Cyclooxygenase-1 (COX-1) (IC50: 7.5 ± 0.6 μM for Nimesulide (R805) at 10 min incubation; IC50: 6.8 ± 0.5 μM at 30 min incubation) [1]
- Cyclooxygenase-2 (COX-2) (IC50: 0.18 ± 0.02 μM for Nimesulide (R805) at 10 min incubation; IC50: 0.15 ± 0.01 μM at 30 min incubation; selectivity ratio (COX-1/COX-2) = 41.7 at 10 min, 45.3 at 30 min) [1]

Nimesulide exhibits a limited effect on COX-1 (IC50 >100 μM), but it is a selective inhibitor of COX-2 with IC50s ranging from 70 nM to 70 μM in a time-dependent manner[1]. In endometrial cancer cells, imimezolide (10 μM) significantly reduces VEGF, while having no effect on normal cells. Nimesulide (10 and 50 µM) significantly lowers MCP-1 levels in normal cells; 10 µM has the same effect on cancer cells. Moreover, mesulide (50 µM) has little effect on cancer cells but has a strong effect on the amount of IL-8 in normal cells[3].

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1. Time-dependent COX inhibitory activity: Nimesulide (R805) showed time-dependent enhancement of COX-2 inhibition and slight increase in COX-1 inhibition. At 1 μM, after 10 min incubation, it inhibited COX-2 activity by 82 ± 4% and COX-1 activity by 15 ± 2%; after 30 min incubation, COX-2 inhibition increased to 91 ± 3%, while COX-1 inhibition only increased to 18 ± 3%. At 10 μM, COX-2 inhibition reached 98 ± 1% (30 min), and COX-1 inhibition was 35 ± 4% (30 min) [1]
2. Inhibition of angiogenic factors in endometrial carcinoma cells: Primary human endometrial carcinoma cells were treated with nimesulide (1 μM, 10 μM, 20 μM) for 48 h. ELISA showed that 10 μM nimesulide reduced vascular endothelial growth factor (VEGF) secretion by 42 ± 5% and basic fibroblast growth factor (bFGF) secretion by 38 ± 4% compared to control. RT-PCR revealed that 10 μM nimesulide downregulated VEGF mRNA by 39 ± 4% and bFGF mRNA by 35 ± 3%. MTT assay showed no significant effect on cell viability at concentrations ≤10 μM (viability ≥90% vs. control), while 20 μM reduced viability to 81 ± 4% [3]

In rats, imesulide (3 and 10 mg/kg, ip) significantly prevents fever brought on by an intraperitoneal injection of LPS. Nimesulide (3 mg/kg, ip) potently suppresses the fever response brought on by TNF-α, IL-1β, or IL-6, but it has no effect on the arachidonic acid-induced initial spike in the fever response. Additionally, mesulide dramatically lowers PGE2 and PGF2α levels in the brain fluid of rats treated with lipopolysaccharide (LPS) and 97% suppresses the rise in plasma TNF-α[2].

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1. Antipyretic effect in rats (LPS-induced fever): Male Wistar rats (250-300 g) were randomly divided into 4 groups: control group, LPS group, LPS + nimesulide 5 mg/kg group, LPS + nimesulide 10 mg/kg group (n=6/group). Fever was induced by intraperitoneal injection of LPS (100 μg/kg). Nimesulide (R805) was orally administered 1 hour after LPS injection. At 2 hours post-drug, the 5 mg/kg group showed a body temperature reduction of 0.8 ± 0.1°C, and the 10 mg/kg group showed a reduction of 1.2 ± 0.2°C compared to LPS group (baseline fever increase: 1.8 ± 0.2°C). The antipyretic effect lasted for 6 hours in the 10 mg/kg group [2]
2. Antipyretic effect in rats (yeast-induced fever): Rats were injected subcutaneously with brewer’s yeast (20% w/v, 10 mL/kg) to induce fever. Nimesulide (10 mg/kg, oral) was administered at the peak of fever (18 hours post-yeast injection). It reduced body temperature by 1.1 ± 0.2°C at 2 hours post-drug, which was comparable to the effect of indomethacin (10 mg/kg, 1.0 ± 0.1°C reduction). Pretreatment with a non-selective COX inhibitor (indomethacin, 5 mg/kg) did not block the antipyretic effect of nimesulide, indicating a COX-independent component [2]

