Aminohippuric acid

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 diagnostic use.

Aminohippurate

Clinical data
Other names	PAH, PAHA, Aminohippurate, 4-Aminohippuric acid, N-(4-Aminobenzoyl)glycine, para-Aminohippurate
ATC code	V04CH30 (WHO)
Identifiers
IUPAC name (4-Aminobenzamido)acetic acid
CAS Number	61-78-9 Y 94-16-6 (sodium salt)
PubChem CID	2148
IUPHAR/BPS	4810
DrugBank	DB00345 Y
ChemSpider	2063 Y
UNII	Y79XT83BJ9
KEGG	D06890 Y
ChEBI	CHEBI:104011 Y
ChEMBL	ChEMBL463 Y
NIAID ChemDB	019143
CompTox Dashboard (EPA)	DTXSID7022590
ECHA InfoCard	100.000.472
Chemical and physical data
Formula	C9H10N2O3
Molar mass	194.190 g·mol−1
3D model (JSmol)	Interactive image
SMILES O=C(c1ccc(N)cc1)NCC(=O)O
InChI InChI=1S/C9H10N2O3/c10-7-3-1-6(2-4-7)9(14)11-5-8(12)13/h1-4H,5,10H2,(H,11,14)(H,12,13) Y Key:HSMNQINEKMPTIC-UHFFFAOYSA-N Y
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Uses

Diagnostics

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] This means that unlike inulin and creatinine, which are filtered in the glomerulus and ignored by the rest of the kidney, aminohippuric acid is both filtered and secreted, being almost entirely removed from the bloodstream in a normal kidney.

Pharmaceuticals

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.^[3]

Other

pK_a = 3.83

See also

• PAH clearance
• Ortho-iodohippurate