Nonsteroidal Antiinflammatory Drugs for Acute and Chronic Pain

Design and evaluation of a drug-in-adhesive patch for the transdermal delivery of ketoprofen

The purpose of this study was to design a drug-in-adhesive (DIA) patch for transdermal delivery of ketoprofen, using hot-melt pressure-sensitive adhesive as the matrix of the patch. The adhesion properties and skin permeation of the patches were examined, and in vivo pharmacokinetics and tissue distribution of patches were evaluated. The novel ketoprofen patch with high adhesion was prepared by holt-melt method. The effects of different percentages of L-menthol on in vitro permeation were screened, 3% was added as the amount of permeation enhancer and the 24 h cumulative permeation amount(277.46 ± 15.58 µg/cm2) comparable to that of commercial patch MOHRUS®(279.74 ± 29.23 µg/cm2). Pharmacokinetic and the tissue distribution study showed no matter in plasma, muscle or skin, the drug concentration of self-made ketoprofen patch was equivalent to that of commercial patch. These data indicated that the self-made patch provided a new reference for the development of ketoprofen dosage forms and promising alternative strategy for analgesic treatment.

Polygonatum sibiricum polysaccharides protect against knee osteoarthritis by inhibiting the TLR2/NF-κB signaling pathway in vivo and in vitro

Polygonatum sibiricum polysaccharides (PSP), the primary constituent of Polygonatum sibiricum, have been shown to exhibit a wide range of pharmacological effects, but their impact on osteoarthritis (OA) remains unclear. The objective of this study was to investigate the protective effects of PSP against OA and to elucidate its underlying molecular mechanism. In our in vitro experiments, PSP not only inhibited the IL-1β-induced inflammatory responses and the nuclear factor kappa-B (NF-κB) signaling pathway in chondrocytes but also regulated the cartilage matrix metabolism. In addition, we detected 394 significantly differentially expressed genes through RNA-seq analysis on PSP-intervened chondrocytes, and the toll-like receptor 2 (TLR2) was identified as the most important feature by functional network analysis and qRT-PCR. It was also revealed that PSP treatment significantly reversed the IL-1-induced up-regulation of TLR2 expression in chondrocytes, while TLR2 overexpression partially inhibited the regulatory effects of PSP on inflammation, NF-κB signaling pathway and matrix metabolism. In our in vivo experiments, PSP treatment alleviated the development of destabilization of medial meniscus (DMM)-induced OA in mouse knee joints, inhibited the DMM-induced activation of the TLR2/NF-κB signaling pathway in mouse knee joint cartilage, and reduced the serum levels of inflammatory cytokines. In conclusion, PSP exerts its anti-inflammatory, matrix synthesis-promoting and matrix catabolism-suppressing effects in knee OA by inhibiting the TLR2/NF-κB signaling pathway, suggesting that PSP may be potentially targeted as a novel all-natural, low-toxicity drug for OA prevention and treatment.

Is physical performance affected by non-steroidal anti-inflammatory drugs use? A systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis aim to analyze the effects of ingesting non-steroidal anti-inflammatory drugs (NSAIDs) on physical performance, muscle strength, and muscle damage in three different moments: immediately, 24 and 48 h after resistance exercise practice.

METHODS

Relevant studies were researched in three databases (PubMed, Web of Science and SPORTDiscus) in April 2023. After excluding duplicates, the decision to include or exclude studies was made by two independent investigators in the following steps: (I) the study title; (II) the study abstract; and (III) the complete study manuscript. The following characteristics were recorded: (I) first author, (II) year of publication, (III) sample size, (IV) method of NSAIDs administration, (V) exercise protocol, and (VI) analyzed variable results. The studies selected were divided into trials that evaluated the effects of NSAIDs ingestion on performance indices of resistance exercise, endurance exercise and resistance training.

RESULTS

The meta-analysis, based only on resistance exercises, revealed that both performance and muscle strength were similar between placebo or NSAID treatment immediately and 24 h after resistance exercise practice. An ergolytic effect was found 48 hours after resistance exercise (mean effect size (ES) = -0.42; 95% CI: -0.71, -0.12; p = 0.132), as well as reduced muscle strength (ES = -0.50; 95% CI: -0.83, -0.16; p = 0.072). Additionally, NSAID use did not prevent muscle waste as seen by the unchanged CK plasma concentration at all timetables.

