Sulfapyridine is a sulfanilamide antibacterial medication. At one time, it was commonly referred to as M&B 693. Sulfapyridine is no longer prescribed for treatment of infections in humans. However, it may be used to treat linear IgA disease and has use in + some more technical info. Chemically identified as 4-amino-N-pyridin-2-yl-benzenesulfonamide, CAS 144-85-4, with molecular formula C11H11N3O2S and a molecular weight of 249.29 g mol, sulfapyridine is a crystalline powder that is sparingly soluble in water and more soluble in alkaline aqueous media and certain organic solvents. Typical physicochemical properties used in quality control include a melting range around 190 to 193 C, a pKa near 6.5 for the aniline nitrogen and near 2.0 for the pyridinium site, and UV absorption maxima used for assay at about 260 nm. Routine analytical methods for identity and assay include IR, NMR and HPLC with UV detection; stability testing monitors hydrolytic and oxidative degradation pathways. In formulations and compendial monographs the active substance is controlled for identity, potency, residual solvents and microbial limits where applicable.
Impurity profiling for sulfapyridine focuses on related synthetic intermediates, oxidative and hydrolytic degradants, and isomeric pyridine derivatives. Typical industry and compendial acceptance limits used for finished active substance batches are: each specified related compound not greater than 0.5 percent w w, unspecified individual impurities not greater than 0.2 percent w w, and total impurities not greater than 2.0 percent w w; limits are set by the manufacturer or pharmacopoeial monograph and can vary. Common impurities observed by reversed phase HPLC or LC MS include sulfapyridine N-oxide (often limited to about 0.1 to 0.3 percent), desulfonylated or dearylated degradants (typically limited to 0.1 to 0.2 percent), residual pyridine-containing intermediates such as 2-aminopyridine-related species (commonly limited to 0.1 to 0.5 percent), and minor amounts of 4-aminobenzenesulfonic acid or related aromatic oxidized products (usually trace to 0.1 percent). Specification setting should follow ICH Q3A and Q3B principles and be supported by validated analytical procedures.
Sulfapyridine was historically used as a broad spectrum sulfonamide antibacterial for systemic infections. Current clinical use in humans as an antibacterial is discontinued in most regions, but it is still used in selected dermatologic immune mediated conditions such as linear IgA disease and in certain specialized investigational or compounding contexts.
A common historical name for sulfapyridine is M&B 693. It is also referred to by its chemical name 4-amino-N-pyridin-2-yl-benzenesulfonamide and by its CAS number 144-85-4.
Sulfapyridine, like other sulfanilamides, is bacteriostatic and acts as a competitive inhibitor of dihydropteroate synthase, an enzyme in the folate biosynthesis pathway of bacteria. By competing with para-aminobenzoic acid at this enzyme, it reduces synthesis of dihydropteroate and downstream folate derivatives required for nucleotide biosynthesis.
