Effects of tramadol and meperidine on respiration, plasma catecholamine concentrations, and hemodynamics

The Role of Adrenaline, Noradrenaline, and Cortisol in the Pathogenesis of the Analgesic Potency, Duration, and Neurotoxic Effect of Meperidine

Background and Objectives: The purpose of the study was to investigate the role of adrenaline (ADR), noradrenaline (NDR), and cortisol in the pathogenesis of the analgesic potency, duration, and epilepsy-like toxic effect of meperidine. Materials and Methods: The experimental animals were separated into 11 groups of six rats. In the meperidine (MPD) and metyrosine + meperidine (MMPD) groups, paw pain thresholds were measured before and after the treatment between the first and sixth hours (one hour apart). In addition, ADR and NDR analyses were performed before and after the treatment, between the first and fourth hours (one hour apart). For the epilepsy experiment, caffeine, caffeine + meperidine, and caffeine + meperidine + metyrapone groups were created, and the treatment was applied for 1 day or 7 days. Groups were created in which caffeine was used at both 150 mg/kg and 300 mg/kg. Epileptic seizures were observed in epilepsy groups, latent periods were determined, and serum cortisol levels were measured. Results: In the MPD group, pain thresholds increased only at the first and second hours compared to pre-treatment, while ADR increased at the third hour, leading to a decrease in pain thresholds. In the MMPD group, the increase in paw pain thresholds at 1 and 6 h was accompanied by a decrease in ADR and NDR. In the caffeine (150 mg/kg) + meperidine group, 1-day treatment did not cause epileptic seizures, while seizures were observed and cortisol levels increased in the group in which treatment continued for 7 days. When cortisol levels were compared between the group in which caffeine (300 mg/kg) + meperidine + metyrapone was used for 7 days and the animals receiving caffeine (300 mg/kg) + metyrapone for 7 days, it was found that cortisol levels decreased and the latent period decreased. Conclusions: The current study showed that if serum ADR and cortisol levels are kept at normal levels, a longer-lasting and stronger analgesic effect can be achieved with meperidine, and epileptic seizures can be prevented.

A Post-Marketing Study of Pethidine in Indonesia: Safety Profile

Introduction Pethidine along with morphine and tramadol, is one of the frequently used drugs for postoperative pain management. It is important to ensure the safety of the product and ultimately the safety of the patients as users of the pethidine. Methods A post marketing surveillance study was conducted with a retrospective cross-sectional design using medical records and hospital pharmacy’s data in patients who were admitted to inpatient or emergency department of Dr. Sardjito General Hospital Yogyakarta between January and December 2016. The data was analyzed descriptively to estimate the proportion of adverse events (AEs) including serious adverse events (SAE). Results Of the 576 patients hospitalized at the at the Dr. Sardjito General Hospital, 200 medical records were selected using consecutive sampling method. A total of 120 of the 200 subjects were found to have 245 any Adverse Events (AE) including Serious Adverse Events (SAE) following the administration of pethidine. There were 23 classifications of expected AE and 148 classifications of unexpected AE following the administration of pethidine. The duration of AE/SAE found ranged from 0 to 11 days. A total of 101 (50.5%) and 85 (42.5%) subjects experienced AE/SAE with duration <24 hours and between 1 to 2 days, respectively. The longest duration of event was pain with duration of 11 days. There were 23 types of expected AE/SAE from pethidine found in subjects, with the highest number of expected AE/SAE were weakness, vomiting, and dizziness of 24 (25%), 16 (16.8%), and 10 (10.5%), respectively. The expert panel team concluded five types of unexpected SAEs which are possible to pethidine, including respiratory acidosis, urinary tract infections, acute kidney injury, icteric, and electrolyte imbalance. Conclusion A post-marketing surveillance study provides safety profile of 50 mg / ml pethidine in Indonesia. A total of 120 of the 200 subjects who received pethidine experienced 245 Adverse Events (AEs) or Serious Adverse Events (SAEs). AEs/SAEs were divided into 23 types of expected events and 148 types of unexpected events. Few numbers of SAEs were considered possible related to the pethidine according to expert panel review.   Keywords: pethidine, meperidine, post-marketing, pharmacovigilance

Local infiltration of tramadol as an effective strategy to reduce post-operative pain: a systematic review protocol and meta-analysis

OBJECTIVE

The purpose of this review is to evaluate the use and effectiveness of the local administration of tramadol in reducing post-operative pain during surgical interventions.

