On-line clean-up system of plasma sample for simultaneous determination of morphine and its metabolites in cancer patients by high-performance liquid chromatography.

A convenient and sensitive analytical method for determination of plasma morphine and its metabolites in cancer patients was established using HPLC with a column-switching technique. Sample plasma which has been deproteinized with trichloroacetic acid is injected onto a precolumn, then the compounds of interest are preferentially introduced into the analytical column for separation and detection after washing out the unnecessary plasma components from the precolumn. Detection was simultaneously performed with coulometry for unchanged morphine and morphine-6-glucuronide and with UV analysis for morphine-3-glucuronide. Analytical recoveries were greater than 99% for these compounds, and the averaged coefficients of within-day or between-day variation did not exceed 5.5%. Detection limits were 0.2 ng/mL for morphine, 0.5 ng/mL for morphine-6-glucuronide, and 10 ng/mL for morphine-3-glucuronide. Correlation between the previously reported solid extraction method and this method was satisfactory in plasma samples after administration of morphine.     

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.     

A simple, rapid method for the simultaneous determination of morphine and its principal metabolites in plasma using high-performance liquid chromatography and fluorometric detection

This article describes a high-performance liquid chromatography (HPLC) method for the simultaneous determination of morphine (M) and its principal metabolites morphine-3-glucuronide (M3G), morphine-6-glucuronide (M6G), and normorphine (NM) in plasma. All four compounds are extracted from plasma using a C8 solid-phase extraction column, separated by reverse-phase HPLC on a C18 analytical column, and detected by spectrofluorometry at 210 nm excitation wavelength. The method takes advantage of the compounds' native fluorescence, so that derivitization is not required. Samples have been quantified over a concentration range of 25-100 ng/ml M and NM, 50-200 ng/ml M3G, and 100-300 ng/ml M6G, using nalorphine (500 ng/ml) as internal standard. Within-run and between-run errors were less than 10% for morphine and less than 13% for all the metabolites. The lower limit of quantitation for morphine is 10 ng/ml. The accuracy of the method was confirmed by including quality controls fitted to the standard curves of each compound. The assay described in this article represents a simplification of previous versions of the method, which included cumbersome extraction procedures and multiple detectors. For the first time, an internal standard has been employed. The assay is reliable and easy to use and can be performed in any therapeutic drug monitoring laboratory.     

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.     

Method for quantification of opioids and their metabolites in autopsy blood by liquid chromatography-tandem mass spectrometry

A method using liquid chromatography-electrospray ionization-tandem mass spectrometry was developed and validated for the determination of morphine, codeine, hydromorphone, dihydrocodeine, oxycodone, buprenorphine, and naloxone with their metabolites morphine-3-glucuronide, morphine-6-glucuronide, normorphine, 6-acetylmorphine, 6-acetylcodeine, codeine-6-glucuronide, norcodeine, hydromorphine-3-glucuronide, dihydrocodeine-6-glucuronide, dihydromorphine, dihydromorphine-3-glucuronide, dihydromorphine-6-glucuronide, oxymorphone, norbuprenorphine, buprenorphine-3-glucuronide, norbuprenorphine-3-glucuronide, and naloxone-3-glucuronide in human whole blood. Polar metabolites (glucuronides) and other analytes were extracted by SPE using Bond Elut C18. Chromatographic separation was performed on a Phenomenex Synergi reversed-phase column with gradient elution based on a mobile phase consisting of 10mM ammonium formate adjusted to pH 3 and acetonitrile. Intraday and interday precision for all analytes were between 0.6% and 13.8%, and recoveries were between 80.3% and 101.4%. Calibration curves were linear for all analytes over the concentration range 5-400 ng/mL, and correlation coefficients (R(2)) were better than 0.999. Limits of detection and quantitation were 0.16-1.2 ng/mL and 0.5-4.09 ng/mL, respectively. The method described consolidates previous work on opioids and their metabolites published in the literature and is the first to include the detection of naloxone-3-glucuronide. The method has been applied in routine postmortem cases after opiate overdose with the threefold purpose of providing interpretive information on the cause and type of death (rapid, sub-acute, or delayed death) and to distinguish heroin, morphine, and codeine users.     

