HPLC-UV determination of morphine in human plasma and its application to the clinical study

A sensitive and specific high-performance liquid chromatography method with ultraviolet detection (HPLC-UV) has been developed for the quantification of morphine sulfate [(5alpha,6alpha)-7,8-didehydro-4,5-epoxy-17-methylmorphinan-3,6-diol], (CAS: 52-26-6) in human plasma. The analyte was extracted from plasma samples with chloroform - isopropyl alcohol (90:10, v/v) and analyzed on a Bondapak C18 column. The calibration curves were linear within the range of 10-150 ng/mL. The lower limit of quantitation was 10 ng/mL with 0.5 mL plasma sample. The mean recovery of the drug from plasma samples was 83.39%. The results from analysis of quality-control samples at concentrations of 30, 75, and 150 ng/mL were indicative of good accuracy and precision. This method was successfully used to analyze morphine in plasma samples of patients after abdominal hysterectomy.

Near-fatal tramadol cardiotoxicity in a CYP2D6 ultrarapid metabolizer

BACKGROUND

Tramadol is a synthetic, centrally acting analgesic for the treatment of moderate to severe pain. The marketed tramadol is a racemic mixture containing 50% (+)tramadol and 50% (-)tramadol and is mainly metabolized to O-desmethyltramadol (M1) by the cytochrome P450 CYP2D6. Tramadol is generally considered to be devoid of any serious adverse effects of traditional opioid receptor agonists, such as respiratory depression and drug dependence.

CASE REPORT

A 22-year-old Caucasian female patient was admitted to our ICU in refractory cardiac arrest requiring extracorporeal membrane oxygenation. This aggressive support allowed resolution of multi-organ dysfunction syndrome. Repeated blood analyses using liquid chromatography-tandem mass spectrometry confirmed high concentrations of both tramadol and its main metabolite O-desmethyltramadol. Genotyping of CYP2D6 revealed the patient to be heterozygous for a duplicated wild-type allele, predictive of a CYP2D6 ultrarapid metabolizer (UM) phenotype, confirmed by calculation of the tramadol/M1 (MR1) metabolic ratio at all time points.

DISCUSSION

We here report a case of near-fatal isolated tramadol cardiotoxicity. Because of the inhibition of norepinephrine reuptake, excessive blood epinephrine levels in this CYP2D6R UM patient following excessive tramadol ingestion could explain the observed strong myocardial stunning. This patient admitted intermittent tramadol consumption to gain a "high" sensation. In patients with excessive morphinomimetic effects, levels of tramadol and its main metabolite M1could be measured, ideally combined with CYP2D6 genotyping, to identify individuals at risk of tramadol-related cardiotoxicity. Tramadol treatment could be optimized in these at-risk individuals, consequently improving patient outcome and safety.

Pharmacokinetics of oxymorphone in titi monkeys (Callicebus spp.) and rhesus macaques (Macaca mulatta)

Oxymorphone is a pure μ-opioid receptor agonist that is commonly used in nonhuman primate medicine and surgery to minimize pain ranging in intensity from moderate to severe. We compared pharmacokinetic profiles and physiologic and behavioral responses to oxymorphone between titi monkeys (Callicebus spp.) and rhesus macaques (Macaca mulatta). Titi monkeys (n = 4) and rhesus macaques (n = 4) were injected intravenously with either a bolus of 0.075 mg/kg oxymorphone or placebo on multiple occasions, with a minimal washout period of 14 d between trials. Blood collection was limited to no more than 3 samples per trial, with samples collected at multiple time points until 10 h after injection. Collection periods, animal order, and testing day were randomized. In addition, macaques underwent a single serial collection at all time points to validate study design. A 2-compartment model best described the disposition of oxymorphone in both species. Clearance was faster in macaques than titi monkeys, in which terminal half-life was longer. Statistically significant physiologic differences were found between species and between treatments within species. Apart from these effects, oxymorphone did not significantly change physiologic parameters over time. After oxymorphone treatment, macaques demonstrated behaviors reflecting pruritis, whereas titi monkeys exhibited sedation. Despite its mild side effects, we recommend the consideration of oxymorphone for pain management protocols in both Old and New World nonhuman primates.

