477. p-Aminosalicylic Acid

Nomenclature

CAS number: 65-49-6
4-Amino-2-hydroxybenzoic acid; 4-aminosalicylic acid; PAS; PASER (Jacobus); Rezipas (BMS).
C7H7NO3; mol wt 153.14.
C 54.90%, H 4.61%, N 9.15%, O 31.34%.

Description and references

Prepn: DE 50835 (1889); US 427564 (1890); Sheehan, J. Am. Chem. Soc. 70, 1665 (1948); Erlenmeyer et al., Helv. Chim. Acta 31, 988 (1948); Wenis, Gardner, J. Am. Pharm. Assoc. 38, 9 (1949); Centolella, US 2844625 (1958 to Miles). Toxicity study: E. M. Bavin et al., J. Pharm. Pharmacol. 2, 764 (1950). Comprehensive description: M. M. A. Hassan et al., Anal. Profiles Drug Subs. 10, 1-27 (1981).

Chemical structure

Properties

Minute crystals from alcohol, mp 150-151° with effervescence. uv max (0.1N HCl): 265, 300 nm. pKa 3.25. pH of 0.1% aq soln: 3.5. One gram dissolves in about 500 ml water, in 21 ml alcohol. Slightly sol in ether. Practically insol in benzene. Sol in dilute nitric acid, dil sodium hydroxide. At temps above 40°, aq solns of PAS and its hydrochloride are readily decarboxylated to give brown solns consisting mainly of m-aminophenol. LD50 orally in mice: 4 g/kg (Bavin).

Derivative

Hydrochloride.
C7H7NO3.HCl; mol wt 189.60.
C 44.34%, H 4.25%, N 7.39%, O 25.32%, Cl 18.70%.

Properties

Crystals, dec 224°.

Derivative

Sodium salt dihydrate.

Nomenclature

CAS number: 6018-19-5
Aminacyl (Wander); Nemasol Sodium (Valeant); Pamisyl Sodium (Parke-Davis); Paramisan Sodium (Smith & Nephew); Pasalon (Bayer).
C7H6NNaO3.2H2O; mol wt 211.15.
C 39.82%, H 4.77%, N 6.63%, Na 10.89%, O 37.89%.

Properties

pH of 1% soln ≈7. One gram dissolves in 2 ml water. Very sparingly sol in acetone. Practically insol in ether, chloroform, benzene. Solns of the sodium salt are more resistant to heat than PAS, but sterilization by bacterial filtration is recommended.

Derivative

Calcium salt.

Nomenclature

CAS number: 133-15-3
Nippas Calcium (Tanabe).
C14H12CaN2O6; mol wt 344.33.
C 48.83%, H 3.51%, Ca 11.64%, N 8.14%, O 27.88%.

Properties

Bittersweet crystals. One gram dissolves in about 7 ml water, slightly sol in alc. Aq solns dec slowly and darken in color.

Derivative

Potassium salt.

Nomenclature

CAS number: 133-09-5
Paskalium (Glenwood).
C7H6NO3K; mol wt 191.23.
C 43.97%, H 3.16%, N 7.32%, O 25.10%, K 20.45%.

Properties

Crystals, freely sol in water. pH of 1% soln about 7. Reported to cause less gastric irritation than the free acid or the sodium salt.

Derivative

Ethyl ester.
C9H11NO3; mol wt 181.19.
C 59.66%, H 6.12%, N 7.73%, O 26.49%.

Properties

Needles from alc, mp 115°. Prepd by reduction of the ethyl ester of 4-nitrosalicylic acid.

Derivative

Phenyl ester see Phenyl Aminosalicylate.

Therapeutic Category

Antibacterial (tuberculostatic).

Keywords

Antibacterial (Tuberculostatic)