Tramadol today

The plausible mechanisms of tramadol for treatment of COVID-19

Currently, no single medication has been approved for the management of coronavirus disease-2019 (COVID-19) caused by the new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Therefore, drug repositioningby investigating the use of existing drugs for management of COVID-19 patients is considered a desperate need. Tramadol is a commonly prescribed analgesic drug for treatment of moderate to severe pain with less potential for dependence and respiratory depression. Multiple evidence support that tramadol is a promising drug for treatment of COVID-19 patients. Herein, we discuss the possible beneficial effects of using tramadol against SARS-CoV-2 infection and their underlying mechanism of action. The anti-inflammatory effect of tramadol may help to suppress the COVID-19 related cytokine storm through decreasing interleukin (IL)-6, tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP). Besides, tramadol activates natural killer (NK) and T-cells and enhances IL-2 secretion, which produce immune-enhancing effect against SARS-CoV-2. Recent studies confirmed that COVID-19 patients with acute respiratory failure showed increased fibrin formation and polymerization that may lead to thrombosis. Tramadol owing to its hypocoagulable effect may protect against venous thromboembolism in these patients. Moreover, tramadol can exert a cardioprotective effect via decreasing lactate dehydrogenase (LDH) level which is elevated in most of patients with COVID-19. Furthermore, the severity and mortality of COVID-19 have been correlated with old age patients, which may be due to the lack of antioxidant mechanisms and increased oxidative damage. Tramadol could protect COVID-19 patient from disease complications by increases the antioxidant enzymes superoxide dismutase and glutathione peroxidase while diminished malondialdehyde. More interestingly, tramadol as an effective analgesic and antitussive may have a beneficial effect on COVID-19 patients suffering from cough, headache, ache, and pain. The tramadol anti-psychotic effect may also protect against psychiatric disorders associated with SARS-CoV-2 infection. Moreover, tramadol has bactericidal activity against a wide range of pathogens including Pseudomonas aeruginosa which is common in severe COVID-19 patients leading to pneumonia with worse clinical outcomes. Therefore, we hypothesize that tramadol might be a promising adjuvant therapeutic option against SARS-CoV-2 infection. Based on that, tramadol should be considered as adjuvant therapy for COVID-19 clinical trials.

Inhibition of Fast Nerve Conduction Produced by Analgesics and Analgesic Adjuvants-Possible Involvement in Pain Alleviation

Nociceptive information is transmitted from the periphery to the cerebral cortex mainly by action potential (AP) conduction in nerve fibers and chemical transmission at synapses. Although this nociceptive transmission is largely inhibited at synapses by analgesics and their adjuvants, it is possible that the antinociceptive drugs inhibit nerve AP conduction, contributing to their antinociceptive effects. Many of the drugs are reported to inhibit the nerve conduction of AP and voltage-gated Na⁺ and K⁺ channels involved in its production. Compound action potential (CAP) is a useful measure to know whether drugs act on nerve AP conduction. Clinically-used analgesics and analgesic adjuvants (opioids, non-steroidal anti-inflammatory drugs, ₂-adrenoceptor agonists, antiepileptics, antidepressants and local anesthetics) were found to inhibit fast-conducting CAPs recorded from the frog sciatic nerve by using the air-gap method. Similar actions were produced by antinociceptive plant-derived chemicals. Their inhibitory actions depended on the concentrations and chemical structures of the drugs. This review article will mention the inhibitory actions of the antinociceptive compounds on CAPs in frog and mammalian peripheral (particularly, sciatic) nerves and on voltage-gated Na⁺ and K⁺ channels involved in AP production. Nerve AP conduction inhibition produced by analgesics and analgesic adjuvants is suggested to contribute to at least a part of their antinociceptive effects.

