Heroin, 6-acetylmorphine and morphine effects on threshold for rewarding and aversive brain stimulation.

Studies investigating the reinforcing and analgesic activity of heroin and morphine have found that heroin is a more potent compound. The rapid deacetylation of heroin to 6-acetylmorphine and morphine raises questions concerning the underlying mechanism responsible for this difference in potency. The present series of experiments addressed this issue by examining, in the rat, the relative potency of heroin and its active metabolites, 6-acetylmorphine and morphine, to lower the threshold for rewarding stimulation of the medial forebrain bundle and raise the threshold for aversive stimulation of the mesencephalic reticular formation. Reward and escape thresholds were determined by using a modification of the psychophysical method of limits. Heroin was found to be approximately 40 times more potent than morphine in lowering the reward threshold and approximately 6.5 times more potent in raising the escape threshold. 6-Acetylmorphine and heroin were approximately equipotent in producing significant effects on the threshold for both rewarding and aversive brain stimulation. These findings suggest that heroin's increased potency when compared to morphine may be due, in part, to the activity of 6-acetylmorphine.     

Urinary excretion of morphine and its metabolites in morphine-dependent subjects.

Morphine, morphine glucuronide, morphine ethereal sulfate, normorphine and total normorphine in three consecutive 24-hour urines of four morphine-dependent subjects receiving morphine sulfate 60 mg s.c. q.i.d. have been determined with thin-layer chromatography and gas-liquid chromatography. With thin-layer chromatography the mean daily excretion of free morphine was 10% of the administered dose; morphine glucuronide, 65%; total (free and acid hydrolyzable conjugate) morphine 85%; and total normorphine, 3.5%. With gas-liquid chromatography, the percentage excretion for free morphine was 10%; total morphine, 74%; free normorphine, 1%; and total normorphine, 4%. The excretion of total drug was linearly related to the volume of the daily urine output.     

The fate of diastereomeric glutathione conjugates of alpha-bromoisovalerylurea in blood in the rat in vivo and in the perfused liver. Stereoselectivity in biliary and urinary excretion

The mixture of the two diastereomeric glutathione (GSH) conjugates of alpha-bromoisovalerylurea, (RS)-IU-G, was administered i.v. to anesthetized rats. Bile and urine were collected for 6 hr. Some 70 to 75% was recovered in urine as mercapturates. The half-lives of the urinary excretion were the same for the two mercapturates: 18 min and approximately 130 min, respectively, for the rapid and the slow phase. In bile only 1.5% of the dose of (R) and (S)-IU-G was found; two unidentified metabolites were also found. In rats with ligated kidneys, 4% of the dose of each glutathione conjugate was excreted in bile. Again, the two unidentified metabolites were found. In the isolated recirculating liver perfusion experiments, 1.4% of the administered GSH conjugates was found in bile. The concentration of the GSH conjugates in the perfusion medium remained constant and no other metabolites were formed. When (RS)-alpha-bromoisovalerylurea itself was added to the perfusate, the GSH conjugates in bile increased rapidly. The results show that the GSH conjugate in blood is little excreted in bile due to a slow uptake of the conjugate by the liver. The diastereomeric GSH conjugates show no stereoselectivity in their pharmacokinetics, indicating that the rate limiting step in this process is not stereoselective.     

Bile acid synthesis and excretion following release of total extrahepatic cholestasis by percutaneous transhepatic drainage

Abstract. Urinary, biliary and serum bile acids were studied in three patients before and after percutaneous transhepatic drainage for total bile duct obstruction.
Before drainage high urinary excretion often different bile acids occurred. The percentage distribution was: cholic and chenodeoxycholic acid (66–86%), hyo-cholic (3–16%), 3β 12α-dihydroxy-5-cholenoic (3–6%) and 3β-hydroxy-5-cholenoic acid (2–8%). These acids were regularly found in serum. In addition small amounts (less than 2%) of norcholic, allocholic, 3β, 7α-dihydroxy-5β-cholanoic, 3α, 7α-dihydroxy-5α-cholanoic and lithocholic acid were excreted in urine. Trace amounts of these bile acids were found in serum.
After start of drainage biliary bile acid excretion increased rapidly during the first day, dropped to a minimum during the second or third day and then slowly increased again. In spite of normal volumes of bile produced, the total serum bile acids and the urinary excretion of bile acids remained increased during a drainage period of 19 days. The bile acids were of the same type as observed during cholestasis. In serum the increase was mainly due to high concentrations of chenodeoxycholic and 3β-hydroxy-5-cholenoic acid, as sulphate esters.
Glycine and taurine conjugates of cholic, chenodeoxycholic and hyocholic acid were mainly excreted in bile. Bile acid sulphate esters were only present in trace amounts in bile and were mainly excreted in urine. This, combined with low renal clearance, explains the elevated serum levels of sulphate esters of chenodeoxycholic and 3β-hydroxy-5-cholenoic acid conjugates.     

