Presurgical ketoprofen, but not morphine, dipyrone, diclofenac or tenoxicam, preempts post-incisional mechanical allodynia in rats

Plasma proteomic changes in response to surgical trauma and a novel transdermal analgesic treatment in dogs

Assessment of pain responses and inflammation during animal surgery is difficult because traditional methods, such as visual analogue scores, are not applicable while under anaesthesia. Acute phase proteins (APPs), such as C-reactive protein and haptoglobin, that are typically monitored in veterinary research, do not show a significant change until at least 2 h post-surgery and therefore, immediate pathophysiological changes are uncertain. The current study used sequential window acquisition of all theoretical mass spectra (SWATH-MS) to investigate plasma proteome changes that occur immediately following surgery in dogs and also to assess the efficacy of a novel transdermal ketoprofen (TK) formulation. Castration was chosen as surgical model in this study. The procedure was performed on twelve dogs (n = 6 in two groups) and blood samples were collected at 0 h, 1 and 2 h after surgery for proteomic analysis. Following surgery, there was a general downregulation of proteins, including complement C- 3, complement factor B, complement factor D, transthyretin, and proteins associated with lipid, cholesterol, and glucose metabolisms, reflecting the systemic response to surgical trauma. Many of these changes were diminished in the transdermal group (TD) since ketoprofen, a non-steroidal anti-inflammatory drug (NSAID), inhibits prostanoids and the associated chemotactic neutrophil migration to site of tissue injury. SIGNIFICANCE: SWATH-MS Proteomic analysis revealed significant changes in plasma proteins, predominantly involved in early acute phase and inflammatory response at 1 & 2 h after surgery in castrated dogs. Pre-operative application of transdermal ketoprofen formulation had reduced the systemic immune response, which was confirmed by negligible alteration of proteins in transdermal treated group. A key outcome of this experiment was studying the efficacy of a novel transdermal NSAID formulation in dogs.

The effect of pre-emptive analgesia on the level of postoperative pain in women undergoing surgery for breast neoplasm

AIM OF THE STUDY

Dynamic development of research on pain has resulted in the formulation of the concept of pre-emptive analgesia, which involves administration of analgesics before the first pain-producing stimulus appears. It is meant to prevent increased sensitivity to pain in the postoperative period. The aim of this study was to assess the possibilities of modifying the intensity of postoperative pain evaluated with the visual analogue scale (VAS) in patients after surgical treatment for breast neoplasm offered by pre-emptive analgesia.

MATERIAL AND METHODS

The intensity of postoperative pain was measured immediately after the surgery as well as 6, 12, 18, and 24 hours later in 100 women who had undergone surgery for breast tumour. The correlation between experienced pain and the type of analgesic administered pre-emptively, including metamizole, tramadol, ketoprofen, and placebo was examined. The effect of other correlates such as the extensiveness of surgery, systolic and diastolic blood pressure, and heart rate on the level of experienced pain as well as the usefulness of physiological parameters for its assessment were also analysed.

RESULTS

The conducted study demonstrated the effectiveness of tramadol (p = 0.004) and ketoprofen (p = 0.039) administered half an hour before the beginning of surgery, but there was no similar effect in the case of metamizole (p = 1.0). A positive correlation was observed between the level of experienced pain and blood pressure values (p < 0.001). Heart rate does not seem to be significantly linked with the intensity of experienced pain (p = 0.157).

Dipyrone has no effects on bone healing of tibial fractures in rats

OBJECTIVE:

To evaluate the effect of dipyrone on healing of tibial fractures in rats.

METHODS:

Fourty-two Wistar rats were used, with mean body weight of 280g. After being anesthetized, they were submitted to closed fracture of the tibia and fibula of the right posterior paw through manual force. The rats were randomly divided into three groups: the control group that received a daily intraperitoneal injection of saline solution; group D-40, that received saline injection containing 40mg/Kg dipyrone; and group D-80, that received saline injection containing 80mg/Kg dipyrone. After 28 days the rats were sacrificed and received a new label code that was known by only one researcher. The fractured limbs were then amputated and X-rayed. The tibias were disarticulated and subjected to mechanical, radiological and histological evaluation. For statistical analysis the Kruskal-Wallis test was used at a significance level of 5%.