METHODS

The PubMed, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) databases will be searched for this review. This systematic review will include studies evaluating the clinical efficacy of the local infiltration of tramadol, with no study design restrictions. Only studies that present clear descriptions of local tramadol administration are published in peer-reviewed journals in the English, Italian, Spanish, French, Portuguese or German language and are published in full will be taken into consideration. A meta-analysis will be performed when there is sufficient clinical homogeneity among the retrieved studies, and only randomized controlled studies and quasi-randomized controlled studies will be included. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach will be used to assess the certainty in the evidence. If a quantitative analysis cannot be conducted, a qualitative description of the results of the retrieved studies will be provided.

RESULTS

A high-quality synthesis of the current evidence on the local administration of tramadol for managing post-surgical pain will be illustrated using subjective reports and objective measures of performance. The primary outcomes will include the magnitude of post-operative pain intensity improvement, with improvement being as defined by a reduction by at least 2 points in the visual analogue scale (VAS) score or numerical rating scale (NRS) score. The secondary outcomes will be the magnitude of reduction in tramadol rescue doses and in other analgesic drug doses.

CONCLUSION

This protocol will present evidence on the efficacy of tramadol in relieving post-surgical pain.

SYSTEMIC REVIEW REGISTRATION

PROSPERO CRD42018087381.

Desmetramadol Is Identified as a G-Protein Biased µ Opioid Receptor Agonist

Tramadol is widely used globally and is the second most prescribed opioid in the United States. It treats moderate to severe pain but lethal opioid-induced respiratory depression is uncommon even in large overdose. It is unknown why tramadol spares respiration. Here we show its active metabolite, desmetramadol, is as effective as morphine, oxycodone and fentanyl in eliciting G protein coupling at the human µ opioid receptor (MOR), but surprisingly, supratherapeutic concentrations spare human MOR-mediated βarrestin2 recruitment thought to mediate lethal opioid-induced respiratory depression.

Desmetramadol Has the Safety and Analgesic Profile of Tramadol Without Its Metabolic Liabilities: Consecutive Randomized, Double-Blind, Placebo- and Active Comparator-Controlled Trials

Desmetramadol is an investigational analgesic consisting of (+) and (-) enantiomers of the tramadol metabolite O-desmethyltramadol (M1). Tramadol is racemic and exerts analgesia by monoaminergic effects of (-)-tramadol and (-)-M1, and by the opioid (+)-M1. Tramadol labeling indicates cytochrome P450 (CYP) isozyme 2D6 ultrarapid metabolizer can produce dangerous (+)-M1 levels, and CYP2D6 poor metabolizers insufficient (+)-M1 for analgesia. We hypothesized that desmetramadol could provide the safety and analgesia of tramadol without its metabolic liabilities. We conducted consecutive double-blind, randomized, placebo-controlled, 3 segment cross-over trials A and B to investigate the steady-state pharmacokinetics and analgesia of 20 mg desmetramadol and 50 mg tramadol in 103 healthy participants without (n = 43) and with (n = 60) cotreatment with the CYP inhibitor paroxetine. In the absence of CYP inhibition (trial A), 20 mg desmetramadol and 50 mg tramadol dosed every 6 hours gave equivalent steady-state (+)-M1, similar adverse events, and analgesia significantly greater than placebo, but equal to each other. In trial B, CYP inhibition significantly depressed tramadol steady-state (+)-M1, reduced its adverse events, and led to insignificant analgesia comparable with placebo. In contrast, CYP inhibition in trial B had no deleterious effect on desmetramadol (+)-M1 or (-)-M1, which gave significant analgesia as in trial A and superior to tramadol (P = .003). Desmetramadol has the safety and efficacy of tramadol without its metabolic liabilities. CLINICALTRIALS.GOV REGISTRATIONS: NCT02205554, NCT03312777 PERSPECTIVE: To our knowledge, this is the first study of desmetramadol in humans and the first to show it provides the same safety and analgesia as tramadol, but without tramadol's metabolic liabilities and related drug-drug interactions. Desmetramadol could potentially offer expanded safety and usefulness to clinicians seeking an alternative to schedule II opioids.

The role of tramadol in pain management in Latin America: a report by the Change Pain Latin America Advisory Panel

OBJECTIVE

Change Pain Latin America (CPLA) was created to enhance chronic pain understanding and develop pain management improving strategies in this region. During its seventh meeting (August 2016), the main objective was to discuss tramadol's role in treating pain in Latin America. Furthermore, potential pain management consequences were considered, if tramadol was to become more stringently controlled.