Excretion of [24-14C] glycochenodeoxycholate-3-sulphate in patients with liver cirrhosis

[24-14C] glycochenodeoxycholate-3-sulphate (GCDC-3S) was given intravenously to seven patients with liver cirrhosis and the elimination of the isotope from blood and the isotope excretion in urine and faeces followed. The bile acid conjugates in serum and urine were separated by HPLC and the change in specific activity in isolated conjugates determined. [24-14C] GCDC-3S was rapidly eliminated either by urinary excretion or faecal excretion and the half-life of the labelled conjugates varied between 76-198 min. No deamination or desulphation of the isotope occurred prior to urinary excretion. Only small amounts of GCDC-3S excreted in bile were absorbed from the intestine, as no isotope was recovered in other bile acid conjugates in serum.     

Differential influence of N-dealkylation on the stimulus properties of some opioid agonists.

The capacity of several opioid agonists and their N-dealkylated derivatives (normetabolites) to substitute for the discriminative and reinforcing stimulus properties of codeine was evaluated in rhesus monkeys, and the affinity of these compounds in binding to mu receptors in rhesus monkey brain membranes was determined. Heroin (0.1 mg/kg), 6-acetylmorphine (0.1 mg/kg), methadone (0.6 mg/kg), 3-acetylmorphine (1 mg/kg), morphine (1 mg/kg) and codeine (1.8 mg/kg) substituted for the codeine cue, but the normetabolites of heroin, 6-acetylmorphine, morphine and codeine did not (up to 10 mg/kg). l-alpha-Acetylmethadol (3 mg/kg) and its mono (0.1 mg/kg) and double (0.6 mg/kg) N-dealkylated derivatives all substituted. In self administration, subjects responded for morphine (0.1 mg/kg/injection) and codeine (0.3 mg/kg/injection), but not for norcodeine (up to 1 mg/kg/injection) or normophine (up to 3 mg/kg/injection). l-alpha-Acetylmethadol (up to 0.3 mg/kg/injection) did not maintain responding, but its mono (0.1 mg/kg/injection) and double (0.1 mg/kg/injection) normetabolites did. In receptor binding, the normetabolites of morphine and 6-acetylmorphine were less potent than their parent agonists in displacing [3H]Tyr-D-Ala-Gly-(Me)Phe-Gly-ol, but the normetabolites of l-alpha-acetylmethadol had greater affinity than their parent. Codeine and norcodeine were inactive in binding. If l-alpha-acetylmethadol is converted only slowly to its active normetabolites, this may explain the lack of efficacy found with this compound in the self administration procedure.     

Conjugation, metabolism and excretion of [24-14C] chenodeoxycholic acid in patients with extrahepatic cholestasis before and after biliary drainage-analysis of conjugated bile acids by HPLC

[24-14C] chenodeoxycholic acid (CDC) was given to patients with total extrahepatic cholestasis two or three days before an external drainage was made, and excretion of the isotope in urine and bile followed. Bile acids were group-separated by anion exchange chromatography on DEAP-Sephadex LH-20 and the individual conjugates isolated by HPLC. 51.0-75.4% of the administered isotope was excreted; 16.2-29.9% as sulphates, 0.1-2.4% as glucuronides and 20.7-58.7% as glycine and taurine conjugates. 5.2-21.0% of excreted isotope consisted of transformation products of CDC, mainly cholic acid, hyocholic acid and ursodeoxycholic acid. Labelled urinary sulphates were the 3-sulphates of glycochenodeoxycholic and taurochenodeoxycholic acid. During cholestasis the renal clearance was about ten times higher for the sulphates compared with the non-sulphated conjugate. The clearance of glycine conjugates and their sulphates was of the same magnitude as that of the corresponding taurine conjugates. During the biliary drainage period, most of the labelled sulphates were excreted in urine, while most of the glycine and taurine conjugates were excreted in bile.     

