Tramadol: a review of its use in perioperative pain

On the mechanism of anticonvulsant effect of tramadol in mice

The present study was conducted to examine the effects of tramadol, an atypical opioid on convulsive behaviour in maximal electroshock (MES) seizure test on mice. Moreover, an attempt was also made to investigate the role of possible receptor mechanisms involved. MES seizures were induced via transauricular electrodes (60 mA, 0.2 sec). Seizure severity was determined by (1) the duration of tonic hindlimb extensor (THE) phase and by (2) mortality due to electroconvulsions. Intraperitoneal (i.p.) administration of tramadol dose-dependently (10-50 mg/kg) decreased the duration of THE phase of MES. The anticonvulsant effect of tramadol was antagonized by the opioid antagonists, naloxone in high dose, and MR2266, a selective kappa antagonist but not by naltrindole, a delta opioid antagonist. Coadministration of either gamma-aminobutyric acid (GABA)-ergic drugs (diazepam, GABA, muscimol and baclofen) or N-methyl-D-aspartate (NMDA) receptor antagonist, MK801 with tramadol augmented the anticonvulsant effect of the latter drug. By contrast, flumazenil, a central benzodiazepine (BZD) receptor antagonist, counteracted the diazepam-induced facilitation of anti-MES effect of tramadol. Similarly, delta-aminovaleric acid (DAVA), a GABAB receptor antagonist, abolished the facilitatory effect of baclofen, a GABAB agonist on anti-MES action of tramadol. These BZD-GABAergic antagonists, flumazenil or DAVA, on their own also antagonized the anti-MES effect of tramadol administered alone. No significant effect on mortality was observed in any of the studied groups. Taken together, the current results have demonstrated a possible role for multitude of important neurotransmitter systems, i.e., opioid (kappa), GABAA-BZD receptors system, GABAB receptors and NMDA channel involvement in the antielectroshock effect of tramadol in mice.

The Analgesic Efficacy of Intravenous Versus Oral Tramadol for Preventing Postoperative Pain After Third Molar Surgery

PURPOSE

The aim of this study was to compare the analgesic efficacy of single-dose preoperative intravenous versus oral tramadol for preventing pain after third molar surgery.

PATIENTS AND METHODS

Seventy-two patients undergoing elective third molar surgery were randomized to receive either intravenous (n = 36) or oral (n = 36) tramadol 50 mg. The intravenous group received an oral placebo capsule followed by intravenous tramadol 50 mg preoperatively. The oral tramadol group received a 50-mg oral tramadol capsule followed by intravenous placebo saline preoperatively. In both groups, a standard intravenous sedation technique was administered and the impacted third molars were removed under local anesthesia. The difference in postoperative pain was assessed by 4 primary end points: hourly pain intensity as measured by a 100-mm visual analog scale for 8 hours, time to rescue analgesic, postoperative acetaminophen consumption, and a 5-point global assessment scale (0 = poor, 1 = fair, 2 = good, 3 = very good, and 4 = excellent).

RESULTS

Throughout the 8-hour investigation period, patients reported significantly lower pain intensity scores in the intravenous versus oral group (15.9 +/- 9.6 mm versus 36.9 +/- 17.2 mm, P = .03). Patients also reported significantly longer time to rescue analgesic (7.0 hours versus 3.5 hours, P = .00001), lesser postoperative acetaminophen consumption (1,823 +/- 1,266 mg versus 3,558 +/- 1,418 mg, P = .000006), and better global assessment (2.6 +/- 0.9 versus 1.1 +/- 0.8, P = .01) for the intravenous versus oral group.

CONCLUSIONS

We conclude that preoperative intravenous tramadol is superior to oral tramadol for preventing postoperative pain following third molar surgery. However, it should be noted that there is a difference in the bioavailability between the 2 formulations of up to 30%, which may explain the findings.

Comparison of Lumbar Epidural Tramadol and Lumbar Epidural Morphine for Pain Relief After Thoracotomy: A Repeated-Dose Study

OBJECTIVE

The purpose of this study was to compare lumbar epidural morphine and lumbar epidural tramadol with respect to onset and duration of analgesia, analgesic efficacy, and drug-related side effects after muscle-sparing thoracotomy.

DESIGN

Prospective, randomized, double-blind, clinical study.

SETTING

Single university hospital.

PARTICIPANTS

Forty patients who underwent elective muscle-sparing thoracotomy.

INTERVENTIONS

Before anesthesia induction, an epidural catheter was placed in the L2-3 or L3-4 interspace using the loss-of-resistance technique. On arrival at the intensive care unit, patients were randomized to receive doses of either 100 mg of tramadol (group T) or 4 mg of morphine (group M) via the lumbar epidural catheter. Each dose was diluted in 10 mL of normal saline. On awakening from anesthesia, if the patient's pain score on a 0- to 100-mm visual analog scale was above 40 mm, the initial epidural drug dose was administered. The initial injection in each case was taken as time 0. Subsequent pain scores above 40 mm were considered indications for epidural dosing; each patient was allowed 2 doses in the first 12 hours postoperatively and 2 more in the second 12 hours.

MEASUREMENTS AND MAIN RESULTS

The groups' analgesia onset times were similar, but duration of analgesia was significantly shorter in group T than in group M (p < 0.01). There were no differences between the groups with respect to pain scores at rest or during coughing at any of the time points investigated. Sedation scores were lower in group T than in group M at 1, 2, 3, 4, and 8 hours (p value range, 0.0001-0.05). Compared with group T, group M showed significantly greater drops in arterial oxygen tension from baseline at 3, 4, 8, and 12 hours (p value range, 0.0001-0.05). The group means for arterial carbon dioxide tension and respiratory rate were similar at all time points investigated.

CONCLUSION

The study revealed that the quality of analgesia achieved with repeated doses of lumbar epidural tramadol after muscle-sparing thoracotomy is comparable to that achieved with repeated doses of lumbar epidural morphine. Compared with morphine, lumbar epidural tramadol results in less sedation and a less-pronounced decrease in oxygenation.

Synergic Antinociceptive Interaction between Tramadol and Gabapentin after Local, Spinal and Systemic Administration

The possible interaction between tramadol and gabapentin on formalin-induced nociception in the rat was assessed. Tramadol, gabapentin or a fixed-dose ratio combination of gabapentin and tramadol were administered peripherally, spinally and orally to rats, and the antinociceptive effect was determined in the 1% formalin test. Isobolographic analyses were used to define the nature of the interactions between drugs. Tramadol, gabapentin and tramadol-gabapentin combinations produced a dose-dependent antinociceptive effect when administered locally, spinally or orally. ED30 values were estimated for the individual drugs and isobolograms were constructed. Theoretical ED30 values for the combination estimated from the isobolograms were 126.8 +/- 11.1 microg/paw, 23.1 +/- 2.6 microg/rat, and 2.23 +/- 0.32 mg/kg for the local, intrathecal and oral routes, respectively. These values were significantly higher than the actually observed ED30 values which were 13.3 +/- 2.1 microg/paw, 8.1 +/- 0.6 microg/rat and 0.71 +/- 0.10 mg/kg, indicating a synergistic interaction. Although efficacy was not improved, local peripheral administration resulted in the highest increase in potency, being about tenfold. Spinal and systemic administration increased potency threefold. Data indicate that low doses of the tramadol-gabapentin combination can interact synergistically to reverse formalin-induced nociception and may represent a therapeutic advantage for clinical treatment of inflammatory pain.

