4-Aminobenzoic Acid

Pharmaceuticals

Pharmaceuticals -> Listed in ZINC15

log Kow = 0.83

0.83

0.83

Monoclinic prisms from dilute alcohol

Light buff crystals; white when pure

Yellowish to red crystals or prisms

White or slightly yellow crystals or crystalline powder

In water, 5,390 mg/L at 25 °C; 6,110 mg/L at 30 °C

One gram dissolves in 90 mL boiling water; in 8 ml alcohol, in 60 mL ether. Soluble in ethyl acetate, glacial acetic acid; slightly soluble in benzene; practically insoluble in petroleum ether.

Freely soluble in alcohol

Soluble in alkalis and ethane (C2H6)

For more Solubility (Complete) data for 4-AMINOBENZOIC ACID (8 total), please visit the HSDB record page.

370 to 372 °F (NTP, 1992)

188.5 °C

188.5 °C

188 °C

0.000278 [mmHg]

4.5X10-6 mm Hg at 25 °C /Extrapolated from measurements at higher temperatures/

This chemical does not meet GHS hazard criteria for 21.9% (53 of 242) of reports.

Warning

H315 (32.2%): Causes skin irritation [Warning Skin corrosion/irritation]

P261, P264, P264+P265, P271, P272, P273, P280, P302+P352, P304+P340, P305+P351+P338, P319, P321, P332+P317, P333+P317, P337+P317, P362+P364, P403+P233, P405, and P501 (click each P-code to see the statement)

Aggregated GHS information provided per 242 reports by companies from 33 notifications to the ECHA C&L Inventory. Each notification may be associated with multiple companies.

Chemical: Benzoic acid, 4-amino-

Status: Active Update: 13-10-2022 https://echa.europa.eu/registration-dossier/-/registered-dossier/17109

4-Aminobenzoic acid: Does not have an individual approval but may be used under an appropriate group standard

Oral LD50 = 1000 mg/kg (dog), 1830 mg/kg (rabbit), and 6000 mg/kg (rat); Causes acute hepatic necrosis in dogs given 2-3 g/kg; [HSDB] May cause irritation; May induce methemoglobinemia; [MSDSonline] May cause allergic dermatitis when applied as a sunscreen; No skin sensitization reported in occupational setting; [AIHA] Patients may be allergic or photoallergic to PABA. If photoallergic, they may not react to PABA alone, but only with sun exposure. [Marks, p. 212]

Sunscreen active ingredients. The active ingredient of the product consists of any of the following, within the concentration specified for each ingredient, and the finished product provides a minimum SPF value of not less than 2 as measured by the testing procedures established in subpart D of this part: Aminobenzoic acid (PABA) up to 15 percent is included on this list.

PABA is known as a sunscreen agent in cosmetics. It absorbs UVB radiation strongly. In the 1940's, dermatologists began to prescribe it in 2-5 % strengths in aqueous creams or in 70 % alcoholic solutions as a sunscreen. PABA was very popular as a sunscreen agent through the 1950's and 1960's and used as such throughout the world. The use of PABA has declined during the last decade/s/.

Incompatible materials: Strong oxidizing agents.

Incompatible with ferric salts and oxidizing agents.

This compound is not very flammable but any fire involving this compound may produce dangerous vapors. You should evacuate the area. All firefighters should wear full-body protective clothing and use self-contained breathing apparatuses. You should extinguish any fires involving this chemical with a dry chemical, carbon dioxide, foam, or halon extinguisher. (NTP, 1992)

EYES: First check the victim for contact lenses and remove if present. Flush victim's eyes with water or normal saline solution for 20 to 30 minutes while simultaneously calling a hospital or poison control center. Do not put any ointments, oils, or medication in the victim's eyes without specific instructions from a physician. IMMEDIATELY transport the victim after flushing eyes to a hospital even if no symptoms (such as redness or irritation) develop.

Advice for firefighters: Wear self contained breathing apparatus for fire fighting if necessary.

Suitable extinguishing media: Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.

Personal precautions, protective equipment and emergency procedures: Use personal protective equipment. Avoid dust formation. Avoid breathing vapors, mist or gas. Ensure adequate ventilation. Evacuate personnel to safe areas. Avoid breathing dust.

Environmental precautions: Do not let product enter drains.

Methods and materials for containment and cleaning up: Pick up and arrange disposal without creating dust. Sweep up and shovel. Keep in suitable, closed containers for disposal.

