A comparison of the effects of tramadol and morphine on gastric emptying in man

Codeine delays gastric emptying through inhibition of gastric motility as assessed with a novel diagnostic intragastric balloon catheter

BACKGROUND

The use of opioids as analgesic is on the rise, despite their inhibitory effect on gastric emptying. A novel feeding catheter with integrated intragastric balloon was developed to continuously assess gastric motility, enabling to investigate the effect of opioids on motility and emptying simultaneously. We aimed to discriminate normal and pharmacologically impaired gastric motility and its impact on gastric emptying in healthy adults.

METHODS

The VIPUN Gastric Monitoring System comprises a nasogastric balloon catheter and a monitoring unit. In a four-way randomized, single-blinded, cross-over study, subjects received either placebo or 58.8 mg codeine phosphate in combination with either an uninflated or an inflated (180 mL) balloon catheter. Motility-induced pressure changes were recorded for 6 hours. During the first 2 hours, nutrients were infused (225 kcal, 75 mL/h). Gastric emptying was assessed with a ¹³ C-octanoate breath test and expressed as gastric half-emptying time (GET½). An algorithm, designed to detect phasic contractility, converted pressure changes to a gastric balloon motility index (GBMI). Results are presented as mean(SD).

KEY RESULTS

Eighteen subjects completed the investigation (32(13) years, 22(2) kg/m² ). After codeine, GBMI was lower (0.31(0.16)) and GET½ was longer (233(57) minutes) compared with placebo (GBMI: 0.48(0.15), P < .01 and GET½: 172(12) minutes, P < .001). Within-subject ΔGET½ correlated significantly with ΔGBMI (r = -0.77 and P < .001).

CONCLUSIONS AND INFERENCES

The VIPUN Gastric Monitoring System allowed to assess gastric motility safely and continuously. The correlation between pharmacologically decreased gastric emptying and motility indicates a strong link between both. Gastric motility, measured with this innovative device, can be an indicator for gastrointestinal intolerance.

Opioid-Induced Foregut Dysfunction

The impact of opioid use on the lower gastrointestinal tract is well described, but recent opioid crisis has caused increased awareness of the detrimental effects of these drugs on esophageal and gastroduodenal motility. Opioid use has been associated with increased incidence of spastic esophageal motility disorders and gastroduodenal dysfunction. Opioid receptors are present with high abundance in the myenteric and submucosal plexus of the enteric nervous system. Activation of these receptors leads to suppressed excitability of the inhibitory musculomotor neurons and unchecked tonic contraction of the autogenic musculature (such as the lower esophageal sphincter and the pylorus).

Reduction in pain: Is it worth the gain? The effect of opioids on the GI tract

The use of opioid medications for acute and chronic pain has increased significantly in the past 20 years in the United States. Given the high density of opioid receptors in the gastrointestinal tract, side effects are common in these patients including constipation, dysphagia, bloating, nausea, and vomiting. These side effects, which are experienced by most patients who take opioids, can lead to significant impairment in quality of life. Unlike other side effects from opioids, gastrointestinal side effects do not diminish with continued use, often leading patients to reduce or discontinue their opioid treatment to relieve these side effects. Therefore, physicians must be aware and anticipate potential side effects in patients receiving opioids to ensure appropriate pain management.

Progress in understanding mechanisms of opioid-induced gastrointestinal adverse effects and respiratory depression

Opioids evoke analgesia through activation of opioid receptors (predominantly the μ opioid receptor) in the central nervous system. Opioid receptors are abundant in multiple regions of the central nervous system and the peripheral nervous system including enteric neurons. Opioid-related adverse effects such as constipation, nausea, and vomiting pose challenges for compliance and continuation of the therapy for chronic pain management. In the post-operative setting opioid-induced depression of respiration can be fatal. These critical limitations warrant a better understanding of their underpinning cellular and molecular mechanisms to inform the design of novel opioid analgesic molecules that are devoid of these unwanted side-effects. Research efforts on opioid receptor signalling in the past decade suggest that differential signalling pathways and downstream molecules preferentially mediate distinct pharmacological effects. Additionally, interaction among opioid receptors and, between opioid receptor and non-opioid receptors to form signalling complexes shows that opioid-induced receptor signalling is potentially more complicated than previously thought. This complexity provides an opportunity to identify and probe relationships between selective signalling pathway specificity and in vivo production of opioid-related adverse effects. In this review, we focus on current knowledge of the mechanisms thought to transduce opioid-induced gastrointestinal adverse effects (constipation, nausea, vomiting) and respiratory depression.