The effects of the tramadol metabolite O-desmethyl tramadol on muscarinic receptor-induced responses in Xenopus oocytes expressing cloned M1 or M3 receptors

O-desmethyl tramadol is one of the main metabolites of tramadol. It has been widely used clinically and has analgesic activity. Muscarinic receptors are involved in neuronal functions in the brain and autonomic nervous system, and much attention has been paid to these receptors as targets for analgesic drugs in the central nervous system. We have reported that tramadol inhibits the function of type-1 muscarinic (M(1)) receptors and type-3 muscarinic (M(3)) receptors, suggesting that muscarinic receptors are sites of action of tramadol. However, the effects of O-desmethyl tramadol on muscarinic receptor functions have not been studied in detail. In this study, we investigated the effects of O-desmethyl tramadol on M(1) and M(3) receptors, using the Xenopus oocyte expression system. O-desmethyl tramadol (0.1-100 microM) inhibited acetylcholine (ACh)-induced currents in oocytes expressing the M(1) receptors (half-maximal inhibitory concentration [IC(50)] = 2 +/- 0.6 microM), whereas it did not suppress ACh-induced currents in oocytes expressing the M(3) receptor. Although GF109203X, a protein kinase C inhibitor, increased the ACh-induced current, it had little effect on the inhibition of ACh-induced currents by O-desmethyl tramadol in oocytes expressing M(1) receptors. The inhibitory effect of O-desmethyl tramadol on M(1) receptor was overcome when the concentration of ACh was increased (K(D) with O-desmethyl tramadol = 0.3 microM). O-desmethyl tramadol inhibited the specific binding of [(3)H]quinuclidinyl benzilate ([(3)H]QNB) to the oocytes expressed M(1) receptors (IC(50) = 10.1 +/- 0.1 microM), whereas it did not suppress the specific binding of [(3)H]QNB to the oocytes expressed M(3) receptors. Based on these results, O-desmethyl tramadol inhibits functions of M(1) receptors but has little effect on those of M(3) receptors. This study demonstrates the molecular action of O-desmethyl tramadol on the receptors and may help to explain its neural function.

Tramadol: does it have a role in emergency medicine?

Tramadol is a synthetic analgesic new to the Australasian market where its use is rapidly increasing. It is used extensively overseas, particularly in Europe where it has been popular since its introduction in Germany in the late 1970s. Tramadol has a dual mechanism of action: weak mu opioid receptor agonist and a reuptake inhibitor of serotonin and noradrenaline. Thus, it has distinct advantages and disadvantages compared to other available analgesics. Its use is advocated in a variety of acute and chronic pain states as well as some non-analgesic applications. The use of tramadol in an emergency setting is not well studied, with most published trials assessing its efficacy and tolerability in postoperative or dental models. This literature review concludes that tramadol does not offer any particular benefits over existing analgesics for the majority of emergency pain relief situations.

[Chiral switch: towards a better benefit-risk ratio?]

The chirality of drugs has emerged as a major theme in drug design, discovery, development and intellectual property. Single enantiomers offer some advantages and two options are available: the switch from an existing racemic drug to the single enantiomer or the development of an enantiomerically pure chiral drug. At present, the second possibility is systematically considered. The possibility of chiral switch has led to innovative drugs. However, this opportunity may be limited by several factors: the spontaneous interconversion of the two enantiomers, the pharmacokinetic profile or the selective toxicity of the most active enantiomer, and the difficulty of demonstrating the clinical superiority of one enantiomer over the racemate. Finally, the small size of the market, the policies of the drug agencies and/or the patent problem also limit the development of enantiomers. All these factors have led the pharmaceutical industry to develop new galenic forms rather than enantiomers when the patent of the racemate is expiring.

The median effective dose of tramadol and morphine for postoperative patients: a study of interactions

Tramadol is a centrally-acting analgesic drug. In a search of an effective balanced analgesia technique with a morphine-sparing component, we studied the median effective analgesic doses (ED(50)) of tramadol, morphine, and their combination to determine the nature of their interaction using an isobolographic analysis. In this double-blind, randomized, two-stage prospective study, 90 postoperative patients were enrolled in one of three groups. The dose of tramadol and morphine received by a particular patient was determined using an up-down allocation technique. Initial doses and increments were, respectively, 100 mg and 10 mg in the tramadol group and 5 mg and 1 mg in the morphine group. In the second part, a 40:3 tramadol:morphine dosing ratio was used. The threshold of effective analgesia was defined as 3 or less on a numerical pain score (0-10). Isobolographic analysis was subsequently applied. The ED(50) values (95% confidence interval) of tramadol and morphine were, respectively, 86 mg (57-115 mg) and 5.7 mg (4.2-7.2 mg). The ED(50) of the combination was 72 mg (62-82 mg) for tramadol and 5.4 mg (4-6.6.2 mg) for morphine. The combination of tramadol and morphine was infra-additive and thus not recommended for postoperative analgesia.

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.

Tramadol premedication in operative extraction of the mandibular third molar: a placebo-controlled crossover study

Anxiolytic drugs are widely used for premedication in oral surgery. Since anxiety is usually associated with the fear of pain, we tested the effects of the analgesic tramadol in premedication before operative extraction of the mandibular third molar under local anesthesia. In a double-blind crossover study, 20 patients were randomized to receive 100 mg oral tramadol or placebo 1 h before operation. Anxiety, nausea, dryness of the mouth, pain and discomfort were recorded before administration of the drug, immediately before and after operation, and 0.5, 1, and 2 h postoperatively using ungraded 0-100 mm VAS scales. Blood pressure and heart rate were measured at the same times; vigilance was tested using the Maddox Wing Test and sensorimotor performance using the Trieger Dot Test; hemoglobin oxygen saturation (SpO2) was measured using a pulse oximeter. In addition, SpO2 and heart rate were recorded continuously in nine patients using a pulse oximeter connected to a computer. The surgeon assessed the quality of operating conditions on the VAS scale. Tramadol delayed and decreased the need of analgesics on the day of operation (p < 0.05). The operating conditions were better in patients on tramadol premedication than in those on placebo during the first operation (p < 0.05), but no differences were seen in patient well-being between treatments. The second operation was less stressful than the first. Tramadol is recommended only with special indications for premedication of patients undergoing third molar extraction under local anesthesia.

Heterotopic cardiac xenotransplantation in rodents: Report of a refined technique in a hamster-to-rat model

Hamster-to-rat heterotopic cardiac xenotransplantation is widely used as an experimental model to study xenograft rejection, accommodation, and tolerance, as well as in studies aimed at developing immunosuppressive strategies in xenotransplantation. Despite its widespread application, no detailed description of a surgical technique for this model has been provided in the literature. Indeed, all publications so far on the use of this species combination refer to the rat allotransplantation technique. Hence the present paper provides a detailed, up-to-date description of the surgical method adopted at our center for the hamster-to-rat heterotopic cardiac xenotransplantation model. Considerable effort went into developing a reliable, reproducible experimental model in rodents, and the description given here is enriched with "tips" that we learned in the process. The discussion of the technique also addresses several significant related issues, e.g., the anesthesia and organ preservation solution used (aspects that, in our experience, are crucial to a good surgical outcome).

Strategies for postoperative pain management

Despite advances in our understanding of the neurobiology of nociception, postoperative pain continues to be undertreated. There are many modalities that may provide effective postoperative analgesia, including systemic (e.g. opioids, non-steroidal anti-inflammatory agents) and regional analgesic options. The particular modality or modalities utilized for a particular patient will depend on the risk-benefit profile and patient preferences. Ideally, analgesic options should be incorporated into a multimodal approach to facilitate patient recovery after surgery.