Product: Offer surplus and nor-recyclable solutions ot a licensed disposal company. Contact a licensed professional waste disposal service to dispose of this material. Contaminated packaging: Dispose of as unused product.

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.

Precautions for safe handling: Avoid contact with skin and eyes. Avoid formation of dust and aerosols. Provide appropriate exhaust ventilation at places where dust is formed.

Appropriate engineering controls: Handle is accordance with good industrial hygiene and safety practice. Wash hands before breaks and at the end of the workday.

Skin protection: ... Gloves must be inspected prior to use. Use proper glove removal technique (without touching glove's outer surface) to avoid skin contact with this product. Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices. Wash and dry hands.

15 [mg/m3]

69 [mg/m3]

410 [mg/m3]

RECOMMENDED RESPIRATOR: Where the neat test chemical is weighed and diluted, wear a NIOSH-approved half face respirator equipped with an organic vapor/acid gas cartridge (specific for organic vapors, HCl, acid gas and SO2) with a dust/mist filter. (NTP, 1992)

Eye/face protection: Face shield and safety glasses. Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (USA) or EN 166(EU).

Respiratory protection: For nuisance exposures use type P95 (US) or type P1 (EU EN 143) particle respirator. For higher level protection use type OV/AG/P99 (US) or type ABEK-P2 (EU EN 143) respirator cartridges. Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU).

Skin protection: Handle with gloves.

Body Protection: Complete suit protecting against chemicals. The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.

Sulfonamides act by competitive inhibition of PABA in the microorganism. PABA administration in sufficient doses thus antagonized the antibacterial effect of the sulfonamides.

PABA appears to block the formatin of salicyluric acid from salicylic acid, resulting in increased salicylate blood levels.

Aminosalicylic acid appears to act on tubercle bacilli in a manner similar to that of sulfonamides on other organisms (by competing with PABA). Thus the administration of PABA may be expected to inhibit the antimicrobial activity of aminosalicylic acid.

Interferon titers induced by 0.007% PABA and poludan were compatible after both injections in the conjunctiva but not in the anterior chamber humor.

For more Interactions (Complete) data for 4-AMINOBENZOIC ACID (14 total), please visit the HSDB record page.

TERRESTRIAL FATE: According to a classification scheme(1), measured Koc values ranging from 19.9 to 316(2-4) suggest that 4-aminobenzoic acid is expected to have very high to moderate mobility in soil. The pKa values of 4-aminobenzoic acid are 2.38 (acid group)(5) and 4.85 (amino group)(6), indicating that this compound will exist almost entirely in the anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(7). However, aromatic amines are expected to bind strongly to humus or organic matter in soils due to the high reactivity of the aromatic amino group(8,9), suggesting that mobility may be much lower in some soils(SRC). Volatilization of 4-aminobenzoic acid from moist soil surfaces is not expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.5X10-10 atm-cu m/mole(SRC), based upon its vapor pressure, 4.5X10-6 mm Hg(10), and water solubility, 5390 mg/L(11). 4-Aminobenzoic acid is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure. An 82% of theoretical BOD using activated sludge in the Japanese MITI test classifies 4-aminobenzoic acid as readily biodegradable(12). Results of other screening studies(13,14) also suggest that biodegradation may be an important fate process(SRC).