Relationship between plasma concentrations of morphine and its metabolites and pain in cancer patients

Objective This study was undertaken to investigate the relationship between the plasma concentration of morphine, morphine-3-glucuronide and morphine-6-glucuronide and pain in cancer patients receiving oral morphine. Methods The trough value of plasma concentrations of morphine and its metabolites were measured by high performance liquid chromatography using an ultraviolet detector. Using this assay system, the plasma concentrations of morphine, morphine-3-glucuronide and morphine-6-glucuronide in 26 cancer pain patients were measured and compared with pain intensity. The pain intensity was assessed at the time of blood sampling using the visual analog scale. Results The trough value of morphine and morphine-6-glucuronide did not show a significant correlation with pain intensity by visual analog scale assessment, but morphine-3-glucuronide and the ratio of morphine-3-glucuronide/morphine showed a significantly positive correlation (r = 0.528, P = 0.006 and r = 0.671, P < 0.001, respectively). By dividing the group according to low (≤ median value) or high (> median value) VAS scores a significant difference was found between the two groups in morphine-3-glucuronide and the ratio of morphine-3-glucuronide/morphine (P = 0.045 and P = 0.007, respectively). Conclusion These results indicated that the level of morphine-3-glucuronide is related to the patient’s perception of morphine effect, and the plasma concentration of morphine-3-glucuronide and the ratio of morphine-3-glucuronide/morphine indicated potency to assess clinical effect.     

Lack of effect of ondansetron on the pharmacokinetics and analgesic effects of morphine and metabolites after single-dose morphine administration in healthy volunteers

AIMS: The purpose of this investigation was to study the influence of ondansetron on the single-dose pharmacokinetics and the analgesic effects elicited by morphine and the 3- and 6-glucuronide metabolites of morphine in healthy volunteers. METHODS: This was a randomized, double-blind, placebo-controlled, two-way crossover study in which six male and six female subjects were administered a single 10 mg intravenous dose of morphine sulphate, followed 30 min later by a single 16 mg intravenous dose of ondansetron hydrochloride or placebo. Serum and urine concentrations of morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) samples were quantified over 48 h using high performance liquid chromatography with detection by mass spectrometry. Analgesia was assessed in the volunteers with a contact thermode device to provide a thermal pain stimulus. Four analgesic response variables were measured including thermal pain threshold, thermal pain tolerance, temporal summation of pain and mood state. RESULTS: The two treatments appeared to be equivalent based on the 90% confidence intervals (0.6, 1.67) of the least squares means ratio. All least squares means ratio confidence intervals for each parameter, for each analyte fell within the specified range, demonstrating a lack of an interaction. CONCLUSIONS: The results of this study suggest that administration of ondansetron (16 mg i.v.) does not alter the pharmacokinetics of morphine and its 3- or 6-glucuronide metabolites to a clinically significant extent, nor does it affect the overall analgesic response to morphine as measured by the contact thermode system.     

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.     

Bioequivalence study of two morphine extended release formulations after multiple dosing in healthy volunteers

AIM: Two extended release (ER) formulations of morphine sulphate (30 mg each), Oramorph SR (test) and a marketed reference formulation (MST Mundipharma Retardtabletten), were investigated for their relative bioavailability at steady-state: METHODS: The study was designed as a single-centre, open-label, two-period crossover, pharmacokinetic comparison in 28 healthy male volunteers and was completed in 23 subjects. The determination of morphine and its metabolite morphine-6-glucuronide in plasma was done by HPLC with electrochemical detection after solid-phase extraction. RESULTS: Under steady-state conditions in the first dosing interval, mean maximum plasma concentrations for morphine were 19.1 ng/ml (CV% 41) for Oramorph SR 30 mg and 19.1 ng/ml (CV% 33) for MST-30 Mundipharma Retardtabletten. Geometric mean AUC(0-12) values were calculated as 108 ngxh/ml (CV% 40) for Oramorph SR 30 mg and as 118 ng x h/ml (CV% 30) for the reference formulation. The plasma concentrations of the major metabolite, morphine-6-glucuronide, were found to be generally in a higher range compared to the parent compound. The 90% confidence intervals of test to reference ratios calculated for all relevant parameters (AUC, C(max), PTF) for both the parent compound and morphine-6-glucuronide were all within the limits of 80 - 125%. The most frequent adverse events (AE > 10%) during Oramorph SR 30 mg treatment were headache (36%), dizziness (18%), nausea (21%), vomiting (21%) and pruritus (11%). During treatment with MST-30 Mundipharma Retardtabletten, the most frequent AEs were headache (29%), dizziness (13%), nausea (29%) and vomiting (29%). CONCLUSION: The results demonstrate bioequivalence of Oramorph SR 30 mg and MST-30 Mundipharma Retardtabletten.     

