Interaction between metamizol and tramadol in a model of acute visceral pain in rats

ADME and toxicity considerations for tramadol: from basic research to clinical implications

INTRODUCTION

Tramadol is widely being used in chronic pain management for improving patients' life quality and reducing trauma. Although it is listed in several medicinal guidelines, its use is controversial because of the conflicting results obtained in pharmacokinetic/pharmacodynamic studies. This multi-receptor drug acts as µ₁ opioid receptor agonist, monoamine reuptake inhibitor, and inhibitor of ligand-gated ion channels and some special protein-coupled receptors.

AREAS COVERED

This review provides a comprehensive view on the pharmacokinetic, pharmacodynamic, and toxicity of tramadol with a deep look on its side effects, biochemical and pathological changes, and possible drug interactions. In addition, the main ways of tramadol poisoning management describe according to in vivo and clinical trial studies.

EXPERT OPINION

Given the broad spectrum of targets, increasing the cases of overdoses and toxicity, and probable drugs interaction, it is necessary to take another look at the pharmacology of tramadol. Regarding the adverse effects of tramadol on different tissues, especially the nervous system and liver tissue, more attentions to tramadol metabolites, their interaction with other drugs, and active agents seem critical. Seizure as the most cited effect of tramadol and its destructive effects on tissues would alleviate by co-administration with drugs with antioxidant properties.

The Antinociceptive Effect of a Tapentadol-Ketorolac Combination in a Mouse Model of Trigeminal Pain is Mediated by Opioid Receptors and ATP-Sensitive K+ Channels

Preclinical Research The aim of the present study was to evaluate the antinoceptive interaction between the opioid analgesic, tapentadol, and the NSAID, ketorolac, in the mouse orofacial formalin test. Tapentadol or ketorolac were administered ip 15 min before orofacial formalin injection. The effect of the individual drugs was used to calculate their ED₅₀ values and different proportions (tapentadol-ketorolac in 1:1, 3:1, and 1:3) were assayed in the orofacial test using isobolographic analysis and interaction index to evaluate the interaction between the drugs. The combination showed antinociceptive synergistic and additive effects in the first and second phase of the orofacial formalin test. Naloxone and glibenclamide were used to evaluate the possible mechanisms of action and both partially reversed the antinociception produced by the tapentadol-ketorolac combination. These data suggest that the mixture of tapentadol and ketorolac produces additive or synergistic interactions via opioid receptors and ATP-sensitive K⁺ channels in the orofacial formalin-induced nociception model in mice. Drug Dev Res 78 : 63-70, 2017. © 2016 Wiley Periodicals, Inc.

[Metamizole (dipyrone): mode of action, drug-drug interactions, and risk of agranulocytosis]

Metamizole (dipyrone) is a nonsteroidal compound with strong analgesic as well as antipyretic and spasmolytic properties. Based on a small number of cases of agranulocytosis, metamizole was withdrawn from the market in some countries. Other countries restricted its use. This paper discusses the safety aspects of metamizole and compares it with other compounds used for similar indications.

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

Combined administration of certain doses of opioid compounds with a non-steroidal anti-inflammatory drug can produce additive or supra-additive effects while reducing unwanted effects. We have recently reported that co-administration of metamizol with tramadol produces antinociceptive effect potentiation, after acute treatment. However, none information about the effect produced by the combination after chronic or repeated dose administration exists. The aims of this study were to investigate whether the antinociceptive synergism produced by the combination of metamizol and tramadol (177.8 + 17.8 mg/kg, s.c. respectively) is maintained after repeated treatment and whether the effects observed are primarily due to pharmacodynamic interactions or may be related to pharmacokinetics changes. Administration of metamizol plus tramadol acute treatment significantly enhanced the antinociceptive effect of the drugs given alone (P < 0.05). Nevertheless, this effect decreased about 53% after the chronic treatment (3 doses per day, for 4 days). No pharmacokinetic interaction between metamizol and tramadol was found under acute treatment (P > 0.05). The mechanism involved in the synergism of the antinociceptive effect observed with the combination of metamizol and tramadol in single dose cannot be attributed to a pharmacokinetic interaction, and other pharmacodynamic interactions have to be considered. On the other hand, when metamizol and tramadol were co-administered under repeated administrations, a pharmacokinetic interaction and tolerance development occurred. Differences found in metamizol active metabolites’ pharmacokinetics (P < 0.05) were related to the development of tolerance produced by the combination after repeated doses. This work shows an additional preclinical support for the combination therapy. The clinical utility of this combination in a suitable dose range should be evaluated in future studies.