AQUATIC FATE: According to a classification scheme(1), measured Koc values ranging from 19.9 to 316(2-4) indicate that 4-aminobenzoic acid may have no to moderate adsorption to suspended solids and sediment(SRC). Volatilization from water surfaces is not expected(5) based upon an estimated Henry's Law constant of 1.5X10-10 atm-cu m/mole(SRC), derived from its vapor pressure, 4.5X10-6 mm Hg(6), and water solubility, 5390 mg/L(7). According to a classification scheme(8), an estimated BCF of 3(SRC), from its log Kow of 0.83(9) and a regression-derived equation(10), suggests the potential for bioconcentration in aquatic organisms is low(SRC). An 82% of theoretical BOD using activated sludge in the Japanese MITI test classifies 4-aminobenzoic acid as readily biodegradable(11). Results of other screening studies(12,13) also suggest that biodegradation may be an important fate process(SRC). 4-Aminobenzoic acid is not expected to undergo hydrolysis in the environment due to the lack of hydrolyzable functional groups(5). Using simulated solar irradiation in aqueous solutions, the direct photolysis of 4-aminobenzoic acid followed pseudo-first order kinetics with the rate constant increasing with increasing pH(14); the direct photolysis rate constants were determined to be 3.46X10-6/sec, 12.57X10-6/sec and 14.96X10-6/sec at respective pH values of 4.8, 7.8 and 9.2(14) which correspond to respective half-lives of 2.32 days, 15.3 hours and 12.9 hours(SRC); it was determined that direct photolysis was the dominant phototransformation process in sunlit natural water with sensitized photolysis occurring at a much slower rate(14); p-hydroxybenzoic acid was identified as a photodegradation product with the photodegradation pathway including di(tri)-polymerization(14).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 4-aminobenzoic acid, which has a vapor pressure of 4.5X10-6 mm Hg at 25 °C(2), will exist in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase 4-aminobenzoic acid is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 9.5 hours(SRC), calculated from its rate constant of 4.0X10-11 cu cm/molecule-sec at 25 °C(SRC) that was derived using a structure estimation method(3). Particulate-phase 4-aminobenzoic acid may be removed from the air by wet and dry deposition(SRC). 4-Aminobenzoic acid has been shown to degrade through direct photolysis in the sunlight spectrum(4,5), therefore, photolysis may have some importance as a fate process in the atmosphere(SRC).

In a Chernozem soil of pH 7.5, the Koc of 4-aminobenzoic acid was determined to be 19.9(1). Using OECD Guideline 106 and three different soils of pH values of 2.8, 6.7 and 7.1, 4-aminobenzoic acid was found to have respective Koc values of 239, 46 and 55(2). A measured log Koc of 2.5 has been reported for 4-aminobenzoic acid(3) which corresponds to a Koc of 316. According to a classification scheme(4), these Koc values suggests that 4-aminobenzoic acid is expected to have very high to moderate mobility in soil. The pKa values of 4-aminobenzoic acid are 2.38 (acid group)(5) and 4.85 (amino group)(6), indicating that this compound will exist almost entirely in the anion form in the environment and anions generally do not adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(7). However, aromatic amines are expected to bind strongly to humus or organic matter in soils due to the high reactivity of the aromatic amino group(8,9), suggesting that mobility may be much lower in some soils(SRC).

4-Aminobenzoic acid is widely distributed in nature as a B complex factor(1). Baker's yeast contains 5 to 6 ppm 4-aminobenzoic acid(1); brewer's yeast contains from 10 to 100 ppm 4-aminobenzoic acid(1). 4-Aminobenzoic acid (PABA) is a chemical found in the folic acid vitamin and also in several foods including grains, eggs, milk, and meat(2).

/HUMAN EXPOSURE STUDIES/ In a dermatological clinic in Norway 23 patients with reactions to sunscreen preparations were seen during the years 1980-1982. The symptoms were eczema, redness, stinging or burning of the face following sun exposure. Patch tests and photopatch tests were carried out on the patients. Allergy to PABA was demonstrated in 11 patients (48%), of which 6 had plain contact allergy (26%) (PABA on non irradiated test sites) and 5 (21.7%) reacted to PABA only after irradiation.

/SIGNS AND SYMPTOMS/ Applications of 5% PABA in sunscreen formulation on human skin have shown that irritation is negligible.

/CASE REPORTS/ Human tests performed on patients contacting a dermatological clinic with a suspected skin disease shows that PABA has a potential to cause photo allergy reactions. Considering the fact that the results are based on patients with suspected dermatological problems rather than the general population, the prevalence is likely to be lower in the general population than in the studied groups. The highest photo allergy reaction to PABA was found in a Norwegian study from 1980 - 82 on 23 patients where 21.7% reacted. In most ... /studies/ the reaction to PABA was in the range 0 - 3%.

/CASE REPORTS/ A case report described that the potassium salt of PABA (administered orally 4 g three times a day for about 2 months) to a 64-year-old woman led to hepatotoxicity in a patient with scleroderma, as evidenced by elevated serum alanine aminotransferase and aspartate aminotransferase. /Potassium salt of PABA/

For more Human Toxicity Excerpts (Complete) data for 4-AMINOBENZOIC ACID (13 total), please visit the HSDB record page.

4-Aminobenzoic acid's production and use in the manufacturer of various esters, folic acid, azo dyes(1), as a cross-linking agent for polyurethane resins(2) and as UV absorber in suntan lotions(3) may result in its release to the environment through various waste streams(SRC).