On the assessment of drug metabolism by assays of codeine and its main metabolites

Codeine and its main metabolites appear to have advantages for assessing drug metabolic phenotypes. The authors have further developed a high-performance liquid chromatography (HPLC) method for the quantification of codeine and six of its metabolites in urine. Quantification was performed by electrochemical detection for morphine, normorphine, morphine-6-glucuronide, and the internal standard 4-O-methyldopamine; and by ultraviolet detection for codeine, norcodeine, and morphine-3-glucuronide. The method had a detection limit of 2 nmol/L(-1) for morphine and normorphine, 4 nmol/L(-1) for morphine-6-glucuronide, 3 nmol/L for the internal standard, 20 nmol/L(-1) for morphine-3-glucuronide, and 60 nmol/L(-1) for codeine and norcodeine. The coefficients of variations were <9% for intraday and <10% for interday analyses. The recovery of codeine and its metabolites ranged from 55% (for morphine-3-glucuronide) to 90% (for codeine, norcodeine, morphine, and morphine-6-glucuronide). Eleven healthy volunteers were phenotyped for CYP2D6 using codeine as well as debrisoquine and dextromethorphan. Ten subjects were extensive metabolizers (EM) and one a poor metabolizer (PM) of codeine, debrisoquine, and dextromethorphan. Significant correlations between the metabolic ratios (MRs) of the different probe drugs were obtained (r2 > 0.95, p < 0.001). This HPLC method is simple, sensitive, accurate, and reproducible for assessing the CYP2D6 phenotype.     

Toxicological analysis in rats subjected to heroin and morphine overdose

In heroin overdose deaths the blood morphine concentration varies substantially. To explore possible pharmacokinetic explanations for variable sensitivity to opiate toxicity we studied mortality and drug concentrations in male Sprague-Dawley rats. Groups of rats were injected intravenously (i.v.) with heroin, 21.5 mg/kg, or morphine, 223 mg/kg, causing a 60–80% mortality among drug-naïve rats. Additional groups of rats were pre-treated with morphine for 14 days, with or without 1 week of subsequent abstinence. Brain, lung and blood samples were analyzed for 6-acetylmorphine, morphine, morphine-3-glucuronide and morphine-6-glucuronide. i.v. morphine administration to drug-naïve rats resulted in both rapid and delayed deaths. The brain morphine concentration conformed to an exponential elimination curve in all samples, ruling out accumulation of morphine as an explanation for delayed deaths. This study found no support for formation of toxic concentration of morphine-6-glucuronide. Spontaneous death among both heroin and morphine rats occurred at fairly uniform brain morphine concentrations. Morphine pre-treatment significantly reduced mortality upon i.v. morphine injection, but the protective effect was less evident upon i.v. heroin challenge. The morphine pre-treatment still afforded some protection after 1 week of abstinence among rats receiving i.v. morphine, whereas rats given i.v. heroin showed similar death rate as drug-naïve rats.     

An automatic 96-well solid phase extraction and liquid chromatography-tandem mass spectrometry method for the analysis of morphine, morphine-3-glucuronide and morphine-6-glucuronide in human plasma.

A bioanalytical method using automated sample transferring, automated solid phase extraction (SPE) and liquid chromatography-tandem mass spectrometry (LC-MS-MS) was developed for morphine (MOR), and its metabolites morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) in human plasma. Samples of 0.25 ml were transferred into 96-well plate using automatic liquid handler (Multiprobe II). Automated SPE was carried out on a 96-channel programmable liquid handling workstation (Quadra 96) using a C(18) sorbent. The extract was injected onto a silica column using an aqueous-organic mobile phase. The chromatographic run time was 3.5 min per injection, with retention times of 1.5, 2.0 and 2.6 min for MOR, M6G, and M3G, respectively. The detection was by monitoring MOR at m/z 286-->152, M6G and M3G at m/z 462-->286. The deuterated internal standards were monitored at m/z 289-->152 for MOR-d(3), and m/z 465-->289 for M6G-d(3) and M3G-d(3). The standard curve range was 0.5-50 ng ml(-1) for MOR, 1.0-100 ng ml(-1) for M6G, and 10-1000 ng ml(-1) for M3G. The inter-day precision and accuracy of the quality control samples were <8% relative standard deviation (RSD) and <7% relative error (RE) for MOR, <5% RSD and <2% RE for M6G, and <2% RSD and <4% RE for M3G.     

