Plasma morphine-3-glucuronide, morphine-6-glucuronide and morphine concentrations in patients receiving long-term epidural morphine.

Plasma morphine concentrations were measured in five cancer patients receiving long-term epidural morphine administration. Peak concentrations were observed within 1 h of dosage and concentrations then declined biexponentially. Plasma morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) concentrations were measured in two patients and plasma M3G concentrations were observed to be much higher than plasma M6G and morphine concentrations. Peak plasma M6G concentrations occurred within 1.0 h of dosing and plasma M6G concentrations then remained higher than plasma morphine concentrations.     

HPLC determination of morphine, morphine-3-glucuronide and morphine-6-glucuronide in human serum of oncological patients after administration of morphine drugs

A simultaneous determination of morphine (M) and its two metabolites, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G), by HPLC in the serum of oncological patients is described. The compounds are extracted from the serum by means of Chromabond C18--EC solid-phase-extraction cartridges, separated on a Symmetry C18 analytical column (150 x 4.9 mm, 5 microm) and detected by a UV detector at 210 nm. The mobile phase consisted of 8% acetonitrile in water, 30 mmol/l phosphate buffer (pH 3) and 1 mmol/l octane sulfonic acid as the ion pairing agent; its flow-rate was 0.8 ml/min. Under these conditions, the detection limits were 10 ng/ml, 60 ng/ml and 90 ng/ml for M, M3G, and M6G, respectively. This paper concerns blood serum concentration levels of M, M3G and M6G in oncological patients, their ratios and their role in pain resistance.     

Antinociceptive and ventilatory effects of the morphine metabolites: morphine-6-glucuronide and morphine-3-glucuronide

Morphine and its major metabolites, morphine-3-glucuronide and morphine-6-glucuronide, were given intracerebroventricularly (i.c.v.) to rats. The antinociceptive effects were assessed in the tail-flick and hot-plate tests as well as the writhing test. Ventilatory effects were studied in halothane-anaesthetized rats. Based on calculated ED50 values, morphine-6-glucuronide was approximately 200 times more potent that morphine itself in the tail-flick and hot-plate tests. In the writhing test the difference in ED50 was approximately 9-fold. Morphine and morphine-6-glucuronide administered i.c.v. induced dose-related decreases in minute ventilation in the dose range 2.7 x 10(-9)-1.3 x 10(-7) mol. The dose-response curve for minute ventilation was steeper for morphine-6-glucuronide than for morphine. Morphine-6-glucuronide was approximately 10 times more potent than morphine in depressing minute ventilation. Morphine-6-glucuronide reduced both tidal volume and respiratory frequency, while morphine reduced only the tidal volume. Morphine-3-glucuronide, in contrast, increased both tidal volume and respiratory frequency, causing an increase in minute ventilation. Apnoea was elicited after the highest doses of morphine-6-glucuronide but not of morphine. The potency difference for depression of minute ventilation between morphine-6-glucuronide and morphine corresponded well to the difference in the writhing test but not to the potency difference in the tail-flick or hot-plate tests. The ventilatory depression induced by morphine and morphine-6-glucuronide was readily reversed by naloxone, while the hyperventilation caused by morphine-3-glucuronide was slightly potentiated by the opioid antagonist. Naloxone pretreatment completely blocked the ventilatory depression induced by morphine-6-glucuronide. These results show that the potent ventilatory depression induced by morphine-6-glucuronide is related to its antinociceptive effects in rats. Furthermore, the fact that morphine-3-glucuronide stimulated ventilation and that morphine had a more shallow ventilatory dose-response curve compared to morphine-6-glucuronide may indicate that morphine-3-glucuronide is a functional antagonist of the depressive effects of morphine and morphine-6-glucuronide on ventilation.     

