydromorphone, morphine, dihydromorphine, dihydroisomorphine, hydromorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide were determined in the rat formalin test following intraperitoneal (i.p.) administration. Only limited antinociception was observed and no significant increase in antinociception was detected at the three doses tested. The increased polarity of norhydromorphone as compared to hydromorphone due to the primary piperidine nitrogen may make it less favorable to cross the blood-brain-barrier (BBB), which may be partly responsible. In addition, lower intrinsic antinociceptive activity, which remains to be determined, could also contribute to the low antinociception. Our results also show that hydromorphone was five times as potent as morphine in the formalin test, while dihydromorphine and dihydroisomorphine were equipotent to and 36% as potent as morphine, respectively. Hydromorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide did not exhibit any antinociceptive effect at the doses tested. The results further underscore the importance of a free C3-OH to the analgesic effect of morphine alkaloids.

[Combined use of intrathecal morphine and diclofenac suppository for postoperative analgesia after caesarean section]

BACKGROUND

Intrathecal morphine for postoperative analgesia after caesarean section has been used in Europe and North America, but its use is not common in Japan.

METHODS

We randomized 40 parturients to two groups, given either intrathecal saline (control group) or intrathecal morphine 0.05 mg (morphine group) for caesarean section. To both groups, we gave a diclofenac suppository 50 mg every 8 hours after surgery.

RESULTS

The area under curve for the visual analogue scale for pain during 24 hours after operation was significantly lower (P < 0.01) in the morphine group than the control group. In addition, the parturients who required pentazocine as a rescue analgesia was significantly fewer in the morphine group (5 parturients) than the control group (11 parturients). There was no significant difference between the two groups in the Apgar score of infants, pH in umbilical cord arterial and venous blood and the incidence of postoperative nausea and vomiting. The incidence of pruritus was significantly higher in the morphine group (11 parturients) than the control group (no parturient).

CONCLUSIONS

Intrathecal morphine 0.05 mg and diclofenac suppository 50 mg given every 8 hours produced effective postoperative analgesia with minimum side effects after caesarean section.

Opioid ligands having delayed long-term antagonist activity: potential pharmacotherapies for opioid abuse

Buprenorphine is a partial agonist at the micro -opioid receptor with long duration of action and also exhibits delayed antagonist activity. Buprenorphine is finding increasing use as a treatment agent for opioid abuse, though its low efficacy is not well tolerated by all addicts. There is interest in developing a higher efficacy version of buprenorphine and in this mini-review some of the ligands recently discovered, that share with buprenorphine a profile of agonism followed by delayed antagonism, are discussed.

A convenient synthesis of delta(7,8)-morphinan-6-one and its direct oxidation to 14-hydroxy-delta(7,8)-morphinan-6-one

Synthesis of Delta(7,8)-morphinan-6-one by Grewe cyclization and bromoketalization reaction as crucial steps is described. Introduction of a hydroxyl group at 14-position is demonstrated by direct oxidation with MnO(2) in the presence of silica gel.

Hydromorphone metabolites: isolation and identification from pooled urine samples of a cancer patient

1. Hydromorphone-3-glucuronide, dihydromorphine, dihydroisomorphine, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide were isolated from a cancer patient's urine and identified as metabolites of hydromorphone by comparison with synthetic standards using LC/MS/MS with gradient elution. 2. The relative urinary recovery of dihydroisomorphine-3-glucuronide was estimated to be 17-fold higher than previously reported. 3. Three new metabolites, including hydromorphone-3-sulphate, norhydromorphone and nordihydroisomorphine, were tentatively identified.

LC-MS-MS analysis of hydromorphone and hydromorphone metabolites with application to a pharmacokinetic study in the male Sprague-Dawley rat

1. A high performance liquid chromatography-mass spectrometry-mass spectrometry (LC-MS-MS) assay was developed for the analysis of hydromorphone and its metabolites, namely dihydromorphine, dihydroisomorphine, hydromorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorphine-3-glucuronide, in rat plasma samples. 2. Analytes were extracted by solid-phase extraction using C2 cartridges. The extraction recoveries were > 76% for all analytes. Both intra- and interassay variabilities were < or = 12%. Using a plasma sample size of 100 microl, the limits of detection were 7.0 nmol(-1) (2.0 ng ml(-1)) for hydromorphone, dihydromorphine and dihydroisomorphine and 11 nmol l(-1) (5.0 ng ml l(-1)) for hydrormorphone-3-glucuronide, dihydromorphine-3-glucuronide and dihydroisomorhine-3-glucuronide at a signal-to-noise ratio = 3. 3. The present assay was applied to a pharmacokinetic study in rat after intraperitoneal administration of hydromorphone.

Engineering novel biocatalytic routes for production of semisynthetic opiate drugs

The morphine alkaloids and their semisynthetic derivatives provide a diverse range of important pharmaceutical drugs. Current production of semisynthetic opiate drugs is by chemical means from naturally occurring morphine, codeine and thebaine. Although various microbial transformations of morphine alkaloids have been identified since the 1960s, more recently there has been considerable effort devoted to engineering biocatalytic routes for producing these important compounds. Such biocatalytic routes are attractive, as they would provide an alternative to the chemical production processes which suffer from limited supply of precursors, often low yields and toxic wastes. The biotransformation of morphine and codeine to the potent analgesic hydromorphone and the mild analgesic/antitussive hydrocodone, respectively, by recombinant Escherichia coli has been demonstrated and the problems encountered when engineering such a system will be discussed.

Hydromorphone-3-glucuronide: a more potent neuro-excitant than its structural analogue, morphine-3-glucuronide

In humans, hydromorphone (HMOR) is metabolised principally by conjugation with glucuronic acid to form hydromorphone-3-glucuronide (H3G), a close structural analogue of morphine-3-glucuronide (M3G), the major metabolite of morphine. In a previous study we described the biochemical synthesis of H3G together with a preliminary evaluation of its pharmacology which revealed that it is a neuroexcitant in rats in a manner analogous to M3G. Thus the aims of the current study were to quantify the neuro-excitatory behaviours evoked by intracerebroventricular (icv) H3G in the rat and to define its potency relative to M3G. Groups of adult male Sprague-Dawley rats received icv injections (1 microL) of H3G (1 - 3 microg), M3G (2 - 7 microg) or vehicle via a stainless steel guide cannula that had been implanted stereotaxically seven days prior to drug administration. Behavioural excitation was monitored by scoring fifteen different behaviours (myoclonic jerks, chewing, wet-dog-shakes, rearing, tonic-clonic-convulsions, explosive motor behaviour, grooming, exploring, general activity, eating, staring, ataxia, righting reflex, body posture, touch evoked agitation) immediately prior to icv injection and at the following post-dosing times: 5, 15, 25, 35, 50, 65 and 80 min. H3G produced dose-dependent behavioural excitation in a manner analogous to that reported previously for M3G by our laboratory and reproduced herein. H3G was found to be approximately 2.5-fold more potent than M3G, such that the mean (+/- S.D.) ED50 values were 2.3 (+/- 0.1) microg and 6.1 (+/- 0.6) microg respectively. Thus, our data clearly imply that if H3G crosses the BBB with equivalent efficiency to M3G, then the myoclonus, allodynia and seizures observed in some patients dosed chronically with large systemic doses of HMOR, are almost certainly due to the accumulation of sufficient H3G in the central nervous system, to evoke behavioural excitation.