Evaluation of a sustained-release formulation of buprenorphine for analgesia in rats

Preventing and minimizing pain in laboratory animals is a basic tenet of biomedical research and is warranted for ethical, legal, and scientific reasons. Postoperative analgesia is an important facet of pain management. A sustained-release formulation of buprenorphine was tested in rats for analgesic efficacy and plasma concentration over a 72-h time period. Rats were injected subcutaneously with either 1.2 mg/kg sustained-release formulation (Bup-SR), 0.2 mL/kg buprenorphine HCl (Bup-HCl), or an equivalent volume of sustained-release vehicle and tested in a thermal nociception model or a surgical postoperative pain model. In both models, Bup-SR showed evidence of providing analgesia for 2 to 3 d. Thermal latency response in rats that received the sustained-release formulation increased 28.4% and 15.6% compared with baseline values on days 1 and 2, respectively. Rats with a unicortical tibial defect and treated with Bup-SR showed similar willingness to bear weight on the hindlimbs as did negative-control animals (no surgery), demonstrated by counting vertical raises; rats treated with Bup-HCl had significantly fewer vertical raises than did control rats for 5 d after surgery. Plasma concentrations of buprenorphine remained over 1 ng/mL for 72 h after a single dose of Bup-SR. Taken together, the results indicate that this formulation of buprenorphine may be a viable option for treating postsurgical pain in laboratory rats.

[Case of non-cancer abdominal pain successfully treated by a large amount of oral morphine]

A 34-year-old woman, with intractable non-cancer abdominal pain was successfully treated with large amounts of oral morphine. Medical records showed that she had been suffering from severe upper right abdominal pain with nausea and vomiting for 11 years. The pain continued all day long and the breakthrough pain occurred sometimes accompanied by nausea and vomiting. Various medical examinations including psychosocial exploration had been done to explain her pain mechanism and vomiting but causes were unknown. Psychological examination revealed she had no mental problems. A year and 6 months, she felt severe pain never experienced at the same area and she was transferred and admitted to our clinic. We conducted the epidural morphine analgesia. Her pain responded to this treatment. The dose of morphine was gradually increased and she was free from pain at the dose of 30 mg x day(-1) epidural morphine. With decreasing pain, her nausea and vomiting also diminished. This epidural dose could be clinically converted into 1,440 mg oral morphine. She was seen at our clinic twice a month for her pain condition and for checking the blood morphine level. In spite of large amount of morphine intake, no accumulation of blood morphine, M-6-G, and M-3-G levels was recognized.

[Double-blind parallel-group dose-titration study comparing a fentanyl-containing patch formulated for 1-day application for the treatment of cancer pain with Durotep MT Patch]

BACKGROUND

The efficacy and safety of a fentanyl-containing patch formulated for 1-day application at the initiation and during continuous treatment of cancer pain were evaluated in patients previously untreated with opioid analgesics.

METHODS

In the dose-titration period (Period I), the 1-day formulation (0.84 mg x day(-1)) was applied for 2 days. If pain relief was insufficient, the dose was titrated, and the success rate was evaluated. In the double-blind period (Period II), the efficacies of the 1-day and the 3-day formulations for pain control were compared.

RESULTS

The dose-titration success rate of the 1-day formulation was 80.6%, and its analgesic effect was comparable to that of the 3-day formulation. Moreover, tolerability of the 1-day formulation was good. Adverse events occurring in the patients were those generally seen after treatments with opioid analgesics, and severe symptoms were also reported.

CONCLUSIONS

Dose titration of the 1-day formulation was accomplished in a short period in patients with cancer pain who had been previously untreated with opioid analgesics; the efficacy of the formulation for pain control after repeated dosing was comparable to that of the 3-day formulation, and its tolerability was good. However, it was considered that the 1-day formulation should be used in patients with good tolerability to opioid analgesics. Further, for safety reasons, the dose should not be increased for at least 2 days after the initial application and the last dose increase.

