Evaluation of the formalin test to assess the analgesic activity of diflunisal in the rat

Antinociceptive Synergism of Pomegranate Peel Extract and Acetylsalicylic Acid in an Animal Pain Model

Several modern drugs, which are derived from traditional herbal medicine are used in contemporary pharmacotherapy. Currently, the study of drug-plant interactions in pain has increased in recent years, looking for greater efficacy of the drug and reduce side effects. The antinociception induced by intragastric co-administration of the combination of pomegranate peel extract (PoPEx) and acetylsalicylic acid (ASA) was assessed using the isobolographic analysis in formalin test (nociceptive and inflammatory pain). The effective dose that produced 30% of antinociception (ED30) was calculated for both drugs from the logarithmic dose-response curves, subsequently generating a curve with the combination on fixed proportions (1:1) of PoPEx and ASA. Through isobolographic analysis, this experimental ED30 was compared with the calculated theoretical additive ED30. The result was a synergistic interaction, the experimental ED30 was significantly smaller (p < 0.05) than the theoretical ED30. The antinociceptive mechanism of the PoPEx-ASA combination involves the l-Arginine/NO/cGMP pathway, antioxidant capacity, and high content of total phenols. These findings suggest that an interaction between PoPEx and ASA could be a novel treatment for inflammatory and nociceptive pain, also diminish the secondary reactions of ASA.

Comparison of analgesic activities of aconitine in different mice pain models

Aconitine (AC) is the primary bioactive and secondary metabolite alkaloidin of Aconitum species which is accounted for more than 60% of the total diester-diterpenoid alkaloids in Aconite. To evaluate the analgesic effects of AC, 4 different pain models including hot plate assay, acetic acid writhing assay, formalin and CFA induced pain models were adopted in this study. In hot plate experiment, AC treatment at concentration of 0.3 mg/kg and 0.9 mg/kg improved the pain thresholds of mice similar to the positive drug aspirin at the concentration of 200 mg/kg (17.12% and 20.27% VS 19.21%). In acetic acid writhing experiment, AC significantly reduced the number of mice writhing events caused by acetic acid, and the inhibition rates were 68% and 76%. These results demonstrated that AC treatment revealed significant analgesic effects in both acute thermal stimulus pain model and chemically-induced visceral pain model. The biphasic nociceptive responses induced by formalin were significantly inhibited after AC treatment for 1h or 2h. The inhibition rates were 33.23% and 20.25% of AC treatment for 1h at 0.3 mg/kg and 0.9 mg/kg in phase I. In phase II, the inhibition rates of AC and aspirin were 36.08%, 32.48% and 48.82% respectively, which means AC showed similar analgesic effect to non-steroidal anti-inflammatory compounds. In the chronic CFA-induced nociception model, AC treatment also improved mice pain threshold to 131.33% at 0.3 mg/kg, which was similar to aspirin group (152.03%). Above all, our results verified that AC had obviously analgesic effects in different mice pain models.

Dereplication and evaluation of the antinociceptive and anti-inflammatory activity of hydroethanolic extract of leaves from Campomanesia xanthocarpa O. Berg

Campomanesia xanthocarpa popularly known as gabiroba is used as a medicinal plant for the treatment of inflammatory diseases, ulcers, among other uses, requiring studies to assist in proving these activities. In this study, the extract of leaves from C. xanthocarpa (CxHE) was submitted to assays of formalin-induced paw-licking, peritonitis induced by lipopolysaccharide and carrageenan-induced mechanical hyperalgesia tests. In chemical analysis, a preliminary phytochemical screening and the determination of phenol and flavonoid content were carried out, in addition to analysis by ESI-MS/MS system and HPLC-DAD system. The CxHE presented compounds such as tannins, triterpenoids, steroids and saponins and content of phenols (35.9 ± 1.3 GAE/g extract) and flavonoids (23.3 ± 2.1 mg EQ/g extract). Protocatechuic acid, gallic acid, ethyl gallate, quercetin, and 3-methyl epigallocatechin gallate, alpha and beta-amyrins were identified. CxHE at doses of 10-1000 mg/kg p.o. demonstrated anti-inflammatory and antinociceptive effects in all in vivo assays employed in this study. [Figure: see text].