Multimodal analgesia with ropivacaine wound infiltration and intravenous flurbiprofen axetil provides enhanced analgesic effects after radical thyroidectomy: a randomized controlled trial

BACKGROUND

Thyroidectomy is a common procedure that causes mild trauma. Nevertheless, postoperative pain remains a major challenge in patient care. Multimodal analgesia comprising a combination of analgesics and analgesic techniques has become increasingly popular for the control of postoperative pain. The present study tested the hypothesis that multimodal analgesia with combined ropivacaine wound infiltration and intravenous flurbiprofen axetil after radical thyroidectomy provided better analgesia than a single dosage of tramadol.

METHODS

This randomized controlled trial was conducted in a tertiary hospital. Forty-four patients (age, 18-75 years; American Society of Anesthesiologists status I or II; BMI < 32 kg/m²) scheduled for radical thyroidectomy were randomly assigned to a multimodal analgesia group (Group M) or a control group (Group C) by random numbers assignments, and 40 patients completed the study. All participants and the nurse in charge of follow-up observations were blinded to group assignment. Anesthesia was induced with sufentanil, propofol, and cisatracurium. After tracheal intubation, Group M received pre-incision wound infiltration with 5 ml of 0.5% ropivacaine mixed with epinephrine at 1:200,000 (5 μg/ml); Group C received no wound infiltration. Anesthesia was maintained with target-controlled infusion of propofol, remifentanil, sevoflurane, and intermittent cisatracurium. Twenty minutes before the end of surgery, Group M received 100 mg flurbiprofen axetil while Group C received 100 mg tramadol. Postoperative pain was evaluated with the numerical rating scale (NRS) pain score. Remifentanil consumption, heart rate, and noninvasive blood pressure were recorded intraoperatively. Adverse events were documented. The primary outcome was analgesic effect according to NRS scores.

RESULTS

NRS scores at rest were significantly lower in Group M than in Group C before discharge from the postoperative anesthetic care unit (P = 0.003) and at 2 (P = 0.008), 4 (P = 0.020), and 8 h (P = 0.016) postoperatively. Group M also had significantly lower NRS scores during coughing/swallowing at 5 min after extubation (P = 0.017), before discharge from the postoperative anesthetic care unit (P = 0.001), and at 2 (P = 0.002) and 4 h (P = 0.013) postoperatively. Compared with Group C, NRS scores were significantly lower throughout the first 24 h postoperatively in Group M at rest (P = 0.008) and during coughing/swallowing (P = 0.003). No serious adverse events were observed in either group.

CONCLUSION

Multimodal analgesia with ropivacaine wound infiltration and intravenous flurbiprofen axetil provided better analgesia than tramadol after radical thyroidectomy.

TRIAL REGISTRATION

Chinese Clinical Trial Registry (registration number # ChiCTR1800020290 ; date of registration: 22/12/2018).

Comparison the Effects of Oral Tizanidine and Tramadol on Intra- and Post-operative Shivering in Patients Underwent Spinal Anesthesia

Background:

Heat loss and core-to-peripheral redistribution of body heat occur in patients undergoing neuraxial anesthesia resulted to decrease of core temperature and early reach of shivering threshold. Because shivering has deleterious metabolic and cardiovascular effects, it should ideally be prevented by pharmacologic or other means. Tizanidine is an alpha-2 agonist. We evaluated the usefulness of oral tizanidine (TI) and tramadol in preventing of shivering in patients undergoing spinal anesthesia for transurethral resection of the prostate (TURP).

Materials and Methods:

Ninety patients, scheduled for TURP with spinal anesthesia, were prospectively enrolled. Patients were randomly assigned to 1 of 3 groups. 90 min before spinal anesthesia, 30 patients received 4 mg oral TI, 30 patients received 50 mg tramadol, and 30 patients received placebo as control group. Spinal anesthesia was induced at the L3–L4 or L4–L5 interspaces with 12.5 mg bupivacaine. An investigator blinded to the drugs recorded the frequency and degree of shivering.

Results:

The overall frequency and severity of shivering were significantly lower in patients treated with TI and tramadol compared to placebo (P = 0.04) (P = 0.001). There was not much difference in the nausea and vomiting of both the drugs (P = 026) (P = 011). There was no difference in hemodynamic parameters between three groups (P = 0.08) (P = 013).