Mechanistic studies of morphine dehydrogenase and stabilization against covalent inactivation

Morphine dehydrogenase (MDH) of Pseudomonas putida M10 catalyses the NADP(+)-dependent oxidation of morphine and codeine to morphinone and codeinone. This enzyme forms the basis of a sensitive detection and assay method for heroin metabolites and a biotransformation process for production of hydromorphone and hydrocodone. To improve these processes we have undertaken a thorough examination of the kinetic mechanism of MDH. Sequence comparisons indicated that MDH belongs within the aldose reductase enzyme family. MDH was shown to be specific for the pro-R hydrogen of NADPH. In steady-state kinetic studies, product inhibition patterns suggested that MDH follows a Theorell-Chance mechanism for codeinone reduction at pH 7, and a non-Theorell-Chance sequential ordered mechanism for codeine oxidation at pH 9.5. Residues corresponding to the catalytically important Tyr-48, Lys-77 and Asp-43 of aldose reductase were modified by site-directed mutagenesis, resulting in substantial loss of activity consistent with a catalytic role for these residues. Loss of activity of MDH in the presence of the reaction product morphinone was found to be due to the formation of a covalent adduct with Cys-80; alteration of Cys-80 to serine resulted in an enzyme with greatly enhanced stability.

[Production of morphinone as a metabolite of morphine and its physiological role]

Morphine is a potent analgesic and is widely used in the clinical management of severe acute and chronic pain; however, its clinical usefulness is limited due to the development of both tolerance and dependence after repeated morphine administration. The morphine metabolism has been studied in order to elucidate its pharmacological actions as well as its adverse effects. Thus far several metabolites have been identified and their analgesic potency and toxicity have been also investigated. In the toxicological viewpoint, the production of reactive metabolites that can bind cellular glutathione and protein has been postulated. We found morphine 6-dehydrogenase, which catalyzes the dehydrogenation of 6-hydroxy group of morphine to produce morphinone, in the guinea pig liver. It was also found that morphinone antagonizes the morphine analgesia and binds with glutathione and protein. We here demonstrate the presence of a metabolic pathway of morphine to morphinone and subsequently to morphinone-glutathione adduct, and compare the property including primary structure among the guinea pig, rabbit, mouse and hamster liver morphine 6-dehydrogenases. We also describe the toxicological significance of morphinone.

Hydromorphone-3-glucuronide: biochemical synthesis and preliminary pharmacological evaluation

Hydromorphone-3-glucuronide (H3G) was synthesized biochemically using rat liver microsomes, uridine-5'-diphosphoglucuronic acid (UDPGA) and the substrate, hydromorphone. Initially, the crude putative H3G product was purified by ethyl acetate precipitation and washing with acetonitrile. Final purification was achieved using semi-preparative high-performance-liquid-chromatography (HPLC) with ultraviolet (UV) detection. The purity of the final H3G product was shown by HPLC with electrochemical and ultraviolet detection to be > 99.9% and it was produced in a yield of = 60% (on a molar basis). The chemical structure of the putative H3G was confirmed by enzymatic hydrolysis of the glucuronide moiety using beta-glucuronidase, producing a hydrolysis product with the same HPLC retention time as the hydromorphone reference standard. Using HPLC with tandem mass spectrometry (HPLC-MS-MS) in the positive ionization mode, the molecular mass (M+1) was found to be 462 g/mol, in agreement with H3G's expected molecular weight of 461 g/mol. Importantly, proton-NMR indicated that the glucuronide moiety was attached at the 3-phenolic position of hydromorphone. A preliminary evaluation of H3G's intrinsic pharmacological effects revealed that following i.c.v. administration to adult male Sprague-Dawley rats in a dose of 5 microg, H3G evoked a range of excitatory behavioural effects including chewing, rearing, myoclonus, ataxia and tonic-clonic convulsions, in a manner similar to that reported previously for the glucuronide metabolites of morphine, morphine-3-glucuronide and normorphine-3-glucuronide.

7-spirobenzocyclohexyl derivatives of naltrexone, oxymorphone, and hydromorphone as selective opioid receptor ligands

On the basis of previous structure-activity studies of the highly potent and selective delta-opioid receptor antagonist naltrindole (1) and the spiroindanyl analogues 2 and 3, we have synthesized epimeric pairs of spirobenzocyclohexyl derivatives of naltrexone, oxymorphone, and hydromorphone (4-9). Pharmacologic evaluation in smooth muscle assays has revealed that the oxymorphone derivatives (6, 7) are delta-selective agonists and possess receptor binding profiles that are consistent with their agonist activity. It is proposed that the spirobenzocyclohexyl group of 6 and 7 orients its benzene moiety orthogonally with respect to the C ring of the opiate in a manner similar to that of the spiroindanyl analogue 3. It is suggested that this orthogonal orientation serves as an "address" to facilitate activation of delta receptors. The finding that the hydromorphone analogues (8, 9) were full mu agonists and exhibited only partial delta agonist activity suggests that the 14-hydroxyl group also contributes to the delta agonist activity. The naltrexone derivatives (4, 5) were mu-selective antagonists and exhibited relatively weak delta antagonist activity. However, the binding data indicated a very high-affinity delta-selective binding profile that was not consistent with the pharmacology. This study illustrates the differential contributions of the delta "address" to agonist and antagonist activity and supports the idea of different recognition sites for interaction of agonist and antagonist ligands with delta-opioid receptors.

In vivo and in vitro formation of morphinone from morphine in rat

1. Morphinone, a toxic metabolite, and its glutathione adduct (MO-GSH) were identified in the bile of rat after subcutaneous injection of morphine (25 mg/kg) by hplc procedures. The amounts of morphinone and MO-GSH excreted in the 12-h bile were 0.8 +/- 0.3 and 8.4 +/- 4.3% respectively. 2. The 9000 g supernatants of rat, guinea pig, rabbit, mouse, hamster and bovine livers produced morphinone from morphine in the presence of either NAD+ or NADP+, NAD+ was a more efficient cofactor than NADP+ except in the guinea pig which equally utilized both cofactors. With NAD+ as cofactor, the amounts of morphinone formed in rat and guinea pig were 5.70 and 5.82 mumol/g liver/30 min respectively and were three-to-four times those in other species. 3. The enzyme activity responsible for formation of morphinone from morphine in the rat was almost exclusively distributed in the microsomal fraction, whereas guinea pig, hamster and bovine expressed the enzyme activity mainly in the cytosolic fraction. Rabbit and mouse gave higher activity in the cytosolic and microsomal fractions respectively, but other fractions of both species contained considerable activity. 4. The enzyme activities in male and female rat microsomes were characterized with respect to developmental pattern, kinetic parameters, pH dependency and susceptibility to inhibitors. 5. In conclusion the metabolism of morphine to morphinone in rat was confirmed by in vivo and in vitro experiments. It is also suggested that this pathway is a common route in morphine metabolism in several mammalian species.

Purification, characterization and partial primary structure of morphine 6-dehydrogenase from rabbit liver cytosol

Morphinone, a toxic metabolite, was formed from morphine by NAD(P)-dependent morphine 6-dehydrogenase(s) in both the cytosol and microsomal fractions of the rabbit liver at pH 7.4. The enzyme activity in the cytosol fraction was about twice that in the microsomal fraction and NAD served as the preferred cofactor in both fractions. The enzyme in the cytosol fraction was purified to a homogeneous protein by the use of various chromatographic techniques. The enzyme is a monomeric protein with a molecular weight of 36,000 and an isoelectric point of 6.4. The enzyme had a dual cofactor specificity but NAD was more efficiently utilized than NADP. With NAD, the enzyme showed an optimal pH of 9.4, and the Km and Vmax values toward morphine were 0.72 mM and 0.59 unit/mg protein, respectively. The enzyme also exhibited a significant activity for morphine analogs having an unsaturated bond at C-7,8 (codeine, ethylmorphine, and normorphine), alicyclic alcohols (3-hydroxyhexobarbital, 1-indanol, and cyclohexene-2-ol) and benzenedihydrodiol. In the reverse reaction, the enzyme exhibited highly restricted specificity for o-quinones. Sulfhydryl re-agents and quercetin inhibited the enzyme but pyrazole, barbital, and indomethacin had little effect on the enzyme activity. Androstanes, lithocholic acid, and estradiol potently inhibited the enzyme in a competitive manner toward morphine binding. The partial amino acid sequence of the random peptides obtained by the proteolytic digestion of the enzyme, which comprised about 40% of the whole protein, revealed a significant homology to the corresponding regions in the members of the aldo-keto reductase family. These results therefore indicate that the present enzyme is a new and unique member of the aldo-keto reductase family.

