Quick Facts
| CAS Number | 36322-90-4 |
|---|---|
| Molecular Formula | C15H13N3O4S |
| Molecular Weight | 331.346 |
| Pharmacopoeia | EP/USP |
| Packaging | 25 KG/DRUM |
Product Overview
Piroxicam was discovered at Pfizer's research laboratories in Groton, Connecticut, and introduced as Feldene in 1980. It was not another propionic acid NSAID like ibuprofen or naproxen — it was the first drug in an entirely new structural class, the oxicams, characterized by a benzothiazine carboxamide scaffold that contains an enolic acid group with a pKa of approximately 6.3. This unique structure accounts for piroxicam's most distinctive clinical property: a plasma elimination half-life of roughly 50 hours. At the time of its introduction, this was by far the longest-acting NSAID available, and it established once-daily dosing as a realistic treatment paradigm for chronic inflammatory diseases.
The long half-life is not just a convenience feature — it has genuine therapeutic significance for rheumatoid arthritis. Morning stiffness, the hallmark symptom of RA, peaks in the 4-6 hours after waking. An NSAID taken at breakfast would be at its trough concentration precisely when symptom severity peaks. Piroxicam's pharmacokinetics mean that a dose taken the previous evening maintains therapeutic plasma levels through the critical early-morning period, providing coverage when short-acting NSAIDs fail. This pharmacodynamic alignment with disease chronobiology is a major reason piroxicam retains a loyal prescriber base four decades after its introduction, despite the existence of newer agents.
Piroxicam is a non-selective COX-1/COX-2 inhibitor that reduces prostaglandin synthesis at sites of inflammation. While its gastrointestinal toxicity profile is similar to other non-selective NSAIDs, decades of clinical experience have established clear risk stratification: patients over 65, those with prior ulcer history, and concurrent corticosteroid users benefit from gastroprotection with proton pump inhibitors. In acute pain settings, particularly post-operative dental pain and acute gouty arthritis, piroxicam's rapid absorption (peak plasma concentration in 2-3 hours) combined with its extended duration makes it suitable for single-dose or short-course therapy.
As of mid-2026, piroxicam remains on the WHO Essential Medicines List and is widely prescribed across Latin America, the Middle East, South Asia, and Africa. While COX-2 selective inhibitors (celecoxib) have captured market share in higher-income countries, piroxicam's cost-effectiveness, once-daily convenience, and extensive clinical experience ensure sustained global demand. China and India are the dominant API producers. The primary quality considerations for API sourcing are polymorphic form consistency (Form I is standard) and compliance with EP/USP impurity profiles. KingWish supplies GMP-certified piroxicam meeting EP and USP specifications for pharmaceutical manufacturers worldwide.
Quality Specifications
| Purity (HPLC) | ≥ 98.5% (dried basis), per EP/USP monograph |
|---|---|
| Related Substances | Individual impurity ≤ 0.2%, total impurities ≤ 0.5% (EP/USP) |
| Polymorphic Form | Form I (most stable) confirmed by IR or XRPD per EP identification test |
| Residual Solvents | Compliant with ICH Q3C |
| Heavy Metals | ≤ 20 ppm |
| GMP Status | Manufactured under ICH Q7 GMP conditions |
Clinical Applications
Oral Capsules (10 mg / 20 mg)
Once-daily 20 mg for RA, OA, ankylosing spondylitis. 40 mg for acute gout and post-op pain. Rapid absorption with peak levels in 2-3 hours, steady state in 7-12 days.
Topical Gel & Injectable Forms
0.5% gel for localized musculoskeletal pain. Injectable form (IM) for acute conditions where oral route is not feasible. Suppository formulation available for patients with upper GI intolerance.
Therapeutic Areas
- Rheumatoid arthritis: 20 mg once daily. Particularly effective for morning stiffness due to sustained overnight plasma concentrations from the 50-hour half-life.
- Osteoarthritis: 20 mg once daily for hip and knee OA. Long half-life provides 24-hour symptomatic relief with once-daily dosing, improving compliance in elderly patients.
- Ankylosing spondylitis: 20 mg once daily for inflammatory back pain and axial symptoms, with proven efficacy over placebo in controlled trials.
- Acute gout: 40 mg daily for 5 days for rapid resolution of acute gouty arthritis flares.
- Post-operative pain: 20-40 mg single dose for dental and minor surgical pain.
Sourcing Piroxicam API: Key Checks
Documentation
Request CoA with HPLC purity data, polymorphic form confirmation (IR or XRPD), residual solvent statement (ICH Q3C), heavy metals report, and GMP certificate. For EP markets, verify that the CoA includes the specific EP identification test for polymorphic form.
Red Flags
Inconsistent polymorphic form between batches (Forms I, II, III have different dissolution profiles affecting bioavailability), missing polymorph identification, elevated individual impurities above 0.3%, and prices significantly below market range.
Packaging & Logistics
Standard: 25 KG/DRUM with PE liner. Store at room temperature, protect from light (piroxicam is photolabile in solution, though the solid is stable). Standard lead time 4-6 weeks. Air and sea freight options available.
Market Context
Piroxicam remains on the WHO Essential Medicines List and is widely prescribed in Latin America, Middle East, South Asia, and Africa. While COX-2 inhibitors have gained share in developed markets, piroxicam's cost-effectiveness and once-daily convenience sustain strong demand. The piroxicam-beta-cyclodextrin inclusion complex is an important differentiated formulation with faster absorption.