A Pilot Study on the use of Tramadol Hydrochloride for Pain Control in an Emergency Department

Introduction

Tramadol hydrochloride is a synthetic μ,-opioid agonist. It has been used in the control of moderate to severe pain. Most of the studies on tramadol were related to post-operative pain control. Data on acute pain control in the emergency setting were limited. This study reported on the initial evaluation of tramadol for pain control in an emergency department.

Materials and methods

It was a prospective observational study. Patients aged 16 years or above attending our emergency department with moderate to severe pain were recruited. Patients with known allergy, current psychiatric medication, intake of alcohol, major systemic illness and opioid dependence were excluded. All patients received 100 mg intramuscular tramadol injection. A 10 cm Visual Analogue Scale (VAS) was used to assess the pain severity before injection, 30 minutes and 60 minutes after injection. Vital signs and side effects were also recorded.

Results

Forty patients (M: 24, F: 16) were recruited from October to December 2002. Their mean age was 53.5 years. The majority of them suffered from acute musculoskeletal pain or arthritis. Tramadol was shown to be effective in pain control. The VAS decreased by 1.90 (p<0.001) and 3.38 (p<0.001) at 30 minutes and 60 minutes respectively. Four patients reported nausea and three patients vomited.

Conclusion

Tramadol appeared to be a safe drug to be used in the emergency setting. Only a few insignificant side effects were reported. The comparison of efficacy with other analgesics requires further studies.

Gastric motility measurement and evaluation based on electrical-mechanical composite mechanism

Gastric motility and emptying are a composite course involving electrical activity and mechanical contraction. In the research of gastric motility, the electrical activity should be closely connected to the subsequent mechanical contraction based on the understanding of electrical-mechanical composite mechanism. Existing simulation research and clinical research suggest that electrogastrogram (EGG) signals can provide physiological time scales, and gastric motility can be extracted from impedance signals. According to the coupling of the myoelectric activity and the mechanical contraction of the stomach, the correlation analysis of multiple signals can be performed. And then the influence of various factors such as the range, time and transmission distance of the gastric contraction can be deeply explored. The method combining gastric impedance and synchronous EGG measurements is effective and promising for evaluating gastric motility.

Gastric motility functional study based on electrical bioimpedance measurements and simultaneous electrogastrography

For some time now, the research on gastric motility and function has fallen behind in the amount of research on gastric endocrine, exocrine secretion, and gastric morphology. In this paper, a noninvasive method to study gastric motility was developed, taking bioimpedance measurements over the gastric area simultaneously with the electrogastrography (EGG). This is based on the concept of observing and analyzing simultaneously the intrinsic electrical gastric activity (basic electric rhythm) and the mechanical gastric activity. Additionally, preliminary clinical studies of healthy subjects and subjects with functional dyspepsia (FD) and gastritis were carried out. The impedance gastric motility (IGM) measurements of the healthy and FD subjects were compared, along with the studies of the FD subjects before treatment and after one week and three weeks of treatment. We also compared IGM measurements of healthy subjects and subjects with erosive gastritis, along with the studies of the subjects with erosive gastritis before treatment and after one week of treatment. Results show that FD subjects have poor gastric motility (P<0.01). After a week of treatment, the gastric motility of FD subjects was not yet improved although the EGG had returned to normal by this time. By three weeks of treatment, the regular IGM rhythm returned in FD subjects. There was a significant difference of IGM parameters between the gastritis and healthy subjects (P<0.05). The EGG rhythm of the gastritis subjects returned to normal at one week post-treatment, while IGM parameters showed a trend to improvement (P>0.05), These results suggest the possibility of clinic application of the proposed method.

Perioperative management of the child on long-term opioids

The strategies used to manage children exposed to long-term opioids are extrapolated from adult literature. Opioid consumption during the perioperative period is more than three times that observed in patients not taking chronic opioids. A sparing use of opioids in the perioperative period results in both poor pain management and withdrawal phenomena. The child's pre-existing opioid requirement should be maintained, and acute pain associated with operative procedures should be managed with additional analgesia. This usually comprises short-acting opioids, regional or local anesthesia, and adjuvant therapies. Long-acting opioids, transdermal opioid patches, and implantable pumps can be used to maintain the regular opioid requirement. Intravenous infusion, nurse controlled analgesia, patient-controlled analgesia, or oral formulations are invaluable for supplemental requirements postoperatively. Effective management requires more than simply increasing opioid dose during this time. Collaboration of the child, family, and all teams involved is necessary. While chronic pain or palliative care teams and other staff experienced with the care of children suffering chronic pain may have helpful input, many pediatric hospitals do not have chronic pain teams, and many patients receiving long-term opioids are not palliative. Acute pain services are appropriate to deal with those on long-term opioids in the perioperative setting and do so successfully in many centers. Staff caring for such children in the perioperative period should be aware of the challenges these children face and be educated before surgery about strategies for postoperative management and discharge planning.

