Aminohippuric acid

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Aminohippuric acid.png
Clinical data
Synonyms PAH, PAHA, Aminohippurate, 4-Aminohippuric acid , N-(4-Aminobenzoyl)glycine, para-Aminohippurate
ATC code
CAS Number
PubChem CID
ECHA InfoCard 100.002.100
Chemical and physical data
Formula C9H10N2O3
Molar mass 194.19 g/mol
3D model (JSmol)

Aminohippuric acid or para-aminohippuric acid (PAH), a derivative of hippuric acid, is a diagnostic agent useful in medical tests involving the kidney used in the measurement of renal plasma flow. It is an amide derivative of the amino acid glycine and para-aminobenzoic acid that is not naturally found in humans; it needs to be IV infused before use diagnostically.



PAH is useful for the measurement of renal plasma flow.[1]

The renal extraction ratio of PAH in a normal individual is approximately 0.92.[2]


Aminohippuric acid is often used as the sodium salt sodium para-aminohippurate. During World War II, para-aminohippurate was given along with penicillin in order to prolong the time penicillin circulated in the blood. Because both penicillin and para-aminohippurate compete for the same transporter in the kidney, administering para-aminohippurate with penicillin decreased the clearance of penicillin from the body by the kidney, providing better antibacterial therapy. Transporters found in the kidney eliminate organic anions and cations from the blood by moving substances, in this case, drug metabolites, from blood into urine.


In vultures, the NSAID diclofenac, which is extraordinarily toxic to vultures, interferes with the renal transport of uric acid via the PAH channel.[3]

pKa = 3.83

See also[edit]


  1. ^ Costanzo, Linda. Physiology, 4th Edition. Philadelphia: Lippincott Williams and Wilkins, 2007. Page 156-160.
  2. ^ Reubi, François C. (1953-04-29). "Glomerular filtration rate, renal blood flow and blood viscosity during and after diabetic coma". Circ. Res. 1 (5): 410–3. ISSN 0009-7330. PMID 13082682. Retrieved 2008-03-19. 
  3. ^ Naidoo V, Swan GE (August 2008). "Diclofenac toxicity in Gyps vulture is associated with decreased uric acid excretion and not renal portal vasoconstriction". Comp. Biochem. Physiol. C Toxicol. Pharmacol. 149 (3): 269–74. doi:10.1016/j.cbpc.2008.07.014. PMID 18727958.