Medical expert of the article
New publications
Preparations
Para-aminobenzoic acid (PABA)
Last reviewed: 07.07.2025
All iLive content is medically reviewed or fact checked to ensure as much factual accuracy as possible.
We have strict sourcing guidelines and only link to reputable media sites, academic research institutions and, whenever possible, medically peer reviewed studies. Note that the numbers in parentheses ([1], [2], etc.) are clickable links to these studies.
If you feel that any of our content is inaccurate, out-of-date, or otherwise questionable, please select it and press Ctrl + Enter.
Stemp (1939) was the first to report the presence of a substance with vitamin properties. This factor was necessary for the reproduction of microorganisms. Woods's research (1940) showed that a substance isolated from Streptococcus haemoliticus was capable of reducing the bacteriostatic effect of sulfonamide administration. This substance turned out to be para-aminobenzoic acid (PABA).
[ Physicochemical properties of para-aminobenzoic acid (PABA)
Two structural analogues with radicals in ortho- and meta-positions are biologically inactive. This crystalline substance is white with a yellowish tint, has a melting point of 186-187° C, is poorly soluble in water, more easily in alcohol and ether. Chemically stable, withstands boiling in acidic and alkaline environments. It is used in medicine for infectious diseases, as a bacteriostatic agent. PABA derivatives (novocaine, anesthesin), which have a local anesthetic effect, are also used.
Metabolism of para-aminobenzoic acid (PABA)
When taken orally, para-aminobenzoic acid (PABA) is partially absorbed in the upper intestine, and partially used by the microflora of the large intestine to synthesize folic acid. PABA is found in significant quantities in the blood: 2-70 μg/dl, and is excreted in urine mainly in acetylated form. The content in the blood and excretion from the body with urine changes with various diseases. The highest content is in patients with cardiovascular diseases, the minimum in chronic hepatitis, Botkin's disease, peptic ulcer disease, etc. 250 μg of PABA is excreted with feces.
Biological functions of para-aminobenzoic acid (PABA)
PABA has a wide range of physiological effects on the body, being a component of folic and folinic acids, it promotes the synthesis of purines and pyrimidines, and, consequently, RNA and DNA. It affects the metabolism of some biogenic amines. Its antihistamine effect has been proven, which is important when using drugs in the postoperative period.
The growth-inhibiting effect of sulfonamides can be removed by administering folic acid. In this case, the presence of PABA is not necessary. A positive effect of PABA on the central nervous system is noted (the processes of internal inhibition are normalized). It affects the function of the thyroid gland. Long-term administration of toxic doses of the drug leads to suppression of thyroxine secretion and hyperplasia of the thyroid gland. Small doses of 100-200 mg per dose reduce hyperfunction of the thyroid gland, which in particular is manifested in the normalization of the basal metabolism, a decrease in the values of gas exchange and oxygen consumption. Para-aminobenzoic acid (PABA) affects hormone metabolism. It slows down the oxidation of adrenaline. Under its influence, the cycle is normalized in oligomenorrhea.
Para-aminobenzoic acid (PABA) is practically non-toxic, hypervitaminosis is not described. However, in case of overdose, a depressive state and hypotension may be observed. The use of acid in large doses of 4-6 g per day in the complex therapy of rickettsiosis turned out to be very effective, the mortality from this disease decreased. Compared with conventional therapeutic methods, a decrease in temperature and recovery occurred earlier. PABA reduces the toxicity of some substances, in particular arsenic and antimony. Due to the photoprotective effect, it is used for photodermatoses, in cosmetic ointments for protection from sunburn.
In a dose of 0.1-0.5 g it was used in the treatment of patients with atherosclerosis and hypertension. As a result of a 20-day course of therapy, an improvement in general well-being was noted, and work capacity increased. Intramuscular administration was effective in muscle bleeding. Its administration enhances the effect of antitumor drugs sarcolysin on sarcoma 45 and Garning-Passey tumor. At the same time, a stimulating effect on erythropoiesis was noted.
Structural analogues of PABA are widely used, in particular sulfonamides, which have antibacterial properties. It is assumed that sulfanilamide preparations, due to their structural similarity, can competitively replace PABA in the enzymatic systems of microorganisms, subsequently stopping their growth and reproduction. The coenzyme functions of this acid have not been established, but, being a component of folic acid coenzymes, PABA thus participates in many metabolic processes.
Sources and requirements of para-aminobenzoic acid (PABA)
Para-aminobenzoic acid (PABA) is widely distributed in food products. It was first isolated from yeast. It is found in significant quantities in the liver (2.5 μg/g), kidneys (1.8 μg/g), heart (1.35 μg/g), yeast (4 μg/g) and mushrooms (1.3 μg/g). Other products: cow's milk, chicken eggs, carrots, spinach, wheat contain significantly less.
The daily requirement has not been established.
Attention!
To simplify the perception of information, this instruction for use of the drug "Para-aminobenzoic acid (PABA)" translated and presented in a special form on the basis of the official instructions for medical use of the drug. Before use read the annotation that came directly to medicines.
Description provided for informational purposes and is not a guide to self-healing. The need for this drug, the purpose of the treatment regimen, methods and dose of the drug is determined solely by the attending physician. Self-medication is dangerous for your health.