AEROBIC: 4-Aminobenzoic acid was decomposed by soil microflora using fill and draw operations at 20 °C. Using adapted activated sludge as the inoculum and 14C-labeled 4-aminobenzoic acid as the sole carbon source, 96.2% chemical oxygen demand removal was observed with a rate of 12.5 mg chemical oxygen demand/g dry inoculum/hr. A lag period for degradation of 16 mg/L was observed for wastewater or soil at pH 7.3 and 30 °C. At 100 mg/L of test sample, no inhibition of ammonia oxidation by Nitrosomonas species was observed.

AEROBIC: 4-Aminobenzoic acid, present at 100 mg/L, reached 82% of its theoretical BOD in 4 weeks using an activated sludge inoculum at 30 mg/L in the Japanese MITI test which classified the compound as readily biodegradable(1). 4-Aminobenzoic acid, present at 50 ppm C, reached 74% of its theoretical BOD in 2 weeks using an activated sludge inoculum at 30 mg/L in the Japanese MITI test(2). Other screening studies give similar results(2,3) indicating that 4-aminobenzoic acid is readily biodegradable(SRC).

ANAEROBIC: Screening studies indicate that 4-aminobenzoic acid may biodegrade under anaerobic conditions(SRC). 4-Aminobenzoic acid, present at 50 ppm C, reached 30-75% of its theoretical methane production in 56 days using 10% of digester sludge(1). However, in a screening test in which fresh sewage was added every 7 days, 4-aminobenzoic acid remained recalcitrant(2).

Sunscreen active ingredients. The active ingredient of the product consists of any of the following, within the concentration specified for each ingredient, and the finished product provides a minimum SPF value of not less than 2 as measured by the testing procedures established in subpart D of this part: Aminobenzoic acid (PABA) up to 15 percent is included on this list.

D - Dermatologicals

QD - Dermatologicals

CoenzymeQ(ubiquinone or Q) is a crucial mitochondrial lipid required for respiratory electron transport in eukaryotes. 4-Hydroxybenozoate (4HB) is an aromatic ring precursor that forms the benzoquinone ring of Q and is used extensively to examine Q biosynthesis. However, the direct precursor compounds and enzymatic steps for synthesis of 4HB in yeast are unknown. Here /the authors/ show that para-aminobenzoic acid (pABA), a well known precursor of folate, also functions as a precursor for Q biosynthesis. A hexaprenylated form of pABA (prenyl-pABA) is normally present in wild-type yeast crude lipid extracts but is absent in yeast abz1 mutants starved for pABA. A stable (13)C6-isotope of pABA (pamino[ aromatic-(13)C6]benzoic acid ([(13)C6]pABA)), is prenylated in either wild-type or abz1 mutant yeast to form prenyl-[(13)C6]pABA. /The authors/ demonstrate by HPLC and mass spectrometry that yeast incubated with either [(13)C6]pABA or [(13)C6]4HB generate both (13)C6- demethoxy-Q (DMQ), a late stage Q biosynthetic intermediate, as well as the final product (13)C6-coenzyme Q. Pulse-labeling analyses show that formation of prenyl-pABA occurs within minutes and precedes the synthesis of Q. Yeast utilizing pABA as a ring precursor produce another nitrogen containing intermediate, 4-imino- DMQ6. This intermediate is produced in small quantities in wildtype yeast cultured in standard media and in abz1 mutants supplemented with pABA. We suggest a mechanism where Schiff base-mediated deimination forms DMQ6 quinone, thereby eliminating the nitrogen contributed by pABA. This scheme results in the convergence of the 4HB and pABA pathways in eukaryotic Q biosynthesis and has implications regarding the action of pABAbased antifolates.

Radiation is absorbed by chemical sunscreens when the electron energy level of the drug is raised from its ground state to a higher energy level or excited state. Chromophore groups (C=C, C=O, O-N=O) with loosely held electrons are easily excited by radiation. Compounds which have several chromophore groups in optimal positions have high absorbance over a broad range of wavelengths. Chemical sunscreens are usually agents that absorb not less than 85% of UVB radiation (thus preventing burning) but may permit transmission of UVA radiation (thus allowing tanning). Some sunscreens may absorb wavelengths over a range that is slightly wider or narrower than that of UVB. All PABA derivatives absorb wavelengths of approximately 290-320 nm, benzophenone derivatives absorb wavelengths of approximately 250-360 nm, cinnamic acid derivatives absorb wavelengths of 280-320 nm, and salicylate derivatives and other miscellaneous chemical sunscreens absorb wavelengths of about 270-320 nm.