Conclusions:

Oral TI and tramadol were comparable in respect to their effect in decreasing the incidence, intensity shivering when used prophylactically in patients who underwent TURP with spinal anesthesia.

Dhcr24 activates the PI3K/Akt/HKII pathway and protects against dilated cardiomyopathy in mice

BACKGROUND

24-dehydrocholesterol reductase (Dhcr24) catalyzes the last step of cholesterol biosynthesis, which is required for normal development and anti-apoptotic activities of tissues. We found that Dhcr24 expression decreased in the cTnTR 141W dilated cardiomyopathy (DCM) transgenic mice. Therefore, we tested whether rescued expression of Dhcr24 could prevent the development of DCM and its possible mechanism.

METHODS

Heart tissue specific transgenic overexpression mice of Dhcr24 was generated, then was crossed to cTnTR 141W mouse to obtain the double transgenic mouse (DTG). The phenotypes were demonstrated by the survival, cardiac geometry and function analysis, as well as microstructural and ultrastructural observations based on echocardiography and histology examination. The pathway and apoptosis were analysed by western blotting and TUNEL assay in vivo and in vitro.

RESULTS

We find that Dhcr24 decreased in hearts tissues of cTnTR 141W and LMNAE 82K DCM mice. The transgenic overexpression of Dhcr24 significantly improves DCM phenotypes in cTnTR 141W mice, and activates PI3K/Akt/HKII pathway, followed by a reduction of the translocation of Bax and release of cytochrome c, caspase-9 and caspase-3 activation and myocyte apoptosis. Knockdown the expression of Dhcr24 reduces the activation of PI3K/Akt/HKII pathway and inhibition of the mitochondrial-dependent apoptosis. The anti-apoptotic effect of Dhcr24 could be completely removed by the inhibition of PI3K pathway and partly removed by the HKII inhibitor in H9c2 cell line.

CONCLUSION

Compensatory expression of Dhcr24 protect against DCM through activated PI3K/Akt/HKII pathway and reduce Bax translocation. This is the first investigation for the molecular mechanism of Dhcr24 participate in development of DCM.

The effects of tramadol on postoperative shivering after sevoflurane and remifentanil anesthesia

BACKGROUNDS

Remifentanil has been reported to cause post-anesthetic shivering (PAS). Higher doses of remifentanil reportedly induce more intense PAS. Tramadol, a synthetic opioid that acts at multiple sites, is considered to be an effective treatment for PAS, but the evidence for its therapeutic benefit after remifentanil anesthesia is limited. We investigated the effect of tramadol on the incidence of PAS after remifentanil anesthesia.

METHODS

Sixty-three patients who had undergone upper abdominal surgery under general anesthesia were studied retrospectively. Tramadol was administered at induction of anesthesia. The patients were divided into four groups: HT(+), high dose remifentanil (1-1.5 μg/kg/min) with tramadol; HT(-), high dose remifentanil without tramadol; LT(+), low dose remifentanil (0.15-0.25 μg/kg/min) with tramadol; and LT(-), low dose remifentanil without tramadol. We recorded perioperative changes in nasopharyngeal temperature and episodes of PAS on emergence from anesthesia.

RESULTS

The incidences of PAS in both tramadol treatment groups were significantly lower than the groups that did not receive tramadol. Nasopharyngeal temperature after surgery fell significantly more from baseline in the tramadol treatment groups compared with the non-treatment groups.

CONCLUSION

Tramadol administered at induction of anesthesia appears to suppress PAS following remifentanil anesthesia.