alpha-Bromoisovalerylurea as model substrate for studies on pharmacokinetics of glutathione conjugation in the rat. II. Pharmacokinetics and stereoselectivity of metabolism and excretion in vivo and in the perfused liver

The hypnotic drug alpha-bromoisovalerylurea (BIU) has been studied in the rat with respect to its potential use as model substrate to investigate the pharmacokinetics of glutathione conjugation in vivo. The major metabolites of racemic BIU are the diastereomeric glutathione conjugates (bile) and mercapturates (urine). BIU was metabolized mainly by glutathione conjugation: after i.v. administration of [14C]BIU to freely moving rats, 89% of the dose was recovered in urine within 24 hr, mostly as mercapturates. The rate-limiting step in the clearance of BIU from blood most likely is glutathione conjugation as it was shown that rate-limitation is not due to flow-limited clearance in the liver (the initial extraction ratio of BIU in the perfused liver preparation was low: hepatic extraction ratio = 0.23), protein binding (60% was unbound in plasma) or enzyme saturation (linear pharmacokinetics in the dose range studied: 22-270 mumol/kg). Water solubility of BIU was sufficient to allow its i.v. administration, whereas the absence of toxic effects enables animal as well as human studies. Thus, BIU is a promising model substrate for studies of glutathione conjugation in vivo. In pentobarbital-anesthetized rats with a bile duct catheter, equal amounts of metabolites were excreted in bile (almost exclusively as the two diastereomeric BIU glutathione conjugates) and urine (mostly as the two diastereomeric mercapturates). Based on similar experiments with bile duct-ligated rats, it was concluded that the appearance of the mercapturates in urine could also occur without biliary excretion and subsequent gut metabolism of the BIU glutathione conjugates. The ability of the liver to metabolize BIU was studied in a hemoglobin-free, recirculating liver perfusion system. Of the recovered radioactivity 40% was excreted in bile within 2 hr, almost exclusively in the form of the two BIU glutathione conjugates. Also, glutathione conjugates were found in the perfusate (16% of the radioactivity present in the perfusate after 2 hr). A distinct stereoselectivity was observed in the metabolite excretion rates. The excretion half-lives of the two diastereomeric glutathione conjugates in bile differed 2- to 3-fold, both in anesthetized rats and in the perfused liver preparation. A similar difference in excretion half-lives was found for the urinary excretion of the diastereomeric mercapturates. Thus, BIU can be used to investigate in vivo the stereoselectivity of glutathione conjugation.     

Urinary excretion of meso-2,3-dimercaptosuccinic acid in human subjects

The urinary excretion of meso-2,3-dimercaptosuccinic acid (DMSA), which is an effective chelating agent for lead, was determined after the oral administration of 10 mg DMSA/kg to six normal young men. The DMSA that was absorbed was extensively biotransformed. After 14 hours only 2.53% of the administered DMSA was excreted in the urine as unaltered DMSA and 18.1% as altered forms. The unaltered DMSA was 12% of the total DMSA found in the urine. The altered form(s) of DMSA was 88% of the total urinary DMSA. The altered DMSA can be converted to unaltered DMSA by electrolytic reduction, which indicates that the altered forms of DMSA are disulfides. The excretion of altered DMSA reached a peak between 2 and 4 hours after DMSA administration. There were small but statistically significant increases in the excretion of zinc, copper, and lead after DMSA administration. DMSA did not influence the urinary excretion of 27 other metals and elements.     

