Oxaprozin is a nonsteroidal anti-inflammatory drug (NSAID) belonging to the propionic acid derivative class. Chemically, it is known as 4,5-diphenyl-2-oxazolepropionic acid and is used for its anti-inflammatory, analgesic and antipyretic properties.
Oxaprozin is a well-characterized small-molecule pharmaceutical API with the molecular formula C18H15NO3 and molecular weight 293.32 g/mol. It is described as a white to off-white or yellowish-white crystalline powder and has a reported melting range of approximately 162–163°C.
The current publicly reproduced USP 2025 monograph specifies 98.0–102.0% oxaprozin on the dried basis, together with numerical requirements for residue on ignition, arsenic, organic impurities and loss on drying.
The chemical identity and molecular data are supported by PubChem and FDA/DailyMed information.
Oxaprozin produces analgesic, anti-inflammatory and antipyretic effects primarily through inhibition of prostaglandin synthesis.
FDA labeling describes oxaprozin as a potent inhibitor of prostaglandin synthesis and attributes its mechanism to cyclooxygenase/prostaglandin-synthesis inhibition.
The current USP 2025 reproduction specifies 98.0–102.0% assay and detailed organic impurity controls.
Oxaprozin API is used in pharmaceutical development and manufacturing of NSAID products intended for management of inflammatory and painful musculoskeletal conditions.
Applications include:
FDA labeling identifies oxaprozin as an NSAID used for the relief of signs and symptoms associated with osteoarthritis and rheumatoid arthritis.
Oxaprozin is a crystalline, aromatic oxazole-containing propionic acid derivative.
FDA/DailyMed describes oxaprozin as slightly soluble in alcohol and insoluble in water, while another USP product description reports it as sparingly soluble in methanol and ethanol, slightly soluble in ether and practically insoluble in water.
Oxaprozin has a well-defined USP analytical profile.
USP identification uses:
The USP identification procedure includes comparison of the oxaprozin HPLC retention time with the reference standard. The UV identification in the earlier monograph specifies an absorbance at 285 nm of 0.455–0.495 using a 10 µg/mL methanolic solution.
The current USP 2025 monograph uses liquid chromatography for assay.
Key parameters include:
System suitability includes a tailing factor of NMT 2.0 and relative standard deviation of NMT 0.73%.
The current USP 2025 monograph provides specific numerical controls for oxaprozin-related impurities.
Specified impurities include:
These are particularly valuable CMS values because they come from the current USP 2025 monograph reproduction rather than generic API assumptions.
The USP monograph includes controls for inorganic impurities.
The current USP 2025 text specifically retains the arsenic limit of NMT 1 ppm and residue-on-ignition limit of NMT 0.3%.
Oxaprozin is tested by loss on drying:
The current USP 2025 monograph specifies NMT 0.3% loss on drying.
Oxaprozin is described as light sensitive. The USP monograph specifically instructs that Oxaprozin samples and standard solutions should be protected from light and recommends tight, light-resistant containers for storage.
Oxaprozin has a USP monograph and is therefore substantially better defined from a public compendial perspective than many newer pharmaceutical APIs.
Quality testing can include:
For a pharmaceutical API page, the USP values should take priority over generic commercial CoA specifications when the two differ.
Oxaprozin should be stored in tight, light-resistant containers under controlled room-temperature conditions.
Because oxaprozin is light sensitive, protection from excessive light exposure is important during handling, sampling and storage.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 0.3% |
| Residue on Ignition | NMT 0.3% |
| Heavy Metals | NMT 10 ppm |
| Water Content | 162–163°C |
| Melting Point | 162–163°C |