Mechanism of action of nonsteroidal anti-inflammatory drugs

Ibuprofen for acute postoperative pain in children

BACKGROUND

Children often require pain management following surgery to avoid suffering. Effective pain management has consequences for healing time and quality of life. Ibuprofen, a frequently used non-steroidal anti-inflammatory drug (NSAID) administered to children, is used to treat pain and inflammation in the postoperative period.

OBJECTIVES

1) To assess the efficacy and safety of ibuprofen (any dose) for acute postoperative pain management in children compared with placebo or other active comparators. 2) To compare ibuprofen administered at different doses, routes (e.g. oral, intravenous, etc.), or strategies (e.g. as needed versus as scheduled).

SEARCH METHODS

We used standard Cochrane search methods. We searched CENTRAL, MEDLINE, Embase, CINAHL and trials registries in August 2023.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) in children aged 17 years and younger, treated for acute postoperative or postprocedural pain, that compared ibuprofen to placebo or any active comparator. We included RCTs that compared different administration routes, doses of ibuprofen and schedules.

DATA COLLECTION AND ANALYSIS

We adhered to standard Cochrane methods for data collection and analysis. Our primary outcomes were pain relief reported by the child, pain intensity reported by the child, adverse events, and serious adverse events. We present results using risk ratios (RR) and standardised mean differences (SMD), with the associated confidence intervals (CI). We used GRADE to assess the certainty of the evidence.

MAIN RESULTS

We included 43 RCTs that enroled 4265 children (3935 children included in this review). We rated the overall risk of bias at the study level as high or unclear for 37 studies that had one or several unclear or high risk of bias judgements across the domains. We judged six studies as having a low risk of bias across all domains. Ibuprofen versus placebo (35 RCTs) No studies reported pain relief reported by the child or a third party, or serious adverse events. Ibuprofen probably reduces child-reported pain intensity less than two hours postintervention compared to placebo (SMD -1.12, 95% CI -1.39 to -0.86; 3 studies, 259 children; moderate-certainty evidence). Ibuprofen may reduce child-reported pain intensity, two hours to less than 24 hours postintervention (SMD -1.01, 95% CI -1.24 to -0.78; 5 studies, 345 children; low-certainty evidence). Ibuprofen may result in little to no difference in adverse events compared to placebo (RR 0.79, 95% CI 0.51 to 1.23; 5 studies, 384 children; low-certainty evidence). Ibuprofen versus paracetamol (21 RCTs) No studies reported pain relief reported by the child or a third party, or serious adverse events. Ibuprofen likely reduces child-reported pain intensity less than two hours postintervention compared to paracetamol (SMD -0.42, 95% CI -0.82 to -0.02; 2 studies, 100 children; moderate-certainty evidence). Ibuprofen may slightly reduce child-reported pain intensity two hours to 24 hours postintervention (SMD -0.21, 95% CI -0.40 to -0.02; 6 studies, 422 children; low-certainty evidence). Ibuprofen may result in little to no difference in adverse events (0 events in each group; 1 study, 44 children; low-certainty evidence). Ibuprofen versus morphine (1 RCT) No studies reported pain relief or pain intensity reported by the child or a third party, or serious adverse events. Ibuprofen likely results in a reduction in adverse events compared to morphine (RR 0.58, 95% CI 0.40 to 0.83; risk difference (RD) -0.25, 95% CI -0.40 to -0.09; number needed to treat for an additional beneficial outcome (NNTB) 4; 1 study, 154 children; moderate-certainty evidence). Ibuprofen versus ketorolac (1 RCT) No studies reported pain relief or pain intensity reported by the child, or serious adverse events. Ibuprofen may result in a reduction in adverse events compared to ketorolac (RR 0.51, 95% CI 0.27 to 0.96; RD -0.29, 95% CI -0.53 to -0.04; NNTB 4; 1 study, 59 children; low-certainty evidence).

AUTHORS' CONCLUSIONS

Despite identifying 43 RCTs, we remain uncertain about the effect of ibuprofen compared to placebo or active comparators for some critical outcomes and in the comparisons between different doses, schedules and routes for ibuprofen administration. This is largely due to poor reporting on important outcomes such as serious adverse events, and poor study conduct or reporting that reduced our confidence in the results, along with small underpowered studies. Compared to placebo, ibuprofen likely results in pain reduction less than two hours postintervention, however, the efficacy might be lower at two hours to 24 hours. Compared to paracetamol, ibuprofen likely results in pain reduction up to 24 hours postintervention. We could not explore if there was a different effect in different kinds of surgeries or procedures. Ibuprofen likely results in a reduction in adverse events compared to morphine, and in little to no difference in bleeding when compared to paracetamol. We remain mostly uncertain about the safety of ibuprofen compared to other drugs.

Design, Synthesis, anti-inflammatory activity Evaluation, preliminary exploration of the Mechanism, molecule Docking, and structure-activity relationship analysis of batatasin III analogs

Most clinical drugs used to treat inflammation have serious gastrointestinal, renal, and cardiovascular side effects during long-term treatment. The development of new anti-inflammatory agents from natural products and their derivatives is a powerful approach to overcome these adverse effects. Batatasin III, a bibenzyl natural product, has been found to have anti-inflammatory activity. Compared with other anti-inflammatory agents, batatasin III has a simple and unique structure. Therefore, batatasin III and its analogs might have the potential to treat inflammation with only mild adverse effects as a new type of anti-inflammatory agent. Herein, we synthesized 26 batatasin III analogs and evaluated the anti-inflammatory activity in vitro. Analog 21 significantly inhibited (p < 0.01) nitric oxide production with an IC50 value of 12.95 μM. Western blot analysis further revealed that 21 reduced iNOS, phosphorylated p65, and β-catenin expression in a concentration-dependent manner. These results indicated that 21 could be a potential lead compound for developing a drug candidate for ulcerative colitis. Molecular docking analysis showed that p65 might be a potential target of 21 for the treatment of inflammatory disease. In addition, we analyzed the structure-activity relationship of the analogs, which provides a basis for future structural modifications.