Metabolism and excretion of a glutathione conjugate of acetaminophen in the isolated perfused rat kidney

Acetaminophen-glutathione (APAP-GSH) is the initial sulfur-containing metabolite of APAP produced by the liver. However, little, if any, APAP-GSH is found in the urine of intact animals. Rather, the cysteine (APAP-CYS) and N-acetylcysteine (APAP-NAC) conjugates are the predominant sulfur-containing metabolites of APAP excreted in the urine. To define more precisely the role of the kidney in total body disposition of APAP, the metabolism and excretion of each of these metabolites was quantified in the isolated perfused rat kidney (IPK). With perfusate concentrations of 0.031, 0.125 and 0.250 mM APAP-GSH, the IPK metabolized APAP-GSH to APAP-CYS rapidly. Further metabolism of APAP-CYS to APAP-NAC proceeded at a much slower rate. Consequently, at 0.031 mM APAP-GSH, negligible amounts of APAP-CYS were found in the urine. However, as the concentration of APAP-GSH was increased so did the excretion of APAP-CYS. In contrast, the excretion of APAP-NAC did not exhibit dependence on APAP-GSH concentration. APAP-NAC was excreted by a probenecid sensitive transport mechanism whereas APAP-CYS excretion appeared to be related only to glomerular filtration. In addition, the disappearance of APAP-GSH was much greater than could be accounted for by glomerular filtration. These data indicate that the IPK is an effective model for the study of metabolism and excretion of xenobiotics that have undergone conjugation with GSH.     

Neuroendocrine system response modulates oxidative cellular damage in burn patients

Oxygen-derived free radicals play important roles in pathophysiological processes in critically ill patients, but the data characterizing relationships between radicals and neuroendocrine system response are sparse. To search the cue to reduce the oxidative cellular damage from the point of view of neuroendocrine system response, we studied the indicators of neuroendocrine and inflammatory responses excreted in urine in 14 burn patients (42.3 +/- 31.4 years old, and 32.3 +/- 27.6% burn of total body surface area [%TBSA]) during the first seven days post burn. The daily mean amounts of urinary excretion of 8-hydroxy-2'-deoxy-guanosine (8-OHdG), a marker of oxidative cellular damage, were above the upper limit of the standard value during the studied period. The total amount of urinary excretion of 8-OHdG in the first day post burn correlated with burn severity indices: %TBSA (r = 0.63, p = 0.021) and burn index (r = 0.70, p = 0.008). The daily urinary excretion of 8-OHdG correlated with the daily urinary excretion of norepinephrine and nitrite plus nitrate (NOx) during the studied period except day 2 post burn, and correlated with the daily urinary excretion of 17-hydroxycorticosteriod (17-OHCS) in days 2, 3, and 7 post burn. These data suggest that oxidative cellular damage correlates with burn severity and neuroendocrine system response modulates inflammation and oxidative cellular damage. Modulation of neuroendocrine system response and inflammation in the treatment in the early phase of burn may be useful to reduce the oxidative cellular damage and to prevent multiple organ failures in patients with extensive burn.     

In vivo catabolism of histamine in the human stomach

The importance of the stomach in the magnitude of excreted amounts of the major histamine metabolite in the urine was studied during total parenteral nutrition in five patients before and after total gastrectomy. In all subjects, a reduction in the 24-h urinary excretion of methylimidazoleacetic acid was observed. No corresponding effect was seen after an operation because of abdominal aortic aneurysm. In patients with duodenal ulcer disease and those submitted to a cholecystectomy because of cholecystolithiasis, we studied the catabolism of histamine in the stomach by injecting 14C-histamine directly into the portal vein and, simultaneously, 3H-histamine intra-arterially to the corpus fundus region of the stomach and subsequently determining the urinary excretion of 14C. 3H-histamine and their basic and acid metabolites, respectively. We found no apparent difference in the pattern of excreted 14C and 3H metabolites between the two patients groups, indicating that the catabolism of histamine in the stomach of patients with duodenal ulcer disease is similar to that in 'healthy' controls.     

Abnormal diurnal urinary sodium and water excretion in diabetic autonomic neuropathy

1. Diurnal patterns of urine output and sodium and potassium excretion were studied in 10 diabetic patients with and 10 without autonomic neuropathy, and in 10 normal subjects. 2. The diurnal patterns of excretion in the diabetic patients with autonomic neuropathy differed significantly from the two other groups, as a smaller proportion of the 24 h output of urine, sodium and potassium was excreted during the day and a larger proportion was excreted at night. 3. Similar changes were noted in the diurnal patterns of urinary kallikrein excretion in diabetic patients with autonomic neuropathy, and urinary kallikrein output correlated significantly with urine volume but not with urinary sodium excretion. 4. The diurnal patterns of excretion of urinary prostaglandin E2 and 6-keto-PGF1 alpha were not significantly different in diabetic patients with autonomic neuropathy. 5. Nocturia was a common complaint in this group, and the number of nocturnal voidings correlated with night urine volume. There was no evidence of premature bladder emptying. 6. The changes observed in the day/night urine output and sodium excretion could not be explained by glycosuria, insulin regimens, impaired renal function or abnormal diurnal prostaglandin excretion; their possible relevance to the diurnal changes of urinary kallikrein excretion is discussed.     