Serotonin syndrome after the use of tramadol and ziprasidone in a patient with a deep brain stimulator for Parkinson disease

Serotonin syndrome (SS) is a life-threatening adverse reaction that can result from the therapeutic use of serotonergic drugs or accidental drug interactions. Tramadol is a drug that is widely prescribed because of its low abuse potential, but physicians need to be aware of its significant potential to cause SS because it inhibits serotonin reuptake. Ziprasidone is an atypical antipsychotic that can also cause dangerous interactions to cause SS because it is not only a potent 5-HT1A agonist but also has been reported to inhibit serotonin reuptake with an affinity similar to tricyclic antidepressants, in addition to inhibiting reuptake of norepinephrine. We are describing the clinical characteristics of a gentleman with bipolar disorder and Parkinson disease who presented with SS, despite having a deep brain stimulator in the subthalamic nucleus, which decreases central serotonin levels, and a discussion of the factors that contributed to his presentation.

Premedication with oral tramadol reduces severity of postoperative shivering after general anesthesia

Background:

Postanesthetic shivering (PAS) is an accompanying part of general anesthesia with different unpleasant and stressful complications. Considering the importance of proper prevention of PAS in order to reduce its related adverse complications in patients undergoing surgery, in this study, we investigated the effect of orally administrated tramadol in the prevention of this common complication of general anesthesia.

Materials and Methods:

In this prospective randomized double-blind clinical trial, 80 ASA I and II patients aged 15-70 years, scheduled for elective surgery under general anesthesia, were randomized to intervention (oral tramadol 50 mg) and placebo groups. PAS was evaluated during surgery and in the recovery room, and compared in the two study groups.

Results:

PAS was seen in 5 patients (12.5%) in the intervention group and 10 patients (25%) in the placebo group (P = 0.12). The prevalence of grade III and IV shivering was 7.5% (3/40) and 25% (10/40) in tramadol and placebo groups, respectively (P = 0.03).

Conclusion:

The overall prevalence of PAS was not significantly different in the two study groups, but the higher grades of shivering which needed treatment were significantly lower in the tramadol group than in the placebo, and those patients who received tramadol experienced milder form of shivering. It is suggested that higher doses of tramadol would have better anti-shivering as well as analgesic effects. Studying different doses of tramadol would be helpful in this regard.

Tramadol combined with fentanyl in awake endotracheal intubation

OBJECTIVE

To explore the feasibility and dosage of tramadol combined with fentanyl in awake endotracheal intubation.

METHODS

Using Dixon's up-and-down sequential design, the study enrolled patients from each of the 20-49, 50-60 and 70-and-above age groups scheduled for elective surgery under general anesthesia. The feasibility and dosage of tramadol combined with fentanyl in awake endotracheal intubation, guided by fiberoptic bronchoscopy, were verified.

RESULTS

After intravenous injection with fentanyl 2.2 μg/kg and tramadol 2.0 mg/kg in the 20-49 age group, fentanyl 1.6 μg/kg and tramadol 1.9 mg/kg in the 50-69 age group and fentanyl 1 μg/kg and tramadol 1.8 mg/kg in those at the age of 70 or above, the patients achieved conscious sedation without obvious respiratory depression. Meanwhile, under these dosages, the patients could easily tolerate the thyrocricocentesis airway surface anesthesia and fiberoptic bronchoscope guided tracheal intubation. Postoperative follow-up showed that most patients had memory of the intubation process but without significant discomfort. No awake endotracheal intubation-related side effect was noted.

CONCLUSIONS

Fiberoptic bronchoscope guided nasotracheal intubation can be successfully completed with background administration of fentanyl and tramadol. However, the specific dosages need to be tailored in different age of patients.

Pre emptive analgesia for reducing pain after cholecystectomy: Oral tramadol vs. acetaminophen codeine

Background:

Considering that protocols of postoperative pain management would be planned regarding the facilities of each center or region and the importance of its proper management to reduce its related complication and improve patient's satisfaction, in this study we compared the effect of orally administrated tramadol and acetaminophen-codeine in this regard.

Materials and Methods:

In this prospective randomized double-blind clinical trial, 136 (68 in tramadol and 68 in acetaminophen codeine groups) ASA I and II patients scheduled for open cholecystectomy under general anaesthesia were enrolled. They randomly allocated to receive oral tramadol (50 mg capsule) or acetaminophen-codeine (325/10 mg) 1 hour before surgery. After surgery they evaluated for postoperative pain using VAS score, analgesic consumption and vomiting.