Drosophila pain sensitization and modulation unveiled by a novel pain model and analgesic drugs

In mammals, pain is regulated by the combination of an ascending stimulating and descending inhibitory pain pathway. It remains an intriguing question whether such pain pathways are of ancient origin and conserved in invertebrates. Here we report a new Drosophila pain model and use it to elucidate the pain pathways present in flies. The model employs transgenic flies expressing the human capsaicin receptor TRPV1 in sensory nociceptor neurons, which innervate the whole fly body, including the mouth. Upon capsaicin sipping, the flies abruptly displayed pain-related behaviors such as running away, scurrying around, rubbing vigorously, and pulling at their mouth parts, suggesting that capsaicin stimulated nociceptors in the mouth via activating TRPV1. When reared on capsaicin-containing food, the animals died of starvation, demonstrating the degree of pain experienced. This death rate was reduced by treatment both with NSAIDs and gabapentin, analgesics that inhibit the sensitized ascending pain pathway, and with antidepressants, GABAergic agonists, and morphine, analgesics that strengthen the descending inhibitory pathway. Our results suggest Drosophila to possess intricate pain sensitization and modulation mechanisms similar to mammals, and we propose that this simple, non-invasive feeding assay has utility for high-throughput evaluation and screening of analgesic compounds.

A Critical Review on the Pharmacodynamics and Pharmacokinetics of Non-steroidal Anti-inflammatory Drugs and Opioid Drugs Used in Reptiles

Non-steroidal anti-inflammatory drugs (NSAIDs) and opioids are analgesics used for moderate to severe pain in many animals, including reptiles. However, reptilian dosing regimens are often extrapolated from other animal species. This is not ideal as inter- and intra-species variability in physiology may result in varied drug disposition. Therefore, this critical review aims to collate data from pharmacological studies of selected NSAIDs and opioids performed in reptile and provide an analysis and discussion on the existing pharmacodynamic knowledge and pharmacokinetic data of NSAIDs and opioids use in reptiles. Additionally, key pharmacokinetic trends that may aid dosing of NSAIDs and opioids in reptiles will also be highlighted. Most of the existing reports of NSAID used in reptiles did not observe any adverse effects directly associated to the respective NSAID used, with meloxicam being the most well-studied. Despite the current absence of analgesic efficacy studies for NSAIDs in reptiles, most reports observed behavioural improvements in reptiles after NSAID treatment. Fentanyl and morphine were studied in the greatest number of reptile species with analgesic effects observed with the doses used, while adverse effects such as sedation were observed most with butorphanol use. While pharmacokinetic trends were drug- and species-specific, it was observed that clearance (CL) of drugs tended to be higher in squamates compared to chelonians. The half-life (t_1/2) of meloxicam also appeared to be longer when dosed orally compared to other routes of drug administration. This could have been due to absorption-rate limited disposition. Although current data provided beneficial information, there is an urgent need for future research on NSAID and opioid pharmacology to ensure the safe and effective use of opioids in reptiles.

Anti-inflammatory, Analgesic, and Cytotoxic Effects of The Phytexponent: A Polyherbal Formulation

The Phytexponent is used to treat pain and inflammation in complementary and alternative medicine practices; however, empirical data supporting its pharmacological efficacy and safety is scanty, hence the present study. We used the carrageenan-induced paw oedema and the acetic acid-induced writhing techniques to determine the anti-inflammatory and analgesic efficacies, respectively, of the Phytexponent in Swiss albino mice models. The 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay technique was used to investigate the in vitro cytotoxic effects of the Phytexponent in the Vero E6 cell line. The Phytexponent exerted significant (P < .05) anti-inflammatory effects in the carrageenan-induced paw oedema mouse model in a dose- and time-dependent manner, with significantly higher efficacy at 250 mg/Kg BW, than indomethacin (4 mg/Kg BW), in the first, second, and third hour (P < .05). Besides, the Phytexponent significantly reduced the acetic acid-induced writhing frequency in mice (P < .05), in a dose-dependent manner, depicting its analgesic efficacy. Notably, the Phytexponent (at doses: 125 mg/Kg BW and 250 mg/Kg BW) exhibited significantly higher analgesic efficacy than the Indomethacin (P<.05). Moreover, the Phytexponent was not cytotoxic to Vero E6 cells (CC₅₀ >1000 µg/ml) compared to cyclophosphamide (CC₅₀ = 2.48 µg/ml). Thus, the Phytexponent has significant in vivo anti-inflammatory and analgesic efficacy in mice models and is not cytotoxic to Vero E6 cell line, depicting its therapeutic potential upon further empirical investigation.

Systematic Review of Systemic and Neuraxial Effects of Acetaminophen in Preclinical Models of Nociceptive Processing

Acetaminophen (APAP) in humans has robust effects with a high therapeutic index in altering postoperative and inflammatory pain states in clinical and experimental pain paradigms with no known abuse potential. This review considers the literature reflecting the preclinical actions of acetaminophen in a variety of pain models. Significant observations arising from this review are as follows: 1) acetaminophen has little effect upon acute nociceptive thresholds; 2) acetaminophen robustly reduces facilitated states as generated by mechanical and thermal hyperalgesic end points in mouse and rat models of carrageenan and complete Freund’s adjuvant evoked inflammation; 3) an antihyperalgesic effect is observed in models of facilitated processing with minimal inflammation (eg, phase II intraplantar formalin); and 4) potent anti-hyperpathic effects on the thermal hyperalgesia, mechanical and cold allodynia, allodynic thresholds in rat and mouse models of polyneuropathy and mononeuropathies and bone cancer pain. These results reflect a surprisingly robust drug effect upon a variety of facilitated states that clearly translate into a wide range of efficacy in preclinical models and to important end points in human therapy. The specific systems upon which acetaminophen may act based on targeted delivery suggest both a spinal and a supraspinal action. Review of current targets for this molecule excludes a role of cyclooxygenase inhibitor but includes effects that may be mediated through metabolites acting on the TRPV1 channel, or by effect upon cannabinoid and serotonin signaling. These findings suggest that the mode of action of acetaminophen, a drug with a long therapeutic history of utilization, has surprisingly robust effects on a variety of pain states in clinical patients and in preclinical models with a good therapeutic index, but in spite of its extensive use, its mechanisms of action are yet poorly understood.

Non-opioid Analgesics and Emerging Therapies

Pain is a common and debilitating symptom of cancer. Cancer-related pain can occur at any point along the continuum from diagnosis to treatment to survivorship¹. A systematic review published in 2016 estimated the prevalence of cancer pain to be 55% in those undergoing antineoplastic treatment, 66.4% in advanced cancer, and 39.3% in the post-treatment population. Thirty-eight percent of cancer patients in this pooled analysis experienced moderate to severe pain².

The effect of oral anti-inflammatory drugs on reducing tooth sensitivity due to in-office dental bleaching: A systematic review and meta-analysis

BACKGROUND

The authors' aim was to evaluate the effectiveness of anti-inflammatory drugs on tooth sensitivity (TS) during and after in-office dental bleaching procedures.

