Diagnostic agent

Peroxidase-like activity: Gold nanoparticles reduced/stabilized by 4-Aminohippuric Acid (4-AHA) exhibited intrinsic peroxidase-like activity. Kinetic analysis showed Michaelis-Menten behavior toward TMB substrate with K_m = 0.094 mM and V_max = 2.68 × 10^-8 M•s^-1. Activity was significantly inhibited by Hg²⁺ (detection limit: 0.1 nM) but enhanced by Fe³⁺ (detection limit: 0.5 μM). [1]
Electrochemical sensing: 4-AHA-functionalized carbon nanotubes enabled selective detection of Cu²⁺ via anodic stripping voltammetry. Optimal response occurred at pH 4.5 with 120 s accumulation time. Linear range: 0.1–100 μM (detection limit: 0.05 μM). [2]
Metabolite profiling: Plasma 4-AHA levels were significantly lower in ADHD patients (0.19 ± 0.07 μg/mL) vs controls (0.31 ± 0.09 μg/mL, p<0.001) using LC-MS with dansylation isotope labeling. [3]

Peroxidase-mimetic kinetics: Activity was measured by mixing 4-AHA-stabilized AuNPs (0.15 nM) with TMB (0.02–0.35 mM) in acetate buffer (pH 4.0). After adding H₂O₂ (50 mM), absorbance at 652 nm was recorded every 30 s for 5 min. Kinetic parameters were calculated from Lineweaver-Burk plots.
Selectivity testing: Interference studies involved adding metal ions (Na⁺, K⁺, Ca²⁺, etc.) at 10 μM to the TMB-H₂O₂-AuNP system. Only Hg²⁺ and Fe³⁺ altered activity significantly. [1]

Absorption, Distribution and Excretion
Excretion of para-aminohippuric acid (PAH) in human sweat: Sweat/plasma ratio: 0.02; PKA = 3.8. (Data from table) In rats, 1.4% of the dose of PAH was excreted via bile 3 hours after administration. (Data from table) Bile excretion of PAH in different species: Percentage of dose excreted within 3 hours: Rats 3.3%; Guinea pigs 6.7%; Rabbits 3.0%; Dogs 3.4%; Cats 0.7%; Chickens 0.5%. /Excerpt from table/ Serum extraction rate...from canine renal cortex.../IS/ 0.74 PAH... For more complete data on the absorption, distribution, and excretion of PAH (8 types), please visit the HSDB records page.

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Metabolism/Metabolites
Production of acetaminophen in pigs: GYRD-HANSEN, N & F RASMUSSEN, ACTA PHYSIOL SCAND, 80, 249 (1970). /Excerpt from Table/
After oral administration of acetaminophen (PAH), para-aminobenzoic acid, para-aminohippuric acid, para-acetaminobenzoic acid, para-acetaminohippuric acid, and para-acetaminobenzoylglucuronic acid are detectable in urine. After intravenous administration, only para-acetaminohippuric acid and unchanged para-aminohippuric acid are excreted.

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Biological Half-Life
The biological half-life of acetaminophen in patients with normal renal function is 24 minutes.

Interactions
Drugs with the same excretion pathway as para-aminohippuric acid (PAH) (e.g., penicillin), drugs that inhibit renal tubular transport (e.g., probenecid), or drugs with uricosuric effects (e.g., salicylates) can interfere with PAH clearance. In chimpanzees, para-aminohippuric acid reduces renal excretion of halofenadine regardless of observed urine pH. Patients taking drugs with the same renal tubular excretion mechanism as PAH may experience reduced drug-to-PAH excretion due to competitive inhibition. Drugs with the same excretion mechanism include diuretics, iodopyridine acetate, penicillin, phenolsulfonamides, probenecid, and salicylates. Drugs that interfere with colorimetric analysis procedures, including procaine, sulfonamides, and thiazolidinone, can hinder accurate measurement of para-aminohippuric acid (PAH) in urine.