Extended-release formulations of tramadol in the treatment of chronic pain

INTRODUCTION

Tramadol is a centrally acting analgesic available throughout the world. Its dual opioid and non-opioid mechanisms of action, favorable efficacy and safety clinical profiles and non-controlled regulatory status in most markets contribute to its widespread use. A drawback of the immediate-release formulation of tramadol (four-times-a-day dosing) might be addressed by an extended-release formulation. Extended-release formulations also can offer advantages in the management of chronic pain: convenience, reduced pill burden (possibly leading to improved compliance) and the attenuation of peaks and troughs in serum concentration (possibly leading to reduced adverse effects).

AREAS COVERED

The authors review tramadol's mechanisms of action and the clinical literature regarding the use of tramadol extended-release formulations for the management of conditions involving chronic pain, such as neuropathic pain syndromes, osteoarthritis and cancer pain.

EXPERT OPINION

Based on the literature cited, extended-release formulations of tramadol seem to offer a rational and important addition to the analgesic armamentarium. As is true for all such options, the benefits and risks must be assessed for each patient.

The influence of morphine on the absorption of paracetamol from various formulations in subjects in the supine position, as assessed by TDx measurement of salivary paracetamol concentrations

The aim of this study was to determine the influence of the type of paracetamol formulation on the rate of absorption when subjects are in the supine position, with or without taking concomitant morphine. Two groups of healthy volunteers were used, who were in the fasting state and remained in the supine position during the study. One group took 1500 mg of paracetamol on three occasions as conventional tablets, dispersible tablets or a suspension in a randomized crossover design. Seventeen saliva samples per subject were obtained (time zero to 360 min post-dose), which were then centrifuged and kept at −20°C prior to analysis. The second group repeated the study following four doses of morphine syrup (10 mg 4 hourly) in the 12 h preceding paracetamol ingestion. In this phase of the study, paracetamol absorption from suspension was not investigated. A TDx assay was used to determine salivary paracetamol concentrations. The tmax for conventional tablets when taken concomitantly with morphine was 160 (+81) min compared to 51 (+58) min for subjects not taking morphine. For dispersible tablets the tmax in the morphine group was 14 (+9) min compared to 15 (+12) min without morphine. The results suggest that patients who are confined to bed and taking morphine will have an unacceptably long delay between taking conventional paracetamol tablets and the paracetamol reaching therapeutic plasma concentrations. Conversely, there is little effect on the absorption of dispersible paracetamol under the same conditions.

Use of electrical bioimpedance for gastric motility measurement and evaluation

Electrical bioimpedance technology is a measurement method to extract biomedical information associated with the physiological and pathological states of human body according to the electrical properties of tissue and organs. It has many outstanding advantages such as noninvasiveness, cheapness, convenience and rich function information. According to the electrical properties of the stomach tissue or the food in the stomach and the characteristics of food digestion, electrical bioimpedance methods permit to extract physiological and pathological information associated with gastric motility, investigate gastric contraction, peristalsis, transmission and emptying, and measure and evaluate gastric motility function noninvasively. In this article, we reveiw the development history of electrical bioimpedance technology and the characteristics of gastric motility impedance signal, and introduce the bioimpedance methods for measurement of gastric motility based on the concept of electrical-mechanical coupling. Besides, we also summarize the application of bioimpedance methods in the basic research of gastric motility, in the measurement of gastric motility in patients with functional dyspepsia, in the evaluation of gastric motility in patients with erosive gastritis, and in the detection and screening of gastric cancer. Moreover, we put forward some suggestions on the future development directions of bioimpedance methods for measurement of gastric motility.

Weak opioids--an educational substitute for morphine?

The World Health Organization guidelines suggest the use of weak opioids on the second step of the analgesic ladder for cancer pain relief. Weak opioids are important substitutes for low doses of morphine, although their analgesic efficacy is lower than that of non-opioid or strong opioid analgesics. The use of weak opioids has great educational impact and has helped spread the use of the guidelines. Furthermore, weak opioids are more freely available and are expected to have a better side-effect profile. Controlled long-term studies are required for confirmation.