TYPES OF STUDIES REVIEWED

The authors selected randomized controlled trials in which the investigators compared anti-inflammatory drugs with a placebo to evaluate in-office dental bleaching TS. The authors performed an electronic search by using PubMed, ScienceDirect, and Embase. In addition, the authors searched other Web sites, such as ClinicalTrials.gov, to identify ongoing studies.

RESULTS

The authors included 7 randomized controlled trials (324 adults) in the review. According to the extracted data, the authors performed the meta-analysis by using risk ratios and their 95% confidence intervals or by using the mean difference with a 95% confidence interval. The authors used the Cochrane Collaboration's tool to assess study quality. After the evaluation, the authors considered 6 studies to be high quality and a single study to be low quality. The overall results of the evaluation process revealed the absence of a clinically significant effect of anti-inflammatory drugs.

CONCLUSIONS AND PRACTICAL IMPLICATIONS

The results of this analytic process indicated that anti-inflammatory drugs have no clinically significant effect on the TS that occurs due to in-office bleaching. Readers must analyze these results carefully given the limitations of this review, such as the small samples size and the heterogeneity among the studies in some stages of the evaluation process. The results of this analytical study highlight the need for more clinical studies to reach a significant conclusion because TS is one of the most important reasons for the cessation of bleaching treatment.

Efficacy of pre-emptive use of cyclooxyenase-2 inhibitors for total knee arthroplasty: a mini-review

Total knee arthroplasty (TKA) is regarded as the most effective surgery for patients with later-stage arthritis of the knee, but the postoperative pain management for functional improvement of the knew is still a challenging task. This review discusses the mechanism by which the selective cyclooxyenase-2 inhibitors, which reduce the peripheral and central sensitization, decrease pain after TKA. This review also covers the protocols, safety, efficacy, and progress of cyclooxyenase-2 inhibitors in pre-emptive analgesia.

The efficacy of pre-emptive analgesia on pain management in total knee arthroplasty: a mini-review

Total knee arthroplasty (TKA) is considered a cost-effective and efficacious treatment for patients with end-stage knee arthritis. Meanwhile, TKA has been regarded as one of the most painful orthopaedic surgeries. Pain control after TKA remains a challenging task. Many analgesic innovations are used to reduce the level of pain, but none has been proven to be the optimum choice till now. Multimodal analgesia incorporates the use of analgesic adjuncts with different mechanisms of action to enhance postoperative pain management. This approach is a preferable choice in relieving postoperative pain with minimum side effects. This paper aims to review pre-emptive analgesia for pain management in TKA. We reviewed the application of pre-emptive analgesia, its physiological mechanism, and the techniques.

Ibuprofen in the treatment of children's inflammatory pain: a clinical and pharmacological overview

Unlike fever, which is often over-treated especially in children, pain is underestimated and under-treated in pediatric age. The pharmacological agents approved for treating pain in these patients are few, also considering the recent limitation for codeine in children younger than 12 years. Paracetamol and the nonsteroidal anti-inflammatory drug (NSAID) ibuprofen are the most used at this purpose. The aim of this overview was to analyze the therapeutic appropriateness of ibuprofen in children based on its pharmacological properties. This work is a critical review of the pediatric literature over the last 20 years on efficacy and adverse events associated with the use of ibuprofen as analgesic in the pediatric population. Ibuprofen resulted effective in several pain conditions in children such as musculoskeletal pain, ear pain and acute otitis media, toothache and the inflammatory disease of the oral cavity and pharynx. The drug is a reasonable and efficacious alternative in postoperative pain, including tonsillectomy and adenoidectomy. It remains the treatment of choice for pain in chronic inflammatory diseases such as arthritis. Side effects and adverse events associated with ibuprofen are mild. It has the lowest gastrointestinal (GI) toxicity among NSAIDs, although some cases of GI toxicity may occur. Its renal effects are minimal, but dehydration plays an important role in triggering renal damage, so ibuprofen should not be given to patients with vomiting and diarrhea. Ibuprofen showed a good safety profile and provided evidence of effectiveness for mild-moderate pain of different origin in children. In case of fever or pain, the choice about the drug to be used should fall on ibuprofen in a clinical context where there is an inflammatory pathogenesis.

Interaction between maropitant and carprofen on sparing of the minimum alveolar concentration for blunting adrenergic response (MAC-BAR) of sevoflurane in dogs

Maropitant, a neurokinin-1 receptor antagonist, may provide analgesic effects by blocking pharmacological action of substance P. Carprofen is a non-steroidal anti-inflammatory drug commonly used for pain control in dogs. The purpose of this study was to evaluate the effect of a combination of maropitant and carprofen on the minimum alveolar concentration for blunting adrenergic response (MAC-BAR) of sevoflurane in dogs. Six healthy adult beagle dogs were anesthetized with sevoflurane four times with a minimum of 7-day washout period. On each occasion, maropitant (1 mg/kg) alone, carprofen (4 mg/kg) alone, a combination of maropitant (1 mg/kg) and carprofen (4 mg/kg), or saline (0.1 ml/kg) was subcutaneously administered at 1 hr prior to the first electrical stimulation for the sevoflurane MAC-BAR determination. The sevoflurane MAC-BAR was significantly reduced by maropitant alone (2.88 ± 0.73%, P=0.010), carprofen alone (2.96 ± 0.38%, P=0.016) and the combination (2.81 ± 0.51%, P=0.0003), compared with saline (3.37 ± 0.56%). There was no significant difference in the percentage of MAC-BAR reductions between maropitant alone, carprofen alone and the combination. The administration of maropitant alone and carprofen alone produced clinically significant sparing effects on the sevoflurane MAC-BAR in dogs. However, the combination of maropitant and carprofen did not produce any additive effect on the sevoflurane MAC-BAR reduction. Anesthetic premedication with a combination of maropitant and carprofen may not provide any further sparing effect on anesthetic requirement in dogs.