CONCLUSION

The data of the present meta-analysis indicate that NSAID use is ineffective in improving resistance performance and muscle strength, as well as exercise recovery. When considering the practical application of using NSAIDs to improve exercise capacity and strength gains, the present data supports that consumption of analgesic drugs as an endurance performance enhancer or as a muscle anabolic must not be recommended.

UiO-66(Zr) as drug delivery system for non-steroidal anti-inflammatory drugs

The toxicity for the human body of non-steroidal anti-inflammatory drugs (NSAIDs) overdoses is a consequence of their low water solubility, high doses, and facile accessibility to the population. New drug delivery systems (DDS) are necessary to overcome the bioavailability and toxicity related to NSAIDs. In this context, UiO-66(Zr) metal-organic framework (MOF) shows high porosity, stability, and load capacity, thus being a promising DDS. However, the adsorption and release capability for different NSAIDs is scarcely described. In this work, the biocompatible UiO-66(Zr) MOF was used to study the adsorption and release conditions of ibuprofen, naproxen, and diclofenac using a theoretical and experimental approximation. DFT results showed that the MOF-drug interaction was due to an intermolecular hydrogen bond between protons of the groups in the defect sites, (μ3 - OH, and - OH2) and a lone pair of oxygen carboxyl functional group of the NSAIDs. Also, the experimental results suggest that the solvent where the drug is dissolved affects the adsorption process. The adsorption kinetics are similar between the drugs, but the maximum load capacity differs for each drug. The release kinetics assay showed a solvent dependence kinetics whose maximum liberation capacity is affected by the interaction between the drug and the material. Finally, the biological assays show that none of the systems studied are cytotoxic for HMVEC. Additionally, the wound healing assay suggests that the UiO-66(Zr) material has potential application on the wound healing process. However, further studies should be done.

Zingiber officinale Root Capsule Extract Synergistically Enhance the Anti-Inflammatory Effects of Diclofenac Sodium in Experimental Acute Inflammation

The present study aimed to evaluate the anti-inflammatory effects of ginger (Zingiber officinale) root capsule extract (GRCE) in doses of 100 mg/kg b.w. (body weight) and 200 mg/kg b.w. alone and in combination with a low dose (5 mg/kg b.w.) of diclofenac sodium (D) on carrageenan-induced acute inflammation (AI). The association of GRCE in a dose of 200 mg/kg b.w. with D offered the highest inhibition percentage for edema, reaching the maximum level of inhibition (95%) after 24 h. The association of GRCE in a dose of 200 mg/kg b.w. with D showed the ability to reduce tissue inflammatory changes when compared to D alone, while GRCE alone did not exhibit such properties. The association of both doses of GRCE with D showed significantly lower plasma and tissue levels of pro-inflammatory cytokines such as tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) by up to 55% (p ≤ 0.0317), with the best results obtained by the group who received GRCE in the higher dose. These associations reduced the serum and tissue levels of prostaglandin-endoperoxide synthase 2 (COX-2) by up to 71% (p ≤ 0.0371). In conclusion, the association of GRCE with a low dose of D could be an appropriate combination to decrease the dose used to reduce serum and tissue levels of inflammatory molecules, edema, and histological changes in acute inflammation. Further research will be necessary to achieve clinical evaluation.

In silico ADMET and anti-inflammatory profiles of the stigmast-4-en-3-one and isolation of isovanillin as the antioxidant principle of Imperata cylindrica (L.) P. Beauv

Imperata cylindrica (L.) P. Beauv. is an invasive species widely used in treatment of several diseases associated with pain and inflammation in different countries including Madagascar. This work aims to report the isolation of the antioxidant, analgesic and anti-nflammatory compounds from the methanol extract of I. cylindrica. The bio-guided method was used to isolate its bioactive compounds by combining chromatographic methods, writhing test in mice and antioxidant assays. Stigmast-4-en-3-one was isolated as one among the compounds responsible for the analgesic and anti-inflammatory properties and isovanillin as one among the antioxidant compounds from the extract. Stigmast-4-en-3-one showed a good oral pharmacokinetic profile and good binding affinities with some pro-inflammatory targets. It did not show any mutagenic effect, nor a carcinogenic one and had a low risk to be a cardiotoxic agent. All of our results provide scientific justification for its traditional medicinal use in the management of pain and inflammatory related diseases.