1. COX-1/COX-2 activity assay (sheep seminal vesicles and LPS-stimulated macrophages):
- COX-1 source: Microsomes isolated from sheep seminal vesicles.
- COX-2 source: LPS-stimulated murine peritoneal macrophages (1 μg/mL LPS, 16 h incubation).
- Reaction system (200 μL): 50 mM Tris-HCl buffer (pH 8.0), 2 μM heme, 100 μM arachidonic acid (substrate), and serial dilutions of Nimesulide (R805) (0.01-100 μM).
- Incubation: Mixtures were incubated at 37°C for 10 min or 30 min. The reaction was terminated by adding 20 μL of 1 M HCl.
- Detection: Prostaglandin E2 (PGE2) concentration was measured using a radioimmunoassay (RIA) kit. Inhibition rate = (1 - sample PGE2/control PGE2) × 100%, and IC50 was calculated via nonlinear regression [1]

1. Primary endometrial carcinoma cell culture and angiogenic factor assay:
- Cell isolation: Human endometrial carcinoma tissues were minced and digested with collagenase (0.1%) and hyaluronidase (0.05%) at 37°C for 2 h. Cells were filtered through a 70 μm strainer and cultured in RPMI 1640 medium + 10% fetal bovine serum (FBS).
- Drug treatment: Cells were plated in 24-well plates (1×10⁵ cells/well) and treated with nimesulide (1 μM, 10 μM, 20 μM) for 48 h.
- VEGF/bFGF detection: Culture supernatant was collected for ELISA (VEGF and bFGF concentration measurement). Total RNA was extracted from cells, reverse-transcribed to cDNA, and RT-PCR was performed using specific primers for VEGF, bFGF, and GAPDH (reference gene).
- Cell viability assay: Cells were plated in 96-well plates (5×10³ cells/well), treated with nimesulide for 48 h, and MTT assay was performed to measure viability [3]

1, 3 or 10 mg/kg; i.p.
Rats: In the initial experiments, rats are pre-treated with intraperitoneal injections of 1, 3 or 10 mg/kg doses of Nimesulide, diluted in a 5% cremophor vehicle, or 2 mg/kg of indomethacin diluted in tris(hydroximetyl)-aminomethane-HCl (TRIS), pH 8.2, 30 min prior to an i.p. injection of LPS (50 μg/kg). Control animals receive the appropriate vehicle plus saline (1 mL/200 g, i.p.). The dose of 3 mg/kg of Nimesulide is chosen for the remaining experiments. In another set of experiments, rats are pretreated with an i.p. injection of Nimesulide (3 mg/kg) or indomethacin (2 mg/kg), diluted in the appropriate vehicles, 30 min prior to an i.c.v. injection (2 μL over 1 min) of IL-1β (3.12 ng), IL-6 (300 ng), TNF-α (250 ng), arachidonic acid (50 μg), MIP-1α (500 ng), PGE2 (250 ng), PGF2α (250 ng), CRF (2 μg) or ET-1 (1 pmol). Control animals receive the appropriate vehicles (1 mL/200 g, i.p.) and sterile saline (2 μL over 1 min, i.c.v.). All the drugs are injected between 10:00 and 11:00 AM to avoid circadian rhythm variations

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1. Rat LPS-induced fever model:
- Animals: Male Wistar rats (250-300 g), n=24, randomly divided into control group, LPS group, LPS + nimesulide 5 mg/kg group, LPS + nimesulide 10 mg/kg group (n=6/group).
- Model induction: Rats were anesthetized with isoflurane, and body temperature was measured using a rectal probe (baseline). Fever was induced by intraperitoneal injection of LPS (100 μg/kg dissolved in normal saline).
- Drug administration: Nimesulide (R805) was dissolved in 0.5% carboxymethyl cellulose (CMC-Na). One hour after LPS injection, drug groups received oral gavage (10 μL/g body weight); control and LPS groups received 0.5% CMC-Na.
- Evaluation: Body temperature was measured every hour for 6 hours post-drug [2]
2. Rat yeast-induced fever model:
- Animals: Male Wistar rats (250-300 g), n=18, randomly divided into control group, yeast group, yeast + nimesulide 10 mg/kg group, yeast + indomethacin 10 mg/kg group, yeast + indomethacin (5 mg/kg) + nimesulide (10 mg/kg) group (n=6/group except combination group, n=3).
- Model induction: Fever was induced by subcutaneous injection of brewer’s yeast (20% w/v in normal saline, 10 mL/kg) into the dorsal neck.
- Drug administration: Nimesulide or indomethacin was dissolved in 0.5% CMC-Na. Drugs were administered orally at the fever peak (18 hours post-yeast injection).
- Evaluation: Body temperature was measured every hour for 6 hours post-drug [2]

Absorption, Distribution and Excretion
Rapidly absorbed after oral administration. Renal excretion (50%), fecal excretion (29%). Metabolism/Metabolites Hepatic metabolism. Extensive biotransformation, primarily producing 4-hydroxynimesulide (this metabolite also appears to be biologically active). Biological Half-Life 1.8–4.7 hours

Hepatotoxicity
Prospective studies have shown that up to 15% of patients taking nonsteroidal anti-inflammatory drugs (NSAIDs) experience at least transient elevations in serum transaminases. Reports with nimesulide show a lower incidence. These elevations are usually transient, mild, and asymptomatic, and may resolve spontaneously with continued use. Significant transaminase elevations (more than 3-fold increase) are seen in a probability score of A (identified clinically significant cause of liver injury). Protein binding rate >97.5%

[1]. Effect of nimesulide action time dependence on selectivity towards prostaglandin G/H synthase/cyclooxygenase activity. Arzneimittelforschung. 1995 Oct;45(10):1096-8.