RESULTS:

There wasn't any type of dipyrone effect on healing of rats tibial fractures in relation to the control group.

CONCLUSION:

Dipyrone may be used safely for pain control in the treatment of fractures, without any interference on bone healing. Level of Evidence II, Controlled Laboratory Study.

Extended duration local anesthetic agent in a rat paw model

Encapsulated local anesthetics extend postoperative analgesic effect following site-directed nerve injection; potentially reducing postoperative complications. Our study aim was to investigate efficacy of our improved extended duration formulation - 15% bupivacaine in poly(DL-lactic acid co castor oil) 3:7 synthesized by ring opening polymerization. In vitro, around 70% of bupivacaine was released from the p(DLLA-CO) 3:7 after 10 days. A single injection of the optimal formulation of 15% bupivacaine-polymer or plain (0.5%) bupivacaine (control), was injected via a 22G needle beside the sciatic nerve of Sprague-Dawley rats under anesthesia; followed (in some animals) by a 1cm longitudinal incision through the skin and fascia of the paw area. Behavioral tests for sensory and motor block assessment were done using Hargreave's hot plate score, von Frey filaments and rearing count. The 15% bupivacaine formulation significantly prolonged sensory block duration up to at least 48 h. Following surgery, motor block was observed for 48 h following administration of bupivacaine-polymer formulation and rearing was reduced (returning to baseline after 48 h). No significant differences in mechanical nociceptive response were observed. The optimized bupivacaine-polymer formulation prolonged duration of local anesthesia effect in our animal model up to at least 48 h.

Ketoprofen produces modality-specific inhibition of pain behaviors in rats after plantar incision

BACKGROUND

Postoperative pain remains a significant problem despite optimal treatment with current drugs. Nonsteroidal antiinflammatory drugs reduce inflammation and provide analgesia but are associated with adverse side effects.

METHODS

We tested low doses (0.5-5 mg/kg) of parenteral ketoprofen against pain-related behaviors after plantar incision in rats. To further evaluate the potential sites of action of ketoprofen in our model, a novel, sustained-release microparticle formulation of ketoprofen was placed into the wound, and tested for its effects on pain behaviors. Intrathecal ketoprofen (150 microg) was also studied. Plasma samples were assayed for drug concentrations.

RESULTS

We found that low doses of parenterally administered ketoprofen produced a modality-specific effect on pain behaviors; guarding after incision was decreased, whereas no inhibition of exaggerated responses to heat or mechanical stimuli was evident. Very low doses, 0.5 mg/kg, could produce inhibition of guarding. The locally applied sustained-release ketoprofen-eluting microparticles and intrathecally administered ketoprofen also produced a modality-specific effect on pain behaviors after incision, inhibiting only guarding. Plasma levels of ketoprofen after parenteral or local administration were in the range of therapeutic blood levels in postoperative patients.

CONCLUSIONS

This study demonstrates that ketoprofen is an effective analgesic for nonevoked guarding in rats after plantar incision. There was no effect on mechanical or heat responses, which highlights the importance of multiple-modality testing of pain behaviors for drug evaluation. We found efficacy at doses used clinically in postoperative patients.

Postoperative Administration of the Analgesic Tramadol, but Not the Selective Cyclooxygenase-2 Inhibitor Parecoxib, Abolishes Postoperative Hyperalgesia in a New Model of Postoperative Pain in Rats

BACKGROUND/AIMS

Using a new animal model of postoperative pain we recently developed, we investigated whether the selective cyclooxygenase-2 (COX-2) inhibitor parecoxib sodium, and the analgesic tramadol hydrochloride, attenuated mechanical primary hyperalgesia induced by minor surgery on the rat tail.

