Sodium phenylbutyrate, sold under the brand name Buphenyl among others, is a salt of an aromatic fatty acid, 4-phenylbutyrate (4-PBA) or 4-phenylbutyric acid.[7] The compound is used to treat urea cycle disorders, because its metabolites offer an alternative pathway to the urea cycle to allow excretion of excess nitrogen.[8][9] Sodium phenylbutyrate is also a histone deacetylase inhibitor and chemical chaperone, leading respectively to research into its use as an anti-cancer agent and in protein misfolding diseases such as cystic fibrosis.[7] Structure and properties Sodium phenylbutyrate is a sodium salt of an aromatic fatty acid, made up of an aromatic ring and butyric acid. The chemical name for sodium phenylbutyrate is 4-phenylbutyric acid, sodium salt. It forms water-soluble off-white crystals.[4] Uses Medical uses Sodium phenylbutyrate is taken orally or by nasogastric intubation as a tablet or powder, and tastes very salty and bitter. It treats urea cycle disorders, genetic diseases in which nitrogen waste builds up in the blood plasma as ammonia glutamine (a state called hyperammonemia) due to deficiences in the enzymes carbamoyl phosphate synthetase I, ornithine transcarbamylase, or argininosuccinic acid synthetase.[8][4] Uncontrolled, this causes intellectual impairment and early death.[4] Sodium phenylbutyrate metabolites allows the kidneys to excrete excess nitrogen in place of urea, and coupled with dialysis, amino acid supplements and a protein-restricted diet, children born with urea cycle disorders can usually survive beyond 12 months.[4] Patients may need treatment for all their life.[4] The treatment was introduced by researchers in the 1990s, and approved by the U.S. Food and Drugs Administration (FDA) in April 1996.[10][11] Adverse effects Nearly 1⁄4 of women may experience an adverse effect of amenorrhea or menstrual dysfunction.[4] Appetite loss is seen in 4% of patients. Body odor due to metabolization of phenylbutyrate affects 3% of patients, and 3% experience unpleasant tastes. Gastrointestinal symptoms and mostly mild indications of neurotoxicity are also seen in less than 2% of patients, among several other reported adverse effects.[4] Administration during pregnancy is not recommended because sodium phenylbutyrate treatment could mimic maternal phenylketonuria due to the production of phenylalanine, potentially causing fetal brain damage.[