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Excerpt of Non-Human Toxicity
Acute or repeated administration of para-aminohippuric acid to rats increased renal blood flow and peripheral blood pressure, but only acute administration increased heart rate. KERSTEN et al.; ACTA BIOL MED GER 38(11-12) 1651 (1979)

[1]. Intrinsic peroxidase-like activity of 4-amino hippuric acid reduced/stabilized gold nanoparticles and its application in the selective determination of mercury and iron in ground water. Spectrochim Acta A Mol Biomol Spectrosc. 2020 Mar 5;228:117805.
[2]. 4-Aminohippuric acid-functionalized carbon nanotubes for stripping voltammetric determination of copper (II) ions[J]. Electrochemistry, 2016, 84(3): 138-142.
[3]. Novel plasma metabolite markers of attention-deficit/hyperactivity disorder identified using high-performance chemical isotope labelling-based liquid chromatography-mass spectrometry. World J Biol Psychiatry. 2021 Feb;22(2):139-148.

4-AHA-AuNPs can be used as nanozymes for colorimetric detection: a blue-green (652 nm) color development indicates the presence of peroxidase activity, which can be inhibited by Hg²⁺ (linear range: 0.1–100 nM) and enhanced by Fe³⁺ (0.5–50 μM). [1] 4-AHA-CNT electrodes exhibit higher selectivity for Cu²⁺ than for Zn²⁺, Cd²⁺, and Pb²⁺ due to selective complexation. [2] Decreased plasma 4-AHA levels may be associated with mitochondrial dysfunction in patients with ADHD. [3]

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p-Aminohippuric acid is a 4-amino derivative of hippuric acid, belonging to N-acylglycine, and can be used as a diagnostic reagent for measuring renal plasma flow. It is also a metabolite of Daphnia magna. It is the conjugate acid of p-aminohippuric acid.
Aminohippuric acid has been reported to exist in Brassica napus and Daphnia magna, and relevant data are available.
Sodium aminohippurate is the sodium salt of aminohippuric acid. Sodium aminohippurate is a non-toxic diagnostic tool used to measure effective renal plasma flow. At low plasma concentrations, the reagent is filtered by the glomerulus and is almost completely cleared from the renal bloodstream by active tubular secretion during a single pass through the kidney. Its clearance rate corresponds to renal plasma flow. Sodium aminohippurate can also be used to measure the function of renal tubular secretion mechanisms. This is achieved by increasing the plasma concentration of the drug to a level sufficient to saturate the maximum secretory capacity of renal tubular cells.
Glycine amide of 4-aminobenzoic acid. Its sodium salt is used as a diagnostic aid to measure effective renal plasma flow (ERPF) and excretion capacity. Drug Indications Used to measure effective renal plasma flow (ERPF) and determine the functional capacity of the renal tubular excretion mechanism. Mechanism of Action Aminohippuric acid is filtered by the glomerulus and secreted into the urine by the proximal tubules. Renal function and effective renal plasma flow can be determined by measuring the drug concentration in the urine. Para-aminohippuric acid (PAH) is the prototype drug excreted via the organic acid transport system…this system is located in the proximal tubule…toxins bound to proteins can be entirely transported actively. This process has all the characteristics of an active transport system; therefore, various compounds compete for secretion. Therapeutic Use Sodium aminohippurate (PAH) is available at plasma concentrations of 10-20 μg/mL for estimating effective renal plasma flow (ERPF), an indicator of renal function. At low plasma concentrations, PAH is almost completely cleared by functional renal tissue via glomerular filtration, and the measured PAH clearance value is considered numerically equal to the effective renal plasma flow (ERPF). When the plasma concentration is 400–600 μg/ml, PAH clearance is used in conjunction with glomerular filtration rate (GFR) measurement to assess the function of the renal tubular secretion mechanism. Since PAH can be excreted through both tubular secretion and glomerular filtration, renal tubular transport capacity can be determined by comparing PAH excretion with the GFR value measured by inulin clearance. Although this test may be the best quantitative method for assessing nephron function, its complexity limits its widespread application. The PAH clearance test is more accurate than the phenolsulfonphthalein excretion test, but it is also more complex and can be used to assess renal blood flow. In most clinical situations, simpler (although less accurate) methods for assessing renal function are used.
Drug: Diagnostic Aid (Renal Function Assay) / SRP: Not Commonly Used for Renal Function Testing /