Postoperative Complications Associated with Non-Steroidal Anti-Inflammatory Combinations Used Status-Post Total Hip and Knee Arthroplasty

Non-steroidal anti-inflammatory drugs (NSAIDs) are commonly used in multimodal pain control following total joint arthroplasty (TJA). However, few studies have assessed the complications associated with the combinations of NSAIDs in this population despite the known risks associated with this class of medications. The Premier Healthcare Database was queried to identify adults who underwent primary total hip or knee arthroplasty from 2005-2014. The following most common inpatient combinations of NSAIDs were chosen for analysis: aspirin + celecoxib (A + C), toradol + aspirin (T + A), toradol + ibuprofen (T + I), celecoxib + ibuprofen (C + I), ibuprofen + aspirin (I + A), and toradol + celecoxib (T + C). Primary outcomes included acute kidney injury (AKI), gastrointestinal bleed, and stroke. Secondary outcomes included periprosthetic joint infection (PJI), deep vein thrombosis, and pulmonary embolism. Univariate and multivariate regression analyses were used to compare differences and address confounds. Overall, 195,833 patients were identified. After controlling for confounds, increased odds of AKI was associated with A + C (adjusted odds ratio [aOR]: 1.20, 95% confidence interval [CI]: 1.09-1.34, p < 0.001) and decreased odds was associated with T + A (aOR 0.76, 95% CI: 0.69-0.83, p < 0.001). Increased odds of stroke was associated with A + C (aOR: 1.80, 95% CI: 1.15-2.84, p = 0.011); T + I (aOR 3.48, 95% CI: 1.25-9.73, p = 0.017); and I + A (aOR 4.29, 95% CI: 1.06-17.9, p = 0.046). Increased odds of PJI was associated with C + I (aOR: 10.3, 95% CI: 1.35-78.3, p = 0.024). In the TJA patient population, NSAID pairings should be regarded as distinct entities. Our results suggest that combinations including A + C, T + I, I + A, and C + I should be used cautiously. With this knowledge, providers should consider tailoring NSAID prescriptions appropriately.

Preemptive effects of etoricoxib, acetaminophen, nimesulide, and ibuprofen on postoperative pain management after single-implant surgery: A randomized clinical trial

BACKGROUND

There is insufficient evidence for pain control in preemptive analgesia (PA) after dental implant surgery, signaling the need for further studies. The objective of this study was to evaluate the efficacy of PA in single dental implant surgeries (SDIS), seeking to identify among the etoricoxib (ETOR), ibuprofen (IBU), nimesulide (NIME), and acetaminophen (ACETA)], which one has the higher efficacy effectiveness in relieving postoperative pain and reducing the use of rescue medication compared to placebo.

METHODS

In this triple-blind, parallel, randomized controlled clinical trial, 135 individuals with a mean age of 57.6 years (±11.7), both genders, were randomly divided into five groups according to the test drug: I-PLACEBO; II-IBU (600 mg); III-NIME (100 mg); IV-ACETA (750 mg); and V-ETOR (90 mg). The occurrence, duration, and intensity of pain were analyzed using the Chi-square, Fisher's exact and ANOVA tests, and the generalized estimating equation models, when appropriate.

RESULTS

Test drugs provided a reduction in postoperative pain scores and lower use of rescue medication when compared to placebo. The ETOR group presented significantly lower pain scores, when compared to other active treatments. The IBU group showed the highest mean number of rescue medication used.

CONCLUSIONS

All test drugs provided a beneficial preemptive effect demonstrated by the reduced postoperative pain and reduced use of rescue medication. The ETOR group presented lower pain scores, and the IBU group showed the highest mean number of rescue medication used among the test groups.