METHODS

For surgery, rats were anesthetized with isoflurane, a 20-mm-long incision was made through the skin and fascia of their tails, and the wound was sutured. Immediately after surgery, rats were injected intraperitoneally with parecoxib sodium (10 or 20 mg x kg(-1)), tramadol hydrochloride (10 mg x kg(-1)), or sterile saline (0.1 ml x kg(-1)). Hyperalgesia was assessed by measuring rats' response latencies to a blunt noxious mechanical stimulus (4 N) applied to their tails. Nociceptive testing was performed before surgery and 90 min after surgery.

RESULTS

Hyperalgesia was present in all saline-injected animals within 90 min of surgery. This hyperalgesia was not attenuated by postoperative injection of parecoxib. However, administration of tramadol completely prevented the development of postoperative hyperalgesia.

CONCLUSION

We have shown that the hyperalgesia in our model of postoperative pain is responsive to treatment with the analgesic tramadol, but it is not responsive to the selective COX-2 inhibitor parecoxib at the doses we used.

Comparison of pre- versus post-incision administration of intraplantar indomethacin and MK886 in a rat model of postoperative pain

The amplification of pain long after the initial stimulus may be avoided if the treatment of pain is introduced before its initiation. However, conflicting evidence exists about the efficacy of such preemptive analgesia for the management of postoperative pain. This study compares the efficacy of intraplantar administration of indomethacin (a non-selective inhibitor of cyclooxygenase) and MK886 (an inhibitor of 5-lipoxygenase-activating protein), separately or in combination to produce preemptive analgesia in a model of surgical incisional pain in male Wistar rats. All incised rats (5 to 6 rats per group) had allodynia at 2, 6, and 24 h after surgery as evaluated using von Frey filaments. MK886, but not indomethacin (50 to 200 microg/paw), reduced the allodynia when injected either 1 h before or 1 h after surgery. The effect of preoperative MK886 (160 microg/paw) against incisional allodynia had a magnitude apparently similar to that produced by postoperative MK886. Pre-, but not postoperative MK886 (80 microg/paw) reduced the allodynia but the effect was seen only at 6 h after surgery. In contrast, MK886 (40 microg/paw) intensified the allodynia observed 2 h after the incision either injected before or after surgery. MK886 or indomethacin alone did not provide preemptive analgesia in the model of incisional pain. In contrast, the combination of MK886 with indomethacin reduced the allodynia more effectively when used before than after surgery, thus fulfilling the criteria for preemptive analgesia. In conclusion, preoperative inhibition of the local generation of both prostaglandins and leukotrienes by surgical incision may be an alternative to provide preemptive analgesia.

From preemptive to preventive analgesia

PURPOSE OF REVIEW

Much effort has been taken to prove that a treatment initiated before surgery is more effective in reducing postoperative pain compared with the same intervention started after surgery. Clinical studies failed to demonstrate major clinical benefits of preemptive analgesia, however, and the results of recent systemic reviews are equivocal. The present review will discuss recent clinical as well as experimental evidence of preemptive analgesia and examine the implications of a preventive postoperative pain treatment.

RECENT FINDINGS

Recent preclinical and clinical studies give strong evidence that neuronal hypersensitivity and nociception after incision is mainly maintained by the afferent barrage of sensitized nociceptors across the perioperative period. This is in contrast to pain states of other origin in which prolonged hypersensitivity is initiated during the injury. Therefore, not timing but duration and efficacy of an analgesic and antihyperalgesic intervention are most important for treating pain and hyperalgesia after surgery.

SUMMARY

Extending a multimodal analgesic treatment into the postoperative period to prevent postoperative pain may be superior compared with preemptive analgesia. In the future, appropriate drug combinations, drug concentrations and duration of preventive strategies need to be determined to be most beneficial for the management of acute and chronic pain after surgery.

