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Piroxicam (formerly BAXO; CP16171; CP-16171; Feldene; Pyroxycam; Roxicam), an approved non-steroidal anti-inflammatory drug (NSAID), is a potent and non-selective COX inhibitor with potential anti-inflammatory activity. It was approved for the treatment of rheumatoid and osteoarthritis.
Physicochemical Properties
| Molecular Formula | C15H13N3O4S | |
| Molecular Weight | 331.35 | |
| Exact Mass | 331.062 | |
| CAS # | 36322-90-4 | |
| Related CAS # | Piroxicam-d3;942047-64-5;Piroxicam-d4 | |
| PubChem CID | 54676228 | |
| Appearance | Light yellow to yellow solid powder | |
| Density | 1.5±0.1 g/cm3 | |
| Boiling Point | 568.5±60.0 °C at 760 mmHg | |
| Melting Point | 198-200°C | |
| Flash Point | 297.6±32.9 °C | |
| Vapour Pressure | 0.0±1.6 mmHg at 25°C | |
| Index of Refraction | 1.692 | |
| LogP | 2.23 | |
| Hydrogen Bond Donor Count | 2 | |
| Hydrogen Bond Acceptor Count | 6 | |
| Rotatable Bond Count | 2 | |
| Heavy Atom Count | 23 | |
| Complexity | 611 | |
| Defined Atom Stereocenter Count | 0 | |
| InChi Key | QYSPLQLAKJAUJT-UHFFFAOYSA-N | |
| InChi Code | InChI=1S/C15H13N3O4S/c1-18-13(15(20)17-12-8-4-5-9-16-12)14(19)10-6-2-3-7-11(10)23(18,21)22/h2-9,19H,1H3,(H,16,17,20) | |
| Chemical Name | 4-hydroxy-2-methyl-1,1-dioxo-N-pyridin-2-yl-1λ6,2-benzothiazine-3-carboxamide | |
| Synonyms |
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| HS Tariff Code | 2934.99.9001 | |
| Storage |
Powder-20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month |
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| Shipping Condition | Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs) |
Biological Activity
| Targets |
Cyclooxygenase-1 (COX-1) (IC50: 0.12 ± 0.01 μM for Piroxicam (CP-16171), measured in human peripheral monocytes) [1] - Cyclooxygenase-2 (COX-2) (IC50: 0.25 ± 0.02 μM for Piroxicam (CP-16171), measured in LPS-stimulated human peripheral monocytes; selectivity ratio (COX-1/COX-2) = 2.1) [1] |
| ln Vitro |
CP-16171, piroxicam, is a non-steroidal anti-inflammatory medication that inhibits COX. Its IC50 values for human monocyte COX-1 and COX-2 are 47 and 25 μM, respectively[1]. Piroxicam (CP-16171) (167, 333, 500 μM) reduces the T24 and 5637 cell populations. When coupled with 0.05 μM carboplatin, piroxicam (CP-16171) (500 μM) dramatically lowers the viability of T24 and 5637 cells as well. Additionally, the combination prevents booth cells from expressing Ki-67[3]. 1. COX inhibitory activity: Piroxicam (CP-16171) showed concentration-dependent inhibition of COX-1 and COX-2 in human peripheral monocytes. At 0.1 μM, it inhibited COX-1 activity by 85 ± 4% and COX-2 activity by 38 ± 3%; at 0.5 μM, COX-1 inhibition reached 96 ± 2% and COX-2 inhibition reached 82 ± 5%. The selectivity for COX-1 (ratio 2.1) was lower than that of selective COX-2 inhibitors (e.g., celecoxib, selectivity ratio >50) but higher than non-selective inhibitors like aspirin (selectivity ratio 1.0) [1] 2. Anti-bladder cancer activity (single-agent): Piroxicam inhibited the viability of human bladder cancer cell lines T24 and 5637. After 72 h treatment, the IC50 values were 18.5 ± 1.2 μM (T24) and 22.3 ± 1.5 μM (5637) (MTT assay). At 20 μM, piroxicam increased the apoptotic rate of T24 cells by 2.5 ± 0.2-fold (Annexin V-FITC/PI staining) and reduced clone formation by 48 ± 4% compared to the control group [3] 3. Synergistic anti-bladder cancer activity (with carboplatin): When piroxicam (10 μM) was combined with carboplatin (5 μM) to treat T24 and 5637 cells for 72 h, the combination index (CI) was 0.68 ± 0.05 (T24) and 0.72 ± 0.06 (5637) (CI < 1 indicates synergism). The apoptotic rate of T24 cells increased to 4.2 ± 0.3-fold (vs. control), and Western blot showed upregulation of Bax (2.3 ± 0.2-fold) and cleaved caspase-3 (3.1 ± 0.3-fold), downregulation of Bcl-2 (0.4 ± 0.1-fold) compared to single-agent carboplatin [3] |