METHODS

Key topics discussed were: main indications for prescribing tramadol, its pharmacological characteristics, safety and tolerability, effects of restrictions on its availability and use, and consequent impact on pain care quality.

RESULTS

The experts agreed that tramadol is used to treat a wide spectrum of non-oncological pain conditions (e.g. post-surgical, musculoskeletal, post-traumatic, neuropathic, fibromyalgia), as well as cancer pain. Its relevance when treating special patient groups (e.g. the elderly) is recognized. The main reasons for tramadol's high significance as a treatment option are: its broad efficacy, an inconspicuous safety profile and its availability, considering that access to strong analgesics - mainly controlled drugs (classical opioids) - is highly restricted in some countries. The CPLA also agreed that tramadol is well tolerated, without the safety issues associated with long-term nonsteroidal anti-inflammatory drug (NSAID) use, with fewer opioid-like side effects than classical opioids and lower abuse risk.

CONCLUSIONS

In Latin America, tramadol is a valuable and frequently used medication for treating moderate to severe pain. More stringent regulations would have significant impact on its availability, especially for outpatients. This could cause regression to older and frequently inadequate pain management methods, resulting in unnecessary suffering for many Latin American patients.

Comparison of preoperative tramadol and pethidine on postoperative pain in cats undergoing ovariohysterectomy

Background

A variety of analgesic agents are available, and which one can be used in dogs and cats is a highly controversial issue, existing however a fear in the use of opiates due to possible adverse effects that these drugs can cause. The aim of this study was to compare the analgesic effect provided by the administration of tramadol or pethidine on early postoperative pain of cats undergoing ovariohysterectomy in a double-blind prospective study. Fourty-two animals were randomly assigned into three groups. Pet received pethidine (6 mg/kg), Tra 2 received tramadol (2 mg/kg) and Tra 4 received tramadol (4 mg/kg); all intramuscularly and associated with acepromazine (0.1 mg/kg). The efficacy of each analgesic regimen was evaluated prior to surgery (baseline - T_BL), during surgery and 1, 3 and 6 hours after extubation with subjective pain scale, physiologic parameters, serum concentrations of glucose, cortisol and IL-6.

Results

Changes in cardiovascular system were not clinically relevant. There were no significant differences in pain scores (P > 0.05) during the study, although the number of rescue analgesia was significantly higher (P < 0.05) at Pet group (5/14) than Tra 4 group (0/14), whereas in Tra 2, two animals (2/14) required additional analgesia. The serum cortisol values of Pet group were significantly higher at T_1h T_3h (P < 0.05) and T_6h (P < 0.01) when compared to baseline (induction), also it was noticed a significant difference among the groups at T_6h (Pet values were higher than Tra 2 and Tra 4; P < 0.05).

Conclusions

Tramadol provided adequate analgesia and it was more effective than pethidine to at least six hours for the studied animals. At the higher dose (4 mg/kg) tramadol is probably more effective, since rescue analgesia was not necessary. No significant changes were observed physiological parameter that could contraindicate the use of these opioid in described doses, for the feline species.

Pharmacokinetics of tramadol after subcutaneous administration in a critically ill population and in a healthy cohort

Background

Tramadol is an atypical centrally acting analgesic agent available as both oral and parenteral preparations. For patients who are unable to take tramadol orally, the subcutaneous route of administration offers an easy alternative to intravenous or intramuscular routes. This study aimed to characterise the absorption pharmacokinetics of a single subcutaneous dose of tramadol in severely ill patients and in healthy subjects.

Methods/design

Blood samples (5 ml) taken at intervals from 2 minutes to 24 hours after a subcutaneous dose of tramadol (50 mg) in 15 patients (13 male, two female) and eight healthy male subjects were assayed using high performance liquid chromatography. Pharmacokinetic parameters were derived using a non-compartmental approach.

Results

There were no statistically significant differences between the two groups in the following parameters (mean ± SD): maximum venous concentration 0.44 ± 0.18 (patients) vs. 0.47 ± 0.13 (healthy volunteers) mcg/ml (p = 0.67); area under the plasma concentration-time curve 177 ± 109 (patients) vs. 175 ± 75 (healthy volunteers) mcg/ml*min (p = 0.96); time to maximum venous concentration 23.3 ± 2 (patients) vs. 20.6 ± 18.8 (healthy volunteers) minutes (p = 0.73) and mean residence time 463 ± 233 (patients) vs. 466 ± 224 (healthy volunteers) minutes (p = 0.97).