Once-daily tramadol in rheumatological pain

New once-daily formulations of tramadol have been recently marketed in various countries. This review focuses on the matrix systems used in sustained-release formulations to control drug delivery, the pharmacokinetics and pharmacodynamic profile and the available clinical trials on once-daily tramadol. Four controlled clinical studies with a limited number of patients have shown that once-daily tramadol is safe and effective for up to 12 weeks in rheumatological pain treatment, with a favourable side effects profile. Once-daily tramadol has established efficacy superior to that of placebo for pain management and functional improvement in patients with osteoarthritis. Two randomised clinical trials demonstrated similar rates of efficacy between immediate-release and once-daily sustained-release formulation, without significant differences in the use of escape medications and the number of nights woken. Once-daily tramadol offers the advantage of a reduced dosing regimen that improves patient compliance.

The effects of tramadol and fentanyl on gastrointestinal motility in septic rats

In this study, we investigated the effects of tramadol and fentanyl on gastrointestinal transit (GIT) during acute systemic inflammation in an experimental model of cecal ligation and perforation (CLP). One-hundred-twenty male Swiss-Albino rats were divided randomly into 6 groups: Group I = sham-operated + saline; Group II = sham-operated + fentanyl; Group III = sham-operated + tramadol; Group IV = CLP + saline; Group V = CLP + fentanyl; Group VI = CLP + tramadol. Suspension of charcoal was administered as an intragastric meal to measure the GIT. GIT% (mean +/- sd) were 46.1% +/- 9.8%, 43.2% +/- 9.8%, 45.9% +/- 10.2%, 33.2% +/- 9.2%, 24.9% +/- 4.1%, and 31.8% +/- 8.4% in Groups I, II, III, IV, V, and VI, respectively. GIT% was significantly less in Group V than in Groups I, II, III, and IV (P < 0.05). The Group VI mean value was significantly lower than those of Groups I, II, and III (P < 0.05) but not different from those of Groups IV and V (P > 0.05). The antitransit effect of fentanyl was shown to have increased in the experimental sepsis model, but no decrease in GIT was obtained with tramadol. This was thought to be the result of an associated endogenic opioid system activation and receptor upregulation in sepsis.

Perioperative and Intraoperative Pain and Anesthetic Care of the Chronic Pain and Cancer Pain Patient Receiving Chronic Opioid Therapy

The expanding role of the anesthesiologist as a "perioperative physician" places ever-increasing demands upon his or her clinical skills and knowledge. One area of growing concern for the anesthesiologist involves the perioperative assessment and management of the opioid-tolerant chronic pain patient. Opioids occupy a position of unsurpassed clinical utility for the treatment of many types of painful conditions. Coupled with noticeable shifts in physician attitudes that have occurred in recent years regarding the use of opioids for the treatment of benign and malignancy-related pain, many more patients are presenting for surgical procedures who are opioid tolerant. It is important therefore that the practicing anesthesiologist become familiar with the currently available opioid formulations, including drug interactions and side effects, in order to better plan the patient's perioperative anesthetic needs and management. Unfortunately, there is a lack of scientifically rigorous studies in this important area, and most of the information must be derived from anecdotal reports and personal experience of anesthesiologists working in this field. In this review, we shall discuss some aspects of current chronic pain management, the newer forms of opioid administration which may be unfamiliar to the anesthesiologist, as well as clinical aspects of opioid use and tolerance including the impact it may have on perioperative anesthetic management.