The wavelength to which the skin is maximally sensitive had been accepted for many years to be 296.7 nm; however, recent evidence suggests that the most erythemogenic UVB wavelength may be slightly lower (e.g., somewhere in the range of 292-295 nm). In addition, of the stronger burning wavelengths that reach the earth's surface, most are approximately 310 nm. Therefore, sunscreens that maximally absorb UVB radiation near either of these wavelengths are particularly effective at preventing sunburn. Maximum absorbance occurs at about 290 nm for PABA, at about 295 nm for glyceryl-p-aminobenzoate, and at about 310 nm for the remaining PABA derivatives. Maximum absorbance occurs at 280-290 nm for benzophenone derivatives, at 310 nm for cinnamic acid derivatives with the exception of diethanolamine-p-methoxycinnamate which has its maximum absorbance at 290 nm, and at 300-305 nm for salicylate derivatives and other miscellaneous sunscreens.

Diminish the penetration of ultraviolet (UV) light through the epidermis by absorbing UV radiation within a specific wavelength range. The amount and wavelength of UV radiation absorbed are affected by the molecular structure of the sunscreen agent. /Sunscreen agents, topical/

Diminish the penetration of ultraviolet (UV) light through the epidermis by absorbing UV radiation within a specific wavelength range. The amount and wavelength of UV radiation absorbed are affected by the molecular structure of the sunscreen agent. /Sunscreen agents, topical/

The two major metabolic pathways in a variety of species (guinea-pigs, rabbits and rats, but not dogs) are acetylation of the amino group and conjugation of the carboxy group, either with glycine or with glucuronic acid. Acetylation occurs in liver, heart, lung, blood and kidneys of rats and in the mucous membranes of the gastrointestinal tract of cattle. N-Acetyl-transferase activity in the presence of para-aminobenzoic acid is similar in liver and lung tissue of rabbits. Acetylation not only of para-aminobenzoic acid (30-40%) but also of para-aminohippuric acid (70%) takes place in the kidney of rabbits; acetylation of para-aminohippurate also occurs in the kidney of guinea-pigs.

Acetylation is dose-dependent. In rats given up to 5 mg/kg bw, 75% of the metabolites were acetylated; with higher doses, the extent of acetylation decreased down to 40%. An inverse relationship exists between acetylation and glycine conjugation: when acetylation decreases, glycine conjugation increases; such a decrease is seen in pantothenic acid-deficient rats. . Male rats excreted a larger amount of acetylated conjugates in the urine than females.

Following ingestion /in man/ of 1.0 g, ...main metabolites were p-aminohippuric acid and acetyl-p-aminohippuric acid.

... PABA is predominantly metabolized by acetylation and glycine conjugation to form p-acetamidobenzoic acid (PAABA), p-aminohippuric acid (PAHA), and p-acetamidohippuric acid (PAAHA). ... The half-lives of PABA were 7.01 +/- 0.32 min in rapid acetylation rabbits and 7.08 +/- 0.78 min in slow acetylation rabbits. Significant differences were obtained in formation of PAABA and PAHA formed from PABA in both acetylation phenotype rabbits.

For more Metabolism/Metabolites (Complete) data for 4-AMINOBENZOIC ACID (9 total), please visit the HSDB record page.

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AMINOBENZOIC ACID

Chemical Structure [CS] - Vitamin B Complex

Established Pharmacologic Class [EPC] - Vitamin B Complex Member

Aminobenzoic acid is a Vitamin B Complex Member.

The toxicokinetics of PABA is characterized by fast oral absorption, biotransformation by the major routes acetylation and glycine conjugation, the minor route by glucuronidation in the liver and kidney, and a fast and almost complete elimination via the urine within 24 hrs. PABA is extensively acetylated during percutaneous absorption in humans. Studies have shown that PABA can cross the placenta rapidly. Furthermore, the results of one study indicate that the human placenta has a significant capacity for acetylation of PABA.