Long-term exposure of rats to tramadol alters brain dopamine and α1-adrenoceptor function that may be related to antidepressant potency

The aim of the present study was to determine whether tramadol, which has a potential antidepressant efficacy, evokes, when administered repeatedly, changes similar to the alterations induced by conventional antidepressant drugs. Repeated administration of tramadol (20 mg/kg i.p. for 21 days) enhanced the d-amphetamine-induced locomotor hyperactivity and increased the density of alpha(1)-adrenoceptors in the rat brain cortex, as measured by saturation analysis of [(3)H]prazosin binding. Autoradiographic analysis of [(3)H]7-OH-DPAT and [(3)H]raclopride binding revealed a significant up-regulation of dopamine D2 and D3 receptors in the rat nucleus accumbens upon repeated treatment with tramadol. All the above-mentioned effects induced by repeated administration of tramadol resemble the effects induced by conventional antidepressants. However, tramadol when administered repeatedly did not increase the levels of mRNA encoding for brain-derived neurotrophic factor (BDNF) and its receptor, TrkB. This is what differs tramadol from conventional antidepressants, since neurotrophic effects of these drugs have recently been postulated.

COMPARISON OF 3 DIFFERENT METHODS OF ANESTHESIA BEFORE TRANSRECTAL PROSTATE BIOPSY: A PROSPECTIVE RANDOMIZED TRIAL

PURPOSE

Periprostatic nerve block (PNB) is the most common anesthesia technique used before prostate biopsy. However, needle punctures for anesthetic infiltration may be painful and cause higher infectious complications. We assessed whether addition of rectal lidocaine gel would improve its efficacy. We also investigated the efficacy and safety of tramadol, a codeine derivative, as a noninvasive method.

MATERIALS AND METHODS

A total of 300 patients who underwent prostate biopsies were randomized into 4 groups of controls, PNB, perianal/intrarectal lidocaine gel plus PNB and tramadol. Pain was assessed with a numeric analog scale.

RESULTS

Each group consisted of 75 patients, and there was a statistically significant difference among pain scores (p = 0.001). Mean pain scores were 4.63 for controls, 2.57 for PNB, 2.03 for infiltration plus gel group and 3.11 for tramadol. Pain and discomfort were least in PNB plus gel arm. The difference of pain score between PNB alone and tramadol group did not reach statistical significance. Infectious complications were higher in the combination group, whereas there were no complications with tramadol.

CONCLUSIONS

Any form of analgesia/anesthesia was superior to none. The combination of PNB plus gel provided significantly better analgesia compared to PNB alone or tramadol. If this can be duplicated in other trials, the combination may be accepted as the new gold standard of anesthesia for prostate biopsy. The efficacy of tramadol was similar to that of PNB, and was free of complications. Therefore, tramadol may have a role before prostate biopsy, which needs to be explored.

Pharmacokinetics of tramadol and the metabolite O-desmethyltramadol in dogs

Tramadol is an analgesic and antitussive agent that is metabolized to O-desmethyltramadol (M1), which is also active. Tramadol and M1 exert their mode of action through complex interactions between opiate, adrenergic, and serotonin receptors. The pharmacokinetics of tramadol and M1 were examined following intravenous and oral tramadol administration to six healthy dogs, as well as intravenous M1 to three healthy dogs. The calculated parameters for half-life, volume of distribution, and total body clearance were 0.80 +/- 0.12 h, 3.79 +/- 0.93 L/kg, and 54.63 +/- 8.19 mL/kg/min following 4.4 mg/kg tramadol HCl administered intravenously. The systemic availability was 65 +/- 38% and half-life 1.71 +/- 0.12 h following tramadol 11 mg/kg p.o. M1 had a half-life of 1.69 +/- 0.45 and 2.18 +/- 0.55 h following intravenous and oral administration of tramadol. Following intravenous M1 administration the half-life, volume of distribution, and clearance of M1 were 0.94 +/- 0.09 h, 2.80 +/- 0.15 L/kg, and 34.93 +/- 5.53 mL/kg/min respectively. Simulated oral dosing regimens at 5 mg/kg every 6 h and 2.5 mg/kg every 4 h predict tramadol and M1 plasma concentrations consistent with analgesia in humans; however, studies are needed to establish the safety and efficacy of these doses.

Effects of tramadol on α2-adrenergic receptors in the rat brain

In recent years, it has been postulated that tramadol, used mainly for the treatment of moderate to severe pain, might display a potential as an antidepressant drug. The present study investigated the effects of acute and repeated tramadol administration on the binding of [3H]RX 821002, a selective alpha2-adrenergic receptor ligand, in the rat brain. Male Wistar rats were used. Tramadol (20 mg/kg, i.p.) administered acutely (single dose), at 24 h after dosing, induced a significant decrease in the alpha2-adrenergic receptors in all brain regions studied. The most pronounced effects were observed in all subregions of the olfactory system, nucleus accumbens and septum, thalamus, hypothalamus, amygdala, and cerebral cortex. Repeated treatment with tramadol (20 mg/kg, i.p., once daily for 21 days) also induced statistically significant downregulation of [3H]RX 821002 binding sites in the rat brain. However, the effect--although statistically significant--was less pronounced than in the group treated acutely with the drug. Since drugs such as mianserin and mirtazapine are potent antagonists of central alpha2-adrenergic receptors and are effective antidepressants, it is tempting to suggest that, in addition to other alterations induced by tramadol, downregulation of these receptors may represent a potential antidepressant efficacy. On the other hand, one should be careful to avoid the treatment of chronic pain with tramadol in patients already receiving antidepressant drugs. Tramadol-induced downregulation of alpha2-adrenergic receptors--when combined with ongoing antidepressant therapy with drugs, which themselves inhibit serotonin reuptake or are antagonists of alpha2-adrenergic receptors--might cause threatening complications.

Migration behaviour and separation of tramadol metabolites and diastereomeric separation of tramadol glucuronides by capillary electrophoresis

Capillary electrophoresis with UV detection was used to separate tramadol (TR), a centrally acting analgesic, and its five phase I (M1, M2, M3, M4, M5) and three phase II metabolites (glucuronides of M1, M4 and M5). Several factors were evaluated in optimisation of the separation: pH and composition of the background electrolyte and the influence of a micellar modifier, sodium dodecyl sulfate. Baseline separation of TR and all the analytes was obtained with use of 65 mM tetraborate electrolyte solution at pH 10.65. The lowest concentrations of the analytes that could be detected were below 1 microM for the O-methylated, below 2 microM for the phenolic and ca. 7 microM for the glucuronide metabolites. The suitability of the method for screening of real samples was tested with an authentic urine sample collected after a single oral dose (50 mg) of TR. After purification and five-fold concentration of the sample (solid-phase extraction with Oasis MCX cartridges), the parent drug TR and its metabolites M1, M1G, M5 and M5G were easily detected, in comparison with standards, in an interference-free area of the electropherogram. Diastereomeric separation of TR glucuronides in in vitro samples was achieved with 10 mM ammonium acetate-100 mM formic acid electrolyte solution at pH 2.75 and with basic micellar 25 mM tetraborate-70 mM SDS electrolyte solution at pH 10.45. Both separations showed that glucuronidation in vitro produces glucuronide diastereomers in different amounts. The authentic TR urine sample was also analysed by micellar method, but unambiguous identification of the glucuronide diastereomers was not achieved owing to many interferences.