Metabolic disposition of DQ-2556, a new cephalosporin, in rats, rabbits, dogs, and monkeys.

The metabolic disposition of DQ-2556 was studied in rats, rabbits, dogs, and monkeys after an intravenous administration of 20 mg of 14C-labeled drug per kg of body weight. The serum data were analyzed by the two-compartment open model. The mean half-lives for the drug in serum at excretion phase were 18.1, 54.4, 21.8, and 63.6 min in rats, rabbits, dogs, and monkeys, respectively. The volume of distribution and total body clearance ranged from 0.18 to 0.30 liter/kg and 0.065 to 0.45 liter/h/kg, respectively. This compound was distributed to the tissues rapidly and well, especially to the kidney, trachea, liver, thyroid, skin, and lung. Tissue concentrations declined rapidly in a few hours and then very slowly. However, no accumulation was observed in any tissues. The results of a protein-binding study by ultracentrifugation indicated that DQ-2556 was 20 to 30% bound to serum proteins in animals and its affinity was low. Almost 90% of the administered radioactivity was excreted into urine in all species. Biliary excretion in rats was 3.1% of the dose. Nearly 70% of the dose or more was excreted into urine as unchanged drug, and the amounts of urinary metabolites were small except in rabbits, in which substantial amounts of polar metabolites were detected.     

Discriminative stimulus effects of intravenous heroin and its metabolites in rhesus monkeys: opioid and dopaminergic mechanisms

Heroin has characteristic subjective effects that contribute importantly to its widespread abuse. Drug discrimination procedures in animals have proven to be useful models for investigating pharmacological mechanisms underlying the subjective effects of drugs in humans. However, surprisingly little information exists concerning the mechanisms underlying the discriminative stimulus (DS) effects of heroin. This study characterized the DS effects of heroin in rhesus monkeys trained to discriminate i.v. heroin from saline. In drug substitution experiments, heroin, its metabolites 6-monoacetylmorphine, morphine, morphine-6-glucuronide, and morphine-3-glucuronide, and the mu-agonists fentanyl and methadone engendered dose-dependent increases in heroin-lever responding, reaching average maximums of >80% (full substitution) at doses that did not appreciably suppress response rate. In contrast, the delta-agonist SNC 80, the kappa-agonist spiradoline, and the dopamine uptake blockers/releasers cocaine, methamphetamine, and GBR 12909 did not engender heroin-like DS effects regardless of dose. In antagonism studies, in vivo apparent pA2 and pK(B) values for naltrexone combined with heroin, morphine, and 6-monoacetylmorphine (8.0-8.7) were comparable with those reported previously for naltrexone antagonism of prototypical mu-agonists. The results show that the DS effects of heroin are pharmacologically specific and mediated primarily at mu-opioid receptors. Moreover, the acetylated and glucuronated metabolites of heroin appear to play significant roles in these effects. Despite previous speculation that morphine-3-glucuronide lacks significant opioid activity, it substituted fully for heroin in our study, suggesting that it can exhibit prominent mu-agonist effects in vivo.     