Clinical pharmacology of tramadol

Tramadol, a centrally acting analgesic structurally related to codeine and morphine, consists of two enantiomers, both of which contribute to analgesic activity via different mechanisms. (+)-Tramadol and the metabolite (+)-O-desmethyl-tramadol (M1) are agonists of the mu opioid receptor. (+)-Tramadol inhibits serotonin reuptake and (-)-tramadol inhibits norepinephrine reuptake, enhancing inhibitory effects on pain transmission in the spinal cord. The complementary and synergistic actions of the two enantiomers improve the analgesic efficacy and tolerability profile of the racemate. Tramadol is available as drops, capsules and sustained-release formulations for oral use, suppositories for rectal use and solution for intramuscular, intravenous and subcutaneous injection. After oral administration, tramadol is rapidly and almost completely absorbed. Sustained-release tablets release the active ingredient over a period of 12 hours, reach peak concentrations after 4.9 hours and have a bioavailability of 87-95% compared with capsules. Tramadol is rapidly distributed in the body; plasma protein binding is about 20%. Tramadol is mainly metabolised by O- and N-demethylation and by conjugation reactions forming glucuronides and sulfates. Tramadol and its metabolites are mainly excreted via the kidneys. The mean elimination half-life is about 6 hours. The O-demethylation of tramadol to M1, the main analgesic effective metabolite, is catalysed by cytochrome P450 (CYP) 2D6, whereas N-demethylation to M2 is catalysed by CYP2B6 and CYP3A4. The wide variability in the pharmacokinetic properties of tramadol can partly be ascribed to CYP polymorphism. O- and N-demethylation of tramadol as well as renal elimination are stereoselective. Pharmacokinetic-pharmacodynamic characterisation of tramadol is difficult because of differences between tramadol concentrations in plasma and at the site of action, and because of pharmacodynamic interactions between the two enantiomers of tramadol and its active metabolites. The analgesic potency of tramadol is about 10% of that of morphine following parenteral administration. Tramadol provides postoperative pain relief comparable with that of pethidine, and the analgesic efficacy of tramadol can further be improved by combination with a non-opioid analgesic. Tramadol may prove particularly useful in patients with a risk of poor cardiopulmonary function, after surgery of the thorax or upper abdomen and when non-opioid analgesics are contraindicated. Tramadol is an effective and well tolerated agent to reduce pain resulting from trauma, renal or biliary colic and labour, and also for the management of chronic pain of malignant or nonmalignant origin, particularly neuropathic pain. Tramadol appears to produce less constipation and dependence than equianalgesic doses of strong opioids.

Pancreas transplantation: indications and consequences

Pancreas transplantation continues to evolve as a strategy in the management of diabetes mellitus. The first combined pancreas-kidney transplant was reported in 1967, but pancreas transplant now represents a number of procedures, each with different indications, risks, benefits, and outcomes. This review will summarize these procedures, including their risks and outcomes in comparison to kidney transplantation alone, and how or if they affect the consequences of diabetes: hyperglycemia, hypoglycemia, and microvascular and macrovascular complications. In addition, the new risks introduced by immunosuppression will be reviewed, including infections, cancer, osteoporosis, reproductive function, and the impact of immunosuppression medications on blood pressure, lipids, and glucose tolerance. It is imperative that an endocrinologist remain involved in the care of the pancreas transplant recipient, even when glucose is normal, because of the myriad of issues encountered post transplant, including ongoing management of diabetic complications, prevention of bone loss, and screening for failure of the pancreas graft with reinstitution of treatment when indicated. Although long-term patient and graft survival have improved greatly after pancreas transplant, a multidisciplinary team is needed to maximize long-term quality, as well as quantity, of life for the pancreas transplant recipient.

The role of tramadol in cancer pain treatment—a review

In most cancer patients pain can be successfully treated with pharmacological measures using opioid analgesics alone or in combination with adjuvant analgesics (coanalgesics). Weak opioids are usually recommended in the treatment of moderate cancer pain. There is still a debate as to whether the second step of the WHO analgesic ladder comprising opioid analgesics such as tramadol, codeine, dihydrocodeine, and dextropropoxyphene is still needed for the treatment of cancer pain. On the basis of our experience and review of the literature we think that there is definitely a place for weak opioids in the treatment of moderate cancer pain. One of the most interesting and useful weak opioids is tramadol (Adolonta, Contramal, Nobligan, Top-Algic, Tramal, Tramal Long, Tramal Retard, Tramundin, Trodon, Ultram, Zydol). Its unique mechanism of action, analgesic efficacy and profile of adverse reactions have been the reason of performing many experimental and clinical studies with tramadol. In this article we summarize data on pharmacology, mechanisms of action, pharmacokinetics, side effects and clinical experience assessing analgesic efficacy, adverse reactions and safety of tramadol in cancer pain.

