Tramadol and its enantiomers differentially suppress c-fos-like immunoreactivity in rat brain and spinal cord following acute noxious stimulus

Concomitant use of pre-emptive analgesia with local and general anesthesia in rat uterine pain surgical model

Preemptive analgesia is used for postoperative pain management, providing pain relief with few adverse effects. In this study, the effect of a preemptive regime on rat behavior and c-fos expression in the spinal cord of the uterine surgical pain model was evaluated. It was a lab-based experimental study in which 60 female Sprague-Dawley rats; eight to 10 weeks old, weighing 150-300 gm were used. The rats were divided into two main groups: (i) superficial pain group (SG) (with skin incision only), (ii) deep pain group (with skin and uterine incisions). Each group was further divided into three subgroups based on the type of preemptive analgesia administered i.e., "tramadol, buprenorphine, and saline subgroups." Pain behavior was evaluated using the "Rat Grimace Scale" (RGS) at 2, 4, 6, 9 and 24 h post-surgery. Additionally, c-fos immunohistochemistry was performed on sections from spinal dorsal horn (T12-L2), and its expression was evaluated using optical density and mean cell count 2 hours postoperatively. Significant reduction in the RGS was noted in both the superficial and deep pain groups within the tramadol and buprenorphine subgroups when compared to the saline subgroup (p ≤ .05). There was a significant decrease in c-fos expression both in terms of number of c-fos positive cells and the optical density across the superficial laminae and lamina X of the spinal dorsal horn in both SD and DG (p ≤ .05). In contrast, the saline group exhibited c-fos expression primarily in laminae I-II and III-IV for both superficial and deep pain groups and lamina X in the deep pain group only (p ≤ .05). Hence, a preemptive regimen results in significant suppression of both superficial and deep components of pain transmission. These findings provide compelling evidence of the analgesic efficacy of preemptive treatment in alleviating pain response associated with uterine surgery.

The effects of tramadol on cancer stem cells and metabolic changes in colon carcinoma cells lines

Opioids are widely used in the treatment of cancer related pain. They mainly exert their effects on opioid receptors. The most common opioid in the treatment of pain is morphine. Previous studies show that they may have effects on cancer cell behavior. These may include apoptosis, angiogenesis, invasion, inflammation and immune reactions. Tramadol, also an opioid is widely used in the treatment of cancer pain and is not well studied in cancer behavior. We aimed to investigate the effects of tramadol on cancer stem cells and metabolic changes in colon carcinoma cells. We used Colo320 (ATCC, CCL-220), Colo741 (ECACC, 93052621) and HCT116 (ATCC, CCL-247) colon cancer cell lines. CD133 was considered colon cancer stem cell marker and used to sort CD133+ and CD133- cells by magnetic cell sorting. MTT (mitochondria-targeted therapeutics) technique was used to detect tramadol's cytotoxic effect on cells in the study groups. Cells were treated with 1 mg/kg, 1.5 mg/kg and 2 mg/kg tramadol for 24 h at 37 °C and 5% CO₂.Caspase-3, Ki-67, Bcl-2 and VGEF distributions were performed using indirect immunoperoxidase staining for immunohistochemical analysis. The study showed that tramadol has triggering effect on apoptosis in Colo320 colon cancer stem cells.

Electrocardiographic changes in patients with tramadol-induced idiosyncratic seizures

Objectives

To assess ECG changes in patients with tramadol-induced seizure(s) and compare these changes in lower and higher than 500 mg tramadol doses as a main goal.

Material and methods

In an analytical-cross sectional manner over 1 year, 170 patients with idiosyncratic seizure(s) after using tramadol, were studied. Full data were recorded for each patient. ECGs were taken from all the patients on admission and 1 h later and were assessed for findings.

Results

70 of 170 patients (41.2%) had used lower than 500 mg doses of tramadol while 90 patients (52.9%) were included in the high dose group. Rate of female patients in the high dose group was significantly higher. The average age of patients in the high dose group was significantly lower (22.04 vs 25.76). The high dose group had significantly higher heart rates. There was no history of cardiovascular diseases; two patients had previous history of seizure. No significant difference was shown between low dose and high dose groups from the point of ECG changes.

Discussion and conclusion

Using doses higher than 500 mg is more frequently seen in women, young people and those who have not experienced previous use of tramadol. Terminal S wave, sinus tachycardia, and terminal R wave in the lead aVR are among the most common ECG changes in tramadol users.

The antinociceptive effect of systemic administration of a combination of low-dose tramadol and dexmedetomidine in a rat model of bone cancer pain

BACKGROUND

Multiple factors are involved in the mechanism of bone cancer pain. Treatment with a single drug is not adequate to target all of the different mechanisms.