Results:

Mean of postoperative pain score during 24 hours after surgery was 2.1 ± 1.0 and 3.8 ± 2.0 in tramadol and acetaminophen-codeine groups, respectively (P < 0.05). Mean of analgesic consumption (morphine) during 24 hours after surgery was 6.2 ± 4.4 mg and 12.9 ± 5.7 mg in tramadol and acetaminophen-codeine groups, respectively (P < 0.05). Mean of vomiting during 24 hours after surgery was 1.2 ±0.9 and 0.4 ± 0.5 in tramadol and acetaminophen-codeine groups, respectively (P < 0.05).

Conclusion:

The findings of current study indicated that in lower dose of tramadol (50 mg) and acetaminophen/codeine (325 mg/10 mg) the analgesic effect of tramadol is better and its side effects are higher than acetaminophen/codeine, which limit its use for mentioned purpose. It seems that administration of each of studied agents it depends on patients’ tolerance and decision of the physician.

Tramadol added to bupivacaine does not prolong analgesia of continuous psoas compartment block

The primary aim of our study was to evaluate the quality and duration of analgesia when tramadol was added to 0.25% bupivacaine for continuous psoas compartment block (CPCB) using visual analog pain scores. Thirty patients were prospectively randomized into two equal groups (n = 15). Visual analog scale pain score was not significantly different between the groups during the 48-hour follow-up period. Rescue analgesic consumption, nausea and vomiting, and the satisfaction scores were comparable between the groups (P > 0.05). Success with catheter placement adjacent to the lumbar plexus was 100%, and none of the patients developed any catheter-related complications. In conclusion, tramadol does not provide a clinically significant analgesic action as an adjunct to 0.25% bupivacaine for CPCB.

Role of 4-aminopyridine-sensitive potassium channels in peripheral antinociception

Previous studies has report the modulation of K+ channels play key roles in the induction of peripheral antinociception induced by many types of drugs. However, the possible participation of 4-aminopyridine-sensitive K+ channels to local antinociception induced by tramadol, a mu opioid receptor agonist, and lidocaine, a local anaesthetic, has been less studied. In this study, we therefore investigated this by using thermal plantar test. Tramadol or lidocaine administered intraplantarly into the hind paw elicited an antinociceptive effect. 4-aminopyridine caused an increase in the antinociception produced by lidocaine. However, tramadol induced antinociception remained unaffected by intraplantar administration of 4-aminopyridine. These results suggest that 4-aminopyridine-sensitive K+ channels may play an important role in the thermal peripheral antinociception produced by lidocaine, but not tramadol.

Tramadol improves patients' tolerance of transrectal ultrasound-guided prostate biopsy

OBJECTIVES

To evaluate the analgesic advantage of tramadol in patients undergoing transrectal biopsy of the prostate in ambulatory settings compared with topical analgesia.

METHODS

A total of 77 patients scheduled for prostate biopsy were randomly assigned to receive 5% lidocaine ointment 5 mL per rectum 10 minutes before the procedure (group 1) or lidocaine ointment combined with tramadol drops 1 mg/kg per os 40 minutes before the procedure (group 2). Pain severity, main cardiorespiratory parameters, difficulty of the procedure, procedure-related side effects, and complications were analyzed.

RESULTS

No significant respiratory or hemodynamic disturbances were observed. The pain severity, as measured on a visual analog scale, was significantly lower in group 2 (P = 0.038), and the rate of overall satisfaction with the level of analgesia was significantly greater (P = 0.027). The urologist's assessment of "very easy" was assigned to 77.1% of procedures in group 2 compared with 54.8% of procedures in group 1 (P = 0.04). The rate of side effects in both groups was similar at 9.5% versus 11.4% (P = 0.785).

CONCLUSIONS

The combination of lidocaine per rectum with tramadol per os is a simple and safe technique providing good analgesic effect and, therefore, can be recommended for transrectal ultrasound-guided prostate biopsy.