High-performance liquid chromatography-mass spectrometry-mass spectrometry analysis of morphine and morphine metabolites and its application to a pharmacokinetic study in male Sprague–Dawley rats

A high-performance liquid chromatography tandem mass spectrometry-mass spectrometry (LC-MS-MS) assay was developed for the analyses of morphine, morphine glucuronides and normorphine in plasma samples from rats. The analytes were extracted by using C₂ solid-phase extraction cartridges. The extraction recoveries were 100% for morphine, 84% for morphine-3-glucuronide, 64% for morphine-6-glucuronide and 88% for normorphine. Both intra- and inter-assay variabilities were below 11%. Using a plasma sample size of 100 μl, the limits of detection were 13 nmol l⁻¹ (3.8 ng ml⁻¹) for morphine, 12 nmol l⁻¹ (5.5 ng ml⁻¹) for morphine-3-glucuronide, 26 nmol l⁻¹ (12 ng ml⁻¹) for morphine-6-glucuronide and 18 nmol l⁻¹ (5.0 ng ml⁻¹) for normorphine, at a signal-to-noise ratio of 3. The present assay was applied to a pharmacokinetic study in rats after intraperitoneal administration of morphine.     

Morphine-6-glucuronide induces contraction of the ileal circular muscle more potently than morphine in mice

It has been reported that morphine-6-glucuronide inhibits small intestinal transit in mice more potently than morphine. In this study, we investigated the effects of morphine, morphine-6-glucuronide and morphine-3-glucuronide on the contractile response of the circular muscle isolated from mouse ileum. Morphine and morphine-6-glucuronide induced tonic contraction dose-dependently, and the contractile force of morphine-6-glucuronide was greater than that of morphine. Morphine-3-glucuronide induced slight contraction at high dose. These results suggest that the strong contraction induced by morphine-6-glucuronide contributed to the inhibition of small intestinal transit in mice.     

Transdermal administration of morphine to healthy subjects.

1. Twelve healthy subjects received 10 mg morphine HCl delivered transdermally from an occlusive reservoir applied to a small area of skin, painlessly de-epithelialised by vacuum suction. On a separate occasion, 10 mg morphine HCl was given as an i.v. infusion over 20 min. 2. Venous blood samples were collected serially for 72 h and assayed for morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) by h.p.l.c. Pupil size, salivation, and central nervous effects (nausea, fatigue, headache, feeling of heaviness and dysphoria/euphoria) were also measured. 3. After transdermal application morphine was absorbed by a first-order process to produce relatively constant plasma drug concentrations over 11 h. The absolute bioavailability of transdermal morphine was 75% (65-85%; 95% CI). The plasma concentrations of both M6G and M3G were lower after transdermal administration than after i.v. infusion, and a considerable delay (of up to 1 h) was observed before the metabolites were detectable. AUC ratios for M3G and M6G relative to morphine were similar after both modes of administration. 4. Non-analgesic effects were less pronounced at the lower plasma drug and metabolite concentrations observed after transdermal delivery than after the i.v. infusion of morphine. 5. Transdermal administration of morphine warrants investigation as an alternative route of morphine delivery.     

A novel metabolic pathway of morphine: formation of morphine glucosides in cancer patients

AIMS: To characterize directly the conjugated metabolites of morphine in urine samples of cancer patients. METHODS: Urine samples from the patients were treated by solid-phase extraction method and chromatographed using three high-performance liquid chromatography systems. Conjugated metabolites were directly detected with liquid chromatographic/ion trap mass spectrometric (LC/MSn) technique by selected ion monitoring, full scan MS/MS and MS3 modes. RESULTS: Six conjugated metabolites including two new metabolites M5 and M6 were found. Morphine-3-glucuronide (M-3-G) and morphine-6-glucuronide (M-6-G) were identified by comparing their l.c. retention times and multistage mass spectra with those of the reference substances. Two novel metabolites, morphine-3-glucoside and morphine-6-glucoside, as well as normorphine glucuronides were identified by comparing their mass fragment patterns and l.c. retention times with those of M-3-G and M-6-G. Hydrolysis of urine samples with beta-glucosidase and beta-glucuronidase provided further evidence of the metabolites M5 and M6 as morphine glucosides. The excretion amounts of morphine conjugates in urines were in the order of morphine glucuronides, morphine glucosides and normorphine glucuronides. CONCLUSIONS: In the present study, the applications of l.c. separation and multistage mass spectra have permitted the direct identification of conjugated metabolites of morphine. To our knowledge, this is the first report about O-linked glucosides of morphine at 3-aromatic and 6-aliphatic hydroxyl groups.     