A double-blind placebo-controlled comparison of tramadol/acetaminophen and tramadol in patients with postoperative dental pain

The objective of this study was to compare the analgesic efficacy of tramadol/acetaminophen (APAP) (total dose 75 mg/650 mg) and tramadol (total dose 100 mg) for the control of pain after oral surgery. A total of 456 patients with moderate-to-severe pain within 5 h after extraction of two or more third molars were randomized to receive two identical encapsulated tablets containing tramadol/APAP 37.5 mg/325 mg, tramadol 50 mg, or placebo. Tramadol/APAP was superior to tramadol (P < 0.001) or placebo (P < 0.001) on all efficacy measures: total pain relief (PAR) over 6 h (7.4, 2.5, and 1.5, respectively, on a scale of 0-24); sum of pain intensity differences (PIDs) (3.1, 0.6, and 0.1, respectively, on a scale of -6 to 18); and sum of PAR and PID (10.5, 3.1, and 1.6, respectively, on a scale of -6 to 42). Median times to onset of perceptible and meaningful PAR were 37.6 and 126.5 min, respectively, for the tramadol/APAP group (P < 0.001) for each, compared with tramadol and placebo arms). The most common adverse events with active treatment were nausea, dizziness, and vomiting; these events occurred more frequently in the tramadol group than in the tramadol/APAP group. This study established the superiority of tramadol/APAP 75 mg/650 mg over tramadol 100 mg in the treatment of acute pain following oral surgery.

Mechanisms of Inflammatory Pain

The study and treatment of clinical pain has historically identified particular pain syndromes and linked their etiology with disease factors. Missing in this approach is consideration of the mechanisms accounting for the pain that is experienced by the patient. The recent increase in our understanding of how peripheral and central mechanisms contribute to the perception of pain, including the identified role of prostaglandins, has led to a shift in treatment strategy to directly target these mechanisms. This article provides a brief overview of pain mechanisms, focusing on inflammatory pain, and discusses the role of cyclooxygenase (COX)-2 inhibitors as analgesic agents.

Postoperative pain control in children: a guide to drug choice

Postoperative pain in children can usually be well controlled with a combination of analgesics, including acetaminophen (paracetamol), NSAIDs, opioids, and local/regional anesthesia. Recent research has shown that the dosage of acetaminophen required to provide analgesia is higher than the traditional dosages used for the regulation of elevated body temperature. Rectal administration of acetaminophen gives a lower and more variable bioavailability compared with oral administration. There is growing experience with the use of NSAIDs in children and several studies have demonstrated the relatively strong analgesic potential of these drugs. Titration of opioids to analgesic effect, and the use of nurse- and patient-controlled continuous opioid infusions in children have gained widespread use and, with proper education and supervision, are considered excellent methods of pain control. Local peripheral and central blocks decrease the need for anesthetics during surgery and provide effective postoperative pain relief.

The Inhibitory Effects of Tramadol on 5-Hydroxytryptamine Type 2C Receptors Expressed in Xenopus Oocytes

Although tramadol is widely available as an analgesic, its mechanism of antinociception remains unresolved. Serotonin (5-hydroxytryptamine, 5-HT) is a monoaminergic neurotransmitter that modulates numerous sensory, motor, and behavioral processes. The 5-HT type 2C receptor (5-HT(2C)R) is one of the major 5-HT receptor subtypes and is implicated in many important effects of 5-HT, including pain, feeding, and locomotion. In this study, we used a whole-cell voltage clamp to examine the effects of tramadol on 5-HT-induced Ca(2+)-activated Cl(-) currents mediated by 5-HT(2C)R expressed in Xenopus oocytes. Tramadol inhibited 5-HT-induced Cl(-) currents at pharmacologically relevant concentrations. The protein kinase C (PKC) inhibitor, bisindolylmaleimide I (GF109203x), did not abolish the inhibitory effects of tramadol on the 5-HT(2C)R-mediated events. We also studied the effects of tramadol on [(3)H]5-HT binding to 5-HT(2C)R expressed in Xenopus oocytes, and found that it inhibited the specific binding of [(3)H]5-HT to 5-HT(2C)R. Scatchard analysis of [(3)H]5-HT binding revealed that tramadol altered the apparent dissociation constant for binding without changing maximal binding, indicating competitive inhibition. The results suggest that tramadol inhibits 5-HT(2C)R function, and the mechanism of this inhibitory effect seems to involve competitive displacement of the 5-HT binding to the 5-HT(2C)R, rather than via activation of the PKC pathway.

IMPLICATIONS

We examined the effects of tramadol on 5-hydroxytryptamine type 2C receptor (5-HT(2C)R) expressed in Xenopus oocytes. Tramadol inhibited 5-HT(2C)R function and the specific binding of [(3)H]5-HT to 5-HT(2C)R in a competitive manner. From these data, the mechanism of the inhibitory effect on 5-HT(2C)R might involve the competitive displacement of 5-HT binding to the 5-HT(2C)R.

Preoperative intravenous tramadol versus ketorolac for preventing postoperative pain after third molar surgery

The objective of this study was to compare the analgesic efficacy of a single-dose of preoperative intravenous tramadol versus ketorolac in preventing pain after third molar surgery. Sixty-four patients undergoing elective third molar surgery were randomly assigned into one of the two groups (32 in each group): Group I received tramadol 50 mg, and Group 2 received ketorolac 30 mg intravenously preoperatively before the surgery. After injection of the study drugs, a standard intravenous sedation technique was administered and the impacted third molars were removed under local anaesthetic. The difference in postoperative pain was assessed by four primary end-points: pain intensity as measured by a 100-mm visual analogue scale hourly for 12 h, median time to rescue analgesic, postoperative acetaminophen consumption, and patient's global assessment. Throughout the 12-h investigation period, patients reported significantly lower pain intensity scores in the ketorolac versus tramadol group (P = 0.05, Mann-Whitney U-test). Patients also reported significantly longer median time to rescue analgesic (9.0 h versus 7.0 h, P = 0.007, log rank test), lesser postoperative acetaminophen consumption (P = 0.02, Mann-Whitney U-test) and better global assessment (P = 0.01, chi2 test) for the ketorolac versus tramadol group. Preoperative intravenous ketorolac 30 mg is more effective than tramadol 50 mg in the prevention of postoperative dental pain.

Nefopam, a nonsedative benzoxazocine analgesic, selectively reduces the shivering threshold in unanesthetized subjects

BACKGROUND

The analgesic nefopam does not compromise ventilation, is minimally sedating, and is effective as a treatment for postoperative shivering. The authors evaluated the effects of nefopam on the major thermoregulatory responses in humans: sweating, vasoconstriction, and shivering.

METHODS

Nine volunteers were studied on three randomly assigned days: (1) control (saline), (2) nefopam at a target plasma concentration of 35 ng/ml (low dose), and (3) nefopam at a target concentration of 70 ng/ml (high dose, approximately 20 mg total). Each day, skin and core temperatures were increased to provoke sweating and then reduced to elicit peripheral vasoconstriction and shivering. The authors determined the thresholds (triggering core temperature at a designated skin temperature of 34 degrees C) by mathematically compensating for changes in skin temperature using the established linear cutaneous contributions to control of each response.