Development and validation of an HPLC/MS/MS method for the determination of sufentanil and morphine in human plasma

A sensitive and fast HPLC/MS/MS method for measurement of sufentanil and morphine in plasma was developed and validated. A single liquid-liquid extraction in alkaline medium was used for the cleanup of plasma, and fentanyl was added as an internal standard (IS). The analyses were carried out using a C18 column and the mobile phase acetonitrile-5 mM ammonium acetate + 0.25% formic acid (70 + 30, v/v). The triple-quadrupole mass spectrometer equipped with an electrospray source in positive mode was set up in the selective reaction monitoring mode to detect precursor --> product ion transition 387.0 > 238.0, 285.7 > 165.1, and 337.0 > 188.0 for sufentanil, morphine, and IS, respectively. The method was linear in the 0.05 (LOQ) - 500 ng/mL range for sufentanil and 10 (LOQ) - 1000 ng/mL range for morphine. Good selectivity, linearity, precision, accuracy, and robustness were obtained for the HPLC/MS/MS method. The proposed method was successfully applied for the determination of sufentanil and morphine in patients undergoing cardiac surgery.

Complications of oral exposure to fentanyl transdermal delivery system patches

PURPOSE

Fentanyl is a synthetic opioid available therapeutically as an intravenous, transbucal, or transdermal preparation. It is also used as a drug of abuse through a variety of different methods, including the oral abuse of transdermal fentanyl patches. This is a series of patients with oral fentanyl patch exposure reported to our center and represents the first series of oral fentanyl patch exposures collected outside of the postmortem setting.

METHODS

In this series, we examined the New York Poison Control Center database for all cases of oral abuse of fentanyl reported between January 2000 and April 2008.

RESULTS

Twenty cases were reported, nine were asymptomatic or had symptoms of opioid withdrawal; 11 had symptoms of opioid intoxication. Eight patients were administered naloxone and all showed improvement in clinical status. Only one case resulted in a confirmed fatality-this patient had an orally adherent patch discovered at intubation.

CONCLUSIONS

Oral exposure may result in life-threatening toxicity. Patients should be closely assessed and monitored for the opioid toxidrome, and if symptomatic, should be managed with opioid antagonists and ventilatory support.

[Distribution of tramadol in acute poisoned rats]

OBJECTIVE

To develop a rapid and accurate gas chromatography method and investigate the distribution of tramadol in acute poisoned rats for information of samples selection and results evaluation in forensic identification.

METHODS

After an oral administration of tramadol at 1140 mg/kg (5 x LD50), concentrations of tramadol in rats' biological fluids and tissues were determined by gas chromatography.

RESULTS

The limit of detection of tramadol in blood and urine was 0.1 microg/mL and the limit of detection in liver was 0.1 microg/g. The intra-day precision and inter-day precision were within 3.1% and 5.5% respectively, and the recovery of tramadol in blood was more than 98%. The average levels of tramadol displayed in descending order of heart blood, liver, peripheral blood, urine, vitreous humor, kidney, lung, spleen, heart, brain respectively.

CONCLUSION

The established method could meet the requirements for toxicological analysis, and the results of the study suggest that blood, urine, liver, lung and kidney are suitable samples for forensic toxicological analysis in tramadol poisoning cases.

Kinetic spectrophotometric method for the determination of morphine in biological samples

In this paper a simple, selective and inexpensive kinetic method was developed for the determination of morphine based on its inhibitory effect on the Janus green-bromate system in sulfuric acid media. The reaction was monitored spectrophotometrically at 618 nm by a fixed time method. The effect of different parameters such as concentration of reactants and temperature on the rate of reaction was investigated and optimum conditions were obtained. The calibration curve was linear in the concentration range 0.07-7.98 mg L(-1) of morphine, and detection limit of the method was 3.0x10(-2)mg L(-1). The relative standard deviation for five determinations of 3.74 mg L(-1) of morphine was 0.57%. Finally, the proposed method was successfully applied to the determination of morphine in human urine and serum as real samples.

