Sodium phenylbutyrate is a salt of an aromatic fatty acid. 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. 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. It is used as adjunctive therapy for the management of chronic urea cycle disorders due to deficiencies in carbamylphosphate (CPS), ornithine transcarbamylase (OTC), or argininosuccinic acid synthetase. It is indicated in all neonatal- onset efficiency presenting within the first 28 days of life. Also indicated in patients with late-onset, presenting after the first month of life with a history of hyperammonemic encephalopathy. Sodium phenylbutyrate is a pro-drug and is rapidly metabolized to phenylacetate. Phenylacetate is a metabolically active compound that conjugates with glutamine via acetylation to form phenylacetylglutamine. The kidneys then excrete Phenylacetylglutamine. PBA (phenylbutyric acid) is absorbed from the intestine and converted by way of β-oxidation to the active moiety, phenylacetic acid (PAA). PAA is conjugated with glutamine in the liver and kidney by way of N-acyl coenzyme A-l-glutamine N-acyltransferase to form phenylacetylglutamine (PAGN). Like urea, PAGN incorporates two waste nitrogens and is excreted in the urine. On a molar basis, it is comparable to urea (each containing two moles of nitrogen). Therefore, phenylacetylglutamine provides an alternate vehicle for waste nitrogen excretion.

Dantrolene is a drug which was approved by FDA for the treatment of chronic spasticity and malignant hyperthermia (a rare life-threatening clinical syndrome). Dantrolene effect was shown both in vivo and in vitro and proved to be mediated by interaction with Ryanodine receptor 1. The drug has a potential for hepatotoxicity and should be used as indicated in the label.

Valproic acid (VPA; valproate; di-n-propylacetic acid, DPA; 2-propylpentanoic acid, or 2-propylvaleric acid) was first synthesized in 1882, by Burton. FDA approved valproic acid for the treatment of manic episodes associated with bipolar disorder, for the monotherapy and adjunctive therapy of complex partial seizures and simple and complex absence seizures and adjunctive therapy in patients with multiple seizure types that include absence seizures and for the prophylaxis of migraine headaches. The mechanisms of VPA which seem to be of clinical importance in the treatment of epilepsy include increased gamma-aminobutyric acid (GABA)-ergic activity, reduction in excitatory neurotransmission, and modification of monoamines. Recently, it was discovered that the VPA is a class I selective histone deacetylase inhibitor. This activity can be distinguished from its therapeutically exploited antiepileptic activity.

Tauroursodeoxycholic acid (TUDCA) is an endogenous hydrophilic bile acid used clinically to treat certain liver diseases. It is approved in Italy and Turkey for the treatment of cholesterol gallstones and is an investigational drug in China, Unites States, and Italy. Tauroursodeoxycholic acid is being investigated for use in several conditions such as Primary Biliary Cirrhosis (PBC), insulin resistance, amyloidosis, Cystic Fibrosis, Cholestasis, and Amyotrophic Lateral Sclerosis. Tauroursodeoxycholate (TUDC) promote choleresis by triggering the insertion of transport proteins for bile acids into the canalicular and basolateral membranes of hepatocytes. In addition, Tauroursodeoxycholate exerts hepatoprotective and anti-apoptotic effects, can counteract the action of toxic bile acids and reduce endoplasmic reticulum stress. Tauroursodeoxycholate can also initiate the differentiation of multipotent mesenchymal stem cells (MSC) including hepatic stellate cells and promote their development into hepatocyte-like cells. Although the hepatoprotective and choleretic action of TUDC is empirically used in clinical medicine since decades, the underlying molecular mechanisms remained largely unclear.