RESULTS

Nefopam did not significantly modify the slopes for sweating (0.0 +/- 4.9 degrees C. microg-1. ml; r2 = 0.73 +/- 0.32) or vasoconstriction (-3.6 +/- 5.0 degrees C. microg-1. ml; r2 = -0.47 +/- 0.41). In contrast, nefopam significantly reduced the slope of shivering (-16.8 +/- 9.3 degrees C. microg-1. ml; r2 = 0.92 +/- 0.06). Therefore, high-dose nefopam reduced the shivering threshold by 0.9 +/- 0.4 degrees C (P < 0.001) without any discernible effect on the sweating or vasoconstriction thresholds.

CONCLUSIONS

Most drugs with thermoregulatory actions-including anesthetics, sedatives, and opioids-synchronously reduce the vasoconstriction and shivering thresholds. However, nefopam reduced only the shivering threshold. This pattern has not previously been reported for a centrally acting drug. That pharmacologic modulations of vasoconstriction and shivering can be separated is of clinical and physiologic interest.

Efeitos da titulação de doses no perfil de tolerabilidade de Tramadol de liberação prolongada* em pacientes com dor crônica não-oncológica

Este estudo multicêntrico teve por objetivo comparar os efeitos de dois esquemas posológicos no perfil de tolerabilidade do tramadol de liberação prolongada em pacientes com dor crônica não-oncológica. A casuística envolveu 189 pacientes com idade entre 14 e 75 anos, divididos em 2 grupos aleatoriamente: grupo A com 96 e o grupo B com 93 pacientes que receberam a medicação do estudo por 15 dias. O grupo A utilizou uma dose inicial de tramadol de liberação prolongada de 50mg a cada 12 horas por 3 a 7 dias, passando para uma dose de manutenção de 100mg a cada 12 horas até o 15º dia. O grupo B fez uso de uma dose padronizada de 100mg a cada 12 horas de tramadol de liberação prolongada durante os 15 dias do estudo. Os aspectos analisados foram o tipo de dor crônica não-oncológica, a intensidade da dor através da escala visual analógica, a aderência ao tratamento prescrito, a necessidade do uso da medicação de resgate, os efeitos adversos, a avaliação global da eficácia pelo médico e pelo paciente, bem como a tolerabilidade global na opinião do médico e do paciente. A dor de origem músculo-esquelética, definida como dor muscular com suas inserções no osso, foi a mais freqüente com 45,8% dos casos no grupo A, enquanto a dor osteoarticular foi a mais observada no grupo B (47,3%). Verificou-se uma melhora altamente significante tanto intra grupos como entre grupos, quanto à intensidade da dor, com redução de 67% em ambos os grupos. No grupo A, 77,1% dos pacientes cumpriram adequadamente o tratamento prescrito e no grupo B, a proporção foi de 75,3%, não havendo diferença estatisticamente significativa entre os grupos. Os grupos foram semelhantes entre si quanto à utilização da medicação de resgate, onde apenas 9,7% dos pacientes do grupo A e 15,1% do grupo B necessitaram-na durante o período do estudo. Não houve diferença significante na freqüência de eventos adversos nos dois grupos ( 30,2% e 36,6% respectivamente). Nos pacientes cuja dose final foi de 200mg/dia, a avaliação global da eficácia foi considerada boa e excelente pelos investigadores no grupo A em 86,7% dos pacientes e no grupo B o resultado foi de 78,8%. Os pacientes do grupo A consideraram a avaliação global da eficácia como boa e excelente em 88,9% e no grupo B 78,8%. A tolerabilidade da droga foi considerada entre boa e excelente pelos investigadores no grupo A em 86% e no grupo B o resultado foi de 77,2%. Os pacientes consideraram a tolerabilidade da droga como boa e excelente no grupo A em 77,4% e no grupo B o resultado foi de 71,5%. Em conclusão, os dois grupos de tratamento foram estatisticamente semelhantes em relação a todos os parâmetros estudados, com exceção da intensidade da dor, a qual foi inicialmente maior no grupo B, sendo equivalente em ambos os grupos ao final do estudo. Houve uma tendência favorável, porém não significante, ao esquema terapêutico de titulação de doses.

Stereochemistry in clinical medicine: a neurological perspective

Stereoisomers are compounds that have identical sets of atoms configured in the same positions but are arranged differently spatially. Approximately 25% of contemporary drugs are marketed and used as racemates (i.e., as equimolar mixtures of stereoisomers). This may have major clinical implications, as stereoisomers may possess qualitative and/or quantitative differences in pharmacological effects, plasma protein and tissue binding, metabolic and renal clearance. There are many examples of racemic drugs manufactured and used as single stereoisomers in the field of neurology including the anti-Parkinsonian drugs levodopa, selegiline, apomorphine and entacapone, the antiepileptic drugs tiagabine and levetiracetam, the secondary stroke prevention agent clopidogrel and the acetylcholinesterase inhibitor rivastigmine. The role of drug stereochemistry in the re-evaluation of established drugs and the production of new agents is becoming increasingly important as pharmaceutical companies endeavour to show proof of "no penalty" for the introduction of a racemic new drug over one or other of its single stereoisomers.

Effect of intrathecal tramadol administration on postoperative pain after transurethral resection of prostate

BACKGROUND

Tramadol administered epidurally has been demonstrated to decrease postoperative analgesic requirements. However, its effect on postoperative analgesia after intrathecal administration has not yet been studied. In this double-blind, placebo-controlled study, the effect of intrathecal tramadol administration on pain control after transurethral resection of the prostate (TURP) was studied.

METHODS

Sixty-four patients undergoing TURP were randomized to receive bupivacaine 0.5% 3 ml intrathecally premixed with either tramadol 25 mg or saline 0.5 ml. After operation, morphine 5 mg i.m. every 3 h was administered as needed for analgesia. Postoperative morphine requirements, visual analogue scale for pain at rest (VAS) and sedation scores, times to first analgesic and hospital lengths of stay were recorded by a blinded observer.

RESULTS

There were no differences between the groups with regard to postoperative morphine requirements (mean (SD): 10.6 (7.9) vs 9.1 (5.5) mg, P=0.38), VAS (1.6 (1.2) vs 1.2 (0.8), P=0.18) and sedation scores (1.2 (0.3) vs 1.2 (0.2), P=0.89). Times to first analgesic (6.3 (6.3) vs 7.6 (6.2) h, P=0.42) and length of hospital stay (4.7 (2.8) vs 4.4 (2.2) days, P=0.66) were similar in the two groups.

CONCLUSION

Intrathecal tramadol was not different from saline in its effect on postoperative morphine requirements after TURP.

Tramadol/paracetamol

The orally administered fixed combination tablet of tramadol (centrally-acting opiate) plus paracetamol (acetaminophen; nonopiate, nonsalicylate analgesic) [37.5/325 mg] provides effective analgesia in patients with moderate to severe acute pain and those with chronic painful conditions characterised by intermittent exacerbations of pain. Two tramadol/paracetamol 37.5/325 mg tablets provided greater relief of dental pain over an 8-hour period than either agent alone, with a faster onset of action than tramadol alone and a longer duration of action than either agent as monotherapy. In patients with postoperative dental pain, two tramadol/paracetamol tablets (37.5/325 mg) provided similar analgesia to hydrocodone/paracetamol 10/650 mg over an 8-hour period. The addition of one or two tramadol/paracetamol 37.5/32 5mg tablets (up to four times daily) for 5 days to existing NSAID or cyclo-oxygenase-2 inhibitor analgesic therapy provided effective pain relief in patients with osteoarthritis flare pain. Tramadol/paracetamol 37.5/325 mg provided similar efficacy to that of codeine/paracetamol 30/300 mg in patients with chronic back pain in a 4-week, randomised, double-blind trial (a maximum of 10 tablets or capsules per day of the active drug).