Ex vivo delta opioid receptor autoradiography: CNS receptor occupancy of two novel compounds over their antihyperalgesic dose range

Discovered as part of an effort to identify delta opioid (DOPr or DOR) agonist analgesics, JNJ-20788560 and JNJ-39204880 exhibited high DOR affinity, with K(i) values of 1.7 and 2.0nM, respectively, and were selective for DOR over the mu opioid receptor (MOPr or MOR), with 596- and 122-fold selectivity, respectively. Both compounds stimulated DOR but not MOR induced GTPgammaS binding and were effective antihyperalgesic agents in the complete Freund's adjuvant model of thermal hyperalgesia in the rat, with oral ED(50) values of 13.5 and 35mg/kg, corresponding to plasma levels of 1 and 9microM, respectively. Autoradiographic analysis of DOR and MOR occupancy in sections of brain (striatum) and lumbar spinal cord (L4-L6) was determined ex vivo, using radiolabeled naltrindole or DAMGO. Quantitative image analysis resulted in striatal DOR ED(50) values of 6.9 and 10.7mg/kg, for JNJ-20788560 and JNJ-39204880 respectively, and spinal cord values of 6.4 and 3.2mg/kg, respectively. Neither compound dose-dependently occupied MOR within the dose range studied. Thus, this study confirmed the DOR selectively over MOR of both compounds following their oral administration, and further demonstrated dose-dependent DOR occupancy by each compound across its antihyperalgesic dose range. Importantly, these in vitro, in vivo, and ex vivo data revealed that the greater in vitro potency of JNJ-20788560 was paralleled by its greater in vivo potency, although JNJ-39204880 achieved higher plasma levels following its oral administration. The receptor occupancy levels observed at the pharmacologic ED(50) doses of these compounds suggest the need for greater target engagement by JNJ-39204880 than by JNJ-20788560 to elicit a similar therapeutic response.

Disposition of morphine in plasma and cerebrospinal fluid varies during neonatal development in pigs

The pharmacological effects of morphine are mediated via the central nervous system (CNS) but its clearance from the CNS in neonates has not been investigated. We have proposed that neonatal development of the blood-brain barrier affected CNS clearance mechanisms and CNS exposure to morphine. Male piglets (n=5) aged one, three and six weeks were given morphine sulfate (0.5 mg kg−1, i.v.). Serial blood and cerebrospinal fluid (CSF) samples were withdrawn over 360 min after morphine administration. Morphine concentration was measured by radioimmunoassay. A three-compartment model was fitted to individual data. Estimated parameters were reported as median and range. The peak morphine concentrations in plasma were not significantly different in the one-, three- or six-week-old piglets. Plasma clearance at one week (4.5, 3.8-8.6 mL min−1 kg−1) was significantly lower than at three weeks (30.0, 19.1- 39.0 mL min−1 kg−1) and six weeks (37.0, 29.7–82.8 mL min−1 kg−1). The peak morphine concentration in CSF at one week (59.84, 31–67 ng mL−1) was higher than at three weeks (18.8, 17.7–25 ng mL−1) and six weeks (24.51, 16.5–84 ng mL−1), while CSF clearance was lower at one week (1.0, 0.18-9 mL min−1 kg−1) compared with three weeks (6.2, 2.3–9.3 mL min−1 kg−1) and six weeks (3.95, 1.3–85.7 mL min−1 kg−1). Apparent plasma: CSF transfer ratio at one week was greater than at three and six weeks. The reduced plasma and CSF morphine clearance in early infancy resulted in elevated systemic and central morphine exposure in neonatal pigs.

Impact of the CYP2D6 genotype on post-operative intravenous oxycodone analgesia

BACKGROUND

Oxycodone is a semi-synthetic opioid with a mu-receptor agonist-mediated effect in several pain conditions, including post-operative pain. Oxycodone is metabolized to its active metabolite oxymorphone by O-demethylation via the polymorphic CYP2D6. The aim of this study was to investigate whether CYP2D6 poor metabolizers (PMs) yield the same analgesia post-operatively from intravenous oxycodone as extensive metabolizers (EMs).

METHODS

Two hundred and seventy patients undergoing primarily thyroid surgery or hysterectomy were included and followed for 24 h post-operatively. The CYP2D6 genotype was blinded until study procedures had been completed for all patients. All patients received intravenous oxycodone as pain treatment for 24 h post-operatively and morphine 5 mg was used as escape medication. A responder was characterized as a patient without the need for escape medication and a positive evaluation in a questionnaire 24 h post-operatively.