Heroin-using drivers: importance of morphine and morphine-6-glucuronide on late clinical impairment

Objective To evaluate the relationship between major heroin metabolites (morphine, morphine-6-glucoronide), pattern of drug use, and late impairment of psychomotor functions.Methods From the database of the Norwegian Institute of Public Health, Oslo, blood morphine concentration in samples from heroin users (n=70) containing only morphine were correlated with results of the clinical test for impairment (CTI). For comparison, test results were explored in individuals without any positive analytical finding in blood samples (n=79) selected from the same database.Results In the “no drug” cases, 86% were judged as not impaired and 14% as impaired. In the morphine only cases, 20% were judged as not impaired, and 80% as impaired. Both daily users and non-daily users had the same proportion of impaired cases. Median blood morphine concentration (M) was 0.09 μmol/l in the “not impaired” group and 0.15 μmol/l in the “impaired” group (P=0.067). For morphine-6-glucuronide (M6G), the median blood concentration was 0.09 μmol/l in the “not impaired” group and 0.14 μmol/l in the “impaired” group (P=0.030). A significant correlation between concentration quartiles and number of cases determined as “impaired” was found for M6G (P=0.018) and for the sum M+M6G (P=0.013).Conclusion In our population of heroin-drugged drivers, blood concentrations of M6G and the sum M+M6G appeared to have concentration-dependent effects on the CNS that may lead to impairment as judged from a CTI. Variations in pattern of use did not seem to have any bearing on the judgement of impairment.     

Pharmacokinetics of morphine-6-glucuronide following oral administration in healthy volunteers

Aim After oral administration, morphine-6-glucuronide (M6G) displays an atypical absorption profile with two peak plasma concentrations. A proposed explanation is that M6G is hydrolysed to morphine in the colon, which is then absorbed and subsequently undergoes metabolism in the liver to morphine-3-glucuronide (M3G) and M6G. The aims of this study were to confirm and elucidate the biphasic absorption profile as well as clarify the conversion of M6G to morphine after a single oral administration of M6G in healthy volunteers. Methods The study was conducted accordingly to a nonblinded, randomised, balanced three-way crossover design in eight healthy male subjects. The subjects received 200 mg oral M6G, 50 mg oral M6G and 30 mg oral morphine. Blood samples were collected until 72 h after M6G administration and until 9 h after morphine administration. Paracetamol and sulfasalazine were coadministered with M6G as markers for the gut contents reaching the duodenum and colon, respectively. Results The plasma concentration peaks of M6G were seen at 4.0 (2.0–6.0) and 18 (12.0–24.0) h after 200 mg M6G and at 3.5 (2.0–6.0) and 21.3 (10.0–23.3) h after 50 mg M6G, which was in agreement with previously published results. The K_{M6G_abs}/K_{M6G_M6G} ratio was found to be 10. Conclusion The pharmacokinetic profile of M6G after oral administration was confirmed and with the presence of M3G and morphine in plasma after oral administration of M6G, proof seems to be found of the constant and prolonged absorption of M6G. The K_{M6G_abs}/K_{M6G_M6G} ratio of 10 indicates that the second absorption peak of M6G consists of approximately 10 times more absorbed M6G than reglucuronidated M6G. However, further studies are required to determine the precise kinetics of the second absorption peak.     

Impact of anti-cancer drugs and other determinants on serum protein binding of morphine 6-glucuronide

BACKGROUND AND THE PURPOSE OF THE STUDY: The aim of the present study was to examine factors that may influence the protein binding of morphine 6-glucuronide (M6G), the most active metabolite of morphine. METHODS: An enzyme-linked immunoabsorbent assay technique was used to measure the M6G concentration in serum of 18 healthy adults, 18 neonatal and 7 children with cancer. Total and free M6G concentrations were measured following equilibrium dialysis for 3 hrs and at physiological pH at 37°C. The influence of vincristine, methotrexate, 6-mercaptopurine, morphine, human albumin, alpha-1-acid glycoprotein, palmitic acid, oleic acid and pH on M6G protein binding was examined. RESULTS: M6G was 66.87±0.73 percent free in human serum at physiological pH and temperature. The percentage free (unbound) was increased significantly by vincristine (4.33%) and methotrexate (9.68%), but 6- mercaptopurine and morphine had no significant effect on it. Free percentages of M6G was reduced by decreasing serum albumin concentration but was unaffected by the presence of alpa-1-acid glycoprotein (AAG) or changes in serum pH. Similar results were obtained in human serum albumin (HAS) solutions. Addition of palmitic acid and oleic acid reduced protein binding significantly by 6.3% and 7.4%, respectively. MAJOR CONCLUSION: Although M6G in this study was not highly bounded, but because of its high analgesic potency, any change in its free concentration due to concurrent medication or disease caused significant changes in its effects. This dearth of evidence has been implicated in the reluctance of professionals to be cautious in prescribing them to children, particularly in the neonatal period.     