Action of β-endorphin and nonsteroidal anti-inflammatory drugs, and the possible effects of nonsteroidal anti-inflammatory drugs on β-endorphin

This study aimed to review research on the effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on β-endorphin. NSAIDs are commonly used as anti-inflammatory and analgesic drugs. They are well known for inducing peripheral analgesia by inhibiting cyclooxygenase (COX). However, an increasing number of studies have shown that NSAIDs have an analgesic effect not only in the periphery but also at the center. It means that a central analgesic mechanism of the action of NSAIDs exists besides the peripheral mechanism, and the central mechanism likely involves β-endorphin. β-Endorphin is one of the most prominent endogenous peptides, existing in the hypophysis cerebri and hypothalamus. It plays an irreplaceable role in the central and peripheral analgesia in the human body mainly through three mechanisms including three parts, the spinal cord, the supraspinal cord, and peripheries. β-Endorphin plays an important role in the development of hyperalgesia. However, the specific signal transduction pathways between prostaglandin E₂ or NSAIDs and β-endorphin are still not quite clear. Whether NSAIDs can lead to the increased content of β-endorphin in all patients after any operation needs further investigation. Further studies should determine the optimal dose when NSAIDs and opioid drugs are used together, and also explore the existence of one NSAID that has the potential to replace the traditional opioid drugs and can achieve adequate analgesia.

Pain Associated with Carotid Artery Surgery Performed under Carotid Plexus Block: Preemptive Analgesic Effect of Ketorolac

Carotid artery surgery (CAS) performed under cervical plexus block is frequently associated with significant intra- and postoperative pain. To evaluate whether preoperative administration of ketorolac may improve analgesia in this type of surgery, 80 patients scheduled for CAS under cervical plexus block were randomly allocated to receive intravenously either 30 mg of ketorolac or placebo 30 minutes before surgery. Verbal rating scale pain scores during surgery and 3 and 6 hours after surgery, the number of patients requiring additional analgesia, and the total analgesic consumption both during and within 6 hours after surgery were significantly lower, whereas the time to first postoperative analgesia was significantly shorter in the ketorolac group than in the control group.

The results of this prospective, randomized, double-blind study show that a single 30 mg dose of ketorolac administered intravenously 30 minutes before surgery reduces intraoperative pain and preempts postoperative pain in patients undergoing CAS under carotid plexus block.

Targeting novel peripheral mediators for the treatment of chronic pain

Research efforts over the past two decades have helped us better understand the biological mechanisms that lead to chronic pain. Despite this, there has been limited progress in developing novel analgesics to treat sufferers of persistent pain conditions, who may account for as many as one-fifth of the population. A re-evaluation of the strategies used to discover pain-relieving drugs is needed to meet this widespread clinical need. Here, we discuss the merits of pursuing peripherally acting pain mediators. We review the significant clinical evidence that neuronal activity from the periphery is a major contributor to painful symptom production and that peripheral mediators play a substantial role in this aberrant nociceptor activity. We discuss the clinical benefits of blocking individual known mediators and describe our own approach to identify novel mediators.

Peripheral inflammatory hyperalgesia depends on the COX increase in the dorsal root ganglion

It is well established that dorsal root ganglion (DRG) cells synthesize prostaglandin. However, the role that prostaglandin plays in the inflammatory hyperalgesia of peripheral tissue has not been established. Recently, we have successfully established a technique to inject drugs (3 μL) directly into the L5-DRG of rats, allowing in vivo identification of the role that DRG cell-derived COX-1 and COX-2 play in the development of inflammatory hyperalgesia of peripheral tissue. IL-1β (0.5 pg) or carrageenan (100 ng) was administered in the L5-peripheral field of rat hindpaw and mechanical hyperalgesia was evaluated after 3 h. Administration of a nonselective COX inhibitor (indomethacin), selective COX-1 (valeryl salicylate), or selective COX-2 (SC-236) inhibitors into the L5-DRG prevented the hyperalgesia induced by IL-1β. Similarly, oligodeoxynucleotide-antisense against COX-1 or COX-2, but not oligodeoxynucleotide-mismatch, decreased their respective expressions in the L5-DRG and prevented the hyperalgesia induced by IL-1β in the hindpaw. Immunofluorescence analysis demonstrated that the amount of COX-1 and COX-2, constitutively expressed in TRPV-1(+) cells of the DRG, significantly increased after carrageenan or IL-1β administration. In addition, indomethacin administered into the L5-DRG prevented the increase of PKCε expression in DRG membrane cells induced by carrageenan. Finally, the administration of EP1/EP2 (7.5 ng) or EP4 (10 µg) receptor antagonists into L5-DRG prevented the hyperalgesia induced by IL-1β in the hindpaw. In conclusion, the results of this study suggest that the inflammatory hyperalgesia in peripheral tissue depends on activation of COX-1 and COX-2 in C-fibers, which contribute to the induction and maintenance of sensitization of primary sensory neurons.

The CGRP receptor antagonist BIBN4096BS peripherally alleviates inflammatory pain in rats

Calcitonin gene-related peptide (CGRP) is known to play a major role in the pathogenesis of pain syndromes, in particular migraine pain. Here we focus on its implication in a rat pain model of inflammation, induced by injection of complete Freund adjuvant (CFA). The nonpeptide CGRP receptor antagonist BIBN4096BS reduces migraine pain and trigeminal neuronal activity. Here we demonstrate that the compound reduces inflammatory pain and spinal neuronal activity. Behavioural experiments reveal a reversal of the CFA-induced mechanical hypersensitivity and monoiodoacetate (MIA)-induced weight-bearing deficit in rats after systemic drug administration. To further investigate the mechanism of action of the CGRP antagonist in inflammatory pain, in vivo electrophysiological studies were performed in CFA-injected rats. Recordings from wide dynamic range neurons in deep dorsal horn layers of the lumbar spinal cord confirmed a reduction of neuronal activity after systemic drug application. The same amount of reduction occurred after topical administration onto the paw, with resulting systemic plasma concentrations in the low nanomolar range. However, spinal administration of BIBN4096BS did not modify the neuronal activity in the CFA model. Peripheral blockade of CGRP receptors by BIBN4096BS significantly alleviates inflammatory pain.

Pharmacology of nonsteroidal antiinflammatory drugs and opioids

Chronic pain affects up to 50 million Americans every day. Traditional treatment has included acetaminophen, nonsteroidal antiinflammatory drugs (NSAIDs), or opioids. The combination of NSAIDs and opioids can provide effective treatment for up to 90% of patients with chronic pain, but the NSAIDs have the potential for significant, even life-threatening side effects. Additionally, the nonselective cyclooxygenase inhibitors with 16,000 deaths per year in the United States might not be any safer. The opioids are great for short-term pain, but may need to be adjusted or changed frequently due to the development of tolerance. Understanding of the mechanism of opioids and NSAIDs has improved greatly over the past decade, but is still incomplete.