RESULTS

Twenty-four patients were PM (8.9%) and 246 were EM (91.1%). One PM (4.17%, CI=0.1-21.1) was a non-responder and 42 EM (17.07%, CI=12.6-22.4) were non-responders. The non-responder rate did not differ between the two genotypes (P=0.14). There was no difference in the total consumption of oxycodone between the two genotypes (EM=14.7 mg, CI=13.0-16.4 and PM=13.0 mg, CI=8.9-17.0, P=0.42). The mean oxymorphone/oxycodone ratios were 0.0031 and 0.00081 in the EMs and PMs, respectively (P<0.0001).

CONCLUSION

This study showed for the first time in patients that the oxymorphone formation depends on CYP2D6, but we found no difference in the post-operative analgesic effect of intravenous oxycodone between the two CYP2D6 genotypes.

The comparative toxicology and major organ pathology of fatal methadone and heroin toxicity cases

In order to determine the comparative toxicology and systemic disease of cases of death due to methadone and heroin toxicity, 1193 coronial cases of opioid overdose that occurred in New South Wales, Australia between 1 January 1998 and 31 December 2007 were inspected. These comprised 193 cases in which cause of death involved methadone toxicity (METH) and 1000 cases in which cause of death involved heroin toxicity in the absence of methadone (HER). METH cases were significantly more likely to have benzodiazepines (63.7% vs. 32.2%), and less likely to have alcohol (23.6% vs. 42.7%) detected. METH cases were significantly more likely to be diagnosed with pre-existing systemic pathology (94.3% vs. 79.9%), and multiple organ system pathology (68.8% vs. 41.4%). Specifically, METH cases were more likely to have cardiac (58.9% vs. 34.5%), pulmonary (53.6% vs. 30.9%), hepatic (80.7% vs. 62.8%) and renal (25.0% vs. 9.5%) disease. Given the notable differences in toxicology and disease patterns, great caution appears warranted in prescribing benzodiazepines to methadone users, and regular physical examinations of methadone treatment patients would appear clinically warranted.

Pharmacokinetics of buprenorphine in a sodium carboxymethylcellulose gel after buccal transmucosal administration in dogs

Alternatives to intravenous administration of opioids are needed in veterinary medicine. Previous research suggests that opioids can be administered through the buccal mucosa in dogs. This study reports the pharmacokinetics of buprenorphine HCl (0.05 mg/kg) administered transmucosally in six dogs compared with those of buprenorphine HCl (0.015 mg/kg) administered intravenously. The results suggest that the pharmacokinetics of buprenorphine HCl administered intravenously or transmucosally are similar and that transmucosal administration may be considered as a noninvasive alternative to intravenous administration.

Quantitation of opioids in blood and urine using gas chromatography-mass spectrometry (GC-MS)

The opioid and 6-acetylmorphine assays utilize gas chromatography-mass spectrometry (GC-MS) for the analysis of morphine, codeine, hydromorphone, hydrocodone, and 6-acetylmorphine in blood and urine. The specimens are fortified with deuterated internal standard and a five-point calibration curve is constructed. Specimens are extracted by mixed-mode solid phase extraction. The morphine, codeine, hydromorphone, hydrocodone, and 6-acetylmorphine extracts are derivatized with N-methyl-bis(trifluoroacetamide) (MBTFA) producing trifluoroacetyl derivatives. The final extracts are then analyzed using selected ion monitoring GC-MS.

Pharmacokinetics of morphine after intramuscular injection in common goldfish Carassius auratus and Atlantic salmon Salmo salar

Teleost fish have a nociceptive system and likely perceive pain. This warrants the development of analgesic protocols both for experimental surgery and for various husbandry procedures. Morphine is the standard analgesic against which the efficacy of other analgesics is assessed, and is the analgesic that has been most used in fish. The aims of this study were to describe the pharmacokinetics of morphine after an intramuscular (i.m.) injection in common goldfish and Atlantic salmon, and to illustrate the whole-body distribution of morphine in salmon following i.m. injection of tritiated morphine. In the kinetic experiment, goldfish and salmon were respectively i.m. injected with 40 and 100 mg morphine kg(-1) in the right dorsal epaxial musculature. Blood was drawn at predetermined time points. Plasma was analysed for morphine and metabolites using liquid chromatography-mass spectrometry (LC-MS/MS). Morphine had a Tmax (time at which the maximum plasma concentration was measured) of 0.5 h in both species. The Cmax (maximum plasma concentration) showed substantial inter-individual variation, with a mean (90% CI) of 187 (167 to 199) mg l(-1) in salmon and 37 (29 to 43) mg l(-1) in goldfish, as determined by bootstrap analysis. The mean elimination half-lives were 12.5 and 13.5 h in goldfish and in salmon, respectively. The degree of metabolism to morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G) was low, with levels of M3G exceeding those of M6G. The distribution study demonstrated that the levels of tritiated morphine in the anterior kidney surpassed those in the other organs. A substantial amount seemed to be excreted through the gastrointestinal tract, while little tritium activity could be detected in the central nervous system.