N-cyclobutylmethyl analog of normorphinone, N-CBM-TAMO: a short-term opioid agonist and long-term Mu-selective irreversible opioid antagonist

The antinociceptive and opioid binding properties of the N-cyclobutylmethyl analog of normorphinone, 14 alpha, 14' beta-[dithiobis[(2-oxo-2, 1-ethanediyl)imino]]bis[7,8-dihydro-N-(cyclobutylmethyl)-normor phinone] (N-CBM-TAMO) were investigated. This compound is a dimer, containing a disulfide capable of binding to thiol groups on the opioid receptor. Competition radioligand binding assays with bovine striatal membranes demonstrated that N-CBM-TAMO displayed a higher affinity for mu opioid receptors than for kappa and delta receptors. Incubation of membranes with N-CBM-TAMO resulted in wash-resistant inhibition of the binding of the mu-selective peptide [3H][D-Ala2,(Me)Phe4, Gly(ol)5]-enkephalin, the kappa-selective opioid [3H]U69,593 ((trans)-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]benzenacetamide+ ++ methanesulfonate hydrate)) and, to a lesser extent, the delta-selective peptide [D-Pen2, p-Cl-phenylalanine4, D-Pen5]enkephalin. Scatchard analysis of saturation binding data showed that N-CBM-TAMO decreased the Bmax value without affecting the Kd value for [3H][D-Ala2,(Me)Phe4, Gly(ol)5]enkephalin binding, whereas, N-CBM-TAMO increased the Kd value without altering the Bmax value for [3H]U69,593, which suggests that N-CBM-TAMO interacted covalently with the mu but not the kappa receptor. In the mouse 55 degrees C warm-water tail-flick test, N-CBM-TAMO given supraspinally acted as an agonist with low efficacy because only submaximal antinociception was observed at doses up to 100 nmol. The antinociception induced by N-CBM-TAMO in the tail-flick test was partially blocked by both the mu-selective antagonist beta-funaltrexamine and the kappa-selective antagonist nor-binaltorphimine. In the mouse acetic acid writhing test, N-CBM-TAMO acted as a full agonist with a D50 value of 0.08 (0.04-0.14) nmol, and the antinociception was blocked by coadministration of the kappa-selective antagonist nor-binaltorphimine. Pretreatment of mice with an i.c.v. dose of N-CBM-TAMO of 10 nmol, a dose that exhibited modest short-term antinociception in the tail-flick test, produced a time- and dose-dependent long-term antagonism of morphine-induced antinociception in an irreversible manner in this assay. Pretreatment of mice with i.c.v. N-CBM-TAMO at doses of 3 nmol and higher, which produced supermaximal short-term antinociception in the writhing test, produced a time- and dose-dependent long-term antagonism of U50,488 (trans)-3, 4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)-cyclohexyl]benzeneacetamide methanesulfonate hydrate)-induced antinociception in a reversible manner, probably because of the development of tolerance. These in vivo data, together with the in vitro binding data, demonstrate that N-CBM-TAMO is a potent kappa agonist and at higher doses produces antinociception mediated by mu receptors. N-CBM-TAMO also produces long-term noncompetitive antagonism of antinociception mediated by mu opioid receptors.

Effects of the structurally novel opioid 14 alpha, 14' beta-[dithiobis [(2-oxo-2,1-ethanediyl)imino]]bis(7,8-dihydromorphinone) on schedule-controlled behavior and thermal nociception in rhesus monkeys

The in vivo pharmacology of the structurally novel opioid 14 alpha, 14' beta-[dithiobis[(2-oxo-2,1-ethanediyl)imino]]bis(7,8-dihydromorphinon e) (TAMO) was examined in rhesus monkeys with assays of schedule-controlled behavior and thermal nociception. TAMO (0.032-1.8 mg/kg) produced dose-dependent decreases in response rates maintained under a fixed-ratio 30 schedule of food delivery (n = 3) and increases in tail-withdrawal latencies in a warm-water tail-withdrawal procedure (n = 3). Both the rate-decreasing and antinociceptive effects of TAMO (1.0 mg/kg) were maximal after 40 to 80 min and lasted at least 160 min. Pretreatment with the mu-selective opioid antagonist quadazocine (0.001-0.1 mg/kg) antagonized the effects of TAMO and shifted the TAMO dose-effect curves to the right. Schild analysis yielded in vivo apparent pA2 values (mean +/- S.E.M.) of 8.8 +/- 0.072 and 8.7 +/- 0.40 for quadazocine antagonism of the rate-decreasing and antinociceptive effects, respectively, of TAMO, which suggests that the effects of TAMO were mediated by mu-opioid receptors. In addition, quadazocine (0.1-1.0 mg/kg) reversed the behavioral effects of TAMO (1.0 mg/kg) when quadazocine was administered immediately after TAMO had attained its maximal effect. Twenty-four-hour pretreatment with 1.0 mg/kg TAMO did not significantly after the rate-decreasing or antinociceptive effects of fentanyl or the rate-decreasing effects of morphine. The dose-effect curve for morphine antinociception was shifted 4-fold to the right 24 hr after pretreatment with 1.0 mg/kg TAMO. However, 24-hr pretreatment with an equiactive dose of morphine (10.0 mg/kg) also produced a small (2-fold) but significant rightward shift in the dose-effect curve for morphine antinociception. Twenty-four-hour pretreatment with 1.8 mg/kg TAMO had no effect on the antinociceptive effects of U69,593 (0.0032-0.1 mg/kg). These results suggest that TAMO acts as a reversible mu agonist with a relatively slow onset and a duration of action and relative efficacy similar to those of morphine in rhesus monkeys. Twenty-four hours after TAMO administration, the highest doses of TAMO that could be safely administered produced little or no mu antagonist effects and no kappa antagonist effects.

Steady-state pharmacokinetics of hydromorphone and hydromorphone-3-glucuronide in cancer patients after immediate and controlled-release hydromorphone

Although the pharmacokinetics of oral hydromorphone has been evaluated in healthy volunteers after small single oral doses, data are not available regarding the disposition of hydromorphone and its principal metabolite, hydromorphone-3-glucuronide (H3G), at steady-state and after large oral doses. The authors studied the pharmacokinetics of hydromorphone and H3G after oral administration of an immediate-release (IR) and controlled-release (CR) formulation of hydromorphone at a daily dose of 48 +/- 11 mg (range 6-216 mg) in a randomized, double-blind, steady-state, two-way crossover evaluation in 18 patients with chronic cancer pain. Controlled-release hydromorphone demonstrated equivalent bioavailability and acceptable CR characteristics, when compared with IR hydromorphone (CR vs. IR: AUC0-12 123.10 +/- 20.38 vs. 118.98 +/- 20.92 ng.hr.mL-1, P = NS, Cmax 17.76 +/- 3.07 vs. 19.70 +/- 4.04 ng.mL-1, P = NS, Cmin 6.04 +/- 1.01 vs. 5.28 +/- 1.000 ng.mL-1, P = NS, and Tmax 4.78 +/- 0.78 vs. 1.47 +/- 0.22 hr, P = 0.0008). A significant linear relationship existed between hydromorphone dose and hydromorphone AUC (r = 0.8315, P = 0.0001) and between hydromorphone AUC and H3G AUC (r = 0.8048, P = 0.0001) over a wide dose range. The steady-state molar ratio of H3G to hydromorphone was 27:1. The authors conclude that CR hydromorphone provides a pharmacokinetic profile consistent with 12 hourly dosing and that at steady state, oral hydromorphone is extensively metabolized to H3G, although the pharmacologic activity of this metabolite remains unknown.