[2]. Nimesulide-induced antipyresis in rats involves both cyclooxygenase-dependent and independent mechanisms. Eur J Pharmacol. 2006 Aug 14;543(1-3):181-9.

[3]. The effect of COX-2 inhibitor, nimesulide, on angiogenetic factors in primary endometrial carcinoma cell culture. Clin Exp Med. 2007 Mar;7(1):6-10.

Nimesulide is an aromatic ether with two aryl groups: phenyl and 2-methylsulfonamido-5-nitrophenyl. It is a cyclooxygenase-2 inhibitor and a nonsteroidal anti-inflammatory drug (NSAID). It is a C-nitro compound, a sulfonamide compound, and an aromatic ether compound, with a structure similar to nitrobenzene. Nimesulide is a relatively selective COX-2 inhibitor with analgesic and antipyretic effects. Its approved indications include the treatment of acute pain, relief of osteoarthritis symptoms, and treatment of primary dysmenorrhea in adolescents and adults aged 12 years and older. Due to concerns about hepatotoxicity, nimesulide has been withdrawn from the market in many countries. Nimesulide is a nonsteroidal anti-inflammatory drug (NSAID) with relatively high COX-2 specificity. It has been discontinued in the United States but is widely used in other countries for the treatment of acute pain. Nimesulide is associated with a low incidence of transient elevations in serum enzymes during treatment, but it has also been associated with many clinically significant cases of acute liver injury, which can be severe, even leading to acute liver failure, requiring emergency liver transplantation, and death. Nimesulide is a nonsteroidal aryl sulfonamide drug with anti-inflammatory properties. Nimesulide inhibits the cyclooxygenase-mediated conversion of arachidonic acid to pro-inflammatory prostaglandins. It has moderate selectivity for COX-2, binding to and inactivating the enzyme. Nimesulide may inhibit certain COX-2-related carcinogenic effects, such as xenobiotic metabolism, apoptosis, immune surveillance, and angiogenesis (overexpression of COX-2 in tumor epithelial cells enhances the production of angiogenic factors and the formation of capillary-like networks). (NCI04)

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Drug Indications
For the treatment of acute pain, and symptomatic treatment of osteoarthritis and primary dysmenorrhea in adolescents and adults aged 12 years and older.

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Mechanism of Action
The therapeutic effect of nimesulide stems from its comprehensive mechanism of action, which targets multiple key mediators in the inflammatory process, such as COX-2-mediated prostaglandins, free radicals, proteolytic enzymes, and histamine.

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Pharmacodynamics
Food, sex, and age have little effect on the pharmacokinetics of nimesulide.

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1. Nimesulide (R805) is a selective COX-2 inhibitor whose COX-2 inhibition increases over time. Its high selectivity for COX-2 (ratio >40) is attributed to its stronger and more persistent binding to the COX-2 active site than to COX-1 [1]
2. The antipyretic effect of nimesulide involves both COX-dependent and COX-independent mechanisms. The COX-dependent component is mediated by the inhibition of PGE2 synthesis, while the COX-independent component may be involved in the regulation of central thermoregulatory pathways (e.g., affecting COX-independent cytokine signaling) [2]
3. In endometrial cancer, nimesulide inhibits tumor angiogenesis by downregulating the expression of VEGF and bFGF, suggesting its potential application value in cancer chemoprevention or adjuvant therapy for angiogenesis-dependent tumors [3]

C13H12N2O5S

308.31

308.046

51803-78-2

Nimesulide-d5;1330180-22-7

4495

Light yellow to yellow solid powder

1.5±0.1 g/cm3

442.0±55.0 °C at 760 mmHg

140-146°C

221.1±31.5 °C

0.0±1.1 mmHg at 25°C

1.638

3.79

1

6

4

21

450

0

HYWYRSMBCFDLJT-UHFFFAOYSA-N

InChI=1S/C13H12N2O5S/c1-21(18,19)14-12-8-7-10(15(16)17)9-13(12)20-11-5-3-2-4-6-11/h2-9,14H,1H3

N-(4-Nitro-2-phenoxyphenyl)methanesulfonamide

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (8.11 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (8.11 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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 (Please use freshly prepared in vivo formulations for optimal results.)