Coadministration of tramadol and tizanidine in an experimental acute pain model in rat

Preclinical Research The use of drug combinations to achieve a desired effect is a common practice in pharmacological reaserch and in clinical practice. The present study was designed to evaluate the potential synergistic antinociceptive interactions between tizanidine, an α-2-adrenoceptor agonist and tramadol on formalin-induced nociception in rat using isobolographic analyses. Tramadol (0.1-100 μg/paw) and tizanidine (0.01-10 μg/paw) were injected into the paw prior to formalin injection (1%). Both drugs produced a dose-dependent antinociceptive effect. The EC50 values were estimated for individual drugs, and isobolograms were constructed. Tizanidine (EC50  = 0.125 ± 0.026 μg) was more potent than tramadol (EC50  = 16.45 ± 6.4 μg). The combination of tramadol-tizanidine at fixed ratios of 1:1 (EC50exp  = 67.43 ± 11 μg; EC50teo  = 8.28 ± 3.2 μg) and 3:1 (EC50exp  = 31.25 ± 9.49 μg; CE50teo  = 12.36 ± 4.8 μg) generated subadditivity (antagonism). On the basis of the current preclinical data, the pharmacological profile of the combination of tramadol-tizanidine produced antagonism. Thus, the utmost caution is required during the use of this combination in clinical practice, due to their antagonistic interaction.

Ascorbic Acid interaction with analgesic effect of morphine and tramadol in mice

Background:

Combining different analgesic drugs for improvement of drug efficacy is a recommended strategy intended to achieve the optimal therapeutic effects.

Objectives:

The purpose of the present study was to assess the nature of the interaction between ascorbic acid and two analgesic drugs, morphine and tramadol.

Materials and Methods:

The analgesic activity was assessed by the acetic acid writhing test in male Naval Medical Research Institute (NMRI) mice. The results were obtained using four to six animals in each group. All the drugs were injected intraperitoneally. The effective doses (ED) that produced 20%, 50%, and 65% antinociception (ED₂₀, ED₅₀ and ED₆₅) were calculated from the dose-response curve of each drug alone as well as co-administration of ascorbic acid and tramadol or morphine. The interaction index was calculated as experimental ED/theoretical ED. For each drug combination, ED₅₀, ED₂₀ and ED₆₅ were determined by linear regression analysis of the dose-response curve, and they were compared to theoretical ED₅₀, ED₂₀ and ED₆₅ using t-test.

Results:

The antinociceptive effects of all drugs were dose-dependent (ED₅₀was 206.1 mg/kg for ascorbic acid, 8.33 mg/kg for tramadol, and 0.79 mg/kg for morphine). The interaction index demonstrated additive effects at ED₅₀ and ED₆₅ for co-administration of ascorbic acid and tramadol or morphine. However, at ED₂₀, combination of ascorbic acid and tramadol or morphine showed synergic effects. The interaction index values of the combinations demonstrated the potency ratio of ascorbic acid/morphine to be lower than ascorbic acid/tramadol.

Conclusions:

This study demonstrated the results of interactions between ascorbic acid and tramadol or morphine. The results showed that the interaction effects on antinociception may be synergistic or additive, depending on the level of effect.

Antinociceptive synergy between diclofenac and morphine after local injection into the inflamed site

BACKGROUND

Combinations of non-steroidal anti-inflammatory drugs with opioids are frequently used to reduce opioid doses required in the clinical management of acute pain. The present study was designed to evaluate the possible antinociceptive interaction between morphine and diclofenac at peripheral level in male rats.

METHODS

Drugs were chosen based on their efficacy in the treatment of this kind of pain and as representative drugs of their respective analgesic groups. For the formalin test, 50 μ of 1% formalin solution was injected subcutaneously into the right hind paw. The interaction between morphine and diclofenac was evaluated by using isobolographic analysis and interaction index. Drug interaction was examined by administering fixed-ratio combinations of morphine-diclofenac (1 : 1 and 3 : 1) of their respective ED30 fractions.

RESULTS

Diclofenac and morphine reduced flinching behavior in a dose-dependent manner during phase 2 but not phase 1 of the formalin test. Isobolographic analysis showed a synergistic interaction for the combination of morphine and diclofenac after local peripheral administration.

CONCLUSIONS

Data suggest that the combination of morphine with diclofenac at the site of injury is synergistic and could be useful in the treatment of wounds, bruises, rheumatisms and other painful peripheral conditions associated with an inflammatory process.