Strategies Aimed at Preventing Chronic Post-surgical Pain: Comprehensive Perioperative Pain Management after Total Joint Replacement Surgery

PURPOSE

Chronic post-surgical pain (CPSP) is a frequent outcome of musculoskeletal surgery. Physiotherapists often treat patients with pain before and after musculoskeletal surgery. The purposes of this paper are (1) to raise awareness of the nature, mechanisms, and significance of CPSP; and (2) to highlight the necessity for an inter-professional team to understand and address its complexity. Using total joint replacement surgeries as a model, we provide a review of pain mechanisms and pain management strategies.

SUMMARY OF KEY POINTS

By understanding the mechanisms by which pain alters the body's normal physiological responses to surgery, clinicians selectively target pain in post-surgical patients through the use of multi-modal management strategies. Clinicians should not assume that patients receiving multiple medications have a problem with pain. Rather, the modern-day approach is to manage pain using preventive strategies, with the aims of reducing the intensity of acute postoperative pain and minimizing the development of CPSP.

CONCLUSIONS

The roles of biological, surgical, psychosocial, and patient-related risk factors in the transition to pain chronicity require further investigation if we are to better understand their relationships with pain. Measuring pain intensity and analgesic use is not sufficient. Proper evaluation and management of risk factors for CPSP require inter-professional teams to characterize a patient's experience of postoperative pain and to examine pain arising during functional activities.

Oxycodone combinations for pain relief

No single analgesic drug provides the perfect therapeutic/adverse effect profile for every pain condition. In addition to convenience and possibly improved compliance, a combination of analgesic drugs offers the potential, requiring verification, of providing greater pain relief and/or reduced adverse effects than the constituent drugs when used individually. We review here analgesic combinations containing oxycodone. We found surprisingly little preclinical information about the analgesic or adverse effect profiles of the combinations (with acetaminophen, paracetamol, nonsteroidal anti-inflammatory drugs, morphine, gabapentin or pregabalin). Clinical experience and studies suggest that the combinations are safe and effective and may offer certain advantages. As with all combinations, the profile of adverse effects must also be determined in order to provide the clinician with the overall benefit/risk assessment.

Topical analgesics

Historically, analgesics were applied by the topical route of administration. With the advent of oral formulations of drugs, topical application became less popular among physicians, although patients still rated this method of drug delivery as efficacious and practical. We now appreciate that peripheral mechanisms of actions of a variety of preparations rationalizes their topical application and gives further opportunity to target peripheral receptors and neural pathways that previously required systemic administration to achieve therapeutic effect. Therefore, a peripheral effect can be generated by using locally applied drug and, consequently, systemic concentrations of that drug may not reach the level at which systemic side effects can occur.

Cyclooxygenase-2 and antagonists in pain management

Non-steroidal anti-inflammatory drugs are widely used for the treatment of pain and inflammation by inhibiting the formation of prostaglandins. However, their use is limited by their side-effects, including gastrointestinal, renal function, cardiovascular and platelet function. Cyclooxygenase activity is the principal target for the action of non-steroidal anti-inflammatory drugs. Two isoforms of cyclooxygenase have been characterized: (i) cyclooxygenase-1, which is found in many tissues and is generally constitutively expressed and synthesizes prostanoids that mediate homeostatic functions; and (ii) cyclooxygenase-2, the inducible isoform, which is mainly expressed at sites of injury or inflammation and synthesizes prostanoids that mediate inflammation, pain and fever. These findings led to the development of selective cyclooxygenase-2 inhibitors, with comparable anti-inflammatory and analgesic properties to traditional non-steroidal anti-inflammatory drugs, but with significantly fewer side-effects. However, these new selective cyclooxygenase-2 inhibitors are not risk free, and care should be taken when using these drugs, especially with elderly patients with multiple medical problems. Finally, the future is bright for the broader usage of these agents in the treatment of diseases other than inflammation and pain, such as Alzheimer's disease, colonic polyp and colon cancer, just to name a few.

Topical analgesics

Our knowledge and understanding of the pathophysiology and treatment of pain is increasing; however, we should not lose sight of the simple opportunities that exist for intercepting pain at peripheral targets. Although systemic medication often has peripheral and central modes of action, the appeal for provision of medication close to where these peripheral targets exist should be high. If these sites can be attacked with relatively high concentrations of active drug while keeping systemic levels of that drug below the level at which systemic side effects become apparent, then this should lead to desirable outcomes. Even though the number of true topical agents with an indication for this use is small, a number of other topical agents are available that evidence suggests have the possibility of being effective. Given the increased understanding of pain, the likelihood of further topical agents becoming available is high.

The Effect of Intravenous Ketorolac on Capsaicin-Induced Deep Tissue Hyperalgesia

Preclinical and clinical studies have emphasized that persistent small afferent input will induce a state of central facilitation that can be attenuated by systemically administered nonsteroidal antiinflammatory drugs. However, these studies have been performed using cutaneous models of hyperalgesia. In this study we evaluated the effects of IV ketorolac on an experimental model of deep tissue hyperalgesia using IM capsaicin. We used a double-blind, placebo-controlled, crossover design. Ten subjects received 60 mg of ketorolac or placebo in 2 sessions separated by 1 wk. Capsaicin (100 microg in 10 microL) was then injected into the flexor carpi ulnaris muscle of the left forearm. After injection, spontaneous pain scores, pressure pain scores, gripping pain, pain distribution, and pain quality were recorded at 0, 5, 10, 15, 20, and 25 min. Cutaneous allodynia and dysesthesia were then mapped and thermal and mechanical thresholds were measured. The IM injection of capsaicin resulted in a reliable report of pain, hyperalgesia, and referred pain. Ketorolac had no effect on spontaneous pain, elicited pain, pain distribution, or secondary hyperalgesia induced by capsaicin. The findings of this study support the feasibility of further pharmacological studies using the IM capsaicin pain model.

The pharmacotherapy of chronic pain: a review

The past two decades have contributed a large body of preclinical work that has assisted in our understanding of the underlying pathophysiological mechanisms that cause chronic pain. In this context, it has been recognized that effective treatment of pain is a priority and that treatment often involves the use of one or a combination of agents with analgesic action. The current review presents an evidence-based approach to the pharmacotherapy of chronic pain. Medline searches were done for all agents used as conventional treatment in chronic pain. Published papers up to June 2005 were included. The search strategy included randomized, controlled trials, and where available, systematic reviews and meta-analyses. Further references were found in reference sections of papers located using the above search strategy. Agents for which there were no controlled trials supporting efficacy in treatment of chronic pain were not included in the present review, except in cases where preclinical science was compelling, or where initial human work has been positive and where it was thought the reader would be interested in the scientific evidence to date.

