Synergistic interaction between tramadol and dipyrone in thermal paw stimulation model in the rat

Pharmacological Interaction Between Cannabidiol and Tramadol on Experimental Diabetic Neuropathic Pain: An Isobolographic Analysis

Introduction: Diabetic neuropathies are the most prevalent chronic complications of diabetes, characterized by pain and substantial morbidity. Although many drugs have been approved for the treatment of this type of pain, including gabapentin, tramadol (TMD), and classical opioids, it is common to report short-term results or potentially severe side effects. TMD, recommended as a second-line treatment can lead to unwanted side effects. Cannabidiol (CBD) has been gaining attention recently due to its therapeutic properties, including pain management. This study aimed to characterize the pharmacological interaction between CBD and TMD over the mechanical allodynia associated with experimental diabetes using isobolographic analysis. Materials and Methods: After diabetes induction by streptozotocin (STZ), diabetic rats were systemically treated with CBD or TMD alone or in combination (doses calculated based on linear regression of effective dose 40% [ED40]) and had the mechanical threshold evaluated using the electronic Von Frey apparatus. Both experimental and theoretical additive ED40 values (Zmix and Zadd, respectively) were determined for the combination of CBD plus TMD in this model. Results: Acute treatment with CBD (3 or 10 mg/kg) or TMD (2.5, 5, 10, or 20 mg/kg) alone or in combination (0.38+1.65 or 1.14+4.95 mg/kg) significantly improved the mechanical allodynia in STZ-diabetic rats. Isobolographic analysis revealed that experimental ED40 of the combination (Zmix) was 1.9 mg/kg (95% confidence interval [CI]=1.2-2.9) and did not differ from the theoretical additive ED40 2.0 mg/kg (95% CI=1.5-2.8; Zadd), suggesting an additive antinociceptive effect in this model. Conclusions: Using an isobolographic analysis, these results provide evidence of additive pharmacological interaction between CBD and TMD over the neuropathic pain associated with experimental diabetes induced by STZ.

Peripheral synergism between tramadol and ibuprofen in the formalin test

Preclinical Research Analgesics with different mechanisms of action can be combined in order to obtain pharmacological synergism, employing lower doses of each agent, thus diminishing side effects. For instance, an atypical dual analgesic such as tramadol (TMD) and a nonsteroidal anti-inflammatory drug such as ibuprofen (IBU) are good candidates to be evaluated when combined and applied peripherally. The present study was conducted to evaluate possible local synergism between TMD and IBU when combined peripherally using the formalin test in rats. The effects of the individual analgesics and their combinations were evaluated simultaneously using a 5% formalin dilution. Dose-effect curves were determined for TMD (50-400 μg/paw) and IBU (1-100 μg/paw). Experimental effective doses were evaluated and isobolographic analyses were constructed to evaluate TMD-IBU combination synergism. Both drugs produced a dose-dependent analgesic effect when applied separately. Isobolographic analysis showed synergism during phase 1 (0-10 min) and phase 2 (15-60 min) when compared with theoretical doses (P < 0.05), with interaction indexes of 0.06 and 0.09, respectively. The present information supports the peripheral analgesic effect of TMD and IBU, especially when combined at appropriate doses.