Adjuvant effect of caffeine on acetylsalicylic acid anti-nociception: Prostaglandin E2 synthesis determination in carrageenan-induced peripheral inflammation in rat

In the present study, we report a synergistic interaction between acetylsalicylic acid (ASA) and caffeine (CAF) on the inhibition of nociception in a model of peripheral inflammation in rat; on the contrary no interaction have been found on anti-inflammatory effects and peripheral prostaglandin E2 (PGE-2) synthesis inhibition. Acute inflammation was induced by the subplantar injection of carrageenan into the right hind paw, and the effects of the drugs were evaluated from 0 to 5h. Nociception was assessed using the Randall & Selitto test, and the inflammatory response by plethismometry. Oral administration of ASA (10-400mg/kg) induced dose-related anti-nociceptive and anti-inflammatory effects. On the other hand, oral CAF administration (5-50mg/kg) did not show a dose-related inhibitory effect, neither on the inhibition of nociception nor on the inflammatory response. To analyze a possible interaction between both drugs a dose-response curve to ASA plus a fixed dose of CAF (5mg/kg) was obtained 3h after the injection of carrageenan, when the inflammatory pain peaked. A fixed dose of CAF was able to improve the anti-nociceptive, but not the anti-inflammatory, effects of ASA. We also assessed, by enzyme immunoassay, the effects of the combination on peripheral PGE-2 levels: CAF did not alter the inhibitory effect of ASA on PGE-2 synthesis. Our results corroborate the well-known clinical effects of combining ASA and CAF; on the other hand, we rule out that prostaglandin synthesis inhibition at peripheral sites would be the mechanism responsible of the adjuvant anti-nociceptive effect of CAF.

Fentanyl-trazodone-paracetamol triple drug combination: multimodal analgesia in a mouse model of visceral pain

Multimodal or balanced analgesia is commonly used in the management of acute and chronic pain in humans, in order to achieve the best analgesic/safety profile. Here, by using a model of visceral acute tonic pain, the acetic acid-induced writhing test of mice, we show a synergistic interaction between fentanyl, trazodone and paracetamol on the inhibition of nociception. First of all, once assessed that all drugs induced dose-related antinociceptive effects, they were mixed in fixed ratio (1:1) combinations and a synergistic drug-drug interaction was obtained in all circumstances. Thereafter, we assayed the effects of the triple combination of fentanyl-trazodone-paracetamol and it was demonstrated that they displayed a potent synergistic interaction on the inhibition of acetic acid-mediated nociception. Interestingly, drug dosage reduction permitted to reduce the incidence of possible adverse effects, namely exploratory activity and motor coordination, thus it was demonstrated that it improved the benefit/risk profile of such treatment. Afterwards, we attempted to elucidate the mechanism of action of such interaction, by means of the non-selective opioid receptor antagonist naloxone. Interestingly, naloxone completely antagonized the antinociceptive effects of fentanyl, and it also partially reversed paracetamol and trazodone mediated analgesia. Furthermore, when naloxone was co-administered with the triple-drug treatment it blocked the previously observed enhanced antinociceptive effects of the combination. Thus, these results indicated that the endogenous opioid system played a main role in the present drug-drug interaction. Overall, the triple combination of fentanyl-trazodone-paracetamol induced a potent synergistic antinociceptive effect, which could be of interest for optimal multimodal clinical analgesia.

Synthesis and investigations of double-pharmacophore ligands for treatment of chronic and neuropathic pain

Acids 9a-f as possible bivalent ligands designed as a structural combination of opioid mu-agonist (Fentanyl) and NSAID (Indomethacin) activities and produced compounds which were tested as analgesics. The obtained series of compounds exhibits low affinity and activity both at opioid receptors and as cyclooxygenase (COX) inhibitors. One explanation of the weak opioid activity could be stereochemical peculiarities of these bivalent compounds which differ significantly from the fentanyl skeleton. The absence of significant COX inhibitory properties could be explained by the required substitution of an acyl fragment in the indomethacin structure for 4-piperidyl.

Supra-additive effects of tramadol and acetaminophen in a human pain model ☆

The combination of analgesic drugs with different pharmacological properties may show better efficacy with less side effects. Aim of this study was to examine the analgesic and antihyperalgesic properties of the weak opioid tramadol and the non-opioid acetaminophen, alone as well as in combination, in an experimental pain model in humans. After approval of the local Ethics Committee, 17 healthy volunteers were enrolled in this double-blind and placebo-controlled study in a cross-over design. Transcutaneous electrical stimulation at high current densities (29.6+/-16.2 mA) induced spontaneous acute pain (NRS=6 of 10) and distinct areas of hyperalgesia for painful mechanical stimuli (pinprick-hyperalgesia). Pain intensities as well as the extent of the areas of hyperalgesia were assessed before, during and 150 min after a 15 min lasting intravenous infusion of acetaminophen (650 mg), tramadol (75 mg), a combination of both (325 mg acetaminophen and 37.5mg tramadol), or saline 0.9%. Tramadol led to a maximum pain reduction of 11.7+/-4.2% with negligible antihyperalgesic properties. In contrast, acetaminophen led to a similar pain reduction (9.8+/-4.4%), but a sustained antihyperalgesic effect (34.5+/-14.0% reduction of hyperalgesic area). The combination of both analgesics at half doses led to a supra-additive pain reduction of 15.2+/-5.7% and an enhanced antihyperalgesic effect (41.1+/-14.3% reduction of hyperalgesic areas) as compared to single administration of acetaminophen. Our study provides first results on interactions of tramadol and acetaminophen on experimental pain and hyperalgesia in humans. Pharmacodynamic modeling combined with the isobolographic technique showed supra-additive effects of the combination of acetaminophen and tramadol concerning both, analgesia and antihyperalgesia. The results might act as a rationale for combining both analgesics.