Spinal phospholipase A2 in inflammatory hyperalgesia: role of group IVA cPLA2

Current work has shown the importance of spinal cyclooxygenase (COX) products in facilitatory processes leading to tissue injury induced hyperalgesia. This cascade must originate with free arachidonic acid (AA) released by the activity of spinal phospholipase A2s (PLA2). In the present work, we studied the role of PLA2s in spinal sensitization. We first demonstrate the presence of constitutive mRNA in the spinal cord for PLA2 Groups IB, IIA, IIC, IVA, V and VI by reverse transcription-polymerase chain reaction (RT-PCR) and sequencing. Using quantitative-PCR, we found that Group IVA cPLA2 and Group VI iPLA2 are the predominant PLA2 messages in the spinal cord. Western blotting and activity assays specific for Group IVA cPLA2 and Group VI iPLA2 verified the presence of these enzymes. PLA2 activity in spinal cord homogenates was suppressed by methyl arachidonyl fluorophosphonate (MAFP) and arachidonyl trifluoromethylketone (AACOCF3), mixed inhibitors of Group IVA cPLA2 and Group VI iPLA2 as well as by bromoenol lactone (BEL), a Group VI iPLA2 inhibitor. The spinal expression of PLA2 mRNA or protein was not altered in the face of peripheral inflammation. Secondly, we showed that intrathecal (i.t.) administration of MAFP and AACOCF3, but not BEL, dose-dependently prevented thermal hyperalgesia induced by intraplantar carrageenan as well as formalin-induced flinching. Finally, i.t. injection of AACOCF3, at antihyperalgesic doses, decreased the release of prostaglandin E2 (PGE2) into spinal dialysate evoked by i.t. NMDA, while i.t. injection of BEL had no effect. Taken together, this work points to a role for constitutive Group IVA cPLA2 in spinal nociceptive processing.

Spinal phospholipase A2 in inflammatory hyperalgesia: role of the small, secretory phospholipase A2

Current work emphasizes that peripheral tissue injury and inflammation results in a heightened sensitivity to subsequent noxious input (hyperalgesia) that is mediated in large part by the spinal synthesis and release of eicosanoids, in particular prostaglandins. Secreted phospholipase A(2)s (sPLA(2)s) form a class of structurally related enzymes that release arachidonic acid from cell membranes that is further processed to produce eicosanoids. We hypothesized that spinal sPLA(2)s may contribute to inflammation-induced hyperalgesia. Spinal cord tissue and cerebrospinal fluid were collected from rats for assessment of sPLA(2) protein expression and sPLA(2) activity. A basal sPLA(2) protein expression and activity was detected in spinal cord homogenate (87+/-17 pmol/min/mg), though no activity could be detected in cisternal cerebrospinal fluid, of naive rats. The sPLA(2) activity did not change in spinal cord tissue or cerebrospinal fluid assessed over 8 h after injection of carrageenan into the hind paw. However, the sPLA(2) activity observed in spinal cord homogenates was suppressed by addition of LY311727, a selective sPLA(2) inhibitor. To determine the role of this spinal sPLA(2) in hyperalgesia, we assessed the effects of lumbar intrathecal (IT) administration of LY311727 in rats with chronic IT catheters in three experimental models of hyperalgesia. IT LY311727 (3-30 microg) dose-dependently prevented intraplantar carrageenan-induced thermal hyperalgesia and formalin-induced flinching, at doses that had no effect on motor function. IT LY311727 also suppressed thermal hyperalgesia induced by IT injection of substance P (30 nmol). Using in vivo spinal microdialysis, we found that IT injection of LY311727 attenuated prostaglandin E(2) release into spinal dialysate otherwise evoked by the IT injection of substance P. Taken together, this work points to a role for constitutive sPLA(2)s in spinal nociceptive processing.

What is the role of NSAIDs in pre-emptive analgesia?

NSAIDs inhibit the cyclo-oxygenase enzymes, and decrease peripheral and central prostaglandin production. In addition to reducing the inflammation that accompanies tissue injury, decreasing prostaglandin production attenuates the response of the peripheral and central components of the nervous system to noxious stimuli. Such a reduction in the response to pain can reduce the peripheral and central sensitisation induced by noxious stimuli, and reduce the pain experienced in response to subsequent noxious stimuli. These properties would seem to make NSAIDs ideal drugs to use in a pre-emptive fashion, where analgesics are administered prior to a noxious stimulus, such as surgery, with the expectation that reduction in peripheral and central sensitisation will lead to a decrease of pain.However, the available perioperative trials of pre-emptive NSAID use have yielded modest or equivocal results, and these may be due, in part, to controversy associated with the definition of pre-emptive analgesia and how to conduct the corresponding clinical trials. Although NSAIDs may have a limited ability by themselves to induce a pre-emptive analgesic effect, the available trials suggest how the perioperative use of these drugs may be made more effective. It is expected that NSAIDs will play an increasing role in multimodal analgesia and pain relief in general.

The heritability of antinociception II: pharmacogenetic mediation of three over-the-counter analgesics in mice

Chromosomal loci containing genes affecting antinociceptive sensitivity to morphine have been identified, but virtually nothing is known about the genetic mediation of sensitivity to over-the-counter analgesics. Such knowledge would be of great clinical interest, as prodigious interindividual variability has been noted in the efficacy of these ubiquitously used drugs. In the present study, we assessed heritability and genetic correlations among three over-the-counter analgesics in mice of 12 inbred mouse strains on the 0.9% acetic acid (i.p.) writhing test. Analgesics included the centrally acting analgesic, acetaminophen (150 mg/kg, s.c.), and the nonsteroidal anti-inflammatory drugs (NSAIDs), indomethacin (40 mg/kg, s.c.) and lysine-acetylsalicylic acid (800 mg/kg, s.c.). Significant strain differences in sensitivity to each of the drugs were observed, with narrow-sense heritability estimates ranging from 23 to 45%. Similar strains were sensitive and resistant, respectively, to the two NSAIDs (r(s) = 0.64). In contrast, a completely different pattern of sensitivities was observed for acetaminophen, implying genetic dissociation (r(s) = 0.29 and 0.02) compared with the NSAIDs. Additional experiments were performed on two strains, C57BL/6 and DBA/2, with extreme sensitivities to acetaminophen. Plasma acetaminophen levels in these strains were not significantly different during the time of antinociception assessment, suggesting the existence of genetic factors affecting acetaminophen pharmacodynamics rather than pharmacokinetics.