Influence of antipyretic drugs on the labeling of blood elements with technetium-99m

Acetaminophen (AAP), acetylsalicylic acid (ASA) and dipyrone (DIP) are antipyretic and analgesics drugs that have wide use in health sciences. Some drugs can modify the labeling of blood elements with technetium-99m (99mTc). This work has evaluated the effect of AAP, ASA and DIP on the labeling of the blood elements with 99mTc. Blood was incubated with different concentrations of the drugs before the 99mTc-labeled process. Plasma (P), blood cells (BC), insoluble (IF-P, IF-BC) and soluble (SF-P, SF-BC) fractions were separated and percentage of radioactivity (%ATI) in each fraction was determined. Data have shown that the antipyretic drugs used in this study did not significantly modify the fixation of 99mTc on the blood elements when the experiments were carried out with the doses usually used in human beings. Although the experiments were carried out with rats, it is possible to suggest that AAP, ASA or DIP should not interfere with the procedures in nuclear medicine involving the labeling of blood elements with 99mTc.

The novel analgesic, F 13640, produces intra- and postoperative analgesia in a rat model of surgical pain

F 13640 is a newly discovered high-efficacy 5-HT(1A) receptor agonist that produces exceptional analgesia in animal models of tonic and chronic, nociceptive and neuropathic pains by novel molecular and neuroadaptive mechanisms. Here we examined the effects of F 13640 and remifentanil (0.63 mg/kg with either compound) when injected i.p. either before or 15 min after rats underwent orthopedic surgery. Surgery consisted of the drilling of a hole in the calcaneus bone and of an incision of the skin, fascia and plantar muscle of one foot. During surgery, the concentration of volatile isoflurane was progressively incremented depending on the animal's response to surgical maneuvers. Other experiments examined the dose-dependent effects of F 13640 (0.04 to 0.63 mg/kg) on surgical pain as well as on the Minimum Alveolar Concentration of isoflurane. Both F 13640 and remifentanil markedly reduced the intra-operative isoflurane requirement. F 13640 also reduced measures of postoperative pain (i.e., paw elevation and flexion). With these postoperative measures, remifentanil produced short-lived analgesia followed by hyperalgesia. F 13640 significantly reduced both surgical pain and the isoflurane Minimum Alveolar Concentration from 0.16 mg/kg onward. F 13640 produced powerful intra- and postoperative analgesia in rats undergoing orthopedic surgery. Unlike the opioid, remifentanil, F 13640 caused no hyperalgesia with ongoing postoperative pain, and should remain effective with protracted postoperative use.

Pharmacological characterisation of a rat model of incisional pain

1. Both clinical and preclinical models of postsurgical pain are being used more frequently in the early evaluation of new chemical entities. In order to assess the validity and reliability of a rat model of postincisional pain, the effects of different classes of clinically effective analgesic drugs were evaluated against multiple behavioural end points. 2. Following surgical incision, under general anaesthesia, of the plantar surface of the rat hind paw, we determined the time course of mechanical hyperalgesia, tactile allodynia and hind limb weight bearing using the Randall-Selitto (paw pressure) assay, electronic von Frey and dual channel weight averager, respectively. Behavioural evaluations began 24 h following surgery, and were continued for 9-14 days. 3. Mechanical hyperalgesia, tactile allodynia and a decrease in weight bearing were present on the affected limb within 1 day of surgery with maximum sensitivity 1-3 days postsurgery. Accordingly, we examined the effect of nonsteroidal antiinflammatory drugs (NSAIDs), morphine and gabapentin, on established hyperalgesia and allodynia, 1 day following plantar incision.4. In accordance with previous reports, both systemic morphine and gabapentin administration reversed mechanical hyperalgesia and tactile allodynia in the incised rat hind paw. Both drugs were more potent against mechanical hyperalgesia than tactile allodynia. 5. All of the NSAIDs tested, including cyclooxygenase 2 selective inhibitors, reversed mechanical hyperalgesia and tactile allodynia in the incised rat hind paw. The rank order of potency for both hyperalgesia and allodynia was indomethacin > celecoxib > etoricoxib > naproxen. 6. We have investigated the potency and efficacy of different classes of analgesic drugs in a rat model of postincisional pain. The rank order of potency for these drugs reflects their utility in treating postoperative pain in the clinic. As these compounds showed reliable efficacy across two different behavioural end points, the Randall-Selitto (paw pressure) assay and electronic von Frey, these methods may prove useful in the study of postsurgical pain and the assessment of novel treatments.