Plasma and Cerebrospinal Fluid Concentrations of Morphine and Morphine Glucuronides in Rabbits Receiving Single and Repeated Doses of Morphine

The pharmacokinetics of morphine in plasma and the distribution of morphine and its glucuronidated metabolites within the cerebrospinal fluid were investigated in rabbits. After single morphine dosage, the plasma AUC ratio of morphine-3-glucuronide/morphine was 11·1 compared with 0·14 for morphine-6-glucuronide/morphine. The similar elimination half-lives of morphine (107 min), morphine-3-glucuronide (122 min), and morphine-6-glucuronide (105 min) suggested the glucuronidation to be the rate-limiting step, which was substantiated by the observation that morphine-3-glucuronide becomes eliminated four times faster when applied intravenously. Both after single and repeated morphine administration, the ratios of CSF and plasma levels of the parent drug were higher than those of morphine-3-glucuronide or morphine-6-glucuronide. These data demonstrate a poor penetration of the glucuronides across the blood-brain barrier and do not support the previously postulated accumulation of morphine-6-glucuronide in the central nervous system during chronic morphine treatment.     

The pharmacokinetics of morphine and morphine glucuronide metabolites after subcutaneous bolus injection and subcutaneous infusion of morphine

AIMS: To investigate the pharmacokinetics of morphine, morphine-6-glucuronide (M6G) and morphine-3-glucuronide (M3G) in healthy volunteers after the administration of morphine by subcutaneous bolus injection (s.c.b.) and subcutaneous infusion (s.c. i.) over 4 h, and to compare the results with the intravenous bolus (i.v.) administration of morphine. METHODS: Six healthy volunteers each received 5 mg morphine sulphate by i.v., s.c.b. and short s.c.i. over 4 h, on three separate occasions, in random order, each separated by at least 1 week. Plasma samples were assayed for morphine, M6G and M3G. RESULTS: After i.v. morphine, the concentrations of morphine, M6G and M3G and their pharmacokinetic parameters were similar to those we have observed previously, in other healthy volunteers (when standardized to nmol l- 1, for a 10 mg dose to a 70 kg subject). After s.c.b. morphine, similar results were obtained except that the median tmax values for morphine and M3G were significantly longer than after i.v. morphine (P< 0.001 and P< 0.05, respectively), with a trend to a longer tmax for M6G (P = 0. 09). The appearance half-lives after s.c.b. morphine for M6G and M3G were also significantly longer than after i.v. morphine (P = 0.03 and P< 0.05, respectively). Comparison of log-transformed AUC values indicated that i.v. and s.c.b. administration of morphine were bioequivalent with respect to morphine, M6G and M3G. In comparison with i.v. morphine, morphine by s.c.i. was associated with significantly longer median tmax values for morphine (P< 0.001), M6G (P< 0.001) and M3G (P< 0.05), and the mean standardized Cmax values significantly lower than after both i.v. and s.c.b. morphine (morphine P< 0.001, M6G P< 0.001 and M3G P< 0.01 for each comparison). Comparison of log-transformed AUC values after i.v. and s.c.i. morphine indicated that the two routes were not bioequivalent for morphine (log-transformed AUC ratio 0.78, 90% CI 0.66-0.93), M6G (0.72, 90% CI 0.63-0.82), or M3G (0.65, 90% CI 0.54-0.78). A small stability study indicated no evidence of adsorptive losses from morphine infused over 4 h using the infusion devices from the study. CONCLUSIONS: Although bioequivalence was demonstrated between the s. c.b. and i.v. routes of morphine administration, the bioavailabilities of morphine, M6G and M3G after s.c.i. were significantly lower than after i.v. administration. However, despite this, the study demonstrates that the subcutaneous route is an effective method for the parenteral administration of morphine.     

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.