OBJECTIVE

To study the analgesic effect of a combination of low-dose dexmedetomidine (DEX) and tramadol (TRA) on bone cancer pain in rats.

DESIGN

A randomised, controlled study.

SETTING

Central Laboratory of Shanghai Chest Hospital, Shanghai Jiaotong University, Shanghai China, from July 2011 to June 2012.

ANIMALS

Adult female Wistar rats weighing 180 to 200g.

INTERVENTIONS

Rats with bone cancer were divided into five groups based on drug treatment (n=12 for each group): T5 group (TRA 5 mg kg), T10 group (TRA 10 mg kg), D1 group (DEX 1 μg kg), T5+D1 group (TRA 5 mg kg+DEX 1μg kg) and IS (isotonic saline 0.5 ml) group.

MAIN OUTCOME MEASURES

The mechanical threshold and spontaneous paw withdrawal were measured in all groups.

RESULTS

Both the T5+D1 group and T10 group showed a significantly increased mechanical threshold and a lower incidence of spontaneous paw withdrawal compared with the IS group. Interestingly, there was no significant difference between the T5+D1 and T10 groups.

CONCLUSION

We found that a combination of DEX and TRA at low doses provided equal or superior analgesic effects on bone cancer pain compared to high-dose TRA alone. Our animal data might indicate the clinical administration of these two drugs in bone cancer pain therapy.

Altered antinociceptive efficacy of tramadol over time in rats with painful peripheral neuropathy

Pain due to peripheral nerve injury or disease is a dynamic process, such that the mechanism that underlies it alters over time. Tramadol has been reported to be analgesic in clinical neuropathic pain, with varying levels of efficacy due to a patient population that has had neuropathic pain for a wide range of time. In order to address and examine the issue, the antinociceptive efficacy of tramadol over time was tested in rats with a chronic constriction injury (CCI) of the left sciatic nerve. Rats developed a robust hind paw hypersensitivity to innocuous mechanical stimulation ipsilateral to CCI surgery. Subcutaneous injection of tramadol in rats two weeks after CCI surgery dose-dependently attenuated mechanical hypersensitivity, which was abolished with the mu-opioid receptor antagonist naloxone but not the alpha(2)-adrenoceptor antagonist yohimbine. Systemic tramadol also attenuated mechanical hypersensitivity four weeks after CCI surgery, but the efficacy significantly diminished at this time point. In addition, the effect of tramadol at this later time point could be reduced with yohimbine as well as naloxone. These data demonstrate that the efficacy of tramadol depends in part on the duration of nerve injury-evoked nociception, and that its antinociceptive mechanism changes over time. Alteration in antinociceptive mechanism over time may explain the inconsistency in efficacy of this and other analgesic drugs in chronic pain patients.

Single opioid administration modifies gonadal steroids in both the CNS and plasma of male rats

While morphine remains one of the most widely used opioids for the treatment of painful conditions, other opioids are also commonly employed. Because of the interactions between opioids and gonadal hormones, in particular opioid-induced hypogonadism, this study investigated the effects of widely used opioids on plasma testosterone and estradiol levels and brain testosterone levels in male rats. Animals were s.c. injected with two concentrations of morphine (5 or 10 mg/kg), fentanyl (0.05 or 0.1 mg/kg), tramadol (10 or 40 mg/kg), buprenorphine (0.05 or 0.1 mg/kg) or saline (0.7 ml/kg). Four or 24 h after treatment, the rats were deeply anesthetized to collect blood samples from the abdominal aorta and to perfuse the brains with saline. Plasma and brain hormone levels were measured by radioimmunoassay. In rats studied 4 h after treatment, all the opioids except tramadol 10 mg/kg decreased plasma testosterone in comparison with saline administration. At the same time, plasma estradiol levels were lower than control in the groups treated with the low doses of morphine, tramadol and buprenorphine, while estradiol remained at control levels in the other groups. Twenty-four hours after treatment, plasma testosterone levels were different (higher) than control in the animals treated with the low doses of morphine, fentanyl and buprenorphine. Estradiol was lower than control in the low dose groups, while the high doses did not produce any changes with respect to control. Four hours after treatment, brain testosterone was drastically decreased in all groups except buprenorphine, in which it remained at control levels. All groups returned to control levels at 24 h after treatment. In conclusion, opioids exert important effects on plasma and CNS sex hormone levels. The different magnitude and time-course of the effects of the different opiates on testosterone and estradiol levels are likely due to their different mechanism of action.