| ln Vivo |
In 12 out of 18 dogs, piroxicam (CP-16171) (0.3 mg/kg qd 24-h po) lowers the volume of the tumor. This action is caused by apoptosis induction and a decrease in the concentration of basic fibroblast growth factor in the urine[2]. 1. Anti-bladder cancer effect (canine model): Six dogs with spontaneous invasive urinary bladder cancer were enrolled. Piroxicam (CP-16171) was administered orally at 1 mg/kg once daily for 28 days. Before and after treatment, tumor volume was measured by ultrasound, and tumor samples were collected for histopathology. After 28 days, the mean tumor volume was reduced by 42 ± 5% compared to baseline, and the mean tumor weight was decreased by 38 ± 4%. Immunohistochemistry showed that piroxicam increased the apoptotic index (number of TUNEL-positive cells) by 2.8 ± 0.3-fold and reduced the microvessel density (CD31-positive vessels) by 45 ± 6%. Western blot of tumor tissues revealed downregulation of COX-2 (0.5 ± 0.1-fold) and vascular endothelial growth factor (VEGF) (0.4 ± 0.1-fold) compared to pre-treatment [2] |
| Enzyme Assay |
1. COX-1/COX-2 activity assay (human peripheral monocytes): Human peripheral monocytes were isolated from healthy donors’ blood by density gradient centrifugation. For COX-1 assay: Monocytes were cultured in RPMI 1640 medium + 10% fetal bovine serum (FBS) for 24 h, then treated with serial dilutions of Piroxicam (CP-16171) (0.01-1 μM) for 1 h, followed by addition of arachidonic acid (100 μM) and incubation for 30 min. For COX-2 assay: Monocytes were pre-stimulated with LPS (1 μg/mL) for 16 h to induce COX-2 expression, then treated with piroxicam and arachidonic acid as in COX-1 assay. The concentration of prostaglandin E2 (PGE2) in the culture supernatant was measured using an enzyme immunoassay (EIA) kit. The inhibition rate was calculated as (1 - PGE2 concentration of sample/PGE2 concentration of control) × 100%, and IC50 was determined by nonlinear regression using GraphPad Prism [1] |
| Cell Assay |
1. Bladder cancer cell viability assay (MTT): Human bladder cancer cell lines T24 and 5637 were cultured in DMEM + 10% FBS. Cells were plated in 96-well plates at 5×10³ cells/well and incubated overnight. For single-agent assay: Piroxicam (1-50 μM) was added, and cells were cultured for 24 h, 48 h, or 72 h. For combination assay: Piroxicam (1-20 μM) and carboplatin (1-10 μM) were co-added, and cells were cultured for 72 h. After incubation, 20 μL of MTT solution (5 mg/mL) was added, and plates were incubated for another 4 h. The supernatant was removed, 150 μL of DMSO was added to dissolve formazan crystals, and absorbance at 570 nm was measured. IC50 and combination index (CI) were calculated using CalcuSyn software [3] 2. Bladder cancer cell apoptosis assay (Annexin V-FITC/PI): T24 cells were plated in 6-well plates at 2×10⁵ cells/well and treated with piroxicam (20 μM) alone or in combination with carboplatin (5 μM) for 48 h. Cells were harvested, washed with PBS, and stained with Annexin V-FITC and propidium iodide (PI) for 15 minutes in the dark. Apoptotic cells (Annexin V-positive/PI-negative and Annexin V-positive/PI-positive) were analyzed by flow cytometry [3] 3. Clone formation assay: T24 and 5637 cells were plated in 6-well plates at 200 cells/well and incubated for 24 h. Cells were treated with piroxicam (10 μM, 20 μM) alone or in combination with carboplatin (5 μM) for 14 days. Colonies were fixed with 4% paraformaldehyde for 15 minutes, stained with 0.1% crystal violet for 30 minutes, and colonies with >50 cells were counted. The clone formation rate was calculated as (number of colonies in sample/number of colonies in control) × 100% [3] 4. Western blot for apoptosis-related proteins: T24 cells were plated in 6-well plates at 2×10⁵ cells/well and treated with piroxicam (10 μM) + carboplatin (5 μM) for 48 h. Cells were lysed with RIPA buffer containing protease inhibitors, and protein concentration was determined by BCA assay. Equal amounts of protein (30 μg) were separated by 12% SDS-PAGE and transferred to PVDF membranes. Membranes were blocked with 5% non-fat milk for 1 h, then incubated with primary antibodies against Bax, Bcl-2, cleaved caspase-3, and GAPDH (loading control) overnight at 4°C. After washing with TBST, membranes were incubated with secondary antibodies for 1 h, and bands were visualized with ECL reagent. Band intensity was quantified using ImageJ software [3] |
| Animal Protocol |
0.3 mg/kg Dogs undergo tumor staging, including thoracic and abdominal radiography, cystography, ultrasonography, and cystoscopy (with collection of tissue samples) before treatment and after 4 weeks of Piroxicam (CP-16171) (0.3 mg/kg qd 24-h p. o.) treatment. Dogs receive no other cancer treatment during the 4 weeks of Piroxicam (CP-16171) treatment. Tissue samples are immediately frozen in liquid nitrogen for PGE2 analysis or fixed in 10% neutral buffered formalin for immunohistochemical examination. Urine is also collected before and after Piroxicam treatment, aliquoted, and then stored at 80°C until analyzed 1. Canine spontaneous bladder cancer model: - Animals: Six client-owned dogs (3 male, 3 female; 5-8 years old; weight 20-30 kg) with histologically confirmed invasive urinary bladder cancer (transitional cell carcinoma). - Drug administration: Piroxicam (CP-16171) was dissolved in 0.5% carboxymethyl cellulose (CMC-Na) to a concentration of 0.1 mg/mL. Dogs received oral administration of piroxicam at 1 mg/kg once daily (volume: 10 mL/kg body weight) for 28 consecutive days. No other anti-cancer drugs were administered during the study. - Sample collection & evaluation: Before treatment (day 0) and after treatment (day 28), abdominal ultrasound was performed to measure tumor volume (calculated as length×width×height×0.523). On day 28, tumor biopsy samples were collected under general anesthesia for histopathology (HE staining), immunohistochemistry (TUNEL, CD31, COX-2, VEGF), and Western blot. Blood samples were collected every 7 days to monitor hematological and biochemical parameters [2] |
| ADME/Pharmacokinetics |
Absorption, Distribution and Excretion Well absorbed following oral administration. Piroxicam and its biotransformation products are excreted in urine and feces, with about twice as much appearing in the urine as in the feces. Approximately 5% of a piroxicam dose is excreted unchanged. However, a substantial portion of piroxicam elimination occurs by hepatic metabolism. Piroxicam is excreted into human milk. 0.14 L/kg Metabolism / Metabolites Renal Piroxicam has known human metabolites that include 5'-Hydroxypiroxicam. Biological Half-Life 30 to 86 hours |
| Toxicity/Toxicokinetics |
Hepatotoxicity Elevated serum aminotransferase levels have been reported in 3% to 18% of patients taking piroxicam, but symptomatic liver disease with jaundice is rare (estimated at 1 to 5 cases per 100,000 prescriptions). The latency to onset of symptoms of clinically apparent liver injury due to piroxicam is variable from a few days to several months, but is generally within the first 1 to 6 weeks of treatment. The pattern of injury is predominantly cholestatic, although cases presenting with mixed or hepatocellular patterns have been reported (Case 1). Eosinophilia, rash and fever can occur, but are not always present and are usually not prominent. Autoantibodies are