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Drug Warnings
At plasma concentrations used to measure maximal renal tubular secretion, PAH significantly increases the clearance of sodium, potassium, and phosphorus in human volunteers. At concentrations used to measure renal plasma flow, it only increases sodium clearance.
Many staff commonly use PAH clearance to estimate renal plasma flow. This method is not recommended for three reasons: 1) Even at low plasma concentrations, the renal extraction rate of PAH is variable; 2) PAH is reabsorbed; 3) If the test drug is a weak organic acid, PAH may inhibit its renal transport.
When the plasma PAH concentration rises rapidly, patients may experience nausea, vomiting, and a sudden fever, which can be avoided by slow infusion of the drug.
Adverse reactions reported with administration of sodium aminohippurate (PAH) include nausea, vomiting, cramps, vasomotor disturbances, flushing, tingling, and paresthesia. Fever and the urge to defecate or urinate may occur during or shortly after medication.
In patients with low cardiac reserve, para-aminohippuric acid (PAH) must be used with caution, as a rapid increase in plasma volume may induce congestive heart failure. To achieve the plasma concentration required for maximal renal tubular secretion, large doses should be administered slowly and cautiously, with continuous monitoring for any adverse reactions. PAH is contraindicated in patients with known hypersensitivity to this drug or any component of its formulations.
Pharmacodynamics

Aminohippuric acid (para-aminohippuric acid, PAH, PAHA) is a glycine amide of para-aminobenzoic acid. It is filtered by the glomerulus and actively secreted by the proximal tubules. At low plasma concentrations (1.0 to 2.0 mg/100 mL), an average of 90% of aminohippuric acid is cleared from the renal bloodstream via the kidneys in a single circulation. Due to its high clearance rate, near-non-toxicity within the recommended plasma concentration range, and relatively simple and accurate analytical methods, aminohippuric acid (APA) is well-suited for measuring effective renal plasma flow (ERPF). APA is also used to measure the functional or transport maximum of the renal tubular secretory mechanism (Tm_PAH). This is achieved by raising the plasma concentration to a level sufficient to induce maximum APA secretion by renal tubular cells (40-60 mg/100 mL). Since glomerular filtration rate (GFR) must be known before calculating the secretory Tm value, inulin clearance is usually measured simultaneously with Tm_PAH.

C9H10N2O3

194.1873

194.069

C, 55.67; H, 5.19; N, 14.43; O, 24.72

61-78-9

61-78-9 (free acid); 94-16-6 (sodium)

2148

Off-white to light brown solid powder

1.4±0.1 g/cm3

517.2±35.0 °C at 760 mmHg

199-200 °C (dec.)(lit.)

266.6±25.9 °C

0.0±1.4 mmHg at 25°C

1.620

-0.58

3

4

3

14

222

0

C1=CC(=CC=C1C(=O)NCC(=O)O)N

HSMNQINEKMPTIC-UHFFFAOYSA-N

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)

2-[(4-aminobenzoyl)amino]acetic acid

4-Aminohippuric acid; aminohippuric acid; 61-78-9; P-AMINOHIPPURIC ACID; N-(4-Aminobenzoyl)glycine; para-Aminohippuric acid; Paha; Glycine, N-(4-aminobenzoyl)-;

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

DMSO : ~50 mg/mL (~257.48 mM)
H2O : ≥ 1.7 mg/mL (~8.75 mM)

Solubility in Formulation 1: ≥ 2.5 mg/mL (12.87 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (12.87 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (12.87 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: 14.29 mg/mL (73.59 mM) in PBS (add these co-solvents sequentially from left to right, and one by one), clear solution; with ultrasonication (<60°C).

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 (Please use freshly prepared in vivo formulations for optimal results.)