A practical approach to determine cutoff concentrations for opiate testing with simultaneous detection of codeine, morphine, and 6-acetylmorphine in urine

BACKGROUND: Both the Department of Defense (DoD) and the Department of Health and Human Services (DHHS) currently require two confirmation tests to verify use of heroin, one test for total morphine and a separate test for 6-acetylmorphine (6-AM). Our aim was to determine appropriate free-codeine, free-morphine, and 6-AM cutoff concentrations that could be substituted for total-morphine, total-codeine, and 6-AM cutoff concentrations and to develop a less labor-intensive method for measuring codeine, morphine, and 6-AM. METHODS: Urine samples containing opiates were extracted, derivatized, and analyzed using gas chromatography-mass spectrometry with selective ion monitoring. RESULTS: The limits of detection for codeine, morphine, and 6-AM were 6, 5, and 0.5 microg/L, respectively. Recoveries were >90%. Quantification was linear over the concentration range of 6-1000 microg/L for codeine, 5-5000 microg/L for morphine, and 0.5-800 microg/L for 6-AM. Cutoff concentrations for confirmation of opiates were 100, 100, and 10 microg/L for free codeine, free morphine, and 6-AM. CONCLUSION: The proposed cutoff concentrations for free morphine and 6-AM provide better detection windows for morphine and heroin use than the cutoff concentrations for total morphine and 6-AM used at present. Detection of free codeine, instead of total codeine, simplifies interpretation of codeine use. The single-extraction method enables simultaneous, less labor-intensive analysis of morphine, codeine, and 6-AM.Copyright 1999 American Association for Clinical Chemistry     

Renal and Biliary Disposition of Dapsone in the Dog

Dapsone (4,4'-diaminodiphenylsulfone [DDS]) was administered intravenously to anesthetized dogs; urine was collected, heparinized venous blood was obtained, and bile was collected from some of the dogs. A constant infusion of inulin was maintained, and isosmotic or hypoosmotic fluids were administered. Dogs were studied under conditions of standardized, increased or decreased urine flow, and before and after plasmapheresis. Plasma, urine, and bile samples were analyzed for DDS and DDS conjugates; the degree of binding of DDS by plasma proteins was also determined. The renal clearances of inulin and DDS were calculated. No monoacetyldapsone (MADDS) was detected in the plasma, and only negligible quantities were found in the urine. Small quantities of DDS and DDS conjugates were detected in the bile in 4 h following the dose. Between 10 and 30% of the administered drug could be identified as DDS plus DDS conjugates in the urine in 8 h after the dose. Renal clearance of unbound DDS was proportional to the urine flow rate, and the clearance ratio of DDS to inulin approached the same maximal value as that for urea. Although the rate of urinary excretion of DDS conjugates was the same in the dog as in man, the rates of excretion of DDS and of DDS plus DDS conjugates were greater in the dog than in man, suggesting that the acetylation of DDS to MADDS by man but not by the dog and the greater degree of plasma protein binding of DDS and MADDS by man account for the longer half-time of disappearance of DDS in man compared to that in the dog.     

Metabolism of pentaerythritol trinitrate

The absorption, excretion, and biotransformation of 14C-labeled pentaerythritol (PE) trinitrate was studied in man. The administration of a single sublingual dose was followed by rapid absorption and extensive biotransformation. Six drug metabolites were identified. Final excretion of the drug and its metabolites was almost totally through the kidney. Low levels of unchanged drug were present in plasma and urine. PE mononitrate was the major drug metabolite in plasma and urine. Glucuronides of PE trinitrate, dinitrate, and mononitrate were identified for the first time in man. PE trinitrate glucuronide appeared in plasma rapidly and about 8% of the dose was excreted in urine. Reversible and irreversible pathways are proposed for the formation of the metabolites. The reconversion of PE trinitrate glucuronide to PE trinitrate is postulated to explain the duration of drug activity and excretion.     

The quantitative relationship of urinary peptide hydroxyproline excretion to collagen degradation

To determine the quantitative relationship of urinary hydroxyproline peptide excretion to collagen breakdown, known quantities of radioactive hydroxyproline peptides were administered to unlabeled animals and excertion of radioactivity in respiratory carbon dioxide, urine, and feces was measured. The major routes of excretion of collagen peptide metabolites were respiratory carbon dioxide (75%) and urine, as hydroxyproline-containing peptides (25%).Since the predominant urine hydroxyproline peptide linkage is proly-hydroxyproline, L-prolyl-L-hydroxyproline-(3)H was administered to unlabeled animals. Greater than 80% of the administered dipeptide was excreted in urine, suggesting that this peptide linkage is not hydrolyzed to a significant extent in vivo.These data suggest that urinary hydroxyproline excretion is a "fairly" sensitive indicator of collagen breakdown and can be used at the clinical level to quantitate changes in collagen breakdown.