Of an oral dose of 1 g para-aminobenzoic acid, 82% was excreted in the urine of 3 male volunteers within 4 hr; para-aminohippuric acid and acetyl-para- aminohippuric acid were the principal metabolites. Concurrent administration of sodium benzoate totally abolished the excretion of these glycine conjugates.

The percutaneous absorption and metabolism of three structurally related compounds, benzoic acid, p-aminobenzoic acid (PABA), and ethyl aminobenzoate (benzocaine), were determined in vitro through hairless guinea pig skin. Benzocaine was also studied in human skin. Absorption of benzocaine was rapid and similar through both viable and nonviable skin. The absorption of the two acidic compounds, benzoic acid and PABA, was greater through nonviable skin. A small portion (6.9%) of absorbed benzoic acid was conjugated with glycine to form hippuric acid. Although N-acetyl-benzocaine had not been observed as a metabolite of benzocaine when studied by other routes of administration, both PABA and benzocaine were extensively N-acetylated during percutaneous absorption. Thus, the metabolism of these compounds should be considered in an accurate assessment of absorption after topical application.

Skin absorption of PABA corresponding to 1.6 to 9.6% of the applied amount of PABA was measured in the urine of six male volunteers after application of PABA in three different preparations. No significant difference where observed between the three preparations.

For more Absorption, Distribution and Excretion (Complete) data for 4-AMINOBENZOIC ACID (10 total), please visit the HSDB record page.

Used to make local anesthetics, folic acid, and azo dyes; Also used in feed additives, sunscreens, and medications; [HSDB] Occurs naturally as B complex factor--about 10-100 ppm in brewer's yeast;

Farming (Feed Additives) [Category: Industry]

For 4-aminobenzic acid (USEPA/OPP Pesticide Code: 233300) there are 0 labels match. /SRP: Not registered for current use in the U.S., but approved pesticide uses may change periodically and so federal, state and local authorities must be consulted for currently approved uses./

Manufacture /of/ various esters (local anesthetics), folic acid, and azo dyes; ... . Used in laboratories as sulfonamide antagonist.

Dye intermediate, pharmaceuticals, nutrition, UV absorber in suntan lotions.

Used principally in the pharmaceuticals industry; other uses are as a cross-linking agent for polyurethane resins, dyes, and feedstock additives.

Production volumes for non-confidential chemicals reported under the Inventory Update Rule.[Table#6344]

Non-confidential 2012 Chemical Data Reporting (CDR) information on the production and use of chemicals manufactured or imported into the United States. Chemical: Benzoic acid, 4-amino-. National Production Volume: Withheld.

p-Nitrotoluene is oxidized with permanganate to p-nitrobenzoic acid, and the nitro group then is reduced to an amino group with iron and hydrochloric acid.

It is manufactured commercially by the catalytic hydrogenation of 4-nitrobenzoic acid using a platinum or palladium catalyst or by reduction with tin or iron and hydrochloric acid.

The Hofmann degradation reaction of terephthalic acid is ... /a/ source of 4-aminobenzoic acid. Dimethyl terephthalate reacts with one equivalent of potassium hydroxide in methanol. The resultant salt is then amidated with liquid ammonia indimethylformamide at 130 - 140 °C to give potassium terephthalamate. This then reacts with sodium hypochlorite solution at 50 - 92 °C. The overall yield is approximately 70%. A two-stage Hofmann reaction has been developed. The yield is 93%.

Sunscreens are available in a variety of dosage forms and formulations. ... Because these formulations frequently change and the manufacturers often are reluctant to reveal specific ingredients in their formulations, a listing of commercially available sunscreens is not included in this monograph.

Technical, National Formulary

Capsules and tablets (as the potassium salt), 500 mg; Packets (as the potassium salt) 2 g; Powder

Benzoic acid, 4-amino-: ACTIVE

Commercially available as the calcium, potassium, and sodium salts.

p-Aminobenzoic acid is also known as anti-gray hair factor (in rats only).

Absorbs UV light of wavelengths in the region of 260 to 313 nm; its molar absorptivity at 288.5 nm is 18,300. However, it does not absorb throughout the near UV range ... Nevertheless, in the 260 to 313 nm range, it has the highest protection index of current sunscreen agents.

The drug occurs as white or slightly yellow, odorless crystals or crystalline powder. The drug is slightly soluble in water and freely soluble in alcohol. PABA is incompatible with ferric salts and oxidizing agents and darkens on exposure to air or light; preparations of the drug should be stored in light-resistant containers.