Topical and peripherally acting analgesics

Acute nociceptive, inflammatory, and neuropathic pain all depend to some degree on the peripheral activation of primary sensory afferent neurons. The localized peripheral administration of drugs, such as by topical application, can potentially optimize drug concentrations at the site of origin of the pain, while leading to lower systemic levels and fewer adverse systemic effects, fewer drug interactions, and no need to titrate doses into a therapeutic range compared with systemic administration. Primary sensory afferent neurons can be activated by a range of inflammatory mediators such as prostanoids, bradykinin, ATP, histamine, and serotonin, and inhibiting their actions represents a strategy for the development of analgesics. Peripheral nerve endings also express a variety of inhibitory neuroreceptors such as opioid, alpha-adrenergic, cholinergic, adenosine and cannabinoid receptors, and agonists for these receptors also represent viable targets for drug development. At present, topical and other forms of peripheral administration of nonsteroidal anti-inflammatory drugs, opioids, capsaicin, local anesthetics, and alpha-adrenoceptor agonists are being used in a variety of clinical states. There also are some clinical data on the use of topical antidepressants and glutamate receptor antagonists. There are preclinical data supporting the potential for development of local formulations of adenosine agonists, cannabinoid agonists, cholinergic ligands, cytokine antagonists, bradykinin antagonists, ATP antagonists, biogenic amine antagonists, neuropeptide antagonists, and agents that alter the availability of nerve growth factor. Given that activation of sensory neurons involves multiple mediators, combinations of agents targeting different mechanisms may be particularly useful. Topical analgesics represent a promising area for future drug development.

Effect of metamizol on promyelocytic and terminally differentiated granulocytic cells. Comparative analysis with acetylsalicylic acid and diclofenac

Metamizol is an analgesic and antipyretic agent that can induce agranulocytosis in certain patients. However, its effects on granulocyte viability and differentiation have been poorly evaluated. Here we analysed the effects of metamizol and its active metabolite, 4-methylaminoantipyrine (MAA), on the viability of HL60 promyelocytes and their dimethyl sulphoxide-induced differentiated granulocytes. Metamizol and MAA at 75 microM (above the peak of plasmatic concentration after 2g intake) did not alter granulocytic differentiation of HL60 cells. Only at concentrations above 100 microM, well over the pharmacological range, metamizol-induced apoptosis in about 30% of the HL60 promyelocytes, while HL60-granulocytic terminally differentiated cells were more resistant to this apoptotic action. When the effects of metamizol were compared with those of acetylsalicylic acid (ASA) and diclofenac on cell viability, at equivalent concentrations used in analgesic and antipyretic therapy (75 microM for metamizol, and ASA and 3 microM for diclofenac) their apoptotic effects were similar. Again, the HL60 promyelocytes were more sensitive to apoptosis than granulocytic differentiated cells, as measured by the percentage of sub-G(1) cells detected by flow cytometry and by determination of caspase activity as a function of poly(ADP-ribose) polymerase cleavage. Furthermore, when human blood-derived granulocytes were treated with metamizol, MAA, and ASA at 75 microM or diclofenac at 3 microM, less than 10% of apoptotic granulocytes were detected, whereas at toxicological/suprapharmacological concentrations (10mM), about 90% of granulocytes were apoptotic. These results demonstrate that metamizol, MAA, ASA, and diclofenac, at pharmacological concentrations, neither affect the granulocytic differentiation process nor induce relevant apoptosis on terminally differentiated granulocytes.

Prostanoids and pain: unraveling mechanisms and revealing therapeutic targets

Advances in our understanding of the synthesis, regulation and function of prostanoids have led to a new appreciation of their actions in health and disease. Prostanoid synthesis is essential for the generation of inflammatory pain and this depends not only on prostanoid production at the site of inflammation, but also on the actions of prostanoids synthesized within the central nervous system (CNS). Moreover, central prostanoid synthesis is controlled both by neural and humoral signals, the latter being a novel form of input to the CNS. Diverse compounds that act along the pathway of prostanoid synthesis and action, both in the periphery and in the CNS, might provide increased benefit for treating inflammatory pain hypersensitivity and its associated sickness syndrome, with a reduced risk of adverse effects.

Indomethacin attenuates the immunosuppressive and tumor-promoting effects of surgery

We have previously shown in rats that both intrathecal and systemic analgesia regimens attenuate surgery-induced increases in tumor susceptibility. The current study used indomethacin to assess the role of prostaglandins and inflammation-associated pain in mediating the deleterious effects of surgery on immunity and tumor susceptibility. Male and female Fischer 344 rats were anesthetized with halothane and were either subjected or not to experimental laparotomy, followed by the administration of indomethacin or vehicle. Tumor susceptibility was assessed by the lung retention assay using the syngeneic MADB106 mammary adenocarcinoma cell line, a natural killer (NK)-sensitive tumor that colonizes only in the lungs. Surgery resulted in a 2- to 3.5-fold increase in lung tumor retention, and indomethacin administration significantly reduced this effect in both sexes without affecting unoperated animals. Indomethacin also attenuated the reductions in rearing behavior evident after surgery, suggesting that it relieved abdominal discomfort. Surgery increased interleukin-6 levels and suppressed NK activity per milliliter blood. Indomethacin restored NK activity in both male and female rats but attenuated surgery-induced interleukin-6 increases only in the male rats. These findings further support our previous work implicating pain in mediating the tumor-enhancing effects of surgery and implicate prostaglandins in mediating this effect. If similar relationships occur in humans, controlling postoperative pain and inflammation must become a priority in the management of cancer patients undergoing surgery.

Involvement of peripheral cyclooxygenase-1 and cyclooxygenase-2 in inflammatory pain

Pain-induced functional impairment in the rat (PIFIR) is a model of inflammatory and arthritic pain similar to that of clinical gout. Nociception is induced by the intra-articular injection of uric acid into the right hind limb, inducing its dysfunction. Animals then receive analgesic drugs and the recovery of functionality over time is assessed as an expression of antinociception. We have examined the role of peripheral prostaglandins synthesized by cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) in inflammatory pain using the PIFIR model. Rofecoxib (a selective COX-2 inhibitor) and SC-560 (a selective COX-1 inhibitor) both produced dose-dependent effects. When the inhibitors were administered before uric acid, they showed similar potency, but the antinociceptive efficacy of SC-560 was lower than rofecoxib; the best antinociceptive effects were obtained with the dose of 100 microg/articulation of each inhibitor (pre-treatment). In post-treatment (inhibitors administered after the uric acid), rofecoxib showed the least antinociceptive effect and SC-560 was more potent than rofecoxib. The inhibition of both COX-1 and COX-2 produced a more profound analgesic effect than the inhibition of either COX-1 or COX-2 alone. The present data support the idea that both COX isoforms contribute to the development and maintenance of local inflammatory nociception. Thus, it could be expected that inhibition of both COX-1 and COX-2 is required for non-steroidal anti-inflammatory drugs (NSAID)-induced antinociception in the rat. These findings suggest that the therapeutic effects of NSAIDs may involve, at least in part, inhibition of COX-1 and COX-2.