A window into the brain: Tools to assess pre-clinical efficacy of biomaterials-based therapies on central nervous system disorders

Therapeutic conveyance into the brain is a cardinal requirement for treatment of diverse central nervous system (CNS) disorders and associated pathophysiology. Effectual shielding of the brain by the blood-brain barrier (BBB) sieves out major proportion of therapeutics with the exception of small lipophilic molecules. Various nano-delivery systems (NDS) provide an effective solution around this obstacle owing to their small size and targeting properties. To date, these systems have been used for several pre-clinical disease models including glioma, neurodegenerative diseases and psychotic disorders. An efficacy screen for these systems involves a test battery designed to probe into the multiple facets of therapeutic delivery. Despite their wide application in redressing various disease targets, the efficacy evaluation strategies for all can be broadly grouped into four modalities, namely: histological, bio-imaging, molecular and behavioural. This review presents a comprehensive insight into all of these modalities along with their strengths and weaknesses as well as perspectives on an ideal design for a panel of tests to screen brain nano-delivery systems.

Anti-nociceptive and anti-inflammatory activities of crude root extract and solvent fractions of Cucumis ficifolius in mice model

Background: Societies in developing countries use traditional medicine as alternatives for management of pain and inflammation. The plant Cucumis ficifolius has been used in Ethiopia to treat many ailments including inflammation and pain. The objective of this study was to evaluate the antinociceptive and anti-inflammatory activities of the crude root extract and solvent fractions of C. ficifolius.

Methods: The analgesic activity of crude extract and solvent fractions of C. ficifolius was evaluated with acetic acid-induced writhing, hot plate, and formalin-induced paw licking tests. The anti-inflammatory effect of crude methanolic root extract and solvent fractions of C. ficifolius was evaluated using carrageenan-induced paw edema. The crude extract was given at 200, 400 and 800 mg/kg. Butanol and aqueous fractions were given at 100 and 200 mg/kg doses. The negative control groups were treated with distilled water (10 mL/kg). Standard drugs used were acetylsalicylic acid (ASA) in acetic acid, formalin tests and carrageenan-induced paw edema and morphine (20 mg/kg) in hot plate test.

Results: The crude extract, at its maximum dose, produced comparable analgesic activity (72.5%) to ASA in acetic acid writhing test. In the hot plate test, both the crude extract and solvent fractions exhibited a significant prolongation of nociception reaction time. Formalin test result indicated a significant reduction of mean lick time with maximal protection of 64% (early phase) and 83% (late phase). Aqueous and butanol fractions showed good analgesic activity in the three models. Inflammation was decreased by 69% with butanol (200 mg/kg); 71% (800 mg/kg) of crude extract and by 41% and 56% with the use of aqueous fraction at 100 and 200 mg/kg, respectively (p<0.001).

Conclusion: The present study indicates that the crude methanolic root extract, as well as butanol and aqueous solvent fractions, showed anti-nociceptive and anti-inflammatory activities.

Biological Screening of Novel Structural Analog of Celecoxib as Potential Anti-Inflammatory and Analgesic Agent

Background and objectives: The clinical use of non-steroidal anti-inflammatory drugs is limited due to high incidence of adverse drug reactions. The pyrrole heterocycle is included in the chemical structure of a number of drugs with various activities and shows relatively good tolerability and safety. The objectives of our study were to evaluate the analgesic and anti-inflammatory activity, as well as possible organ toxicity, of 2-[3-acetyl-5-(4-chloro-phenyl)-2-methyl-pyrrol-1-yl]-3-(1H-indol-3-yl)-propionic acid (compound 3g), a novel N-pyrrolylcarboxylic acid structurally similar to celecoxib. Materials and methods: All experiments were performed on 6-week-old male Wistar rats divided into parallel groups (n = 8). Antinociception was assessed using animal pain models with thermal and chemical stimuli (paw withdrawal, tail-flick, and formalin tests). Criteria for the analgesic effect were increased latency in the paw withdrawal and tail-flick tests and decreased paw licking time in the formalin test compared to animals treated with saline (control). Anti-inflammatory activity was measured using a carrageenan-induced paw edema model; the criterion for anti-inflammatory effect was decreased edema compared to control. Blood samples were obtained after animals were sacrificed to assess possible organ toxicity. Statistical analysis was performed with IBM SPSS 20.0. Results: 2-[3-Acetyl-5-(4-chloro-phenyl)-2-methyl-pyrrol-1-yl]-3-(1H-indol-3-yl)-propionic acid had analgesic action against chemical stimulus after single and multiple administration and against thermal stimulus after single administration. Compound 3g significantly suppressed carrageenan-induced paw edema after both single and continuous administration. After continuous administration, hematological tests showed that compound 3g decreased leukocyte and platelet levels and elevated serum creatinine levels. Conclusions: Antinociception with the tested compound is most likely mediated by spinal, peripheral, and anti-inflammatory mechanisms. Possible tolerance of the analgesic action at the spinal level develops after continuous administration. Anti-inflammatory activity is significant and probably the leading cause of antinociception. After multiple administration, compound 3g showed signs of potential nephrotoxicity and antiplatelet activity, as well as suppression of leukocyte levels.