Buprenorphine and major metabolites in blood specimens collected for drug analysis in law enforcement purposes

A liquid chromatographic/electrospray ionization tandem mass spectrometric method for the quantification of buprenorphine (BUP), norbuprenorphine (NBUP), buprenorphine-3-beta-D-glucuronide (BUPG) and norbuprenorphine-3-beta-D-glucuronide (NBUPG) in serum samples was developed and validated. Pre-treatment of BUP and NBUP was by liquid-liquid extraction, while glucuronides were favourably isolated by solid phase extraction. Separation in 2 separate runs (2 x 5 min) was achieved using isocratic elution. The method was applied to 20 authentic serum specimens collected for law enforcement purposes where BUP intake had been indicated. The parent drug was not detectable in half of the specimens at a lower limit of detection of 0.2 ng/mL, whereas NBUP could be determined from any sample but one. NBUPG is the major metabolite present, which could be identified along with BUPG in all samples under investigation. In authentic specimens it could be advisable to monitor BUP metabolites along with the parent drug.

Haloperidol and risperidone have specific effects on altered pain sensitivity in the ketamine model of schizophrenia

RATIONALE

The ketamine (ket) model reflects features of schizophrenia as well as secondary symptoms such as altered pain sensitivity.

OBJECTIVES

In the present study, we investigated the effect of subchronic oral treatment with haloperidol (hal, 0.075 mg/kg) and risperidone (ris, 0.2 mg/kg) on altered pain perception and locomotor activity in this model.

RESULTS

In reaction to 5 mg/kg morphine, ket pretreated animals showed a diminished analgesic response. Hal had no analgesic effect per se, but the compound normalised the analgesic reaction to morphine in the ket pretreated animals. The effect of ris was complex. First, there was no analgesic effect per se, and control animals showed a dose-dependent increase in the analgesic index after morphine injection. In the ket group treated with ris, the analgesic response to 5 mg/kg morphine was attenuated and in response to 10 mg/kg analgesia was comparable with that measured in controls. The reduced analgesic effect was not due to pharmacokinetic differences in morphine metabolism. After administration via drinking water in saline-injected control animals, the hal blood serum concentration was 2.6 +/- 0.45 ng/ml. In ket-injected animals, the mean serum concentration of hal amounted to 1.2 +/- 0.44 ng/ml. In the experiment using ris, animals in the control group had higher ris serum concentrations compared with ket-injected animals. In control animals, morphine dose dependently decreased locomotor activity. This effect was significantly stronger in the ket pretreated groups.

CONCLUSIONS

Hal and ris had different effects on altered pain sensitivity. It was hypothesised that these results are connected with alterations in dopamine D2 and mu opioid receptor binding.

Passive absorption of fentanyl from the fentanyl HCl iontophoretic transdermal system

BACKGROUND

The fentanyl HCl iontophoretic transdermal system (ITS) is a patient-controlled analgesic delivery system that actively administers bolus doses of fentanyl transdermally upon patient activation.

OBJECTIVE

To determine the amount of fentanyl absorbed from fentanyl ITS via passive absorption over a 24.5-h period.

METHODS

Serial blood samples for pharmacokinetic analyses were obtained from healthy adults who received fentanyl ITS for 24 h.

FINDINGS

The average absorption rate was 2.3 microg/h. An average total of 57.4 microg fentanyl was absorbed during the study. The mean maximum observed serum fentanyl concentration was 0.06 ng/mL.

