Local analgesic effect of tramadol is not mediated by opioid receptors in early postoperative pain in rats

Nitric oxide and potassium channels but not opioid and cannabinoid receptors mediate tramadol-induced peripheral antinociception in rat model of paw pressure withdrawal

Tramadol, an analgesic classified as an "atypical opioid", exhibits both opioid and non-opioid mechanisms of action. This study aimed to explore these mechanisms, specifically the opioid-, cannabinoid-, nitric oxide-, and potassium channel-based mechanisms, which contribute to the peripheral antinociception effect of tramadol, in an experimental rat model. The nociceptive threshold was determined using paw pressure withdrawal. To examine the mechanisms of action, several substances were administered intraplantarly: naloxone, a non-selective opioid antagonist (50 µg/paw); AM251 (80 µg/paw) and AM630 (100 µg/paw) as the selective antagonists for types 1 and 2 cannabinoid receptors, respectively; nitric oxide synthase inhibitors L-NOArg, L-NIO, L-NPA, and L-NIL (24 µg/paw); and the enzyme inhibitors of guanylatocyclase and phosphodiesterase of cGMP, ODQ, and zaprinast. Additionally, potassium channel blockers glibenclamide, tetraethylammonium, dequalinium, and paxillin were used. The results showed that opioid and cannabinoid receptor antagonists did not reverse tramadol's effects. L-NOarg, L-NIO, and L-NPA partially reversed antinociception, while ODQ completely reversed, and zaprinast enhanced tramadol's antinociception effect. Notably, glibenclamide blocked tramadol's antinociception in a dose-dependent manner. These findings suggest that tramadol's peripheral antinociception effect is likely mediated by the nitrergic pathway and sensitive ATP potassium channels, rather than the opioid and cannabinoid pathways.

Tramadol as a local anaesthetic agent in dentistry: A systematic review of local and systemic adverse effects

Tramadol is an effective alternative local anaesthetic (LA) agent available in dentistry. This review aims to help guide practice by providing clinicians with relevant data regarding adverse effects (AE) associated with locally administered tramadol in the oral environment. A systematic search of three electronic databases was performed to identify relevant studies reporting AE associated with locally administered tramadol in the oral setting. Selected studies were reviewed and included based on inclusion and exclusion criteria. Data collected included: publication year, study design, participant numbers, adverse effects and follow-up duration. Fifteen articles were included comprising of 547 tramadol participants across eight exodontia and seven non-exodontia studies. Thirty-eight associated AE were reported. Nausea was the most commonly reported (4.6%), followed by dizziness (1.3%), vomiting (0.7%) and local erythema (0.4%). No other AE were reported. The prevalence of total AE was similar in ≥ 50 mg tramadol doses (7.2-7.3%); however the total affected number is not dose dependent. The prevalence of AE and affected participants was less when tramadol was used as a sole LA rather than as an adjunct (5.6% vs. 7.9% and 3.4-5.6% vs. 6.3%, respectively). Thus, tramadol is a safe LA agent with a low prevalence of AE when administered in the dental setting.

Analgesic Efficacy and Safety of Local Infiltration Following Lumbar Decompression Surgery: A Systematic Review of Randomized Controlled Trials

This systematic review aims to appraise available clinical evidence on the efficacy and safety of wound infiltration with adjuvants to local anesthetics (LAs) for pain control after lumbar spine surgery. A database search was conducted to identify randomized controlled trials (RCTs) pertinent to wound infiltration with analgesics or miscellaneous drugs adjunctive to LAs compared with sole LAs or placebo. The outcomes of interest were postoperative rescue analgesic consumption, pain intensity, time to first analgesic request, and the occurrence of adverse events. Twelve double-blind RCTs enrolling 925 patients were selected for qualitative analysis. Most studies were of moderate-to-good methodological quality. Dexmedetomidine reduced analgesic requirements and pain intensity within 24 h postoperatively, while prolonged pain relief was reported by one RCT involving adjunctive clonidine. Data on local magnesium seem promising yet difficult to interpret. No clear analgesic superiority could be attributed to steroids. Τramadol co-infiltration was equally effective as sole tramadol but superior to LAs. No serious adverse events were reported. Due to methodological inconsistencies and lack of robust data, no definite conclusions could be drawn on the analgesic effect of local infiltrates in patients undergoing lumbar surgery. The probable positive analgesic efficacy of adjunctive dexmedetomidine and magnesium needs further evaluation.

Local infiltration of tramadol as an effective strategy to reduce post-operative pain: a systematic review protocol and meta-analysis

OBJECTIVE

The purpose of this review is to evaluate the use and effectiveness of the local administration of tramadol in reducing post-operative pain during surgical interventions.