Fentanyl or tramadol, with midazolam, for outpatient colonoscopy: analgesia, sedation, and safety

The present study determined the acceptability of colonoscopy in outpatients treated with tramadol or fentanyl for analgesia and sedation. One hundred fifty patients were randomly assigned to receive midazolam, 0.05 mg/kg, and fentanyl, 2 microg/kg, intravenously (group 1), midazolam, 0.05 mg/kg, and tramadol, 1 mg/kg, per os (group 2), or midazolam, 0.05 mg/kg, and tramadol, 2 mg/kg, per os (group 3). Pain severity, level of sedation, cardiorespiratory parameters, and procedure-related side effects and complications were registered and analyzed. No significant cardiorespiratory disturbances were observed. Sedation level during the procedure was similar in all groups. Pain severity values measured during the procedure was significantly higher in groups 2 and 3 than in group 1 (P < 0.001). Both hospital and home adverse events occurred more frequently in groups 2 and 3 compared to group 1 (P < 0.03). The patients receiving fentanyl-based analgesia tolerated colonoscopy better than patients treated with tramadol.

Tramadol, but not its major metabolite (mono-O-demethyl tramadol) depresses compound action potentials in frog sciatic nerves

BACKGROUND AND PURPOSE

Although tramadol is known to exhibit a local anaesthetic effect, how tramadol exerts this effect is not understood fully.

EXPERIMENTAL APPROACH

The effects of tramadol and its metabolite mono-O-demethyl-tramadol (M1) on compound action potentials (CAPs) were examined by applying the air-gap method to frog sciatic nerves, and the results were compared with those of other local anaesthetics, lidocaine and ropivacaine.

KEY RESULTS

Tramadol reduced the peak amplitude of the CAP in a dose-dependent manner (IC50=2.3 mM). On the other hand, M1 (1-2 mM), which exhibits a higher affinity for mu-opioid receptors than tramadol, did not affect CAPs. These effects of tramadol were resistant to the non-selective opioid receptor antagonist naloxone and the mu-opioid receptor agonist, DAMGO, did not affect CAPs. This tramadol action was not affected by a combination of the noradrenaline uptake inhibitor, desipramine, and the 5-hydroxytryptamine uptake inhibitor, fluoxetine. Lidocaine and ropivacaine also concentration-dependently reduced CAP peak amplitudes with IC50 values of 0.74 and 0.34 mM, respectively.

CONCLUSIONS AND IMPLICATIONS

These results indicate that tramadol reduces the peak amplitude of CAP in peripheral nerve fibres with a potency which is less than those of lidocaine and ropivacaine, whereas M1 has much less effect on CAPs. This action of tramadol was not produced by activation of mu-opioid receptors nor by inhibition of noradrenaline and 5-hydroxytryptamine uptake. It is suggested that the methyl group present in tramadol but not in M1 may play an important role in producing nerve conduction block.

Comparative effects of lidocaine and tramadol on injured peripheral nerves

The aim of the present study was to investigate the action of lidocaine and tramadol on the abnormal impulse characteristics of injured peripheral nerves. The ultrastructure of nerves was studied with electron microscopy and the action of lidocaine and tramadol on intact and injured rat sciatic nerves was examined by using the sucrose gap recording technique. Tramadol and lidocaine caused concentration- and frequency-dependent decreases in the amplitude of the compound action potential. Injured nerves were more sensitive to lidocaine than to tramadol. Lidocaine suppressed the delayed depolarization and decreased the hyperpolarizing afterpotentials to a greater extent than did tramadol. A low concentration of lidocaine may restore the abnormal impulse characteristics of injured nerves without changing the normal impulse pattern. The efficacy of lidocaine and inefficacy of tramadol on abnormal impulse characteristics may contribute, at least in part, to our understanding of the mechanisms of action of these drugs in neuropathic pain therapy.