A comparison of pentamorphone and fentanyl in balanced anaesthesia during general surgery

The purpose of our randomized, double-blind study of 64 unpremedicated healthy patients undergoing surgical procedures with a duration of at least 60 min was to compare 0.75 micrograms.kg-1 and 1 microgram.kg-1 pentamorphone with 5 micrograms.kg-1 and 7.5 micrograms.kg-1 fentanyl to determine which dose of opioid would reduce the requirement for isoflurane supplementation needed to maintain haemodynamic stability. At 21 points during the procedure, the haemodynamic variables of heart rate and systolic, diastolic, and mean arterial pressures were recorded. The use of isoflurane was quantified; the number of patients requiring inhaled anaesthetic, concentration peaks, MAC minutes, and duration of isoflurane use were noted. The number of equal-volume supplemental opioid analgesic doses, postoperative analgesics, occurrence of postoperative nausea, emesis, and antiemetic doses were compared. The four groups exhibited similar patient demographics, total dose of muscle relaxants, types of surgical procedures, and duration of surgery or anaesthesia. Haemodynamic variables were stable with no difference among the four study groups. The patients given pentamorphone demonstrated both delayed requirement (P < 0.05) and shorter duration (P < 0.05) of isoflurane supplementation. Patients given either 5 micrograms.kg-1 or 7.5 micrograms.kg-1 fentanyl needed isoflurane supplementation within 12 +/- 16 min and 12 +/- 17 min from induction respectively; while patients given either 0.75 micrograms.kg-1 or 1 microgram.kg-1 pentamorphone did not require isoflurane supplementation for 37 +/- 10 min and 43 +/- 26 min respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

14 alpha,14' beta-[Dithiobis[(2-oxo-2,1-ethanediyl)imino]]bis (7,8-dihydromorphinone) and 14 alpha,14' beta-[dithiobis[(2-oxo-2,1- ethanediyl)imino]]bis[7,8-dihydro-N-(cyclopropylmethyl)normorphinone]: chemistry and opioid binding properties

14 alpha,14' beta-[Dithiobis[(2-oxo-2,1-ethanediyl)imino]] bis(7,8-dihydromorphinone) (TAMO) (13) was synthesized by condensing 14 beta-amino-7,8-dihydromorphine (4) with acetylthioglycolyl chloride and hydrolyzing the resulting ester with mild base to give a mixture of the thiol 9 and the disulfide 13. Chromatography of the mixture resulted in conversion of the bulk of the thiol 9 to the disulfide 13 by air oxidation. The disulfide 13 was also prepared by condensing the tert-butyldimethylsilyl ether of 4 with the dithiodiglycolyl chloride and treating the resulting product with F- to give the desired product. The pure thiol 9 free of contamination with the disulfide was prepared by treating 13 with excess N-acetyl-L-cysteine and processing the reaction mixture without resorting to chromatography for purification. The corresponding N-(cyclopropylmethyl) nor compound 15 was prepared from the silyl ether 6 and acetylthioglycolyl chloride followed by hydrolysis, treatment with F-, and air oxidation. Incubation of bovine striatal membranes with 13 and 15 resulted in wash-resistant inhibition of the binding of the mu-selective peptide [3H][D-Ala2,(Me)Phe4,Gly(ol)5]-enkephalin (DAMGO). Incubation of membranes with mu but not kappa or delta ligands protected the mu binding sites from alkylation by 13 and 15. The wash-resistant inhibition of mu opioid binding was partially reversed by the addition of the reducing reagent dithiothreitol (DTT). A Scatchard plot of the effect of 13 and 15 on [3H]DAMGO binding showed that these affinity ligands caused a marked decrease in the Bmax value without affecting the Kd value. The wash-resistant inhibition of binding, the reduction in the number of binding sites, the partial reversal of wash-resistant inhibition of binding by DTT, and previously observed long-term antagonism of mu opioid receptors in vivo support the conclusion that 13 and 15 bind covalently to the mu opioid receptor.

5 beta-Methyl-14 beta-(p-nitrocinnamoylamino)-7,8-dihydromorphinone and its corresponding N-cyclopropylmethyl analog, N-cyclopropylmethylnor-5 beta-methyl-14 beta-(p-nitrocinnamoylamino)- 7,8-dihydromorphinone: mu-selective irreversible opioid antagonists

5 beta-Methyl-14 beta-(p-nitrocinnamoylamino)-7,8-dihydromorphinone (MET-CAMO) and its corresponding N-cyclopropylmethyl analog, N-cyclopropylmethylnor-5 beta-methyl-14 beta-(p-nitrocinnamoylamino)- 7,8-dihydromorphinone (N-CPM-MET-CAMO) were tested in opioid receptor binding assays and in the mouse tail-flick test in order to characterize the affinity, selectivity and antinociceptive properties of these two compounds. Incubating bovine striatal membranes with either MET-CAMO or N-CPM-MET-CAMO produced a wash-resistant, concentration- and time-dependent inhibition of the binding of the mu-selective ligand, [3H]-[D-Ala2,MePhe4,Gly(ol)5]enkephalin, but with no change in delta or kappa binding. Preincubating membranes with N-CPM-MET-CAMO decreased the maximum binding value for [3H]-[D-Ala2,MePhe4,Gly(ol)5]enkephalin binding without changing the Kd value. In the mouse tail-flick assay, MET-CAMO and N-CPM-MET-CAMO did not produce any antinociception up to a dose of 100 nmol after i.c.v. administration. However, pretreatment of mice with either compound produced a time- and dose-dependent antagonism of morphine-induced antinociception. Analgesia mediated by delta or kappa opioids was not altered by either MET-CAMO or N-CPM-MET-CAMO at a dose of up to 100 nmol. The mu antagonistic effect of 1 nmol of MET-CAMO and N-CPM-MET-CAMO appeared at 8 hr and lasted up to 72 hr, with a maximal effect at 16 to 24 hr after i.c.v. administration. Pretreatment of mice with 1 nmol of MET-CAMO or N-CPM-MET-CAMO, given by i.c.v. administration at -24 hr, produced a rightward and downward shift of dose-response line of i.c.v. morphine.(ABSTRACT TRUNCATED AT 250 WORDS)

14 beta-[(p-nitrocinnamoyl)amino]morphinones, 14 beta-[(p-nitrocinnamoyl)amino]-7,8-dihydromorphinones, and their codeinone analogues: synthesis and receptor activity