Codeine in post-operative pain Study of the influence of sparteine phenotype and serum concentrations of morphine and morphine-6-glucuronide

Objective: Within the past decade, human experimental pain studies have supported the 50-year-old hypothesis that codeine is a prodrug, which has to be converted to morphine to exert an analgesic effect. This study aimed at evaluating the impact of sparteine phenotype and serum concentrations of morphine on the efficacy of codeine in post-operative pain. Methods: Eighty-one patients with a pain rating of 3 or more on a 0–10 numerical rating scale 0.5 h after surgery were included in the study. The patients were given an oral dose of 100 mg codeine and rated pain with the numerical rating scale 0.5 h and 1 h after medication. Blood for determination of serum concentration of codeine and its metabolites was collected 1 h after medication, and a 12-h urine sample after administration of 100 mg sparteine was used to determine the sparteine phenotype. Results: Eight patients were poor metabolizers and 66 were extensive metabolizers of sparteine, while the urine samples for the remaining seven patients were lost. In 22 patients, including the eight poor metabolizers, the serum concentrations of both morphine and morphine-6-glucuronide (M6G) were below the limit of determination of the assay, i.e. 1.5 nmol · l⁻¹ and 2 nmol · l⁻¹, respectively. A sum of the concentration of these two substances below 10 nmol · l⁻¹ was found in an additional eight patients. The sum of differences between pre- and post-operative pain ratings did not differ between the two phenotypes (P= 0.60), whereas the 30 patients with serum concentrations of morphine plus M6G below 10 nmol · l⁻¹ had a marginally significant lower sum than the 51 patients with higher levels of these substances (median 1.5 vs 2.5, P = 0.058). Conclusion: A low serum concentration of morphine and M6G seems to be common in patients treated with codeine for post-operative pain, and low concentrations of these active substances may be related to decreased efficacy of codeine. Received: 23 September 1997 / Accepted in revised form: 11 May 1998     

Pharmacokinetic modelling of morphine,morphine-3-glucuronide and morphine-6-glucuronide in plasma and cerebrospinal fluid of neurosurgical patients after short-term infusion of morphine

AIMS: Concentrations in the cerebrospinal fluid (CSF) are a useful approximation to the effect site for drugs like morphine. However, CSF samples, are available only in rare circumstances. If they can be obtained they may provide important insights into the pharmacokinetics/pharmacodynamics of opioids. METHODS: Nine neurological and neurosurgical patients (age 19-69 years) received 0.5 mg kg-1 morphine sulphate pentahydrate as an intravenous infusion over 30 min. Plasma and CSF were collected for up to 48 h. Concentration time-course and interindividual variability of morphine (M), morphine-3-glucuronide (M3G) and morphine-6 glucuronide (M6G) were analysed using population pharmacokinetic modelling. RESULTS: While morphine was rapidly cleared from plasma (total clearance = 1838 ml min-1 (95% CI 1668, 2001 ml min-1)) the glucuronide metabolites were eliminated more slowly (clearance M3G = 44.5 ml min-1 (35.1, 53.9 ml min-1), clearance M6G = 42.1 ml min-1 (36.4, 47.7 ml min-1)) and their clearance could be described as a function of creatinine clearance. The central volumes of distribution were estimated to be 12.7 l (11.1, 14.3 l) for morphine. Transfer from the central compartment into the CSF was also rapid for M and considerably slower for both glucuronide metabolites. Maximum concentrations were achieved after 102 min (M), 417 min (M3G) and 443 min (M6G). A P-glycoprotein exon 26 polymorphism previously found to be linked with transport activity could be involved in CSF accessibility, since the homozygous mutant genotype was associated (P < 0.001) with high maximum CSF concentrations of M but not M3G or M6G. CONCLUSIONS: From the population pharmacokinetic model presented, CSF concentration profiles can be derived for M, M3G and M6G on the basis of dosing information and creatinine clearance without collecting CSF samples. Such profiles may then serve as the link between dose regimen and effect measurements in future clinical effect studies.     