The anti-inflammatory effects of N-methyl-(2S,4R)-trans-4-hydroxy-l-proline from Syderoxylon obtusifolium are related to its inhibition of TNF-alpha and inflammatory enzymes

BACKGROUND

Sideroxylon obtusifolium (Roem. & Schult.) T.D. Penn., Sapotaceae family, is a medicinal species native to the Brazilian Northeastern region. The plant is popularly used as an anti-inflammatory and hypoglycemic.

PURPOSE

To evaluate the anti-inflammatory properties of the N-methyl-(2S,4R)-trans-4-hydroxy-l-proline (NMP) from S. obtusifolium leaves in models of inflammation and to clarify its action mechanisms.

METHODS

Male Swiss mice were distributed intocontrols and groups treated with NMP (25, 50 and 100mg/kg, p.o.), indomethacin or morphine (reference drugs). The animals were subjected to the formalin, carrageenan-induced edema and peritonitis tests. Furthermore, peritoneal lavage and slices from edematous paws were used for histological and immunohistochemical (iNOS, TNF-alpha, COX-2 and NF-kB) assays.

RESULTS

Decreases in licking time, in the 1st and mainly in the 2nd phases of the formalin test, were shown after NMP treatments. In addition, decreases (around 50%) in paw edema were noticed at the 3rd h. The HE staining of paw slices demonstrated a complete reversion of the increased PMN cell numberafter NMP treatment. Similarly, decreases higher than 70% were also demonstrated in PMN cells, in the peritoneal fluid. Furthermore, NMP significantly decreased iNOS, TNF-alpha, COX-2 and NF-kB immunoreactivities.

CONCLUSIONS

We showed that S. obtusifolium presents a potent anti-inflammatory activity, due to the presence of the N-methyl-(2S,4R)-trans-4-hydroxy-l-proline(NMP) in the plant extract. This action is related to the inhibition by NMP of TNF-alpha and inflammatory enzymes.

Anti-inflammatory and antinociceptive effect of Pachygone ovata leaves

CONTEXT

Pachygone ovata (Poir.) Miers ex Hook. F. et Thoms (Menispermaceae) is a rich source of bioactive bisbenzylisoquinoline and aporphine alkaloids.

OBJECTIVE

This study investigates the in vitro and in vivo anti-inflammatory and antinociceptive potential of Pachygone ovata leaves.

MATERIALS AND METHODS

Lipoxygenase (LOX) assay for anti-inflammatory activity was conducted using MeOH, EA, H and Aq extracts; followed by alkaloid isolation. The anti-inflammatory potential was determined using carrageenan-induced paw oedema and formalin tests for evaluation of Pachygone ovata analgesic effect. Different doses (100, 300 and 400 μg/kg) were administered orally to Wistar rats for a period of one week, once daily.

RESULTS

MeOH and EA extract efficiently inhibited LOX (IC₅₀ 1.43 and 2.15 μg/mL, respectively). MeOH extract had better inhibiting capacity (57%) than indomethacin (51%) in carrageenan induced rats. MeOH extract (300 μg/kg) significantly reduced the increased levels of nitric oxide (8 ± 0.57 M), total leukocyte count (4.5 ± 0.05 cells 10³/cells) and C-reactive protein (55 ± 0.45 mg/mL). There was a decrease in various serum biochemical markers (ALT, AST). Histopathological studies revealed reduction in oedema and decreased cellular infiltration on supplementation with MeOH extract. Furthermore, MeOH extract (300 μg/kg) and alkaloid fraction (400 μg/kg) effected both phases (neurogenic and inflammatory) of formalin injected models.

DISCUSSION AND CONCLUSION

Inflammatory mediators play a key role in inflammation; therefore, keeping it in control is of utmost importance. The usefulness of Pachygone ovata leaves on pain and inflammation has been described, probably due to its effect on inflammatory mediators and high alkaloid content.

Analgesic properties of aqueous leaf extract of Haematostaphis barteri: involvement of ATP-sensitive potassium channels, adrenergic, opioidergic, muscarinic, adenosinergic and serotoninergic pathways

BACKGROUND

Pain is the most common cause of patients seeking medical advice as a result of its association with different pathologies. This study evaluated the antinociceptive property of Haematostaphis barteri as well as the possible mechanism(s) associated with its antinociceptive property.

