65-49-6

Indications

p-Aminosalicylic acid is a bacteriostatic that inhibits most tuberculous mycobacteria. In terms of tuberculostatic activity it is inferior to isoniazid and streptomycin. It is nephroand hepatotoxic, and is rarely used. A synonym of this drug is apacizin.

Manufacturing Process

As described in US Patent 427,564, aminosalicylic acid may be prepared from m-aminophenol by heating with ammonium carbonate in solution under pressure. Alternatively, aminosalicylic acid may be made from sodium p-aminosalicylate as described in US Patent 2,844,625 as follows: 196 grams of commercial sodium para-aminosalicylate (18.5% H2O) was dissolved in 196 ml of water and 150 ml of isopropanol. 6 grams of sodium bisulfite was dissolved in the solution and the solution filtered. While stirring and keeping the temperature between 25-31°C, seven grams of 85% formic acid and 27.5 grams of 95% sulfuric acid in 150 ml of water was added during 1 ? hours. The mixture was stripped 1 hour longer, cooled to 23°C and filtered. The filter cake was washed with 100 cubic centimeters of water, further washed with 100 cc of 25% isopropanol and 100 cc of water, and vacuum dried to constant weight at 45- 50°C. Weight of p-aminosalicylic acid was 76.5 grams (92.7% yield) exhibiting a bulk density of 47 cc/oz.

Therapeutic Function

Antitubercular

Biological Activity

4-Aminosalicylic acid is an antimetabolite of p-aminobenzoic acid (PABA) that has antibacterial activity.It is active against streptomycin-sensitive and -resistant strains of M. tuberculosis (MICs = 0.78 and 0.39 μg/ml, respectively), an effect that can be reversed by PABA. 4-Aminosalicylic acid is an alternative substrate for mycobacterial dihydropteroate synthase (FolP1) and misincorporation into the folate pathway leads to accumulation of several folate-dependent metabolites including serine, homocysteine, dUMP, and AICAR, markers of folate pathway inhibition, in a concentration-dependent manner. It reverses manganese-induced increases in rat hippocampal levels of NOD-like receptor protein 3 (NLRP3), cleaved caspase-1, and phosphorylated p65, markers of NLRP3 inflammasome-dependent pyroptosis, when administered at a dose of 300 mg/kg. 4-Aminosalycilic acid is also a building block that has been used in the synthesis of luminescent lanthanide complexes. Formulations containing 4-aminosalicylic acid have been used in the treatment of tuberculosis.

Mechanism of action

p-aminosalicylic acid is thought to act as an antimetabolite interfering with the incorporation of p-aminobenzoic acid into folic acid. When coadministered with INH, PAS is found to reduce the acetylation of INH, itself being the substrate for acetylation, thus increasing the plasma levels of INH. This action may be especially valuable in patients who are rapid acetylators.

Safety Profile

Moderately toxic ingestion andother routes. An eye irritant. Mutation data reported.When heated to decomposition it emits toxic fumes ofNOx.

Synthesis

p-Aminosalicylic acid, 5-amino-2-hydroxybenzoic acid (34.1.22), is synthesized in a Kolbe reaction, which consists of direct interaction of m-aminophenol with potassium bicarbonate and carbon dioxide while heating at a moderate pressure of 5–10 atm.

Metabolism

p-aminosalicylic acid is extensively metabolized by acetylation of the amino group and by conjugation with glucuronic acid and glycine at the carboxyl group. It is used primarily in cases of resistance, retreatment, and intolerance of other agents and is available from the CDC.

Purification Methods

Crystallise the acid from EtOH. [Beilstein 14 IV 1967.]

Definition

ChEBI: An aminobenzoic acid that is salicylic acid substituted by an amino group at position 4.

Application

4-Aminosalicylic acid (4-ASA) can be used in the synthesis of:Azo derivatives of 4-ASA with anti-inflammatory effects.Ammonium 4-aminosalicylate salt polymorphs which are used as pharmaceutical ingredients.Salicylic acid-triazole analogs which are used as quorum sensing inhibitors against Pseudomonas aeruginosa.

Brand name

Parasal (Panray); Paser (Jacobus).

General Description

4-Aminosalicylic acid occurs as a white to yellowish white crystalline solid that darkens on exposure to light or air. It is slightly soluble in water but more soluble in alcohol. Alkali metal salts and the nitric acid salt are soluble in water, but the salts of hydrochloric acid and sulfuric acid are not. The acid undergoes decarboxylation when heated. An aqueous solution has a pH of approximately 3.2. PAS is administered orally in the form of the sodium salt, usually in tablet or capsule form. Symptoms of gastrointestinal irritation are common with both the acid and the sodium salt. Various enteric-coated dosage forms have been used in an attempt to overcome this disadvantage. Other forms that are claimed to improve gastrointestinal tolerance include the calcium salt, the phenyl ester, and a combination with an anion exchange resin (Rezi-PAS). An antacid such as aluminum hydroxide is frequently prescribed. The oral absorption of PAS is rapid and nearly complete, and it is widely distributed into most of the body fluids and tissues, with the exception of the CSF, in which levels are significantly lower.It is excreted primarily in the urine as both unchanged drug and metabolites.