Plasma morphine and morphine-6-glucuronide patterns in cancer patients after oral, subcutaneous, sublabial and rectal short-term administration

Clinical studies on the effectiveness of morphine administered through different routes are contradictory. In order to further elucidate this point, the plasma concentrations of morphine and its 3- and 6-glucuronated metabolites were measured after short-term oral, sublabial, rectal and subcutaneous administration of the opiate. The bioavailability of free morphine and the 6-glucuronated active metabolite was comparable through the different routes. It was concluded that the choice of the route of morphine administration should be mainly guided by the needs of each individual patient.     

吗啡处理大鼠的戒断症状以及血浆吗啡及其代谢物M3G含量的性别差异

本文旨在评价阿片依赖行为是否存在性别差异。纳洛酮催促戒断研究：20只大鼠,单次注射吗啡后1小时注射纳洛酮。评价大鼠戒断症状,同时应用HPLC-UV方法测定血浆中吗啡和M3G浓度。自然戒断研究：97只大鼠,吗啡组以剂量递增法给药28天,于最后一次给药后,评价大鼠自然戒断症状和血浆中吗啡以及M3G的含量。急性给药催促戒断的戒断症状未观察到性别差异。自然戒断后身体戒断症状存在性别差异,雄鼠重于雌鼠（P〈0.05）。在急性给药实验和慢性给药实验中,吗啡的Cmax雄鼠比雌鼠含量高,M3G的Cmax雌鼠比雄鼠含量高。吗啡药代动力学特征在急性给药实验和慢性给药实验中存在性别差异。成瘾大鼠自然戒断后身体戒断症状的程度和血浆中吗啡、M3G浓度以及M3G/MOR的比值相关。     

15例晚期肿瘤病人持续皮下泵注大剂量吗啡的回顾性分析

目的通过回顾2005至2010年间15例晚期癌症所实施的持续皮下泵注大剂量吗啡,分析其应用于癌性止痛的可行性及疗效。方法在患者脐周皮下留置普通的留置针,根据输注速度选择百特泵,计算出24小时吗啡总量并加入百特泵中持续进行泵注。根据病人疼痛情况的变化调整吗啡的用量。结果15例患者镇痛有效率达到100％,其中完全缓解率73．3％（11／15）,部分缓解率26．7％（4／15）。结论晚期癌症病人采用持续皮下泵注大剂量吗啡应用于癌性止痛效果可靠,副作用轻微,值得临床推广应用。     

Renal tubular transport of morphine, morphine-6-glucuronide, and morphine-3-glucuronide in the isolated perfused rat kidney.

The isolated perfused rat kidney was used to examine the renal handling of morphine and its inactive metabolite morphine-3-glucuronide (M3G), and active metabolite morphine-6-glucuronide (M6G). The kidneys were perfused with Krebs-Henseleit buffer (pH 7.4) containing albumin, glucose, and amino acids, and drug concentrations were measured by high performance liquid chromatography. There was no conversion of morphine to the glucuronides or deconjugation of M3G or M6G. At an initial morphine concentration of 100 ng/ml, the unbound renal clearance to glomerular filtration rate ratio (CLur/GFR) was 5.5 +/- 3.2 (mean +/- SD), indicating that net tubular secretion of morphine occurred. In the presence of M3G (2000 ng/ml) and M6G (500 ng/ml) this Clur/GFR ratio was elevated to 17.3 +/- 4.8 (p less than .001), which implicates an interaction between these compounds at an active reabsorption transport system. The CLur/GFR ratio for M3G at 2000 ng/ml was 0.90 +/- 0.04, indicating the possibility of a small component of tubular reabsorption, and this ratio was not significantly altered in the presence of morphine and M6G. M6G was reabsorbed, probably actively, to a greater extent than M3G, with an initial CLur/GFR ratio of 0.67 +/- 0.04, which was not affected when morphine and M3G were coadministered. These data demonstrate an unusual phenomenon in that the glucuronide metabolites, which are larger and less lipophilic than the parent drug morphine, undergo net tubular reabsorption. The renal handling of morphine is a complex combination of glomerular filtration, active tubular secretion, and possibly active reabsorption.     

