Effect of tramadol on metamizol pharmacokinetics and pharmacodynamics after single and repeated administrations in arthritic rats

Dynamic Distribution and Postmortem Redistribution of Tramadol in Poisoned Rats

In the past dozen years, the cases of tramadol intoxication have become frequent in many countries. Most previous studies focused on tramadol's pharmacology, such as pharmacokinetics, pharmacodynamics and pharmacogenetics. However, the dynamic distribution and postmortem redistribution (PMR) of tramadol remain unclear. Our study aimed to investigate these two issues systematically in various specimens of 216 poisoned male rats. A validated gas chromatography-mass spectrometry method was used in this study to measure the concentrations of tramadol. In the first part, 66 tramadol poisoned rats were sacrificed at 11 different time points and their organs were collected separately for the study of tramadol's dynamic distribution, which made it feasible to investigate its PMR later on. The results of this part showed that tramadol's concentrations varied according to the organ and time, and peaked 2 h after intragastric administration in the specimens of liver, kidney, spleen, lung, brain and heart-blood (except stomach and heart). Based on the results of the first part, the concentration of tramadol peaked 2 h in most tissues. Therefore, this time point was used for the study of tramadol's PMR. In the second part, the remaining 150 rats were sacrificed 2 h after intragastric administration of tramadol, and the carcasses were stored under three different conditions (-20, 4 and 20°C). The autopsy was carried out at eight different time points and their organs were collected separately. The results of this part showed that under storage temperatures of -20 and 4°C, the concentrations of tramadol in individual organs showed no significant changes at different time points whereas under a storage temperature of 20°C, the concentrations in certain organs (liver, kidney, spleen, lung, brain and heart-blood) increased significantly at the last few time points. PMR of tramadol was therefore confirmed. The process of PMR of tramadol could be slowed or stopped at lower storage temperatures (-20 or 4°C), which is significant in cases of suspected tramadol poisoning.

Analysis of Animal Well-Being When Supplementing Drinking Water with Tramadol or Metamizole during Chronic Pancreatitis

Simple Summary

Pain management during in vivo experiments can considerably improve the wellbeing of animals. However, often it is not clear, which drugs are best for the animals and how to apply these drugs without causing stress. In this study, we evaluated mice when metamizole or tramadol was provided via drinking water. Neither of these two drugs reduced the amount of consumed water or body weight in healthy mice or influenced their natural behavior, such as nest building or burrowing activity. Both analgesics were then given to mice suffering from chronic pancreatitis. Mice drinking tramadol supplemented water, at some time-points, experienced less loss in body weight and consumed more water than mice drinking metamizole. However, no major differences in other methods measuring wellbeing of mice was observed. In conclusion, both analgesics can be used during chronic pancreatitis, but tramadol seems to be moderately advantageous when compared to metamizole.

Abstract

Pain management during in vivo experiments is an animal welfare concern and is in many countries also legally required. In this study, we evaluated C57Bl/6J mice when 3 g/L metamizole or 1 g/L tramadol was provided via drinking water, before and during cerulein-induced chronic pancreatitis. Supplementation of drinking water with metamizole or tramadol did not significantly reduce the amount of consumed water. In order to evaluate the wellbeing of mice, a distress score, burrowing activity, nesting behavior, and body weight was assessed. Before induction of pancreatitis, neither tramadol nor metamizole influenced these readout parameters. Chronic pancreatitis caused a significantly increased distress score, decreased burrowing activity and a reduction in body weight. Mice drinking tramadol-supplemented water experienced less loss in body weight and consumed more water than mice drinking metamizole, at a few time-points during chronic pancreatitis. Pancreatic atrophy, a characteristic feature of chronic pancreatitis was not differentially influenced by either analgesic. In conclusion, both analgesics can be used during 33 days of chronic pancreatitis, but tramadol seems to be moderately advantageous when compared to metamizole.

Combining opioids and non-opioids for pain management: Current status

Pain remains a global health challenge. For decades, clinicians have been primarily relying on μ-opioid receptor (MOR) agonists and nonsteroidal anti-inflammatory drugs (NSAIDs) for pain management. MOR agonists remain the most efficacious analgesics available; however, adverse effects related to MOR agonists use are severe which often lead to forced drug discontinuation and inadequate pain relief. The recent opioid overdose epidemic urges the development of safer analgesics. Combination therapy is a well-established clinical pharmacotherapeutic strategy for the treatment of various clinical disorders. The combination of MOR agonists with non-MOR agonists may increase the analgesic potency of MOR agonists, reduce the development of tolerance and dependence, reduce the diversion and abuse, overdose, and reduce other clinically significant side effects associated with prolonged opioid use such as constipation. Overall, the combination therapy approach could substantially improve the therapeutic profile of MOR agonists. This review summarizes some recent developments in this field. This article is part of the Special Issue entitled 'New Vistas in Opioid Pharmacology'.

A comparative study about the immunomodulatory effects of tramadol and metamizole in a murine model of postoperative ileus

Postoperative ileus (POI) is a common complication after abdominal surgery characterized by motility disturbances leading to increased morbidity and mortality in surgical patients. Intestinal manipulation of the murine small bowel is an established animal model resulting in an increased postsurgical inflammation within the intestinal muscular externa and a delayed gastrointestinal transit. Some analgesics have been shown to affect inflammation. In this study, we compared the immunomodulatory effects of two different analgesics. Mice were treated with tramadol, metamizole or saline as a control in our established POI model. The postoperative inflammatory response was assessed by gene expression of pro-inflammatory cytokines at different time points and immunocytes extravasation into the muscularis externa. Functional motility analyses were performed by a gastrointestinal transit measurement. Metamizole application reduced the pro-inflammatory response after surgery and improved gastrointestinal motility, while tramadol showed no alteration in cytokine gene expression, influx of immunocytes and gastrointestinal transit compared with the controls. In conclusion. we suggest tramadol as analgesia in immunological studies on POI in mice as it does not affect the underlying inflammation of POI.

Pharmacokinetics and pharmacodynamics of metamizol in co-administration with morphine under acute and chronic treatments in arthritic rats

Objective

To investigate the relationship between metamizol pharmacokinetics and the antinociceptive effect produced after subcutaneous administration of metamizol (177.8 mg/kg) alone or in combination with morphine (3.2 mg/kg), under acute and chronic treatments.

Methods

Antinociception was assessed using the pain-induced functional impairment model in rat (PIFIR). Serial blood samples were collected from the same animals to study the pharmacokinetics of metamizol.

Key findings

The co-administration of the drugs in single dose, confirmed the potentiation of their individual antinociceptive effects. When the drugs were administered alone following the chronic schedule, a pronounced tolerance development to their antinociceptive effects was found, whereas it was significantly attenuated when they were administered together. Metamizol pharmacokinetics was unaltered by the presence of morphine. Plasma concentrations of 4-methylaminoantipyrine, an active metabolite markedly decreased under chronic administration.

Conclusions

The mechanism involved in the potentiation of the antinociceptive effect produced by the combination, cannot be explained by the interaction of morphine on metamizol pharmacokinetics. Other pharmacokinetic interactions along with known pharmacodynamic interactions in which metamizol active metabolites contribute, should be considered. The frequency of administration enhances tolerance development and induces metamizol elimination process.