Para-Aminosalicylic Acid (PAS)

Also known as: Paser, Pasiniazid component, Monopas, Sodium PAS

CAS Number: 65-49-6

Antitubercular (Folate Pathway Antagonist, Second-Line)

Pharmacopeia Standards

USPIPWHO

Mechanism of Action

Para-aminosalicylic acid is a structural analogue of para-aminobenzoic acid that is processed by dihydropteroate synthase and dihydrofolate synthase into a hydroxy-dihydrofolate antimetabolite. This false cofactor inhibits dihydrofolate reductase and blocks the thymidine nucleotide supply needed for DNA replication. The resulting folate pathway disruption is bacteriostatic and highly selective for Mycobacterium tuberculosis, with no cross-resistance to other antitubercular classes.

Technical Specifications

Generic / INN Name	Para-Aminosalicylic Acid (PAS)
CAS Registry Number	65-49-6
Molecular Formula	C7H7NO3
Molecular Weight	153.14 g/mol g/mol
Typical Purity	98.0% - 102.0% (on anhydrous basis, USP assay)
Storage Conditions	Store at 2-8 degrees C in tightly closed, light-resistant containers under nitrogen; heat and light labile, protect from moisture and air
Shelf Life	24 months from date of manufacture when stored refrigerated as directed
Category	Anti-Tubercular Agents

Specifications are indicative and intended for sourcing reference only. Always confirm against the supplier's Certificate of Analysis and the applicable pharmacopeial monograph before issuing a purchase specification.

Typical Applications

Bulk API for enteric-coated granules and delayed-release formulations, and as the precursor for sodium aminosalicylate and calcium aminosalicylate salts used in longer multidrug-resistant tuberculosis regimens.

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