Lack of crosstolerance between morphine and morphine-6-glucuronide as revealed by locomotor activity

Morphine-6beta-glucuronide is a major metabolite of morphine. We wanted to examine whether the effects related to opiate CNS stimulation could be mediated by different receptors for morphine and M6G by studying the development of crosstolerance between these two drugs. The effect studied was locomotor activity in C57BL/6JBom mice. We observed a dose-dependent development of tolerance to daily injections of morphine, with 20 micromol/kg giving the most rapid development of tolerance, apparent already on the second day of treatment. This was also observed for the same dose of M6G. Crosstolerance to M6G was measured both after 1 day pretreatment and 7 days pretreatment with morphine 20 micromol/kg, while the crosstolerance to morphine was tested only after 1 day pretreatment with M6G (20 micromol/kg). Lack of crosstolerance towards M6G after 1 day of morphine pretreatment was observed, whereas crosstolerance to M6G was observed after 7 days of exposure to morphine pretreatment. Crosstolerance after M6G pretreatment to morphine was observed. It was concluded that the main part of the effect caused by M6G was mediated through a specific M6G receptor.     

Pharmacokinetics and pharmacodynamics of morphine-3-glucuronide in rats and its influence on the antinociceptive effect of morphine

In this study the pharmacokinetics and pharmacodynamics of morphine-3-glucuronide (M3G) were investigated in rats after i.v. administration as a bolus dose (86.7 μmol kg^?1) and as a constant rate infusion (2.9 μmol h^?1) over 5 days. After the bolus dose, the clearance (Cl) was 12.1 ± 0.6 ml min ^?1* kg, the volume of distribution at steady state (V_ss) 1.68 ± 0.89 1 kg^?1, the half-life of the first phase 13.2 ± 1.8 min and the halflife of the second phase 11.6 ± 7.7 h. After the constant rate infusion, Cl was 10.5 ± 1.7 ml min^?1*kg. The antagonistic effect of M3G on the antinociceptive effect of a bolus dose of morphine (35 μmol kg^?1) was tested during steady state concentrations of M3G on day 4 and to M3G naïve rats. No antinociceptive, hyperalgesic or withdrawal effects were observed as a result of M3G administration, but a significantly lower antinociceptive effect of morphine was found in the M3G infusion group compared to the control group. Systemically administered M3G antagonized the antinociceptive effect of morphine, but this cannot be the only explanation to the tolerance development observed after morphine administration.     

Determination of morphine, morphine-3-glucuronide and morphine-6-glucuronide in monkey and dog plasma by high-performance liquid chromatography-electrospray ionization tandem mass spectrometry

A specific and simultaneous assay of morphine, morphine-3-glucuronide (M-3-G) and morphine-6-glucuronide (M-6-G) in monkey and dog plasma has been developed. These methods are based on rapid isolation using solid phase extraction cartridge, and high-performance liquid chromatography (HPLC)-electrospray ionization (ESI)-tandem mass spectrometric (MSMS) detection. Analytes were separated on a semi-micro ODS column in acetonitrile-formic (or acetic) acid mixed solution. The selected reaction monitoring for assay in monkey and dog plasma, as precursor-->product ion combinations of m/z 286-->286 for morphine, m/z 462-->286 for glucuronides and m/z 312-->312 for internal standard (IS, nalorphine) were used. The linearity of morphine, M-3-G and M-6-G was confirmed in the concentration range of 0.5-50, 25-2500, 2.5-250 ng/ml in monkey plasma, 0.5-100, 25-5000, 2.5-500 ng/ml in dog plasma, respectively. The precision of this assay method, expressed as CV, was less than 15% over the entire concentration range with adequate assay accuracy. Therefore, the HPLC-ESI-MSMS method is useful for the determination of morphine, M-3-G and M-6-G with sufficient sensitivity and specificity in pharmacokinetic studies.     