A series of 14 beta-[(nitrocinnamoyl)amino]codeinones and morphinones, some of which contain a 5 beta-methyl group, were prepared from 14 beta-aminocodeinones and 14 beta-[N-(cyclopropylmethyl)-amino]norcodeinones. The affinities of the target compounds for the mu, delta, and kappa opioid receptors were determined by radiolabeled binding experiments using bovine brain membranes. An analogous series of 7,8-dihydrocodeinones and morphinones was prepared and assayed in the same systems. The 3-methoxy derivatives 3 and 4 were more selective than the corresponding morphinones for the mu receptor. The 5 beta-methylcodeinones 25 and 27 had lower affinity at all receptors than the corresponding morphinones, but the 5 beta-methylmorphinones had affinities similar to the morphinones 5 and 6. A similar pattern was observed in the 7,8-dihydro series. Two compounds, 5 beta-methyl-14 beta-[(p-nitrocinnamoyl)amino]-7,8-dihydromorphinone, 20 (MET-CAMO), and N-(cyclopropylmethyl)-14 beta-[(p-nitrocinnamoyl)amino]-7,8-dihydronormorphinone, 22 (N-CPM-MET- CAMO), acted as nonequilibrium ligands in antinociception and membrane binding studies. In mice after icv administration, neither ligand showed any agonist activity but 8-24 h after administration both compounds acted as potent mu antagonists. A Scatchard plot of the effect of N-CPM-MET-CAMO on [3H]DAMGO ([3H]D-Ala2, (Me)-Phe4, Gly(ol)5] enkephalin) binding to bovine striatal membranes showed that there was a significant decrease in the Bmax value and a marginal effect on the Kd value suggesting that the number of binding sites was reduced. When taken together, these results support the view that 20 and 22 bind covalently to the mu receptor. On the other hand, when N-acetylcysteine and 22 were allowed to react in a buffered solution, 22 was recovered unchanged. Under these conditions no Michael reaction was observed.

Antinociceptive evaluation of 14 beta-(bromoacetamido)-7,8-dihydro- N(cyclopropylmethyl)-normorphinone in mice

This study evaluated the supraspinal opioid effects of 14 beta-(bromoacetamido)-7,8-dihydro-N(cyclopropylmethyl)-normorphinone+ ++ (N-CPM-H2BAMO) in the mouse acetic acid-induced writhing and tail-flick assays. In the writhing test, N-CPM-H2BAMO produced a time- and dose-dependent antinociception after i.c.v. administration, with a 50% antinociceptive response being obtained with 0.28 (0.19-0.39) nmol when given 10 min before testing. The antinociceptive effect of N-CPM-H2BAMO was antagonized in a dose-dependent manner by the kappa-selective opioid receptor antagonist, nor-binaltorphimine. In the mouse tail-flick assay, N-CPM-H2BAMO failed to produce any antinociception after i.c.v. administration. N-CPM-H2BAMO produced a dose-dependent antagonism of morphine-induced antinociception but not antinociception induced by the delta-opioid receptor agonist [D-Pen2,D-Pen5]enkephalin. Nor-binaltorphimine (0.3 nmol) at dose that completely antagonized N-CPM-H2BAMO-induced antinociception in the writhing assay did not prevent the antagonistic effect of N-CPM-H2BAMO on morphine-induced antinociception. Therefore, these data indicate that N-CPM-H2BAMO produces antinociception by acting at supraspinal kappa-opioid receptors in the writhing assay, and also acts as a mu-opioid receptor antagonist.

Affinity labeling of the mu opioid receptor in bovine striatal membranes with [3H]-14 beta-(bromoacetamido)-7,8-dihydromorphine

[3H]-14 beta-(Bromoacetamido)-7,8-dihydromorphine ([3H]H2BAM) was synthesized and tested for its ability to selectively label mu opioid receptors in bovine striatal membranes. Incubating membranes with N-tosyl-L-phenylalanine chloromethyl ketone and dithiothreitol before the addition of [3H]H2BAM reduced nonspecific [3H]H2BAM binding so that [3H]H2BAM binding to opioid receptors was up to 70% of the total [3H]H2BAM binding and was dependent on [3H]H2BAM concentration, incubation time, and pH of the reaction. At pH 7.5, [3H]H2BAM bound selectively to the mu opioid receptor, but mainly noncovalently. After the initial binding of [3H]H2BAM to the receptor, membranes were washed and then incubated at 37 degrees C in 50 mM Tris-HCl, pH 8.5, for 3 h, a time that resulted in greater than 80% of the [3H]H2BAM associated with the receptor becoming covalently bound to the opioid receptor. The mu-selective peptide [D-Ala2,(Me)Phe4,Gly(ol)5]enkephalin inhibited [3H]H2BAM labeling of membranes, while delta- or kappa-selective compounds were ineffective. Both NaCl and the nonhydrolyzable guanine nucleotide analog guanylyl 5'-imidodiphosphate reduced the incorporation of [3H]H2BAM into membranes. When [3H]H2BAM-labeled striatal membranes were separated under reducing conditions on a sodium dodecyl sulfate-polyacrylamide gel, two proteins with molecular weights of 54,000 and 44,000 were specifically labeled. The 54-kDa protein was present in a greater amount than the 44-kDa protein. Both proteins bound to wheat germ agglutinin-Sepharose and concanavalin A-Sepharose, suggesting that both proteins contain multiple carbohydrate moieties. Despite the inclusion of protease inhibitors, the 44-kDa protein may be a proteolytic fragment of the 54-kDa protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacological study of 14 beta-(thioglycolamido)-7,8-dihydro-N(cyclopropylmethyl)-normor phinone (N-CPM-TAMO)

Opioid effects of 14 beta-(thioglycolamido)-7,8-dihydro-N(cyclopropylmethyl)- normorphinone (N-CPM-TAMO) were studied in the mouse tail-flick and acetic acid writhing assays. In the tail-flick test, N-CPM-TAMO failed to produce any antinociception after i.c.v. administration of up to 300 nmol. However, pretreatment of mice with N-CPM-TAMO produced a time- and dose-dependent antagonism of morphine-induced antinociception. The antagonism by N-CPM-TAMO lasted up to 48 hr, with a maximal effect at 24 hr after i.c.v. administration. Similarly, pretreatment of mice with N-CPM-TAMO at 24 hr also produced a dose-dependent antagonism of kappa-mediated antinociception, induced by U50,488 However, the antagonistic potency of N-CPM-TAMO against U50,488 was 100-fold less than against morphine. Pretreatment with N-CPM-TAMO had no effect on delta opioid receptor-mediated antinociception, as measured with [D-Pen2,D-Pen5]enkephalin. In the writhing assay, N-CPM-TAMO produced a time- and dose-dependent antinociception after i.c.v. administration, with a value of the dose producing 50% analgesia of 18.4 (10.6-31.9) nmol. The antinociceptive effect lasted up to 3 hr after administration. N-CPM-TAMO-induced antinociception was antagonized by coadministration of the kappa-selective antagonist, norbinaltorphimine. Pretreatment of mice with N-CPM-TAMO also produced a time- and dose-dependent antagonism of U50,488-induced antinociception, which lasted up to 72 hr, with a maximal effect at 24 hr after administration. These data indicate that N-CPM-TAMO is a mu-selective, long-term antagonist.(ABSTRACT TRUNCATED AT 250 WORDS)

5 beta-Methyl-14 beta-(p-nitrocinnamoylamino)-7,8-dihydromorphinone: a long-lasting mu-opioid receptor antagonist devoid of agonist properties

5 beta-Methyl-14 beta-(p-nitrocinnamoylamino)-7,8-dihydromorphinone (MET-CAMO) suppressed morphine-induced antinociception but had no effect on antinociception mediated by delta- or kappa-opioid receptors after a single i.c.v. 1-nmol injection from 8 to 72 h before testing. MET-CAMO had no agonist effects in the mouse tail-flick assay in doses up to 100 nmol. MET-CAMO is the first N-methylated morphine derivative which shows such long-lasting mu-selective opioid receptor antagonism with no agonistic properties.