Synergistic interaction between dexamethasone and tramadol in a murine model of acute visceral pain

Tramadol is effective in the management of mild to moderate postoperative pain, but its administration is associated with nausea and vomiting. Patients treated with tramadol, often receive dexamethasone as antiemetic. The aim of our investigation was to assess if the two drugs interact in a murine model of acute visceral pain. Using the acetic acid writhing test in mice, we assessed the antinociceptive effects of tramadol and dexamethasone (a glucocorticoid with antiemetic effect) administrated individually and in a 1 : 1 fixed ratio combination. Tramadol and dexamethasone induced a dose-dependent inhibition of the writhing response when administered individually, with ED(50) values of 2.9 [2.09-4.31, 95% confidence limit (CL)] mg/kg, and 0.13 (0.05-0.29, 95% CL) mg/kg, respectively. The ED(50) of the combination was 0.13 (0.01-0.29, 95% CL) mg/kg; the isobolographic and interaction index analysis revealed a synergistic interaction. The results suggest that the combination of tramadol and dexamethasone could be beneficial in the management of postoperative pain in humans.

Isobolographic analyses of the gabapentin-metamizol combination after local peripheral, intrathecal and oral administration in the rat

This study was designed to evaluate the possible antinociceptive interaction between gabapentin and metamizol on formalin-induced nociception. Gabapentin, metamizol or a fixed dose-ratio combination of both drugs were assessed after local peripheral, intrathecal and oral administration in rats. Isobolographic analyses were employed to define the nature of the interaction between drugs. Gabapentin, metamizol and gabapentin-metamizol combinations yielded a dose-dependent antinociceptive effect when administered by the three different routes. ED30 values were estimated for the individual drugs and isobolograms were constructed. Theoretical ED30 values for the combination estimated from the isobolograms were 21.11 +/- 1.17 microg/paw, 104.6 +/- 5.5 microg/rat and 78.8 +/- 5.5 mg/kg for the local peripheral, intrathecal and oral administration routes, respectively. These values were significantly higher than the experimentally obtained ED30 values which were 11.3 +/- 1.5 microg/paw, 36.8 +/- 3.1 microg/rat and 15 +/- 1.2 mg/kg indicating a synergistic interaction. Systemic administration resulted in the highest synergism. Data confirm that low doses of the gabapentin and metamizol can interact synergistically to reduce formalin-induced nociceptive behavior suggesting that this combination could be useful to treat inflammatory pain in humans.

Interaction between tramadol and two anti-emetics on nociception and gastrointestinal transit in mice

BACKGROUND

Clinical studies suggest that tramadol-induced analgesia is partially antagonized by ondansetron.

AIMS

To investigate the type of interaction between tramadol and two anti-emetics on antinociception and gastrointestinal transit in mice.

METHODS

We assessed the antinociceptive (acetic acid writhing test, plantar test) and antitransit (charcoal meal) effects of tramadol individually, and combined with ondansetron or droperidol in female Swiss CD-1 mice. Isobolograms and analysis of variance were used to determine the type of interaction.

RESULTS

In the writhing test, tramadol, ondansetron and droperidol, each induced dose-related inhibition of nociception. The ED(50)'s were: tramadol 4.2+/-0.33 mg kg(-1); ondansetron 1.03+/-0.05 mg kg(-1), and droperidol 1.00+/-0.14 mg kg(-1). Dose-response curves were also obtained with tramadol combined with ondansetron or droperidol at 1:1 fixed ratios. The isobolographic analysis demonstrated antagonism for both combinations. In the plantar test, the ED(50) for tramadol was 51.4+/-2.3 mg kg(-1), but no dose-response curves could be obtained with ondansetron or droperidol individually. The interaction was assessed from dose-response curves to tramadol in the presence of a fixed dose of ondansetron (0.1 mg kg(-1)) or droperidol (0.05 mg kg(-1)). The results show antagonism between tramadol-ondansetron (p<0.05) and no interaction for the tramadol-droperidol combination. Both anti-emetics antagonized the antitransit effects of tramadol.

CONCLUSIONS

The interaction of tramadol with ondansetron or droperidol on antinociception can be antagonistic or additive, depending on the type of stimuli. Both anti-emetics antagonize the anti-transit effects of tramadol. The results demonstrate antagonism between tramadol and the two anti-emetics for analgesia and inhibition of gastrointestinal transit, supporting previous clinical studies.