Emerging Advances in Nanocarriers Approaches in the Effective Therapy of Pain Related Disorders: Recent Evidence and Futuristic Needs

Pain disorders are the primary cause of disability nowadays. These disorders, such as rheumatoid arthritis (RA) and osteoarthritis (OA), cause loss of function, joint pain and inflammation and deteriorate the quality of life. The treatment of these inflammatory diseases includes anti-inflammatory drugs administered via intra-articular, topical or oral routes, physical rehabilitation or surgery. Owing to the various side effects these drugs could offer, the novel approaches and nanomaterials have shown potential to manage inflammatory diseases, prolonged half-life of anti-inflammatory drugs, reduced systemic toxicity, provide specific targeting, and refined their bioavailability. This review discusses in brief about the pain pathophysiology and its types. The review summarizes the conventional therapies used to treat pain disorders and the need for novel strategies to overcome the adverse effects of conventional therapies. The review describes the recent advancements in nanotherapeutics for inflammatory diseases using several lipids, polymers and other materials and their excellent efficiency in improving the treatment over conventional therapies. The results of the nanotherapeutic studies inferred that the necessity to use nanocarriers is due to their controlled release, targeting drug delivery to inflamed tissues, low toxicity and biocompatibility. Therefore, it is possible to assert that nanotechnology will emerge as a great tool for advancing the treatment of pain disorders in the near future.

Opioid Utility and Hospital Outcomes Among Inpatients Admitted With Osteoarthritis and Spine Disorders

OBJECTIVE

The aim of the study is to evaluate opioid analgesic utilization and predictors for adverse events during hospitalization and discharge disposition among patients admitted with osteoarthritis or spine disorders.

DESIGN

This is a retrospective study of 12,747 adult patients admitted to six private community hospitals from 2017 to 2020. Opioid use during hospitalization and risk factors for hospital-acquired adverse events and nonhome discharge were investigated.

RESULTS

The total number of patients using opioids decreased; however, the daily morphine milligram equivalent use for patients on opioids increased from 2017 to 2020. Increased odds of nonhome discharge were associated with older age, Medicaid, Medicare insurance, and increased lengths of stay, increased body mass index, daily morphine milligram equivalent, and electrolyte replacement in the osteoarthritis group. In the spine group, older age, Black race, Medicaid, Medicare, no insurance, increased Charlson Comorbidity Index, lengths of stay, polypharmacy, and heparin use were associated with nonhome discharge. Adverse events were associated with increased age, lengths of stay, Medicare, polypharmacy, antiemetic, and benzodiazepine use in the osteoarthritis group and increased Charlson Comorbidity Index, lengths of stay, and electrolyte replacement in the spine group.

CONCLUSIONS

Despite the decreasing number of patients using opioids over the years, patients on opioids had an increased daily morphine milligram equivalent over the same period.

Optimal low-intensity pulsed ultrasound stimulation for promoting anti-inflammatory effects in macrophages

In this paper, we stimulated M1-like macrophages (obtained from U937 cells) with low-intensity pulsed ultrasound (LIPUS) to lower pro-inflammatory cytokine production. A systematic screening of different frequencies, intensities, duty cycles, and exposure times was performed. The optimal stimulation conditions leading to a marked decrease in the release of inflammatory cytokines were determined to be 38 kHz, 250 mW/cm², 20%, and 90 min, respectively. Using these parameters, we verified that up to 72 h LIPUS did not affect cell viability, resulting in an increase in metabolic activity and in a reduction of reactive oxygen species (ROS) production. Moreover, we found that two mechanosensitive ion channels (PIEZO1 and TRPV1) were involved in the LIPUS-mediated cytokine release modulation. We also assessed the role of the nuclear factor κB (NF-κB) signaling pathway and observed an enhancement of actin polymerization. Finally, transcriptomic data suggested that the bioeffects of LIPUS treatment occur through the modulation of p38 MAPK signaling pathway.

