Olsalazine is an aminosalicylate anti-inflammatory pharmaceutical compound used primarily in the management of ulcerative colitis. The pharmaceutical form is olsalazine sodium, the disodium salt of olsalazine. It is designed as a colon-targeted prodrug that is converted by intestinal bacterial activity into 5-aminosalicylic acid (mesalamine, 5-ASA), the pharmacologically active anti-inflammatory moiety.
Olsalazine sodium is chemically known as disodium 3,3′-diazenediylbis(6-hydroxybenzoate). The compound contains an azo linkage connecting two salicylate-derived moieties. Current BP/Ph. Eur. 2025 information describes it as a yellow, fine, crystalline powder with a content requirement of 98.0% to 102.0% on the dried substance basis.
The identity and chemical information are supported by the BP/Ph. Eur. monograph, PubChem and official product labeling.
Olsalazine sodium acts primarily as a prodrug of mesalamine (5-aminosalicylic acid).
The drug is classified as an aminosalicylate and is used for the treatment of ulcerative colitis.
These values correspond to the BP 2025 / Ph. Eur. 11.6 monograph.
Olsalazine sodium is primarily associated with:
Olsalazine is converted into mesalamine by bacterial metabolism in the colon, allowing the active anti-inflammatory component to act locally in the gastrointestinal tract.
Olsalazine sodium is reported as a yellow, fine, crystalline powder in the BP/Ph. Eur. monograph.
The BP/Ph. Eur. characterization describes it as sparingly soluble in water, soluble in dimethyl sulfoxide and very slightly soluble in methanol. The US product labeling reports decomposition at approximately 240°C and describes the material as soluble in water and DMSO; for a CMS API specification, the current compendial description is preferred.
BP/Ph. Eur. provides multiple identification approaches:
For UV identification, absorption maxima occur at 255 nm and 362 nm, with an A255/A362 ratio of 0.53–0.56.
The BP/Ph. Eur. monograph identifies nine specified impurities:
Each specified impurity has a principal limit of NMT 1.0%, with the additional requirement that no more than one impurity peak may exceed 0.5%. The total related substances limit is NMT 2.0%, with a disregard limit of 0.025%.
The current monograph separately controls:
This is particularly relevant when developing or qualifying olsalazine sodium API manufacturing processes.
Olsalazine sodium shows polymorphism according to the BP/Ph. Eur. monograph. Therefore, solid-state characterization such as XRPD can be relevant when establishing the physical form of API batches and maintaining consistency during pharmaceutical development.
Quality evaluation of olsalazine sodium can include:
The BP 2025 / Ph. Eur. monograph provides numerical acceptance criteria for content, related substances, acetate, methanesulfonic acid and loss on drying.
Olsalazine sodium should be stored in a tightly closed, appropriately controlled pharmaceutical container, protected from excessive moisture and unsuitable environmental conditions. Actual storage conditions should follow the validated API stability data and approved manufacturer specification.
| Parameter | Specification |
|---|---|
| Appearance | White crystalline powder or crystals |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 2.0% |
| Residue on Ignition | NMT 0.5% |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 2.0% |
| Water Content | NMT 2.0% |
| Melting Point | Approximately 240°C with decomposition |