CONCLUSIONS

Results indicate that the average amount of fentanyl absorbed passively or via passive delivery from fentanyl ITS is minimal. Maximum serum fentanyl concentrations fell below the range associated with analgesia and respiratory depression. The variability in fentanyl exposure was likely exaggerated by the low amounts of drug absorption resulting in overall fairly low fentanyl concentrations.

Comparison of effects and plasma concentrations of opioids between elderly and middle-aged patients after cardiac surgery

BACKGROUND

In elderly patients, opioids may cause prominent postoperative sedation and respiratory depression. We evaluated the influence of age on the effects of opioids and plasma concentrations of fentanyl and oxycodone in cardiac surgery patients.

METHODS

Thirty (>or=75 years, gender M9/F21) and 20 (<or=60 years, gender M20/F0) patients scheduled to undergo cardiac surgery. A standard anesthesia with fentanyl as an opioid was used. Fentanyl plasma concentrations were measured at the end of surgery and 2 h later. After tracheal extubation, when the pain intensity was at least moderate, blood samples for fentanyl and oxycodone plasma concentration measurements were taken. Thereafter, oxycodone hydrochloride 0.05 mg/kg i.v. was administered. After 15 and 45 min, pain intensity, sedation and oxycodone plasma concentration were determined. This test protocol was repeated twice.

RESULTS

The elderly had a higher plasma concentration of fentanyl at the end of surgery than younger patients (5.7+/-2.2 vs. 3.8+/-1.2 ng/ml, P=0.001). The plasma concentrations of oxycodone were comparable between the groups. The interval between the second and the third oxycodone dose was longer in the elderly patients (P=0.036). Pain intensity on the verbal rating scale was lower at the 45-min assessment point after all three oxycodone test doses (P=0.008) and sedation scores were significantly higher after the third dose in the elderly patients (P=0.035).

CONCLUSIONS

In elderly patients, the plasma concentration of fentanyl was higher but plasma levels of oxycodone were at a similar level compared with middle-aged patients. However, the elderly patients had less pain and were more sedated after doses of oxycodone.

Intrathecal morphine plus general anesthesia in cardiac surgery: effects on pulmonary function, postoperative analgesia, and plasma morphine concentration

OBJECTIVES

To evaluate the effects of intrathecal morphine on pulmonary function, analgesia, and morphine plasma concentrations after cardiac surgery.

INTRODUCTION

Lung dysfunction increases morbidity and mortality after cardiac surgery. Regional analgesia may improve pulmonary outcomes by reducing pain, but the occurrence of this benefit remains controversial.

METHODS

Forty-two patients were randomized for general anesthesia (control group n=22) or 400 microg of intrathecal morphine followed by general anesthesia (morphine group n=20). Postoperative analgesia was accomplished with an intravenous, patient-controlled morphine pump. Blood gas measurements, forced vital capacity (FVC), forced expiratory volume (FEV), and FVC/FEV ratio were obtained preoperatively, as well as on the first and second postoperative days. Pain at rest, profound inspiration, amount of coughing, morphine solicitation, consumption, and plasma morphine concentration were evaluated for 36 hours postoperatively. Statistical analyses were performed using the repeated measures ANOVA or Mann-Whiney tests (*p<0.05).

RESULTS

Both groups experienced reduced FVC postoperatively (3.24 L to 1.38 L in control group; 2.72 L to 1.18 L in morphine group), with no significant decreases observed between groups. The two groups also exhibited similar results for FEV1 (p=0.085), FEV1/FVC (p=0.68) and PaO2/FiO2 ratio (p=0.08). The morphine group reported less pain intensity (evaluated using a visual numeric scale), especially when coughing (18 hours postoperatively: control group= 4.73 and morphine group= 1.80, p=0.001). Cumulative morphine consumption was reduced after 18 hours in the morphine group (control group= 20.14 and morphine group= 14.20 mg, p=0.037). The plasma morphine concentration was also reduced in the morphine group 24 hours after surgery (control group= 15.87 ng.mL-1 and morphine group= 4.08 ng.mL-1, p=0.029).

CONCLUSIONS

Intrathecal morphine administration did not significantly alter pulmonary function; however, it improved patient analgesia and reduced morphine consumption and morphine plasma concentration.