A review focusing on the benefits of plant-derived polysaccharides for osteoarthritis

Osteoarthritis (OA) is a chronic joint disease characterized by progressive cartilage degeneration, which imposes a heavy physical and financial burden on the middle-aged and elderly population. As the pathogenesis of OA has not been fully elucidated, it is of great importance to develop targeted therapeutic or preventive medications. Traditional therapeutic drugs, such as non-steroidal anti-inflammatory drugs, steroids and opioids, have significant side effects, making the exploration for safe and effective alternative therapeutic drugs urgent. In recent years, many studies have reported the role of plant-derived polysaccharides in anti-inflammation, anti-oxidation, regulation of chondrocyte metabolism and proliferation, and cartilage protection, and have demonstrated their great potential in the treatment of OA. Therefore, by focusing on studies related to the intervention of plant-derived polysaccharides in OA, including in vivo and in vitro experiments, this review aimed to classify and summarize the existing research findings according to different mechanisms of action. In addition, reports on plant-derived polysaccharides as nanoparticles were also explored. Then, candidate monomers and theoretical bases were provided for the further development and application of novel drugs in the treatment of OA.

Quali-Quantitative Fingerprinting of the Fruit Extract of Uapaca bojeri Bail. (Euphorbiaceae) and Its Antioxidant, Analgesic, Anti-Inflammatory, and Antihyperglycemic Effects: An Example of Biodiversity Conservation and Sustainable Use of Natural Resources in Madagascar

Antioxidants are important supplements for the human body for their roles in human life for the maintenance of homeostasis. Tapia fruits (Uapaca bojeri) are used by the riverain population of the Tapia forests in Madagascar as complementary foods. This study aims to quantify the main antioxidants in the U. bojeri fruits to verify their contribution to the enhancement of their anti-inflammatory and antihyperglycemic effects. Standard phytochemical screening was used for qualitative analysis, while spectrophotometric (TPC, TAC, and TFC) and chromatographic analyses (HPLC) were used to quantify several phytochemicals in U. bojeri fruits. The antioxidant activity was evaluated using DPPH and FRAP assays. The writhing test was used for the analgesic effects, the carrageenan-induced paw edema was used for the anti-inflammatory activity, and OGTT was used to test the anti-hyperglycemia property of the MEUB in mice. Several phytocompounds were detected and quantified in the fruits, including succinic acid (67.73%) as the main quantified compound. Fruits exerted a good antioxidant capacity and showed analgesic, anti-inflammatory, and antihyperglycemic activities in mice. Isolation of the bioactive compounds should be carried out to confirm these pharmacological properties and develop health-promoting food products or medicinal applications derived from this species.

Anti-Inflammatory and Analgesic Effects of Curcumin Nanoparticles Associated with Diclofenac Sodium in Experimental Acute Inflammation

The present study evaluated the anti-inflammatory and analgesic effects of conventional curcumin (cC) and curcumin nanoparticles (nC) associated with diclofenac sodium (D) in experimental acute inflammation (AI) induced by carrageenan administration. Seven groups of eight randomly selected Wistar-Bratislava white rats were evaluated. One group was the control (C), and AI was induced in the other six groups. The AI group was treated with saline solution, the AID group was treated with D, the AIcC200 and AInC200 groups were treated with cC and nC, respectively, while AIcC200D and AInC200D were treated with cC and nC, respectively, both associated with D. Conventional curcumin, nC, and D were administered in a single dose of 200 mg/kg b.w. for cC and nC and 5 mg/kg b.w. for D. Association of cC or nC to D resulted in significant antinociceptive activity, and improved mechanical pressure stimulation and heat thresholds at 3, 5, 7 and 24 h (p < 0.03). The association of cC and nC with D (AIcC200D and AInC200D groups) showed significantly lower plasma and tissue levels of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) up to 2.5 times, with the best results in the group who received nC. Moreover, AInC200D presented the least severe histopathological changes with a reduced level of inflammation in the dermis and hypodermis. The combination of nC to D showed efficiency in reducing pain, inflammatory cytokines, and histological changes in acute inflammation.