METHODS

Mice were administered H. barteri (30-300 mg kg-1; p.o.), followed by intraplantar injection of 10 μL of 5% formalin into the hind paws. The pain score was determined for 1 h in the formalin test. The possible nociceptive pathways involved in the antinociceptive action of H. barteri were determined by pre-treating mice with theophylline (5 mg kg-1, a non-selective adenosine receptor antagonist), naloxone (2 mg kg-1, a non-selective opioid receptor antagonist), glibenclamide (8 mg kg-1; an ATP-sensitive K+ channel inhibitor), and atropine (3 mg kg-1; non-selective muscarinic antagonist).

RESULTS

H. barteri (30-300 mg kg-1) significantly and dose dependently precluded both first and second phases of nociception. Pre-treatment with naloxone had no effect on the analgesic activities of H. barteri in the first phase. Again, pre-treatment with atropine and glibenclamide did not significantly reverse the neurogenic antinociception of the extract in phase 1. However, theophylline reversed the analgesic effect of the extract in the first phase. In phase 2, theophylline had no effect on the analgesic activities of the extract. Naloxone, atropine, and glibenclamide significantly blocked the antinociception of H. barteri in the inflammatory phase of the formalin test.

CONCLUSIONS

H. barteri possesses antinociceptive property mediated via the opioidergic, adrenergic, muscarinic, ATP-sensitive K+ channels, and adenosinergic nociceptive pathways.

Preclinical Assessment of Inflammatory Pain

While acute inflammation is a natural physiological response to tissue injury or infection, chronic inflammation is maladaptive and engenders a considerable amount of adverse pain. The chemical mediators responsible for tissue inflammation act on nociceptive nerve endings to lower neuronal excitation threshold and sensitize afferent firing rate leading to the development of allodynia and hyperalgesia, respectively. Animal models have aided in our understanding of the pathophysiological mechanisms responsible for the generation of chronic inflammatory pain and allowed us to identify and validate numerous analgesic drug candidates. Here we review some of the commonly used models of skin, joint, and gut inflammatory pain along with their relative benefits and limitations. In addition, we describe and discuss several behavioral and electrophysiological approaches used to assess the inflammatory pain in these preclinical models. Despite significant advances having been made in this area, a gap still exists between fundamental research and the implementation of these findings into a clinical setting. As such we need to characterize inherent pathophysiological pathways and develop new endpoints in these animal models to improve their predictive value of human inflammatory diseases in order to design safer and more effective analgesics.

Bioactive Polyphenols from the Methanol Extract of Cnicus arvensis (L.) Roth Demonstrated Antinociceptive and Central Nervous System Depressant Activities in Mice

Cnicus arvensis is used by many ethnic groups for inflammation, pain, and other ailments. In this study, reducing sugar, carbohydrate, alkaloid, steroid, tannin, flavonoid, and saponin groups were identified using standard chromogenic method. In high-performance liquid chromatography, vanillic acid and epicatechin were identified in the extract. Antinociceptive test by acetic acid induced writhing inhibition resulted 43.17 and 95.08% inhibition for 100 and 200 mg/kg body weight, comparing with standard diclofenac Na with 74.86% inhibition for 25 mg/kg body weight. In formalin induced paw licking test for antinociceptive activity, the extract inhibited 69.87 and 75.55% licking for 150 and 300 mg/kg body weight comparing with the inhibition (68.56%) of diclofenac Na for 10 mg/kg body weight at first phase. At late phase, the extract showed 73.12 and 87.46% licking comparing with licking inhibition (71.69%) by diclofenac Na at the same dose. In open field test for CNS depressant activity, the extract showed depression of locomotor activity for 150 and 300 mg/kg body weight comparing with diazepam for 10 mg/kg body weight. All results were statistically significant (P < 0.01). The identified polyphenols are reputed for antinociceptive and CNS depressant activity. The present findings support the use of this plant in pain.