Pain during bone marrow aspiration: prevalence and prevention

The prevalence, intensity, determinants and prevention of pain during bone marrow aspiration (BMA) in adults are not well defined. In the first part of this prospective study (observational phase), 132 adult hematological patients undergoing BMA after local anesthesia scored the procedural pain by means of a visual analogue scale (VAS). Moderate to severe pain was defined as a VAS score exceeding 30 mm. Eighty-six percent reported procedural pain. The VAS score (mean+/-SEM) was 27.2+/-2.1 mm. Thirty-six percent of patients graded the pain as moderate to severe. In a linear regression analysis, VAS score correlated positively with the duration of the procedure (P=0.029) and negatively with the age of the patient (P=0.006). In the second part of the study (interventional phase), 100 patients were randomized to 50 mg tramadol or placebo, given orally at least one hour before BMA. VAS scores during aspiration were significantly lower in tramadol recipients versus placebo recipients (16.5+/-3.0 mm and 28.8+/-3.4 mm, respectively, P=0.003). Pretreatment with tramadol reduced the percentage of patients with at least moderate pain from 40% to 20% (P=0.029). Four tramadol and 3 placebo recipients reported side effects (dizziness or sedation). In conclusion, notwithstanding local anesthesia, the great majority of adult hematological patients experience transient pain during BMA that is of at least moderate intensity in over a third. Pretreatment with tramadol lowers pain intensity significantly and is well tolerated.

Development of electrochemical methods for determination of tramadol--analytical application to pharmaceutical dosage forms

A square-wave voltammetric (SWV) method and a flow injection analysis system with amperometric detection were developed for the determination of tramadol hydrochloride. The SWV method enables the determination of tramadol over the concentration range of 15-75 microM with a detection limit of 2.2 microM. Tramadol could be determined in concentrations between 9 and 50 microM at a sampling rate of 90 h(-1), with a detection limit of 1.7 microM using the flow injection system. The electrochemical methods developed were successfully applied to the determination of tramadol in pharmaceutical dosage forms, without any pre-treatment of the samples. Recovery trials were performed to assess the accuracy of the results; the values were between 97 and 102% for both methods.

HPLC determination of tramadol in human breast milk

Tramadol is a centrally acting analgesic used for prevention and treatment of moderate to severe pain. It is estimated that 0.1% of the administered dose passes into breast milk causing potentially unwanted effects in nursing babies. Pharmacokinetically, breast milk is supposed to be a separate compartment into which the drug is excreted-mainly by passive diffusion. Due to a complex composition of breast milk, a suitable sample preparation procedure is needed with a subsequent chromatographic analysis for drug determination. Among several sample cleanup procedures tested we chose the liquid-liquid extraction procedure using n-hexane as an organic phase with back extraction into aqueous phase since it was considered the most suitable and the most compatible with the subsequent HPLC analysis. The precision and the reproducibility of the method were improved approximately two times by using metoprolol as an internal standard thus making the method also more robust with regard to a variable composition of milk samples. These characteristics, together with low detection limit and short analysis time, proved that the developed method is suitable for monitoring of tramadol in human breast milk.

Postoperative sensitization and pain after cesarean delivery and the effects of single im doses of tramadol and diclofenac alone and in combination

Combining different analgesic mechanisms can reduce postoperative pain. We investigated postoperative pain and sensory sensitization in a double-blinded, placebo-controlled, randomized, single-dose comparison of the monoaminergic and micro -opioid agonist tramadol, 100 mg, and diclofenac 75 mg given IM in combination or alone in 120 patients who had elective cesarean delivery. The time to first postoperative demand for rescue analgesia, pain, tramadol pharmacokinetics, and electrical sensory thresholds at or distant from the incision were studied. The median time to first rescue (interquartile range) was 197 min (70-1000 min) with tramadol plus diclofenac, 48 min (25-90 min) with tramadol plus placebo, 113 min (35-270 min) with diclofenac plus placebo, and 55 min (30-100 min) with double placebo (tramadol plus diclofenac versus all other groups, P < 0.05). Pain intensity decreased markedly over time in all groups, and time and drug effects were significant (analysis of variance; P < 0.00001). Side effects were similarly minimal with all treatments. Pain thresholds at or distant from the incision increased significantly after surgery only with tramadol plus diclofenac. Preoperative sensory thresholds correlated with postoperative sensory changes (r > 0.53; P < 0.0001). The pharmacokinetics of tramadol and O-desmethyltramadol were unchanged by diclofenac. The combination of tramadol and diclofenac resulted in improved analgesia compared with monotherapy. Only the analgesic combination prevented both primary and secondary hyperalgesia. Preoperative sensory thresholds may allow prediction of postoperative sensitization.

IMPLICATIONS

The parenteral combination of tramadol and diclofenac resulted in more prolonged and pronounced postoperative analgesia and reduced sensory sensitization compared with the single drugs, with no increase in side effects.

Post-mortem SNP analysis of CYP2D6 gene reveals correlation between genotype and opioid drug (tramadol) metabolite ratios in blood

Tramadol is an opioid drug metabolised in phase I by cytochrome P450 (CYP) enzymes, of which CYP2D6 is mainly responsible for the O-demethylation of tramadol, but is not involved in N-demethylation. Defects in the genes encoding drug metabolising enzymes (DMEs) may lead to adverse drug effects, even to death. To aid interpretation of the forensic toxicology results, we studied how the genetic variation of the CYP2D6 gene is reflected in tramadol metabolite ratios found in post-mortem samples. In 33 Finnish autopsy cases where tramadol was found, we analysed both the CYP2D6 genotype and the concentrations of tramadol and its metabolites O- and N-demethyltramadol. As expected, we found a correlation between the number of functional CYP2D6 alleles and the ratio of tramadol to O-demethyltramadol. We also found a correlation between the number of functional alleles and the ratio of tramadol to N-demethyltramadol. This can be explained by the complementary nature of the two main tramadol demethylation pathways. No known CYP2D6 inhibitors were associated with exceptional metabolic ratios. Furthermore, no accidental tramadol poisonings were associated with a defective CYP2D6 gene. Our results on the tramadol are among the first to demonstrate that genetic variation in drug metabolising enzymes can be analysed in post-mortem blood, and that it correlates well with the parent drug to metabolite ratios. The results also suggest that genetic factors play, in general, a dominant role over other factors in the metabolism of individual drugs.

Drug effects on salivary glands: dry mouth

OBJECTIVE

To identify drugs associated with the complaint of dry mouth.

MATERIALS AND METHODS

MEDLINE was searched for papers 1980-2002 using keywords, oral, mouth, salivary, drugs, dry mouth and xerostomia, and relevant secondary references were hand-searched.

RESULTS

Evidence was forthcoming for a number of xerogenic drugs, especially antimuscarinic agents, some sympathomimetic agents, and agents affecting serotonin and noradrenaline uptake, as well as a miscellany of other drugs such as appetite suppressants, protease inhibitors and cytokines.

CONCLUSION

Dry mouth has a variety of possible causes but drugs--especially those with anticholinergic activity against the M3 muscarinic receptor--are the most common cause of reduced salivation.

