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. Uses. Diagnostics. PAH is useful for the measurement of renal plasma flow. The renal extraction ratio of PAH in a normal individual is approximately 0.92. 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. Other. p"K" = 3.83