p-Aminosalicylic Acid
Title: p-Aminosalicylic Acid
CAS Registry Number: 65-49-6
CAS Name: 4-Amino-2-hydroxybenzoic acid
Additional Names: 4-aminosalicylic acid; PAS
Trademarks: PASER (Jacobus); Rezipas (BMS)
Molecular Formula: C7H7NO3
Molecular Weight: 153.14
Percent Composition: C 54.90%, H 4.61%, N 9.15%, O 31.34%
Literature 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).
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).
Melting point: mp 150-151° with effervescence
pKa: pKa 3.25
Absorption maximum: uv max (0.1N HCl): 265, 300 nm
Toxicity data: LD50 orally in mice: 4 g/kg (Bavin)
 
Derivative Type: Hydrochloride
Molecular Formula: C7H7NO3.HCl
Molecular Weight: 189.60
Percent Composition: C 44.34%, H 4.25%, N 7.39%, O 25.32%, Cl 18.70%
Properties: Crystals, dec 224°.
 
Derivative Type: Sodium salt dihydrate
CAS Registry Number: 6018-19-5
Trademarks: Aminacyl (Wander); Nemasol Sodium (Valeant); Pamisyl Sodium (Parke-Davis); Paramisan Sodium (Smith & Nephew); Pasalon (Bayer)
Molecular Formula: C7H6NNaO3.2H2O
Molecular Weight: 211.15
Percent Composition: 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 Type: Calcium salt
CAS Registry Number: 133-15-3
Trademarks: Nippas Calcium (Tanabe)
Molecular Formula: C14H12CaN2O6
Molecular Weight: 344.33
Percent Composition: 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 Type: Potassium salt
CAS Registry Number: 133-09-5
Trademarks: Paskalium (Glenwood)
Molecular Formula: C7H6NO3K
Molecular Weight: 191.23
Percent Composition: 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 Type: Ethyl ester
Molecular Formula: C9H11NO3
Molecular Weight: 181.19
Percent Composition: 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.
Melting point: mp 115°
 
Derivative Type: Phenyl ester see Phenyl Aminosalicylate
 
Therap-Cat: Antibacterial (tuberculostatic).
Keywords: Antibacterial (Tuberculostatic).

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