Postoperative pain management: morphine versus ketorolac

Without proper management, postoperative pain can grow to intolerable levels and interfere with functioning and healing. Historically, morphine had no equal for postoperative pain management. Its side effects, however, are troubling. Recently, researchers have developed many analgesics that do not induce the same side effects as morphine. Ketorolac is one example. Nevertheless, a single drug with an efficacy comparable with morphine remains elusive. In this article, the physiology of pain is reviewed and ketorolac is compared with morphine. Perianesthesia nurses are given pertinent information to enhance their ability to provide the best pain relief available for the patients in their care.

The acute antihyperalgesic action of nonsteroidal, anti-inflammatory drugs and release of spinal prostaglandin E2 is mediated by the inhibition of constitutive spinal cyclooxygenase-2 (COX-2) but not COX-1

Western blots show the constitutive expression of COX-1 and COX-2 in the rat spinal dorsal and ventral horns and in the dorsal root ganglia. Using selective inhibitors of cyclooxygenase (COX) isozymes, we show that in rats with chronic indwelling intrathecal catheters the acute thermal hyperalgesia evoked by the spinal delivery of substance P (SP; 20 nmol) or NMDA (2 nmol) and the thermal hyperalgesia induced by the injection of carrageenan into the paw are suppressed by intrathecal and systemic COX-2 inhibitors. The intrathecal effects are dose-dependent and stereospecific. In contrast, a COX-1 inhibitor given systemically, but not spinally, reduced carrageenan-evoked thermal hyperalgesia but had no effect by any route with spinal SP hyperalgesia. Using intrathecal loop dialysis catheters, we showed that intrathecal SP would enhance the release of prostaglandin E(2) (PGE(2)). This intrathecally evoked release of spinal PGE(2) was diminished by systemic delivery of nonspecific COX and COX-2-selective inhibitors, but not a COX-1-selective inhibitor. Given at systemic doses that block SP- and carrageenan-evoked hyperalgesia, COX-2, but not COX-1, inhibitors reduced spinal SP-evoked PGE(2) release. Thus, constitutive spinal COX-2, but not COX-1, is an important contributor to the acute antihyperalgesic effects of spinal as well as systemic COX-2 inhibitors.

[Pain, fever and prostanoids]

Although it has been known that prostanoids are involved in pain regulation and fever, the precise roles of their receptors and receptor subtypes are unclear. All prostanoid receptors have been cloned and mice deficient in each receptor have been developed. Recent studies using prostanoid-receptor-knockout mice are shedding some light on these issues. Nociceptive responses to an intraperitoneal injection of acetic acid and hyperalgesia induced by carrageenan were abolished by IP-receptor deficiency. In addition, the use of mice lacking prostanoid receptor is revealing an interesting role of prostanoid in neuropathic as well as inflammatory pain. With regard to pyrexia, PGE2 injected intracerebroventricularly induced the febrile response in wild-type mice, but it was without effect in mice lacking the EP3 receptor. Furthermore, febrile responses induced by IL-1 beta, an endogenous pyrogen, and LPS, an exogenous pyrogen, were specifically suppressed in mice lacking the EP3 receptor. These results indicate that PGE2 works as a common final mediator of the febrile response and that this action of PGE2 is mediated by the EP3 receptor. The determination of precise roles of prostanoids in pain and fever may provide novel targets for antipyretic analgesics with fewer side effects.

Effects of flurbiprofen and its enantiomers on the spinal c-Fos protein expression induced by noxious heat stimuli in the anaesthetized rat

We have evaluated the effects of either intravenous or intraplantar administration of racemic-, S(+)- and R(-)-flurbiprofen on the spinal c-Fos protein expression after a single noxious heat stimulation (52 degrees C for 15 s) of the rat hindpaw in urethane anaesthetized rats. Two hours after noxious heat, numerous c-Fos protein immunoreactive (c-Fos-IR) nuclei (>70 c-Fos-IR nuclei per section at the level of L4-L5 segments) were observed with essential localization in the superficial (I-II) laminae of the spinal dorsal horn, i.e. areas containing numerous neurons driven exclusively by noxious stimuli. Considering the number of c-Fos-IR nuclei in laminae I-II, the intravenous injection of racemic-flurbiprofen (0.3, 3 and 9 mg/kg) was inefficacious and S(+)-flurbiprofen had weak and non-dose-related effects. The same doses of R(-)-flurbiprofen produced dose-related effects (r=0.58, P<0.05) with weak, but significant, effects for doses of 3 and 9 mg/kg (18+/-6% and 26+/-5% reduction of the number of noxious heat-evoked c-Fos-IR nuclei in laminae I-II, P<0.05 and P<0.01, respectively). The weak effects of R(-)-flurbiprofen are probably due to the central site of action since the intraplantar injection of a relatively high dose of 30 microg is inefficacious. These results provide further evidence for weak effects of non-steroidal anti-inflammatory drugs and their enantiomers on the acute responses to nociceptive stimulus which are very efficacious upon inflammatory nociception, but not upon brief noxious heat-evoked nociception.

Nonsteroidal anti-inflammatory analgesics. Indications and contraindications for pain management in dogs and cats

Nonsteroidal anti-inflammatory analgesics (NSAIAs) are effective in controlling most acute and chronic pain conditions. In veterinary practice these analgesics may be superior to opioids in that the duration of action is much longer, with equal efficacy in many instances, making effective pain management possible for most veterinary patients. NSAIAs act synergistically in combination with other modalities of pain management, including all opioids, local anesthetics, and various sedatives. Because of their mechanism of action, however, there is a potential for perturbation of several homeostatic functions mediated by prostaglandins. Not all NSAIAs are equal in efficacy and safety, so careful patient and NSAIA selection with appropriate monitoring is advised. This article discusses the indications and contraindications for NSAIA use with a short description of the currently available NSAIAs approved for use in veterinary patients.