Non-opioid induction of morphine-6-glucuronide synthesis is elicited by prolonged exposure of rat hepatocytes to heroin

Background

Liver metabolism of morphine leads to the formation of morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G), the latter possessing strong opioid activity that however differs from that of the parent compound. In previous studies conducted in rats we have shown that repeated in vivo exposure to phenanthrene class of mu opioid receptor (MOR) agonists or antagonists (heroin, morphine, and naltrexone), but not to non-phenanthrene class of MOR agonist methadone, affects morphine glucuronidation by liver microsomes.

Methods

In the present study, we measured the in vitro formation of M3G and M6G by rat hepatocytes incubated for 120 min with morphine (0.1–1.0 mM) after 72 h pre-incubation with one of the following MOR agonists: heroin (3.3 or 6.6 μM), morphine (7.8 μM), or methadone (12 μM). The MOR antagonist naltrexone (10 or 25 μM) was also tested, alone or in combination with heroin. The amount of M3G and M6G synthesized was then measured by HPLC method.

Results

Heroin inhibited M3G synthesis and induced the formation of M6G, which under basal conditions is not synthesized in rats. Heroin effects were not blocked by naltrexone. Morphine, but not methadone, produced effects similar to those of heroin but more modest in intensity. Pre-incubation with naltrexone alone slightly increased M3G synthesis, but had no effect on M6G formation.

Conclusions

These results are in agreement with those of previous ex vivo studies and indicate that exposure to heroin or, to a lesser extent, morphine, can affect morphine glucuronidation via direct non-opioid actions on the hepatocytes.     

Morphine-6-glucuronide: potency and safety compared with morphine

Background: In contemporary medicine, morphine remains the drug of choice in the treatment of severe postoperative pain. Nevertheless, morphine has several side effects, which can seriously compromise its analgesic effectiveness and the patient safety/compliance. The search for opioid analgesics with a better side-effect profile than morphine has led to a morphine metabolites, morphine-6-glucuronide (M6G). Objective: The objectives of the current paper are to give an overview of the analgesic properties of M6G, assess the dose range at which it produces equianalgesia to morphine and explore its side-effect profile. Methods: A review of published clinical studies (Phase II – III) on M6G in the treatment of experimental and clinical pain is given. Results/conclusions: M6G > 0.2 mg/kg is an effective analgesic with a slower onset but longer duration of action (> 12 h) compared with morphine. Side effects, most importantly postoperative nausea and vomiting, occur less frequent after M6G treatment. M6G is an attractive alternative to morphine in the treatment of severe postoperative pain.     

Stress and morphine analgesia: alterations following p-chlorophenylalanine

Recent studies have shown that while the analgesic responses induced by certain stressors appear to be related to morphine analgesia, the analgesic responses to other stressors do not. Para-chlorophenylalanine (PCPA), a potent tryptophan-hydroxylase inhibitor has been shown to decrease both basal pain thresholds and morphine analgesia on the flinch-jump test. To assess further the relationship between morphine and stress-induced analgesia, PCPA's effect upon the analgesic responses to cold-water swims, 2-deoxy-D-glucose, inescapable foot shock and morphine were determined using the flinch-jump and tail-flick tests. PCPA, which produced an 85% depletion of brain serotonin, significantly decreased jump thresholds while significantly increasing tail-flick latencies. Similarly, while morphine analgesia was decreased by PCPA on the flinch-jump test, it was not affected on the tail-flick test. The analgesic jump thresholds induced by cold-water swims and 2-deoxy-D-glucose as well as the increase tail-flick latencies induced by foot shock were unaffected by PCPA. These results are discussed in terms of PCPA's differential effects upon basal nociception and morphine analgesia and in terms of further dissociation between morphine and stress-induced analgesia.     