Conclusions

The similar time to maximum venous concentration and mean residence time suggest similar absorption rates between the two groups. These results indicate that the same dosing regimens for subcutaneous tramadol administration may therefore be used in both healthy subjects and severely ill patients.

Trial registration

ACTRN12611001018909

Abuse liability and reinforcing efficacy of oral tramadol in humans

BACKGROUND

Tramadol, a monoaminergic reuptake inhibitor, is hepatically metabolized to an opioid agonist (M1). This atypical analgesic is generally considered to have limited abuse liability. Recent reports of its abuse have increased in the U.S., leading to more stringent regulation in some states, but not nationally. The purpose of this study was to examine the relative abuse liability and reinforcing efficacy of tramadol in comparison to a high (oxycodone) and low efficacy (codeine) opioid agonist.

METHODS

Nine healthy, non-dependent prescription opioid abusers (6 male and 3 female) participated in this within-subject, randomized, double blind, placebo-controlled study. Participants completed 14 paired sessions (7 sample and 7 self-administration). During each sample session, an oral dose of tramadol (200 and 400 mg), oxycodone (20 and 40 mg), codeine (100 and 200 mg) or placebo was administered, and a full array of abuse liability measures was collected. During self-administration sessions, volunteers were given the opportunity to work (via progressive ratio) for the sample dose or money.

RESULTS

All active doses were self-administered; placebo engendered no responding. The high doses of tramadol and oxycodone were readily self-administered (70%, 59% of available drug, respectively); lower doses and both codeine doses maintained intermediate levels of drug taking. All three drugs dose-dependently increased measures indicative of abuse liability, relative to placebo; however, the magnitude and time course of these and other pharmacodynamic effects varied qualitatively across drugs.

CONCLUSIONS

This study demonstrates that, like other mu opioids, higher doses of tramadol function as reinforcers in opioid abusers, providing new empirical data for regulatory evaluation.

Side-effects of analgesic kyotorphin derivatives: advantages over clinical opioid drugs

The adverse side-effects associated with opioid administration restrain their use as analgesic drugs and call for new solutions to treat pain. Two kyotorphin derivatives, kyotorphin-amide (KTP-NH₂) and ibuprofen-KTP-NH₂ (IbKTP-NH₂) are promising alternatives to opioids: they trigger analgesia via an indirect opioid mechanism and are highly effective in several pain models following systemic delivery. In vivo side-effects of KTP-NH₂ and IbKTP-NH₂ are, however, unknown and were evaluated in the present study using male adult Wistar rats. For comparison purposes, morphine and tramadol, two clinically relevant opioids, were also studied. Results showed that KTP-derivatives do not cause constipation after systemic administration, in contrast to morphine. Also, no alterations were observed in blood pressure or in food and water intake, which were only affected by tramadol. A reduction in micturition was detected after KTP-NH₂ or tramadol administrations. A moderate locomotion decline was detected after IbKTP-NH₂-treatment. The side-effect profile of KTP-NH₂ and IbKTP-NH₂ support the existence of opioid-based mechanisms in their analgesic actions. The conjugation of a strong analgesic activity with the absence of the major side-effects associated to opioids highlights the potential of both KTP-NH₂ and IbKTP-NH₂ as advantageous alternatives over current opioids.

Evaluation of the analgesic effects of oral and subcutaneous tramadol administration in red-eared slider turtles

OBJECTIVE

To determine the dose- and time-dependent changes in analgesia and respiration caused by tramadol administration in red-eared slider turtles (Trachemys scripta).

DESIGN

Crossover study.

ANIMALS

30 adult male and female red-eared slider turtles.

PROCEDURES

11 turtles received tramadol at various doses (1, 5, 10, or 25 mg/kg [0.45, 2.27, 4.54, or 11.36 mg/lb], PO; 10 or 25 mg/kg, SC) or a control treatment administered similarly. Degree of analgesia was assessed through measurement of hind limb thermal withdrawal latencies (TWDLs) at 0, 3, 6, 12, 24, 48, 72, and 96 hours after tramadol administration. Nineteen other freely swimming turtles received tramadol PO (5, 10, or 25 mg/kg), and ventilation (V(E)), breath frequency, tidal volume (V(T)), and expiratory breath duration were measured.

