4-Aminobenzoic acid Other names: PABA Para-aminobenzoic acid Vitamin Bx

4-aminobenzoic acid (also known as para-aminobenzoic acid or PABA because the two functional groups are attached to the benzene ring across from one another in the para position) is an aminobenzoic acid in which the amino group is para to the carboxy group. PABA is an intermediate in the synthesis of folate by bacteria, plants, and fungi. The potassium salt is used as a drug against fibrotic skin disorders, such as Peyronie’s disease. PABA is also occasionally used in pill form by sufferers of irritable bowel syndrome to treat its associated gastrointestinal symptoms, and in nutritional epidemiological studies to assess the completeness of 24-hour urine collection for the determination of urinary sodium, potassium, or nitrogen levels.