硫酸吗啡缓释片联合普瑞巴林治疗癌性神经病性疼痛的疗效及对患者疼痛缓解的影响

目的分析硫酸吗啡缓释片联合普瑞巴林治疗癌性神经病性疼痛的疗效及对患者疼痛缓解的影响。方法102例癌性神经病性疼痛患者,根据随机数字表法分为对照组及观察组,各51例。对照组采用硫酸吗啡缓释片治疗,观察组在对照组基础上联合普瑞巴林治疗。对比两组患者的治疗效果、疼痛程度、睡眠质量和不良反应发生情况。结果观察组治疗总有效率92.16%高于对照组的76.47%,差异具有统计学意义(P<0.05)。治疗后,两组患者的视觉模拟评分法(VAS)评分均较本组治疗前降低,且观察组降低程度优于对照组,差异均具有统计学意义(P<0.05)。两组患者的睡眠干扰(SLPD)、睡眠量(SLPQ)、睡眠充足度(SLPA)、综合睡眠障碍指数(9-items)评分均较本组治疗前改善,且观察组改善程度优于对照组,差异均具有统计学意义(P<0.05)。观察组不良反应发生率9.80%低于对照组的25.49%,差异具有统计学意义(P<0.05)。结论硫酸吗啡缓释片联合普瑞巴林治疗癌性神经病性疼痛的疗效显著,能有效缓解患者的疼痛情况,提高睡眠质量,降低不良反应发生率,安全性较高,值得应用。     

The bioavailability and pharmacokinetics of subcutaneous, nebulized and oral morphine-6-glucuronide

AIMS: Morphine-6-glucuronide (M6G), one of the active metabolites of morphine, has attracted considerable interest as a potent opioid analgesic with an apparently superior therapeutic index. To date studies have used the intravenous route, which is generally unacceptable in the treatment of cancer related pain. The aim of this study was to define the pharmacokinetics, toxicity and cardio-respiratory effects of three alternative routes of administration of M6G. METHODS: Ten healthy volunteers participated in an open randomized study. Subjects received M6G 2 mg as an intravenous bolus, 20 mg orally, 2 mg subcutaneously and 4 mg by the nebulized route. Pulse, blood pressure, respiratory rate and peak flow rate were monitored and subjective toxicity recorded on rating and visual analogue scales. RESULTS: After i.v. M6G the mean (+/- s.d.) AUC(0,infinity) standardized to a dose of 1 mg was 223 +/- 57 nmol l(-1) h, mean elimination half-life was 1.7 +/- 0.7 h and the mean clearance was 157 +/- 46 ml min(-1). These parameters were virtually identical after subcutaneous administration which had a bioavailability (F(0,infinity)) of 102 +/- 35% (90% CI 82, 117%) and t(max) of 0.5 +/- 0.2 h. The mean bioavailability of nebulized M6G was 6 +/- 2% (90% CI 4, 7%) with a t(max) of 1.2 +/- 0.8 h. Following oral M6G two plasma M6G peaks were seen in 7 of the 10 subjects, the first with a t(max) of 3.1 (+/- 0.9) h. The second peak had a t(max) of 13.4 (+/-5.0) h, started approximately 4 h after dosing, and was associated with the detection of plasma M3G and morphine, suggesting that M6G was significantly hydrolysed in the gut to morphine, which was then glucuronidated following absorption. Although the overall mean bioavailability was 11 +/- 3% (90% CI 9, 12%), confining the analysis to data from the first peak suggested a bioavailability of directly absorbed M6G of only 4 +/- 4%. Apart from a characteristic dysphoria following intravenous and subcutaneous M6G, there was no significant toxicity. CONCLUSIONS: With the minimal toxicity reported in this and previous studies, subcutaneous infusion of M6G may potentially provide clinically useful analgesia for advanced cancer pain. Nebulized M6G is not significantly absorbed via the lungs, and if opiates are shown to have a local effect in the lung, reducing the sensation of breathlessness, then nebulized administration is likely to minimize systemic effects. Oral M6G has poor bioavailability, but is significantly hydrolysed in the gut to morphine, which is subsequently glucuronidated following absorption. This circuitous route accounts for the majority of systemically available M6G after oral administration.