RESULTS

The highest tramadol doses (10 and 25 mg/kg, PO) yielded greater mean TWDLs 6 to 96 hours after administration than the control treatment did, whereas tramadol administered at 5 mg/kg, PO, yielded greater mean TWDLs at 12 and 24 hours. The lowest tramadol dose (1 mg/kg, PO) failed to result in analgesia. Tramadol administered SC resulted in lower TWDLs, slower onset, and shorter duration of action, compared with PO administration. Tramadol at 10 and 25 mg/kg, PO, reduced the V(E) at 12 hours by 51% and 67%, respectively, and at 24 through 72 hours by 55% to 62% and 61 % to 70%, respectively. However, tramadol at 5 mg/kg, PO, had no effect on the V(E).

CONCLUSIONS AND CLINICAL RELEVANCE

Tramadol administered PO at 5 to 10 mg/kg provided thermal analgesia with less respiratory depression than that reported for morphine in red-eared slider turtles.

Efficacy of tramadol vs meperidine in vasoocclusive sickle cell crisis

Despite progress in management, patients with sickle cell disease who are experiencing acute painful episode are often incompletely treated. We compared meperidine and tramadol with respect to their effects on the hemodynamics and pain relief in patients with sickle cell disease who were admitted to the emergency department with painful crisis. A total of 68 patients with sickle cell disease were randomly assigned to receive either tramadol 1.5 mg/kg (n = 34) or meperidine 1 mg/kg (n = 34). Hemodynamic parameters were recorded at regular intervals after analgesic infusions. Pain intensity and relief were documented by visual analog and pain relief scale, respectively. Sedation level was defined according to Ramsay sedation scale. Both meperidine and tramadol administration resulted in a significant reduction in systolic and diastolic blood pressure after 2 hours (P < .05). Efficacy in pain relief between the analgesics was more rapid and better in the meperidine group, although the degree of relief were significantly improved compared to baseline levels in both groups (P < .05). Sedation was more commonly seen in the meperidine arm. None of the patients had experienced neurotoxicity. In summary, both agents had proven safe and effective for emergent use in patients with sickle cell disease. Avoiding meperidine injections as recommended with previous guidelines needs to be carefully reconsidered especially when low doses are mentioned.

Cardiorespiratory variables, bispectral index and recovery of anesthesia in dogs anesthetized with isoflurane, treated or not with tramadol

It was studied fortuitous cardiorespiratory and bispectral index changes in dogs anesthetized with isoflurane associated or not to tramadol. Sixteen dogswere distributed in two groups named CG (control group) and TG (tramadol group). General anesthesia was induced in all animals with isoflurane via mask. After 10 minutes, the animals of CG received 0.05ml/kg of saline solution at 0.9%, and TG received 2mg/kg of tramadol, both via intramuscular. It was evaluated heart rate, systolic, diastolic and mean arterial pressures; electrocardiography; respiratory rate; oxihemoglobin saturation; end tidal carbon dioxide; bispectral index and recovery of anesthesia. The administration of tramadol in dogs anesthetized with isoflurane did not produce changes in cardiorespiratory variables, bispectral index and anesthetic recovery time. In addition, this association promoted good quality of anesthetic recovery.

In vitro and in vivo vasodilator activity of racemic tramadol and its enantiomers in Wistar rats

Tramadol ((+/-)-tramadol) is an analgesic agent formulated as a racemic mixture (1:1) of (-)- and (+)-tramadol, which differ in their potency to bind to mu-opioid receptors and to inhibit monoamine-reuptake. We investigated the stereoselectivity of in vitro tramadol-induced vasodilatation of aortic rings and its effect on the arterial blood pressure measured in conscious Wistar rats. (+)-Tramadol, but not (-)-tramadol, produced a concentration-dependent relaxation of aorta precontracted with phenylephrine. The concentration-response curve was significantly altered by the removal of endothelium. Vascular relaxation was also inhibited by pre-incubation of endothelium-intact aorta with naloxone, suggesting the involvement of opioid receptors. The vasodilatation produced by tramadol was stereoselective, and the (+)-tramadol-induced vasodilatation was mediated by mu-opioid receptors and partially dependent on endothelium integrity. The hypotensive response induced by (+)-tramadol was also observed after bolus injection of 5.0 and 10.0 mg/kg. The results indicate that only high doses of tramadol cause cardiac depression and hypotension, indicating that it can be used safely.

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.

Dexmedetomidine in combination with morphine PCA provides superior analgesia for shockwave lithotripsy

PURPOSE

To compare the analgesic effects of dexmedetomidine/morphine with those of tramadol/midazolam in patients undergoing extracorporeal shockwave lithotripsy (ESWL) for urinary calculi.