Synthesis and biological evaluation of some novel 1-substituted fentanyl analogs in Swiss albino mice

Fentanyl [N-(1-phenethyl-4-piperidinyl)propionanilide] is a potent opioid analgesic agent, but a has narrow therapeutic index. We reported earlier on the synthesis and bioefficacy of fentanyl and its 1-substituted analogs (1–4) in mice. Here we report the synthesis and biological evaluation of four additional analogs, viz. N-isopropyl-3-(4-(N-phenylpropionamido)piperidin-1-yl)propanamide (5), N-t-butyl-3-(4-(N-phenylpropionamido)piperidin-1-yl)propanamide (6), isopropyl 2-[4-(N-phenylpropionamido)piperidin-1-yl]propionate (7) and t-butyl 2-[4-(N-phenylpropionamido)piperidin-1-yl]propionate (8). The median lethal dose (LD₅₀) determined by intravenous, intraperitoneal and oral routes suggests these analogs to be comparatively less toxic than fentanyl. On the basis of observational assessment on spontaneous activities of the central, peripheral, and autonomic nervous systems, all the analogs were found to be similar to fentanyl. Naloxone hydrochloride abolished the neurotoxic effects of these analogs, thereby ascertaining their opioid receptor-mediated effects. All the analogs displayed significant analgesic effects, measured by formalin-induced hind paw licking and tail immersion tests at their respective median effective dose (ED₅₀). They also exhibited 8–12 fold increase in therapeutic index over fentanyl. However, 5 and 6 alone produced lower ED₅₀ (20.5 and 21.0 µg/kg, respectively) and higher potency ratio (1.37 and 1.33, respectively) compared to fentanyl. They could thus be considered for further studies on pain management.

Pharmacodynamics of Piroxicam from Self-Emulsifying Lipospheres Formulated with Homolipids Extracted fromCapra hircus

A self-emulsifying system is a mixture of oil and surfactant that forms oil-in-water emulsion when exposed to aqueous fluid. It enhances the in vitro dissolution and improves the in vivo absorption of lipophilic drugs that have poor aqueous solubility. In this study, a poorly water soluble drug, piroxicam, was incorporated into self-emulsifying lipospheres consisting of a mixture of a homolipid from Capra hircus and Tween 65. Various solid self-emulsifying lipospheres were formulated having different ratios of the homolipid and Tween 65 to contain piroxicam. The self-emulsifying lipospheres were evaluated using the following parameters: particle size, absolute drug content, and dissolution profile. The pharmacodynamics of the drug from the lipospheres were also evaluated using antinociceptive activity on albino mice. Based on our results the self-emulsifying lipospheres containing 4:11 ratio of the homolipid and Tween 65 had the best performance in terms of antiinflammatory effect, particle size, and dissolution. They possibly could be employed in the formulation of self-emulsifying lipospheres for various administration.

Polyelectrolyte complexes of Eudragit l30 d-55 and gelatin: antinociceptive activity of entrapped piroxicam

The electrostatic interaction between oppositely charged polyelectrolytes leads to the formation of polyelectrolyte complexes, which are of considerable interest because of their potential applications as both drug carriers or surface modifying agents. In this study, in vitro and in vivo studies were carried out on polyelectolyte complexes formulated with Eudragit L30 D-55 and gelatin. The complexes of Eudragit L30 D-55 and gelatin were formulated by nonstoichiometric method. The polyelectrolyte complexes formulated were then granulated and evaluated by percentage yield, particle size, and swelling behavior. The pharmacodynamic effects of piroxicam entrapped in the complexes were determined using healthy rats. Results showed that gelatin and Eudragit L30 D-55 formed polyelectrolyte complexes that prolonged the antinociceptive effects of piroxicam in experimental rats. The performance of the polyelectrolyte complexes could be stated in the following descending rank order: 1:1 > 2:1 > 1:2 ratios of Eudragit L30 D-55 and gelatin. Nonstoichiometric interactions of gelatin and Eudragit L30 D-55 could yield matrices with adequate characteristics for the formulation of sustained release systems of drugs.

Preparation and analgesic activity of Eudragit RS100 microparticles containing diflunisal

Two different techniques, the quasi-emulsion solvent diffusion method and spray drying that provide polar and nonpolar preparation environments, were used to prepare microspheres from Eudragit RS100 (RS) (acrylic/methacrylic copolymer) incorporating the nonsteroidal anti-inflammatory drug diflunisal. The effects of pH on the preparation medium and drug/polymer ratio on production yield and drug incorporation, as well as on the in vitro drug release at pH 1.2 and 6.8 from tabletted microparticles, were evaluated. The drug-polymer interactions and the effect of diflunisal incorporation in the polymer matrix on drug crystallinity have been evaluated by using differential scanning calorimetry, IR and ultraviolet spectroscopy, x-ray diffraction, and microscopy analysis. A preliminary biological assay confirmed that diflunisal maintains its analgesic activity after intraperitoneal administration to rats.