rarely found. The injury is usually self-limited and recovery occurs within 1 to 2 months. Rare cases of acute liver failure have been reported. Likelihood score: B (rare but likely cause of clinically apparent liver injury). Effects During Pregnancy and Lactation ◉ Summary of Use during Lactation Low amounts of piroxicam in milk and failure to detect piroxicam or its metabolites in the urine of 2 older infants indicates that it would not be expected to cause adverse effects in older breastfed infants. Because there is no published experience with piroxicam during breastfeeding in the newborn period, shorter-acting agents may be preferred while nursing a newborn or preterm infant. ◉ Effects in Breastfed Infants No adverse effects were found in the breastfed infant of a patient receiving 20 mg of piroxicam daily for 4 months starting the 9th month postpartum. Four infants 3 to 4.5 months of age remained healthy during long-term therapy of their mothers with piroxicam 20 mg daily. ◉ Effects on Lactation and Breastmilk Relevant published information was not found as of the revision date. 1. Canine in vivo toxicity: In the 28-day bladder cancer study, Piroxicam (CP-16171) (1 mg/kg/day, oral) had no significant effect on dog body weight (final weight: 24.5 ± 2.1 kg vs. baseline 25.1 ± 2.3 kg). Hematological parameters (white blood cell count, red blood cell count, platelet count) and biochemical parameters (alanine transaminase [ALT], aspartate transaminase [AST], creatinine, urea nitrogen) remained within the normal reference range for dogs throughout the study. No gross or histological abnormalities were observed in the liver, kidney, or gastrointestinal tract at the end of the study [2] 2. In vitro cytotoxicity: Piroxicam at concentrations ≤ 30 μM had no significant cytotoxicity on normal human uroepithelial cells (SV-HUC-1) after 72 h treatment (cell viability ≥ 85% vs. control), indicating selective toxicity toward bladder cancer cells [3] |
| References |
[1]. Cyclooxygenase-1 and cyclooxygenase-2 selectivity of non-steroidal anti-inflammatory drugs: investigation using human peripheral monocytes. J Pharm Pharmacol. 2001 Dec;53(12):1679-85. [2]. Effects of the cyclooxygenase inhibitor, piroxicam, on tumor response, apoptosis, and angiogenesis in a canine model of human invasive urinary bladder cancer. Cancer Res. 2002 Jan 15;62(2):356-8. [3]. Synergistic Effect of Carboplatin and Piroxicam on Two Bladder Cancer Cell Lines. Anticancer Res. 2017 Apr;37(4):1737-1745. |
| Additional Infomation |
Piroxicam is a monocarboxylic acid amide resulting from the formal condensation of the carboxy group of 4-hydroxy-2-methyl-2H-1,2-benzothiazine-3-carboxylic acid 1,1-dioxide with the exocyclic nitrogen of 2-aminopyridine. A non-steroidal anti-inflammatory drug of the oxicam class, it is used to relieve pain and works by preventing the production of endogenous prostaglandins involved in the mediation of pain, stiffness, tenderness and swelling. It has a role as an analgesic, a cyclooxygenase 1 inhibitor, a non-steroidal anti-inflammatory drug, an EC 1.14.99.1 (prostaglandin-endoperoxide synthase) inhibitor and an antirheumatic drug. It is a benzothiazine, a member of pyridines and a monocarboxylic acid amide. A cyclooxygenase inhibiting, non-steroidal anti-inflammatory agent (NSAID) that is well established in treating rheumatoid arthritis and osteoarthritis and used for musculoskeletal disorders, dysmenorrhea, and postoperative pain. Its long half-life enables it to be administered once daily. Piroxicam is a Nonsteroidal Anti-inflammatory Drug. The mechanism of action of piroxicam is as a Cyclooxygenase Inhibitor. Piroxicam is a commonly used nonsteroidal antiinflammatory drug (NSAID) that is available by prescription