Tramadol reduces the 5-HTP-induced head-twitch response in mice via the activation of mu and kappa opioid receptors

Tramadol, an atypical opioid analgesic, stimulates both opiatergic and serotonergic systems. Here we have investigated the effect of tramadol in mice on 5-hydroxyptrytophan (5-HTP)-induced head twitch response (HTR), which is an animal model for the activation of the CNS 5-HT(2A) receptors in mice. Tramadol attenuated 5-HTP-induced HTR in a dose-dependent manner as morphine. Furthermore, the nonselective opioid receptor antagonists, naloxone and diprenorphine (M5050), reversed the effect of tramadol on 5-HTP-induced HTR dose-dependently. Interestingly, in contrast to the selective delta opioid receptor antagonist NTI, beta-FNA, a selective mu receptor antagonist, and nor-BNI, a selective kappa opioid receptor antagonist, antagonized the attenuation of 5-HTP-induced HTR by tramadol. In conclusion, administration of tramadol systemically inhibits 5-HTP-induced HTR in mice by activating opiatergic system in the CNS. Our findings show that mu and kappa opioid receptors, but not delta opioid receptor, play an important role in the regulation of serotonergic function in the CNS.

Tramadol 2.5 mg x kg(-1) appears to be the optimal intraoperative loading dose before patient-controlled analgesia

PURPOSE

We previously established that a 5 mg x kg(-1) intraoperative dose can reduce the nausea/vomiting associated with tramadol patient-controlled analgesia (PCA). This study was conducted to identify the most appropriate initial dose to improve the quality of tramadol PCA.

METHODS

During general anesthesia, 60 patients undergoing knee arthroplasty were randomly allocated to receive 1.25 mg x kg(-1) (Group I), 2.5 mg x kg(-1) (Group II), 3.75 mg x kg(-1) (Group III), or 5 mg x kg(-1) (Group IV) tramadol. The emergence condition was recorded. The titration of additional tramadol 20 mg + metoclopramide 1 mg doses by PCA every five minutes was performed in the postanesthesia care unit (PACU) until the visual analogue scale (VAS) score was < or = 3. An investigator blinded to study group recorded the VAS and side effects every ten minutes.

RESULTS

In the PACU, significantly more tramadol (8.4 +/- 3.1 vs 4.3 +/- 2.1, 2.5 +/- 1.8, and 0.4 +/- 0.3, P < 0.05), and a higher incidence (15/15 vs 5/15, 3/15, and 2/15, P < 0.05) of PCA use was observed in Group I compared to Groups II-IV. VAS was significantly higher in Group I than in Groups II-IV at zero and ten minutes (P < 0.05). Unexpected delayed emergence anesthesia (> 30 min) was observed in Group III (n = 1) and in Group IV (n = 2). Sedation was more important in Groups III and IV than in Groups I and II (P < 0.05).

CONCLUSION

When considering efficacy and side-effect profile, 2.5 mg x kg(-1) of tramadol is the optimal intraoperative dose of this drug to provide effective postoperative analgesia with minimal sedation.

Controlled release formulation of tramadol hydrochloride using hydrophilic and hydrophobic matrix system

The effect of concentration of hydrophilic (hydroxypropyl methylcellulose [HPMC]) and hydrophobic polymers (hydrogenated castor oil [HCO], ethylcellulose) on the release rate of tramadol was studied. Hydrophilic matrix tablets were prepared by wet granulation technique, while hydrophobic (wax) matrix tablets were prepared by melt granulation technique and in vitro dissolution studies were performed using United States Pharmacopeia (USP) apparatus type II. Hydrophobic matrix tablets resulted in sustained in vitro drug release (>20 hours) as compared with hydrophilic matrix tablets (<14 hours). The presence of ethylcellulose in either of the matrix systems prolonged the release rate of the drug. Tablets prepared by combination of hydrophilic and hydrophobic polymers failed to prolong the drug release beyond 12 hours. The effect of ethylcellulose coating (Surelease) and the presence of lactose and HPMC in the coating composition on the drug release was also investigated. Hydrophobic matrix tablets prepared using HCO were found to be best suited for modulating the delivery of the highly water-soluble drug, tramadol hydrochloride.

Anaesthesia and postoperative analgesia in older patients with chronic obstructive pulmonary disease: special considerations

Chronic obstructive pulmonary disease (COPD) and older age are known to be independent risk factors for severe perioperative adverse outcomes after surgery. A basic understanding of the disease, careful preoperative evaluation and preparation of the patient, as well as a tailored anaesthetic management plan might help to decrease complications in this patient population. Aging affects the pharmacokinetics and pharmacodynamics of almost all drugs and therefore the dosage must be adapted in older patients. The type of anaesthesia (general versus regional anaesthesia) has no substantial effect on perioperative morbidity and mortality. Most patients, even with severe COPD, tolerate general anaesthesia without major problems. One important goal of the anaesthetic management is to prevent reflex-induced bronchoconstriction, which can be accomplished by the use of volatile anaesthetics. Early recovery can be facilitated by the use of short-acting drugs, such as propofol and the new opioid remifentanil. Judicious use of neuromuscular blocking agents is necessary because of the risk of residual paralysis, and those agents associated with histamine liberation should be avoided. Ventilation requires long expiration times to avoid air trapping, and hyperinflation to avoid the possible threat of pneumothorax and a decrease in cardiac output. For postoperative analgesia, a balanced regimen consisting of regional analgesia with local anaesthetics and NSAIDs should be preferred. This will enhance analgesia and reduce opioid toxicity, which is important in patients with COPD, where respiratory depression is especially dangerous.

Metoclopramide decreases emesis but increases sedation in tramadol patient-controlled analgesia

PURPOSE

To evaluate the clinical benefits and disadvantages of adding metoclopramide to tramadol for patient-controlled analgesia (PCA).

METHODS

Forty adult patients, undergoing elective arthroplasties, were recruited into this prospective, randomized, double-blind study. During general anesthesia all patients received 2.5 mg x kg(-1) of tramadol as a loading dose at the beginning of wound closure. In the postanesthesia care unit (PACU) patients were randomly allocated to receive PCA containing either 20 mg tramadol + 1 mg metoclopramide per millilitre (n = 20, Group T+M) or tramadol 20 mg per millilitre (n = 20, Group T). The PCA setup was 1 mL/bolus with a lockout interval of five minutes. A blinded investigator assessed the vital signs, visual analogue scale, and severity of postoperative nausea and/or vomiting in the PACU. The PCA demand and delivery, overall satisfaction rate and adverse effects were recorded in the PACU and on postoperative days one and two.

RESULTS

Nausea/vomiting scores were more severe (1.7 +/- 1.0 vs 0.2 +/- 0.5, 2.3 +/- 1.2 vs 0.6 +/- 0.6, 1.9 +/- 0.9 vs 0.2 +/- 0.5, at 12 hr, 18 hr, 24 hr, respectively, P < 0.05) and more frequent (7/20 vs 1/20, 5/20 vs 0/20 for nausea and vomiting respectively, P < 0.05) on postoperative day one in Group T compared to Group T+M. However, the incidence of sedation was higher in Group T+M (7/20 vs 1/20, P < 0.05).

CONCLUSIONS

The incidence and severity of nausea/vomiting decreased if metoclopramide was added to tramadol for PCA. An increased incidence of sedation was noticed with this drug combination.