Naproxen sodium nanoparticles are less toxic and gastroprotective agents than the conventional NSAID drug naproxen sodium in Balb/c mice

Use of non-steroidal anti-inflammatory drugs (NSAIDs) is one of the leading causes of gastric ulcers. Excellent therapeutic properties have made the use of NSAIDs widespread. Nano-drug delivery to reduce systemic toxicity through modulating drug pharmacokinetics may be a better choice. Presently, we investigated if naproxen nanoformulation (PVA capped NPRS-MgO NPs) is less toxic to be used as an alternative drug. Groups of mice were assigned to control, NPRS-treated, CNF-treated, UNF-treated, and MgO NPs-treated groups. Analyses included gross examination of gastric mucosa, calculation of ulcer and inhibition indices, determination of tissue levels of reactive oxygen species (ROS), malondialdehyde (MDA), catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and reduced glutathione (GSH), histological and immunohistochemical assessment of i-NOS, COX-2, and caspase-3 of stomach mucosa, q-PCR for the detection of mRNA expression of IL-1β, IL-6, and TNF-α. Results were compared statistically at P < 0.05. Compared to NPRS-treated mice which developed multiple ulcers, had elevated MDA and ROS levels, and deceased CAT, POD, SOD, and GSH levels, significantly increased expression of IL-1β, IL-6, and TNF-α mRNA, damaged surface epithelium with disrupted glandular architecture and leucocyte infiltration of lamina propria with a marked increase in mucosal COX-2, i-NOS, and caspase-3 expression, oral administration of coated and uncoated naproxen nanoformulations prevented the gross mucosal damage by a restoration of all biochemical, histological, and immunohistochemical alterations to near control levels. The present study demonstrates that naproxen sodium nanoformulation has a gastroprotective action and in the clinical setting can be a better alternative to conventional naproxen.

Lactoferrin and Its Potential Impact for the Relief of Pain: A Preclinical Approach

Pain is one of the most disabling symptoms of several clinical conditions. Neurobiologically, it is classified as nociceptive, inflammatory, neuropathic and dysfunctional. Opioids and nonsteroidal anti-inflammatory drugs (NSAIDs) are conventionally prescribed for the treatment of pain. Long-term administration of opioids results in the loss of analgesic efficacy, leading to increased dosage, tolerance, and addiction as the main drawbacks of their use, while the adverse effects of NSAIDs include gastric ulcer formation, intestinal bleeding, acute kidney injury, and hepatotoxicity. Lactoferrin is an iron-binding, anti-inflammatory glycoprotein that displays analgesic activities associated, in part, by interacting with the low-density lipoprotein receptor-related protein (LRP), which may result in the regulation of the DAMP-TRAF6-NFκB, NO-cGMP-ATP K⁺-sensitive channel and opioid receptor signaling pathways. This review summarizes and discusses for the first time the analgesic effects of lactoferrin and its presumable mechanisms based on pre-clinical trials. Given its anti-nociceptive and anti-inflammatory properties, lactoferrin may be used as an adjunct to enhance the efficacy and to decrease the tolerogenic effects of canonical therapeutic drugs prescribed for pain treatment.

A Recent Update on Drug Delivery Systems for Pain Management

Pain remains a global health challenge affecting approximately 1.5 billion people worldwide. Pain has been an implicit variable in the equation of human life for many centuries considering different types and the magnitude of pain. Therefore, developing an efficacious drug delivery system for pain management remains an open challenge for researchers in the field of medicine. Lack of therapeutic efficacy still persists, despite high throughput studies in the field of pain management. Research scientists have been exploiting different alternatives to curb the adverse side effects of pain medications or attempting a more substantial approach to minimize the prevalence of pain. Various drug delivery systems have been developed such as nanoparticles, microparticles to curb adverse side effects of pain medications or minimize the prevalence of pain. This literature review firstly provides a brief introduction of pain as a sensation and its pharmacological interventions. Second, it highlights the most recent studies in the pharmaceutical field for pain management and serves as a strong base for future developments. Herein, we have classified drug delivery systems based on their sizes such as nano, micro, and macro systems, and for each of the reviewed systems, design, formulation strategies, and drug release performance has been discussed.