Tramadol infusion for postthoracotomy pain relief: a placebo-controlled comparison with epidural morphine

We compared continuous IV tramadol as an alternative to neuraxial or systemic opioids for the management of postthoracotomy pain in a prospective, randomized, double-blinded, controlled study. General anesthesia was supplemented by thoracic epidural analgesia with 0.25% bupivacaine. At rib approximation, patients received one of the following: IV tramadol (150-mg bolus followed by infusion, total 450 mg/24 h, n = 29), epidural morphine (2 mg, then 0.2 mg/h, n = 30), or patient-controlled analgesia (PCA) morphine only (n = 30). All patients received PCA morphine and rescue morphine as necessary postoperatively. For the first 24 h, pain and sedation scores and respiratory, cardiovascular, and side effect measures were monitored. There was no significant difference in pain scores and PCA morphine use between tramadol and epidural morphine. Pain scores at rest and on coughing were lower in the Tramadol and Epidural Morphine groups than in the PCA Morphine group at various time points over the first 12 h. The Tramadol and Epidural Morphine groups used significantly less hourly PCA morphine than the PCA Morphine group at specific time points in the first 10 h. Vital capacities in the Tramadol group were significantly closer to baseline values at the 20-h point than in the PCA Morphine group. We conclude that an intraoperative bolus of tramadol followed by an infusion was as effective as epidural morphine and avoided the necessity of placing a thoracic epidural catheter.

IMPLICATIONS

A prospective, randomized, double-blinded, placebo-controlled study of postthoracotomy pain relief showed that IV tramadol in the form of a bolus followed by continuous infusion was as effective as epidural morphine. The use of tramadol avoids the necessity of placing a thoracic epidural catheter.

Tramadol: a review of its use in perioperative pain

Tramadol is a synthetic, centrally acting analgesic agent with 2 distinct, synergistic mechanisms of action, acting as both a weak opioid agonist and an inhibitor of monoamine neurotransmitter reuptake. The 2 enantiomers of racemic tramadol function in a complementary manner to enhance the analgesic efficacy and improve the tolerability profile of tramadol. In several comparative, well designed studies, oral and parenteral tramadol effectively relieved moderate to severe postoperative pain associated with surgery. Its overall analgesic efficacy was similar to that of morphine or alfentanil and superior to that of pentazocine. Tramadol provided effective analgesia in children and in adults for both inpatient and day surgery. Tramadol was generally well tolerated in clinical trials. The most common adverse events (incidence of 1.6 to 6.1%) were nausea, dizziness, drowsiness, sweating, vomiting and dry mouth. Importantly, unlike other opioids, tramadol has no clinically relevant effects on respiratory or cardiovascular parameters at recommended doses in adults or children. Tramadol also has a low potential for abuse or dependence.

CONCLUSIONS

The efficacy of tramadol for the management of moderate to severe postoperative pain has been demonstrated in both inpatients and day surgery patients. Most importantly, unlike other opioids, tramadol has no clinically relevant effects on respiratory or cardiovascular parameters. Tramadol may prove particularly useful in patients with poor cardiopulmonary function, including the elderly, the obese and smokers, in patients with impaired hepatic or renal function, and in patients in whom nonsteroidal anti-inflammatory drugs are not recommended or need to be used with caution. Parenteral or oral tramadol has proved to be an effective and well tolerated analgesic agent in the perioperative setting.

A comparison of the effects of intravenous tramadol, codeine, and morphine on gastric emptying in human volunteers

We compared the effects of i.v. tramadol (1.25 mg/kg), codeine (1 mg/kg), morphine (0.125 mg/kg), and saline on gastric emptying in 10 healthy human volunteers using a double-blind, randomized, cross-over design. Subjects received one treatment at each of four sessions, 2 wk apart. Gastric emptying was studied using the paracetamol absorption test. There were significant differences when comparing all treatments for concentration-time data (P = 0.002), peak serum paracetamol concentrations (Cmax; P < 0.001), times at Cmax (Tmax; P = 0.003), and areas under the curves from Time 0 to 360 min (AUC(0-360); P = 0.049). Morphine profoundly inhibited gastric emptying. Tramadol had measurable but statistically insignificant inhibitory effects on gastric emptying compared with saline (mean +/- SEM: Cmax 22.4 +/- 2.2 vs 26.8 +/- 2.5 mg/L [P = 0.19], Tmax 33 +/- 5.4 vs 19.5 +/- 2.3 min [P = 0.054] for tramadol versus saline, respectively). Compared with morphine, the Cmax (P < 0.01), Tmax, and AUC(0-360) (P < 0.05) values for tramadol were significantly different. The Tmax value for codeine (63.3 +/- 11.7) was greater than that for tramadol (P = 0.034). We conclude that tramadol has a measurable but smaller inhibitory effect on gastric emptying compared with other opioids.

IMPLICATIONS

We compared the effect of tramadol, an unconventional opioid painkiller, on stomach emptying with that of codeine and morphine in a human volunteer study. Tramadol had a measurable but smaller effect and may have clinical and economic advantages in acute pain management compared with conventional painkillers.