Antinociceptive properties of two alkylating derivatives of morphinone: 14 beta-(thioglycolamido)-7,8-dihydromorphinone (TAMO) and 14 beta-(bromoacetamido)-7,8-dihydromorphinone (H2BAMO)

This study investigated the antinociceptive properties of two alkylating derivatives of morphinone, 14 beta-(thioglycolamido)-7,8- dihydromorphinone (TAMO) and 14 beta-(bromoacetamido)-7,8-dihydromorphinone (H2BAMO) in the mouse tail-flick assay. Intracerebroventricular administration of either TAMO or H2BAMO produced short-term antinociception. Both TAMO and H2BAMO were 11.6-fold more potent than an i.c.v. administration of morphine. These effects were antagonized by the mu-selective antagonist, beta-funaltrexamine, but not by the delta-selective antagonist, N,N-diallyl-Tyr-Aib-Aib-Phe-Leu-OH. TAMO pretreatment from 8 to 48 hr produced a time-related, dose-dependent antagonism of morphine-induced antinociception without showing any agonistic effect. Pretreatment with TAMO for 24 hr antagonized antinociception produced by both H2BAMO and morphine, as well as TAMO itself, but not that of the delta-selective agonist [D-Pen2,D-Pen5]enkephalin (DPDPE) or U50,488, a kappa-selective agonist. In order to distinguish this antagonistic effect from cross-tolerance between TAMO and morphine, two mu agonists, [D-Ala2,N(Me)Phe4,Gly-ol]enkephalin (DAMGO) and H2BAMO, were chosen for comparison. A single i.c.v. pretreatment of DAMGO or H2BAMO, at a dose that had equivalent analgesic effects as TAMO, attenuated morphine-induced antinociception, reaching a maximal effect at the time of the disappearance of agonistic effects of DAMGO and H2BAMO and lasting up to 24 hr. Additionally, a 16-hr pretreatment with TAMO, but not DAMGO or H2BAMO, reduced the development of physical dependence to morphine at 24 hr after morphine pellet implantation. Therefore, this study demonstrated that both TAMO and H2BAMO act as mu opioid agonists to produce short-term antinociception.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydroxyl radical-mediated conversion of morphine to morphinone

1. The hydroxyl radical-mediated conversion of morphine to morphinone (MO) was examined as an alternative to the enzymic reaction. 2. Hydroxyl radicals were generated by autoxidation of ascorbate in the presence of iron and EDTA. This system oxidized morphine to MO which was identified by h.p.l.c. and t.l.c. The reaction was dependent on the concentration of added Fe2+ and required the addition of ascorbate when Fe3+ was used. 3. Catalase inhibited production of MO whereas superoxide dismutase (SOD) had no effect. Addition of a large amount of H2O2 to the system resulted in a significant decrease in production of MO. No MO production was initiated by H2O2 itself. The oxidation of morphine was inhibited by typical hydroxyl radical-scavenging agents. These results indicate that morphine undergoes oxidation to MO by hydroxyl radical.

Pharmacodynamics of pentamorphone during coronary artery bypass grafting in humans

Pentamorphone is a new, highly potent opioid reported to have minimal cardiovascular effects in humans and a high therapeutic index in animals. Pentamorphone was injected intravenously (IV) as the sole anesthetic in 10 patients with left ventricular ejection fractions greater than 0.35 who were undergoing elective coronary artery bypass grafting (CABG). After premedication with lorazepam, 40 micrograms/kg, and establishment of hemodynamic monitoring, pentamorphone was infused at a rate of 2 micrograms/kg/min until unconsciousness occurred (5.1 +/- 1.6 micrograms/kg). Anesthetic induction was accompanied by an average 30% decrease in systolic, diastolic, and mean arterial pressure (MAP), a 19% decrease in heart rate (HR), but no change in cardiac output (CO) or pulmonary artery occlusion pressure. Five patients had a MAP less than 60 mm Hg after induction. Following incision, blood pressure, pulmonary artery occlusion pressure, and CO were unchanged from baseline but HR remained significantly lower. Despite additional pentamorphone (total dose 9.6 +/- 1.8 micrograms/kg), 6 patients required thiopental and/or enflurane to control hypertension intraoperatively. When pentamorphone is used as the sole IV anesthetic in lorazepam-premedicated patients with normal or mildly impaired ventricular function, there is a high incidence of hypotension during induction, and poor control of hemodynamic responses to stimulation. Pentamorphone, 10 micrograms/kg, does not seem to offer any significant advantage over opioids currently used for anesthesia in patients undergoing CABG.

In vivo formation of codeinone and morphinone from codeine. Isolation and identification from guinea pig bile

Codeinone (CO) and morphinone (MO) were isolated and identified in the bile of guinea pigs given sc injections of codeine. Authentic CO was synthesized and characterized by the NMR and mass spectra of its 2-mercaptoethanol (ME) adduct. This material was then used as the standard to identify the CO-ME adduct in the bile of codeine-treated animals. The MO-ME adduct was also identified in the bile with authentic materials prepared earlier. The results of our investigations indicated that 10.5 and 2.7% dose of CO and MO, respectively, were produced for 6 hr after the codeine was given. The metabolites were separated by preparative HPLC on a reverse phase column packed with C18 gel using a 10 mM sodium phosphate buffer, pH 6.8/CH3CN, 1:1 (v/v) as an eluate. For the further purification of metabolites, we used another reverse phase column with the same mobile phase. A structural elucidation of the ME adduct of metabolites was then performed by fast atom bombardment mass spectroscopy and 400 MHz fourier transform-NMR spectrometric analysis, and identified as (8S)-(2-hydroxyethylthio)dihydrocodeinone and (8S)-(2-hydroxyethylthio)dihydromorphinone, respectively.

Pentamorphone for management of postoperative pain

The efficacy, duration, and safety of the synthetic opioid pentamorphone in the treatment of acute postoperative pain were evaluated in a randomized, double-blind study of 72 patients given 0.08, 0.16, or 0.24 micrograms/kg of pentamorphone or a placebo intravenously in the recovery room after major abdominal or orthopedic surgery. Only patients given 0.24 micrograms/kg of pentamorphone experienced decreased pain intensity and increased sedation, both transient in duration. Although the two higher doses of pentamorphone delayed the patient's request for supplemental morphine, the total amount of morphine required within the first hour was not different between treatments. No acute cardiorespiratory changes were observed. Pentamorphone (0.08-0.24 micrograms/kg) was ineffective for treating acute postoperative pain after major surgery.

Sensitive method for the determination of pentamorphone in serum by liquid chromatography-mass spectrometry with thermospray interface

A liquid chromatographic-mass spectrometric method for the determination of 14-beta-n-pentylaminomorphinone (pentamorphone) and 14-beta-n-pentylaminocodeinone (PAC) as internal standard is developed. Concentration levels in serum were calculated by the ratio of the peak areas of pentamorphone to PAC versus the concentration of pentamorphone. Peak areas were measured using selected-ion-recording of the pseudo-molecular ions of pentamorphone and PAC (m/z 369 and m/z 383, respectively). Aliquots (50 microliters) of sample were injected on a C18 mu Bondapak column following solid-phase extraction. The lowest limit of quantitation observed was 43 pg/ml. The sensitivity, accuracy and reproducibility of the method were demonstrated to be satisfactory for application in pharmacokinetic study of pentamorphone.