METHODS

Sixty patients were randomized to receive either dexmedetomidine 1 micro g*kg(-1) iv followed by 0.5 micro g*kg(-1)*hr(-1) infusion together with morphine patient-controlled analgesia [(PCA); 2 mg bolus, five minutes lockout, 2 mg*hr(-1) infusion; (Group DEX)], or tramadol 1.5 mg*kg(-1) pre-mixed with midazolam 30 micro g*kg(-1) iv followed by tramadol PCA [20 mg bolus, five minute lockout, 20 mg*hr(-1) infusion; (Group TRA)]. Pain was assessed at baseline and every 15 min thereafter. Patients' and urologist's satisfaction with analgesia and sedation were determined on a seven-point scale ranging from 1 (extremely dissatisfied) to 7 (extremely satisfied). Patient's discharge time was also documented.

RESULTS

Visual analogue scale scores over time were consistently lower in Group DEX compared with Group TRA (P = 0.001). Patients' satisfaction with analgesia (5 +/- 1 vs 4 +/- 2, P = 0.012) and with sedation (6 +/- 1 vs 5 +/- 1, P = 0.020), and urologist's satisfaction (6 +/- 1 vs 4 +/- 2, P = 0.001) were all higher amongst Group DEX patients compared with Group TRA. There was no difference between discharge times of patients in Group DEX compared with those in Group TRA [85 (60,115) min vs 65 (40,95) min, P = 0.069].

CONCLUSION

Dexmedetomidine in combination with morphine PCA provided better analgesia for ESWL and was associated with higher patients' and urologist's satisfaction when compared with a tramadol/midazolam PCA combination.

A comparison of preoperative tramadol and morphine for the control of early postoperative pain in canine ovariohysterectomy

OBJECTIVE

To compare morphine with tramadol for the management of early postoperative pain following ovariohysterectomy after pyometra in dogs.

STUDY DESIGN

Prospective randomized blinded clinical trial.

ANIMALS

Thirty female dogs, 2-14 years old.

METHODS

Animals were randomly divided into two equal groups. Group 1 received 0.2 mg kg-1 of morphine IV and group 2 received 2 mg kg-1 of tramadol IV after the induction of anesthesia. The dogs were premedicated with acepromazine, and anesthesia was induced with intravenous midazolam and ketamine. Isoflurane was used for the maintenance of anesthesia. The variables measured were: analgesia; sedation; cardiac and respiratory rates; arterial blood pressure; end-tidal isoflurane and carbon dioxide (Pe'CO2); oxyhemoglobin saturation (SpO2); plasma catecholamines; serum cortisol and glucose concentrations; pH and blood gases. The animals were monitored for 6 hours after the administration of the analgesic agent.

RESULTS

There were no differences between the two groups with regard to analgesia, sedation, SpO2, pH and blood gases, cardiovascular variables, glucose, catecholamine and cortisol concentrations. Forty minutes postopioid administration, the end-tidal isoflurane concentration was significantly lower in the morphine-treated group as compared to the tramadol group. At 30 minutes following opioid injection, Pe'CO2 was significantly higher in the morphine group than in the tramadol group. Two dogs in the tramadol group and one in the morphine group were given morphine postoperatively because of increasing pain scores.

CONCLUSION AND CLINICAL RELEVANCE

Morphine and tramadol, administered preemptively can be used safely in dogs to control early pain after ovariohysterectomy without significant adverse effects.

Tramadol--present and future

The atypical opioid, tramadol, has recently been introduced into Australia and New Zealand. Tramadol's efficacy in a wide range of acute and chronic pain states, its multi-formulation availability, and its low serious side-effect potential at high doses and in prolonged therapy, combine to bestow on it a user-friendly profile, for short- and long-term use in hospitals and communities. This paper reviews the following: its formulation and routes of administration; its unique enantiomeric biochemistry and metabolism; its triple mechanisms of action; its pharmacokinetics and pharmacodynamics; its analgesic efficacy compared with other opioids; the indications for its clinical use in a variety of acute and chronic (including cancer) painful states; its specific use in the elderly, in paediatric and in obstetric patients; its adverse event (including drug interaction) and safety profile; its advantages in terms of its relative lack of respiratory depression, major organ toxicity and histamine release, and dependence and abuse potential. The review looks at new uses for this drug and what can be expected in this area in the future.