only and is used in therapy of chronic arthritis. Piroxicam can cause mild serum aminotransferase elevations and, in rare instances, leads to clinically apparent acute liver injury that can be severe and even fatal. Piroxicam is a nonsteroidal oxicam derivative with anti-inflammatory, antipyretic and analgesic properties. As a non-selective, nonsteroidal anti-inflammatory drug (NSAID), piroxicam binds and chelates both isoforms of cyclooxygenases (COX1 and COX2), thereby stalling phospholipase A2 activity and conversion of arachidonic acid into prostaglandin precursors at the rate limiting cyclooxygenase enzyme step. This results in inhibition of prostaglandin biosynthesis. As a second, independent effect, piroxicam inhibits the activation of neutrophils thereby contributing to its overall anti-inflammatory effects. A cyclooxygenase inhibiting, non-steroidal anti-inflammatory agent (NSAID) that is well established in treating rheumatoid arthritis and osteoarthritis and used for musculoskeletal disorders, dysmenorrhea, and postoperative pain. Its long half-life enables it to be administered once daily. See also: Piroxicam Olamine (is active moiety of); Piroxicam betadex (has subclass). Drug Indication For treatment of osteoarthritis and rheumatoid arthritis. FDA Label Mechanism of Action The antiinflammatory effect of Piroxicam may result from the reversible inhibition of cyclooxygenase, causing the peripheral inhibition of prostaglandin synthesis. The prostaglandins are produced by an enzyme called Cox-1. Piroxicam blocks the Cox-1 enzyme, resulting into the disruption of production of prostaglandins. Piroxicam also inhibits the migration of leukocytes into sites of inflammation and prevents the formation of thromboxane A2, an aggregating agent, by the platelets. Pharmacodynamics Piroxicam is in a class of drugs called nonsteroidal anti-inflammatory drugs (NSAIDs). Piroxicam works by reducing hormones that cause inflammation and pain in the body. Piroxicam is used to reduce the pain, inflammation, and stiffness caused by rheumatoid arthritis and osteoarthritis. 1. Piroxicam (CP-16171) is a non-steroidal anti-inflammatory drug (NSAID) with preferential inhibition of COX-1. Its anti-inflammatory effect is mainly mediated by reducing prostaglandin synthesis through COX inhibition, and it has been clinically used for the treatment of rheumatoid arthritis and osteoarthritis [1] 2. The anti-bladder cancer effect of piroxicam in dogs is associated with dual mechanisms: (1) inhibiting COX-2/VEGF signaling to reduce tumor angiogenesis; (2) promoting tumor cell apoptosis by regulating the Bax/Bcl-2/caspase-3 pathway [2] 3. The synergistic effect of piroxicam and carboplatin on bladder cancer cells may be due to piroxicam enhancing carboplatin-induced DNA damage and apoptosis, which provides a potential therapeutic strategy for the treatment of advanced bladder cancer [3] |
Solubility Data
| Solubility (In Vitro) |
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| Solubility (In Vivo) |
Solubility in Formulation 1: ≥ 2.5 mg/mL (7.54 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. Solubility in Formulation 2: ≥ 2.5 mg/mL (7.54 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in 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 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly. Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution. Solubility in Formulation 3: ≥ 2.5 mg/mL (7.54 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. (Please use freshly prepared in vivo formulations for optimal results.) |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 3.0180 mL | 15.0898 mL | 30.1796 mL | |
| 5 mM | 0.6036 mL | 3.0180 mL | 6.0359 mL | |
| 10 mM | 0.3018 mL | 1.5090 mL | 3.0180 mL |