A new metabolic pathway of morphine: in vivo and in vitro formation of morphinone and morphine-glutathione adduct in guinea pig

The biliary excretion of morphine and its metabolites by guinea pigs after s.c. injection of morphine (25 mg/kg) was determined by high-performance liquid chromatography procedures. The amounts of morphinone (MO), morphinone-glutathione adduct (MO-GSH), morphine and morphine-3-glucuronide excreted over a 4-hr period were 1.27, 9.35, 1.13 and 7.54% of the administeral dose, respectively. In addition, trace amounts of morphine-GSH adduct and morphinone-cysteine adduct, derived from MO-GSH, were detected. Although MO-GSH formation from MO proceeded nonenzymatically with a relatively high rate, GSH S-transferases participated in the reaction, especially at lower GSH concentrations. Pretreatment of the animals with diethyl maleate and lithocholic acid-3-sulfate decreased the total biliary excretion of MO. On the other hand, pretreatment with naloxone increased the excretion of total MO. In vitro experiments using liver cytosolic preparations showed that lithocholic acid-3-sulfate inhibited the enzymatic formation of MO from morphine and of MO-GSH from MO. The effects of naloxone on MO formation in vitro were more complex. A reaction was stimulated at low and suppressed at higher concentrations. The results indicated that MO-GSH formation from morphine is inhibited by lithocholic acid-3-sulfate through actions on both morphine 6-dehydrogenase and GSH S-transferases. Low levels of naloxone were found to stimulate the morphine 6-dehydrogenase-mediated dehydrogenation of morphine to MO.

Microbial degradation of the morphine alkaloids: identification of morphine as an intermediate in the metabolism of morphine by Pseudomonas putida M10

A strain of Pseudomonas putida was isolated by selective enrichment with morphine that was capable of utilising morphine as a primary source of carbon and energy for growth. Experiments with whole cells showed that both morphine and codeine, but not thebaine, could be utilised. A novel NADP-dependent dehydrogenase, morphine dehydrogenase, was purified from crude cell extracts and was shown to be capable of oxidising morphine and codeine to morphinone and codeinone, respectively. This NADP-dependent morphine dehydrogenase was not observed in any other species of pseudomonads examined and was quite distinct from the beta-hydroxysteroid dehydrogenase found in Pseudomonas testosteroni, which had previously been shown to have activity against morphine.

Depression of ventilatory responses to hypoxia and hypercapnia after pentamorphone

Pentamorphone is a novel, potent opiate with rapid onset and short duration of action that has been reported to produce analgesia with limited depression of ventilation. We quantified the effects of pentamorphone (0.08, 0.24, and 0.60 micrograms/kg, IV) on ventilatory responses to hypercapnia and hypoxia in 12 healthy volunteers. Normoxic hypercapnia and isocapnic hypoxia were induced through a rebreathing method. During each test we recorded ventilation (VE), end tidal carbon dioxide tension (PETCO2), and arterial oxygen saturation (SO2) using a pulse oximeter. Using linear regression analysis of the relationships between VE and PCO2 during hypercapnia and VE and SO2 during hypoxia, we determined the slope (slope CO2) and intercept (V55), both at PCO2 55 mm Hg, and the slope (slope O2) and intercept (V80) at SO2 80%. Pentamorphone produced dose-related reductions in the ventilatory responses to both hypercapnia and hypoxia. Maximal depression occurred 15 min after injection of pentamorphone with all doses; the highest dose (0.60 micrograms/kg) produced 48% and 53% reductions in slope CO2 and V55, and 42% and 22% reductions in slope O2 and V80, respectively, relative to parallel saline controls. The respiratory depressant actions of pentamorphone were short-lived, as all parameters returned to baseline levels within 45 min. Testing was continued for 180 min after injection, but no delayed ventilatory effects were detected, and minimal side effects were reported, even at the highest dose. The findings confirm previous reports that pentamorphone has limited ventilatory depressant effects in humans in doses that (in other studies) have been associated with clinically effective analgesia.

Quaternary naloxone blocks morphine analgesia in spinal but not intact rats

Quaternary derivatives of naloxone and other compounds are assumed not to enter the central nervous system following systemic administration. We report that i.p. naloxone methylbromide (5 mg/kg) completely reversed the antinociceptive effect of systemically administered morphine (6 mg/kg) in acutely spinalised rats, although it had no effect in the same animals prior to the transection. Naloxone hydrochloride was effective both before and after transection. Nuclear resonance spectra confirmed the purity of both compounds. These results suggest that acute spinal transection allows rapid entry of quaternary naloxone into the spinal cord. Quaternary compounds therefore may need to be used with caution in spinalised animals.

Cardiovascular effects of large doses of pentamorphone in the dog

The cardiovascular effects of large doses of pentamorphone were evaluated in nine mongrel dogs basally anesthetized with sodium thiopental, 25 to 30 mg/kg, intravenously. All dogs were mechanically ventilated with 100% oxygen, and the PaCO2 was maintained between 35 and 40 mm Hg. Mean arterial pressure (MAP), central venous pressure, heart rate (HR), cardiac output (CO), pulmonary artery pressure, and pulmonary artery occluded pressure were measured, and stroke volume and systemic and pulmonary vascular resistances were calculated. Baseline measurements were obtained, then pentamorphone, 10 micrograms/mL, was given as an intravenous infusion at 2.5 micrograms/kg/min. Additional data were obtained after infusion of 25, 50, 75, 100, 125, 150, 200, 250, 300, and 350 micrograms/kg of pentamorphone. The inspired gases were then changed to 50% nitrous oxide in oxygen, and after a 20-minute equilibration period, an additional set of data was collected. Pentamorphone, 25 micrograms/kg, decreased HR 50%, MAP 65%, and CO 54%. No further changes in any measured or calculated variables were observed with additional doses of pentamorphone. The addition of 50% nitrous oxide to the inspired gas mixture had no effect on any measured or calculated hemodynamic variable. The minimal hemodynamic effects of pentamorphone in the dog suggest that further investigation into its use as an anesthetic is warranted.

Affinity labeling of mu opioid receptors by sulfhydryl alkylating derivatives of morphine and morphinone

After reduction of a disulfide bond at or near the mu opioid binding site in rat brain membranes, incubating membranes with 14 beta-bromoacetamido derivatives of either morphine, dihydromorphine, morphinone, or dihydromorphinone resulted in the irreversible inhibition of mu opioid binding to rat brain membranes. Without the addition of the disulfide bond-reducing reagent dithiothreitol, these affinity ligands bound reversibly to opioid binding sites. Binding to either delta or kappa opioid binding sites was not altered by alkylation of the membranes with the affinity ligands. The percentage of irreversible inhibition of mu opioid binding was dependent on the time and temperature of the incubation of membranes with the affinity ligands and on the concentrations of dithiothreitol and the affinity ligands. Incubating membranes with morphine afforded almost complete protection from alkylation of the mu opioid binding site. Naloxone and the l-isomer levorphanol also protected the site from alkylation, whereas the d-isomer dextrorphan and the kappa-selective opioid U50,488H did not protect the site. The mu-selective peptide [D-Ala2, (Me)Phe4,Gly(ol)5]enkephalin was the peptide that afforded the greatest protection. These studies have shown that, after the reduction of a disulfide bond at or near the mu opioid binding site, this sulfhydryl group can be specifically alkylated, resulting in the affinity labeling of the mu opioid binding site.