The inhibitory effects of tramadol on muscarinic receptor-induced responses in Xenopus oocytes expressing cloned M(3) receptors

Tramadol is a widely used analgesic, but its mechanism of action is not completely understood. Muscarinic receptors are involved in neuronal function in the brain and autonomic nervous system, and much attention has been paid to these receptors as targets of analgesic drugs in the central nervous system. In this study, we investigated the effects of tramadol on type-3 muscarinic (M(3)) receptors using the Xenopus oocyte expression system. Tramadol (10 nM-100 micro M) inhibited acetylcholine-induced currents in oocytes expressing M(3) receptor. Although GF109203X, a protein kinase C inhibitor, increased the basal current, it had little effect on the inhibition of acetylcholine-induced currents by tramadol. Moreover, tramadol inhibited the specific binding sites of [(3)H]quinuclidinyl benzilate. These findings suggest that tramadol at clinically relevant concentrations inhibits M(3) function via quinuclidinyl benzilate-binding sites. This may explain the modulation of neuronal function and the anticholinergic effects of tramadol.

IMPLICATIONS

Muscarinic receptors are involved in neuronal function and are targets of analgesic drugs. We here report that tramadol inhibits type-3 muscarinic receptors function via quinuclidinyl benzilate-binding sites at clinically relevant concentrations. These findings may explain the modulation of neuronal function and the anticholinergic effects of tramadol.

The efficacy of combination analgesic therapy in relieving dental pain

BACKGROUND

An experience of poorly managed pain related to dental treatment can lead patients to avoid or postpone treatment. The development of new pain management strategies equips dental clinicians with additional treatment options that can provide more effective pain relief

LITERATURE REVIEWED

The author reviewed dental and medical literature dealing with the safety, efficacy and mechanisms of action of common analgesic treatments.

CONCLUSIONS

For the treatment of mild to moderate pain, acetaminophen and non-steroidal anti-inflammatory drugs, or NSAIDs, continue to be the most appropriate options. The use of cyclo-oxygenase2-inhibitor NSAIDs should be strongly considered for use with patients at risk of experiencing gastrointestinal toxicity. The pathophysiology of pain is a complex central and peripheral nervous system process, and the use of combination analgesics that act at multiple pain sites can improve pain relief after a dental procedure. For moderate to moderately severe pain, tramadol or combination medications such as tramadol with acetaminophen or codeine with acetaminophen are appropriate. For severe pain, use of opioids or opioid combinations is advised.

CLINICAL IMPLICATIONS

Providing appropriate treatment after dental surgery requires a careful medical history and an educated anticipation of the level of pain the patient may encounter. New analgesic options are available and should be considered, particularly combination analgesics, which can provide faster onset and prolonged duration of action and can combat pain at multiple sites of action.

A double-blind, single-dose comparison of the analgesic efficacy of tramadol/acetaminophen combination tablets, hydrocodone/acetaminophen combination tablets, and placebo after oral surgery

BACKGROUND

Improved clinical outcomes have been documented with combinations of oral analgesic agents, particularly those with complementary activities. However, because not all combinations or dose ratios lead to enhanced analgesia or reduced adverse events (AEs), each combination and dose ratio must be evaluated individually in carefully designed preclinical and clinical trials.

OBJECTIVE

The goal of the study was to compare the efficacy and safety of 37.5 mg tramadol/325 mg acetaminophen tablets (T/APAP), 10 mg hydrocodone bitartrate/650 mg acetaminophen tablets (HC/APAP), and placebo in the treatment of postoperative dental pain.

METHODS

This was a single-center, double-blind, parallel-group, placebo- and active-controlled study in adults with at least moderate pain (score > or =50 on a 100-mm pain visual analog scale) after extraction of > or =2 impacted third molars. Patients were randomized to receive 1 or 2 T/APAP tablets, 1 HC/APAP tablet, or placebo. Scores for hourly pain relief (PAR), pain intensity difference (PID), and combined PAR and PID (PRID) were based on reported pain at 30 minutes and each successive hour for 8 hours. Primary efficacy measures were summary pain intensity and pain relief scores (total pain relief [TOTPAR], sum of pain intensity differences [SPID], and sum of pain relief and pain intensity differences [SPRIDI) for 0 to 4 hours, 4 to 8 hours, and 0 to 8 hours. Secondary efficacy measures were hourly PAR, PID, and PRID scores; onset and duration of pain relief; time to remedication with a supplemental analgesic agent; and patients' overall assessment of medication.

RESULTS

Two hundred adults took part in the study (50 per treatment group) and were included in the efficacy and safety analyses. T/APAP 75/650 mg and HC/APAP were statistically superior to placebo on the primary efficacy measures of TOTPAR, SPID, and SPRID (P < or = 0.024), as well as on hourly PAR, PID, and PRID over 6 hours (P < or = 0.045). All active treatments were statistically superior to placebo in terms of onset of pain relief (P < or = 0.001), duration of pain relief (P < or = 0.024), time to remedication (P < 0.001), and patients' overall assessment of medication (P < 0.001). A statistically significant dose response with T/APAP (2 tablets > 1 tablet > placebo) was seen for TOTPAR, SPID, and SPRID (all, P < or = 0.018). The median time to onset of pain relief was approximately 34.0 minutes with 2 T/APAP tablets and 25.4 minutes with HC/APAP. Although the median time to onset of pain relief was shorter with HC/APAP, two T/APAP tablets had comparable efficacy to HC/APAP. The median time to remedication with a supplemental analgesic agent was 169.0 minutes in the T/APAP 75/650 mg group and 204.0 minutes in the HC/APAP group. However, the duration of pain relief, as defined by time to remedication, was not significantly different between these 2 groups. The overall incidence of AEs was lower with T/APAP (0% treatment-related AEs) than with HC/APAP (4%) or placebo (10%). The incidence of nausea (18% T/APAP, 36% HC/APAP) and vomiting (12% T/APAP, 30% HC/APAP) was approximately 50% lower with 2 T/APAP tablets than with HC/APAP (P < 0.05).

CONCLUSIONS

T/APAP tablets provided effective, rapid (< or = 34 minutes), dose-dependent analgesia for the treatment of postoperative dental pain. Two T/APAP tablets provided analgesia comparable to that provided by HC/APAP with better tolerability.

High-performance liquid chromatographic determination of tramadol and its O-desmethylated metabolite in blood plasma. Application to a bioequivalence study in humans

Simultaneous HPLC determination of the analgetic agent tramadol, its major pharmacodynamically active metabolite (O-desmethyltramadol) in human plasma is described. Simple methods for the preparation of the standard of the above-mentioned tramadol metabolite and N1,N1-dimethylsulfanilamide (used as the internal standard) are also presented. The analytical procedure involved a simple liquid-liquid extraction of the analytes from the plasma under the conditions described previously. HPLC analysis was performed on a 250x4 mm chromatographic column with LiChrospher 60 RP-selectB 5-microm (Merck) and consists of an analytical period where the mobile phase acetonitrile-0.01 M phosphate buffer, pH 2.8 (3:7, v/v) was used, and of a subsequent wash-out period where the plasmatic ballast compounds were eluted from the column using acetonitrile-ultra-high-quality water (8:2, v/v). The whole analysis, including the equilibration preceding the initial analytical conditions lasted 19 min. Fluorescence detection (lambda(ex) 202 nm/lambda(em) 296 nm for tramadol and its metabolite, lambda(ex) 264 nm/lambda(em) 344 nm for N1,N1-dimethylsulfanilamide) was used. The validated analytical method was applied to pharmacokinetic studies of tramadol in human volunteers.