Differential effects of lidocaine and tramadol on modified nerve impulse by 4-aminopyridine in rats

We have used the sucrose gap method to measure the effects of drugs on the electrophysiological properties of rat sciatic nerves. The results showed that 4-aminopyridine produced a slight conduction block, prolonged the duration of action potential, enhanced the hyperpolarizing afterpotential, and elicited a hump that followed the action potential. In the presence of 4-aminopyridine, the impulse-blocking activity of lidocaine and tramadol was enhanced. Both lidocaine and tramadol effectively depressed the delayed depolarization generated by 4-aminopyridine. While tramadol decreased the activity-evoked hyperpolarizing afterpotentials, lidocaine completely removed them. These findings indicate that lidocaine may be more effective in blocking the Na(+) channels than tramadol. Tramadol may be more effective on the delayed rectifier K(+) channels than lidocaine.

Impact of CYP2D6 genotype on postoperative tramadol analgesia

Genetic polymorphisms result in absent enzyme activity of CYP2D6 (poor metabolizers, PM) in about 10% of the Caucasian population. This study investigates whether the PM genotype has an impact on the response to tramadol analgesia in postoperative patients. A prospective study design was used and 300 patients recovering from abdominal surgery were enrolled. After titration of an individual loading dose, patients could self-administer 1 ml bolus doses of the drug combination tramadol 20 mg/ml, dipyrone 200 mg/ml and metoclopramide 0.4 mg/ml via patient-controlled analgesia (PCA). Patients' genotype was analyzed considering the most prevalent PM associated CYP2D6 mutations using a real-time PCR and hybridization based genotyping method. Demographic data, surgery related variables, pain scores, analgesic consumption and need for rescue medication were compared between extensive metabolizers (EM) and PM. The primary outcome criterion 'response' was defined as responder or non-responder status by the need for rescue medication and patients' satisfaction at the final interview. Demographic and surgery related data were comparable between EM (n=241) and PM (n=30). The percentage of non-responders was significantly higher in the PM group (46.7%) compared with the EM group (21.6%; p=0.005). Tramadol loading dose amounted to 108.2+/-56.9 and 144.7+/-22.6 mg (p<0.001) in EM and PM, respectively. More patients displaying the PM genotype needed rescue medication in the recovery room and during PCA period than patients with at least one wild type allele (21.6 versus 43.3%, p=0.02). PM for CYP2D6 showed a lower response rate to postoperative tramadol analgesia than EM. Therefore, CYP2D6 genotype has an impact on analgesia with tramadol. Pharmacogenetics may explain some of the varying response to pain medication in postoperative patients.

Postanaesthetic shivering--a new look at tramadol

We studied whether tramadol administered at the time of wound closure can prevent postanaesthetic shivering. One hundred and fifty patients scheduled for general anaesthesia and surgery were randomly allocated and tramadol was administered intravenously at a dose of 2 mg.kg(-1) in the high-dose group, 1 mg.kg- in the low-dose group and 0.9% saline in the control group. In the high-dose group, 2% of patients had postanaesthetic shivering, compared to 4% in the low-dose group and 48% in the control group (p < 0.001 vs. tramadol groups). There was no delay in tracheal extubation after reversal of neuromuscular blockade. The incidence of adverse side-effects such as sedation and vomiting did not differ statistically and were clinically not significant. This study strongly supports the use of tramadol at wound closure for prevention of postanaesthetic shivering.

Comparison of nerve conduction blocks by an opioid and a local anesthetic

The experiments were done on frog sciatic nerves, using a sucrose-gap recording technique. The aim of our study was to investigate and to compare the tonic and phasic conduction blocking potency of tramadol and lidocaine on whole nerve and their interactions with Ca(2+). The concentration of a tramadol solution producing the same amount of tonic and phasic conduction blocks was three and six times higher than that needed for lidocaine, respectively. Increasing the Ca(2+) concentration in the test solution enhanced the conduction blocking potency of tramadol, but decreased that of lidocaine. It is concluded that tramadol blocks nerve conduction like a local anesthetic but with a weaker effect than that of lidocaine. Interactions of Ca(2+) and these drugs suggested that these drugs might have either different binding sites or different action mechanisms.