Naloxone reversal of oxymorphone effects in dogs

Oxymorphone was administered IV to dogs 4 times at 20-minute intervals (total dosage, 1 mg/kg of body weight, IV) on 2 separate occasions. Minute ventilation, mixed-expired carbon dioxide concentration, arterial and mixed-venous pH and blood gas tensions, arterial, central venous, pulmonary arterial, and pulmonary wedge pressures, and cardiac output were measured. Physiologic dead space, base deficit, oxygen transport, and vascular resistance were calculated before and at 5 minutes after the first dose of oxymorphone (0.4 mg/kg) and at 15 minutes after the first and the 3 subsequent doses of oxymorphone (0.2 mg/kg). During 1 of the 2 experiments in each dog, naloxone was administered 20 minutes after the last dose of oxymorphone; during the alternate experiment, naloxone was not administered. In 5 dogs, naloxone was administered IV in titrated dosages (0.005 mg/kg) at 1-minute intervals until the dogs were able to maintain sternal recumbency, and in the other 5 dogs, naloxone was administered IM as a single dose (0.04 mg/kg). Naloxone (0.01 mg/kg, IV or 0.04 mg/kg, IM) transiently reversed most of the effects of oxymorphone. Within 20 to 40 minutes after IV naloxone administration and within 40 to 70 minutes after IM naloxone administration, most variables returned to the approximate values measured before naloxone administration. The effects of oxymorphone outlasted the effects of naloxone; cardiovascular and pulmonary depression and sedation recurred in all dogs. Four hours and 20 minutes after the last dose of oxymorphone, alertness, responsiveness, and coordination improved in all dogs after IM administration of naloxone. Cardiac arrhythmia, hypertension, or excitement was not observed after naloxone administration.

Antinociceptive activity of pentamorphone, a 14-beta-aminomorphinone derivative, compared to fentanyl and morphine

The analgesic potency of pentamorphone, a 14-beta-aminomorphinone derivative, was compared to that of fentanyl and morphine by examining quantal dose-effect curves generated from data obtained in the mouse hot plate, rabbit tooth-pulp, and dog tail clamp tests. Onset and duration of antinociceptive effects were also compared. The ED50 values (mg/kg) were determined in mice for pentamorphone (0.0039), fentanyl (0.016), and morphine (7.3). In the rabbit tooth pulp test the ED50 values were 0.0009 mg/kg for pentamorphone, 0.0074 mg/kg for fentanyl, and 1.1 mg/kg for morphine; in the dog tail clamp test these values were 0.012 mg/kg for pentamorphone and 0.018 mg/kg for fentanyl. Duration of action (defined as the time until response to tooth pulp stimulation declined to 50% of maximum possible effect [MPE]) was 10 min with twice the IV ED50 for pentamorphone in mice. This duration was similar to that of the equipotent dose of fentanyl but much shorter than the duration of an equipotent potent dose of morphine (60 min). The duration in rabbits of the ED98 (IV) dose of pentamorphone was 65 min compared to 35 min for an equipotent dose of fentanyl and 200 min for morphine. Intramuscular doses of pentamorphone had significantly faster onset and shorter duration times than equipotent doses of morphine in both mice and rabbits. Pretreatment with naloxone in mice and rabbits attenuated the development of the antinociceptive effects of pentamorphone. This study shows that pentamorphone is a potent analgesic with a duration of action similar to that of fentanyl.

An evaluation of morphine and oxymorphone administered via patient-controlled analgesia (PCA) or PCA plus basal infusion in postcesarean-delivery patients

The analgesic efficacy and adverse effects of morphine and oxymorphone in 32 patients who received traditional patient-controlled analgesia (PCA) following cesarean delivery were compared with those in 32 other patients receiving the same agents via PCA plus basal opioid infusion (PCA + BI). All patients were operated upon during epidural anesthesia with 2% lidocaine and 1:200,000 epinephrine to achieve a T4 sensory level. Upon first complaint of pain in the recovery room, patients were given a titrated iv loading dose of the assigned opioid until comfortable and were then provided with a programmable PCA device. Group I (PCA) consisted of two subsets in which incremental boluses of morphine (1.8 mg, n = 16) or oxymorphone (0.3 mg, n = 16) could be self-administered via conventional PCA. Patients in group II (PCA + BI) received a basal infusion of morphine (0.6 mg/hour, n = 16) or oxymorphone (0.1 mg/hour, n = 16) in addition to self-administered boluses of 1.8 and 0.3 mg, respectively. Patients were evaluated for 24 h following initiation of analgesic therapy, and 10-cm visual analog scales (VAS) were utilized at selected intervals to assess pain at rest, pain during movement, and satisfaction with therapy. The level of sedation and incidence of nausea/vomiting and pruritus were also recorded. Patients utilizing PCA + BI noted significant reductions in resting pain scores with oxymorphone and decreased pain during movement with both opioids when compared with individuals using PCA alone (P less than 0.05). There were no significant differences between treatment groups in 24-h dose requirements or patient satisfaction with therapy (P = ns).(ABSTRACT TRUNCATED AT 250 WORDS)

Outpatient premedication: use of midazolam and opioid analgesics

The perioperative effects of administering sedative and analgesic drugs prior to outpatient surgery were evaluated. One hundred fifty adult outpatients were randomly assigned to one of six study groups according to a double-blind protocol design. Patients were given placebo (saline) or midazolam (5 mg im) 30-60 min prior to surgery, and then either placebo, oxymorphone (1 mg iv), or fentanyl (100 micrograms iv) 3-5 min prior to a standardized anesthetic technique. Preoperatively, midazolam premedication was associated with a significantly lower anxiety level (37 +/- 29 mm vs. 50 +/- 32 mm, P less than 0.05), higher sedation level (254 +/- 136 mm vs. 145 +/- 109 mm, P less than 0.01), worsening of psychomotor skill (5 +/- 5 vs. 2 +/- 2 dots missed, P less than 0.01; midazolam vs. placebo), and impaired recall abilities. In addition, use of midazolam did not prolong the discharge time. Compared to control patients, those who received fentanyl had a decreased incidence of intraoperative airway difficulties such as coughing (28% vs. 0%, P less than 0.01). Although use of opioids increased the incidence of postoperative nausea (42% vs. 18%, P less than 0.01) and vomiting (23% vs. 2%, P less than 0.01; opioid vs. no opioid), average recovery times were not affected by opioid administration. Oxymorphone use was associated with a lower incidence of pain at home compared with that following fentanyl (46% vs. 74%, P less than 0.05). Finally, preoperative administration of both midazolam and fentanyl or oxymorphone prior to a standardized methohexital-nitrous oxide anesthetic technique did not adversely affect recovery after outpatient surgery.

Opioid agonist and antagonist activities of peripherally selective derivatives of naltrexamine and oxymorphamine

A series of beta-naltrexamine and beta-oxymorphamine derivatives that contain ionizable moieties coupled to the 6 beta-amino group were synthesized in an effort to develop antagonists and agonists that have negligible access into the central nervous system (CNS). Among the beta-naltrexamine derivatives 1-7, all displayed partial agonism on the guinea pig ileal longitudinal muscle preparation except for aspartyl derivative 6, which was a full agonist with activity in the range of morphine. The beta-oxymorphamine derivatives 8-12 were all full agonists with potencies ranging from 1.5 to 6.1 times that of morphine. Among the compounds evaluated in mice for antinociceptive or opioid antagonist activities, aspartyl derivative 6 possessed the greatest difference between peripheral (po or iv) and icv equiactive antagonist doses. Compared to naltrexone, 6 was greater than 100 times more potent by the icv route, but 6000-10,000 times less potent when administered po or icv. The present study suggests that zwitterionic groups are highly effective in preventing penetration of ligands into the CNS. Such ligands may be useful pharmacologic tools for investigation of peripheral opioid mechanisms. Moreover, they could find clinical applications when the central actions are unwanted.