Review on experimental study and clinical application of low-intensity pulsed ultrasound in inflammation

Low-intensity pulsed ultrasound (LIPUS), as physical therapy, is widely used in both research and clinical settings. It induces multiple bioeffects, such as alleviating pain, promoting tissue repair, and shortening disease duration. LIPUS can also mediate inflammation. This paper reviews the application of LIPUS in inflammation and discusses the underlying mechanism. In basic experiments, LIPUS can regulate inflammatory responses at the cellular level by affecting some signaling pathways. In a clinical trial, LIPUS has been shown to alleviate inflammatory responses efficiently. As a cheap, safe, and convenient physical method, LIPUS is promising as anti-inflammatory therapy.

The role of carbon monoxide, heme oxygenase 1, and the Nrf2 transcription factor in the modulation of chronic pain and their interactions with opioids and cannabinoids

Chronic pain and its associated comorbidities are difficult to treat, even when the most potent analgesic compounds are used. Thus, research on new strategies to effectively relieve nociceptive and/or emotional disorders accompanying chronic pain is essential. Several studies have demonstrated the anti-inflammatory and antinociceptive effects of different carbon monoxide-releasing molecules (CO-RMs), inducible heme oxygenase 1 (HO-1), and nuclear factor-2 erythroid factor-2 (Nrf2) transcription factor activators in several models of acute and chronic pain caused by inflammation, nerve injury or diabetes. More recently, the antidepressant and/or anxiolytic effects of several Nrf2 transcription factor inducers were demonstrated in a model of chronic neuropathic pain. These effects are mainly produced by inhibition of oxidative stress, inflammation, glial activation, mitogen-activated protein kinases and/or phosphoinositide 3-kinase/phospho-protein kinase B phosphorylation in the peripheral and/or central nervous system. Other studies also demonstrated that the analgesic effects of opioids and cannabinoids are improved when these drugs are coadministered with CO-RMs, HO-1 or Nrf2 activators in different preclinical pain models and that these improvements are generally mediated by upregulation or prevention of the downregulation of µ-opioid receptors, δ-opioid receptors and/or cannabinoid 2 receptors in the setting of chronic pain. We reviewed all these studies as well as studies on the mechanisms of action underlying the effects of CO-RMs, HO-1, and Nrf2 activators in chronic pain. In summary, activation of the Nrf2/HO-1/carbon monoxide signaling pathway alone and/or in combination with the administration of specific analgesics is a valid strategy for the treatment of chronic pain and some associated emotional disorders.

Determination of Non-Steroidal Anti-Inflammatory Drugs in Animal Urine Samples by Ultrasound Vortex-Assisted Dispersive Liquid–Liquid Microextraction and Gas Chromatography Coupled to Ion Trap-Mass Spectrometry

A low solvent consumption method for the determination of non-steroidal anti-inflammatory drugs (NSAIDs) in animal urine samples is studied. The NSAIDs were extracted with CH2Cl2 by the ultrasound vortex assisted dispersive liquid–liquid microextraction (USVA-DLLME) method from urine samples, previously treated with β-glucuronidase/acrylsulfatase. After centrifugation, the bottom phase of the chlorinated solvent was separated from the liquid matrix, dried with Na2SO4, and derivatized with N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) + trimethylchlorosilane (TMCS) (99 + 1). After cooling at room temperature, the solution was concentrated under nitrogen flow, and 1 µL of solution was analyzed in gas chromatography/ion trap-mass spectrometry (GC-IT-MS). The enrichment factor was about 300–450 times and recoveries ranged from 94.1 to 101.2% with a relative standard deviation (RSD) of ≤4.1%. The USVA-DLLME process efficiency was not influenced by the characteristics of the real urine matrix; therefore, the analytical method characteristics were evaluated in the range 1–100 ng mL−1 (R2 ≥ 0.9950). The limits of detection (LODs) and limits of quantification (LOQs) were between 0.1 and 0.2 ng mL−1 with RSD ≤4.5% and between 4.1 and 4.7 ng mL−1 with RSD ≤3.5%, respectively, whereas inter- and intra-day precision was 3.8% and 4.5%, respectively. The proposed analytical method is reproducible, sensitive, and simple.