METHODS

The PubMed, EMBASE and Cochrane Central Register of Controlled Trials (CENTRAL) databases will be searched for this review. This systematic review will include studies evaluating the clinical efficacy of the local infiltration of tramadol, with no study design restrictions. Only studies that present clear descriptions of local tramadol administration are published in peer-reviewed journals in the English, Italian, Spanish, French, Portuguese or German language and are published in full will be taken into consideration. A meta-analysis will be performed when there is sufficient clinical homogeneity among the retrieved studies, and only randomized controlled studies and quasi-randomized controlled studies will be included. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach will be used to assess the certainty in the evidence. If a quantitative analysis cannot be conducted, a qualitative description of the results of the retrieved studies will be provided.

RESULTS

A high-quality synthesis of the current evidence on the local administration of tramadol for managing post-surgical pain will be illustrated using subjective reports and objective measures of performance. The primary outcomes will include the magnitude of post-operative pain intensity improvement, with improvement being as defined by a reduction by at least 2 points in the visual analogue scale (VAS) score or numerical rating scale (NRS) score. The secondary outcomes will be the magnitude of reduction in tramadol rescue doses and in other analgesic drug doses.

CONCLUSION

This protocol will present evidence on the efficacy of tramadol in relieving post-surgical pain.

SYSTEMIC REVIEW REGISTRATION

PROSPERO CRD42018087381.

Comparative Study between Preemptive and Postoperative Intra-Articular Injection of Levobupivacaine and Tramadol for Control of Postoperative Pain

Background:

This study had been formulated to evaluate and compare the analgesic effect of preemptive (PE), postoperative (PO), and combined knee intra-articular injection (IAI) of levobupivacaine and tramadol after knee arthroscopy.

Materials and Methods:

A total of 220 patients assigned for therapeutic knee arthroscopy were divided into four equal groups. Patients in Group C received IAI of 20 mL (0.5%) levobupivacaine preoperative, meanwhile patients in Group PE received IAI of 18 mL (0.5%) levobupivacaine with 100 mg tramadol (2 mL). Patients in Group PO received IAI of 18 mL (0.5%) levobupivacaine with 100 mg tramadol (2 mL) postoperatively, whereas patients in Group PE/PO received IAI of 19 mL (0.25%) levobupivacaine with 50 mg tramadol (1 mL) preoperatively and postoperatively. Numeric rating scale (NRS) had been used to assess pain sensation. Duration till the first request of rescue analgesia and number of requests were recorded.

Results:

NRS scores were significantly higher in Group C compared to other groups and in Group PE in comparison to PO and PE/PO groups. Frequency of rescue analgesia requests was significantly higher in Group C with significantly higher mean times of requests, while was significantly lower in Group PE/PO with significantly lower mean times of requests when compared to groups PE and PO.

Conclusions:

PE levobupivacaine and tramadol IAI provided satisfactory level of PO analgesia after therapeutic arthroscopy. However, combined PE and PO levobupivacaine and tramadol IAI of half dose provided PO analgesia superior to that provided by either PE or PO full-dose IAI.

Local analgesic effect of tramadol is mediated by opioid receptors in late postoperative pain after plantar incision in rats

Tramadol is a drug used to treat moderate to severe pain. It is known to present a peripheral effect, but the local mechanisms underlying its actions remain unclear. The role of peripheral opioid receptors in postoperative pain is not well understood. In the present study, we examined the peripheral opioid receptors to determine the local effect of tramadol in a plantar incision pain model. Rats were subjected to plantar incision and divided into four groups on postoperative day (POD) 1: SF_SF, 0.9% NaCl injected into the right hindpaw; SF_TraI, 0.9% NaCl and tramadol injected into the right hindpaw; SF_TraC, 0.9% NaCl and tramadol injected into the contralateral hindpaw; and Nal_Tra, naloxone and tramadol injected into the ipsilateral hindpaw. To determine the animals' nociceptive threshold, mechanical hyperalgesia was measured before incision, on POD1 before treatment and at 15, 30, 45, and 60 minutes after the incision. The same procedure was repeated on the POD2. The expression levels of μ-opioid receptor (MOR) and δ-opioid receptor (DOR) were obtained through immunoblotting assays in the lumbar dorsal root ganglia (L3-L6) in naïve rats and 1, 2, 3, and 7 days after the incision. Our results showed that the plantar incision was able to cause an increase in mechanical hyperalgesia and that tramadol reversed this hyperalgesia on POD1 and POD2. Tramadol injections in the contralateral paw did not affect the animals' nociceptive threshold. Naloxone was able to antagonize the tramadol effect partially on POD1 and completely on POD2. The DOR expression increased on POD2, POD3, and POD7, whereas the MOR expression did not change. Together, our results show that tramadol promoted a local analgesic effect in the postoperative pain model that was antagonized by naloxone in POD2, alongside the increase of DOR expression.