Phenylalanine is a biologically essential amino acid that acts as a precursor to tyrosine and the catecholamines (epinephrine, norepinephrine, dopamine, and tyramine), and is a constituent of many central nervous system neuropeptides. Normal dietary levels of phenylalanine are approximately 1-2 grams daily. Phenylalanine appears in two forms which are identical mirror images of each other: L-phenylalanine, a nutritional supplement, and D-phenylalanine, an effective painkiller and antidepressant due to its ability to inhibit the breakdown of enkephalins, the brain’s natural pain killers.

Tryptophan is alpha-aminoacid that is used in the biosynthesis of proteins. It is essential aminoacid in humans, meaning the body cannot synthesize and it must be obtained from the diet. Tryptophan is a precursor of serotonin, and as such is sold over the counter in many countries as a dietary supplement for use as an antidepressant, anxiolytic and sleep aid, however application of tryptophan in these indications is not approved by FDA.

Alanine is a non-essential aminoacid encoded by GCU, GCC, GCA, and GCG codons. Besides being a building block of proteins, alanine plays a key role in glucose-alanine cycle. Alanine is medically used as a dietary supplement for conditions such as fructose intolerance, muscle atrophy, low birth weight.

Isoleucine is an essential α-amino acid that is used in the biosynthesis of proteins. L-isoleucine is commonly used in parenteral and enteral nutrition. It is used in combination with the other branched chain amino acids to improve the nutritional status of patients with hepatic diseases. BCAAs serve as important fuel sources for skeletal muscle during periods of metabolic stress

Lysing is an essential basic amino-acid encoded by codone AAA and AAG, and used in the biosynthesis of proteins. The daily requirement for lysine is 38 mg/kg body weight. The most rich source of lysine is fish, beef, chicken. In a clinical study lysine supplements was found to be an effective for reduction of occurrence, severity and healing time for recurrent HSV infection, however Cochrane Review concluded that the evidence is insufficient. Lysine was investigated for improving anxiety, ameliorating angina prectoris. Lysine acetylsalicylate has been used to treat pain and to detoxify the body after heroin use. Lysine clonixinate has been used for its analgesic properties for the treatment of migraine headaches and other painful conditions. However, limited clinical trials exist for these conditions.

Histidine is an essential amino acid. L-histidine is converted to histamine by histidine decarboxylase, a pyridoxal 5'-phosphate-dependent enzyme. The copper(II)–l-histidine (1:2 complex at physiological pH) has been widely used in the treatment of Menkes disease (a genetic neurodegenerative disorder that leads to early death in the children due to impaired copper metabolism) and more recent use has been reported in the treatment of infantile hypertrophic cardioencephalomyopathy (a condition caused by mutations in SCO2, a cytochrome c oxidase assembly gene). CUSTODIOL HTK (Histidine-tryptophan-ketoglutarate) Solution is indicated for perfusion and flushing of donor kidneys, liver, and heart prior to removal from the donor or immediately after removal from the donor.

Valine is an α-amino acid that is used in the biosynthesis of proteins. It is essential in humans, meaning the body cannot synthesize it and thus it must be obtained from the diet. There is a mixed scientivic evidence that as a dietary supplement valine improves training efficacy, delays central fatigue.

Tyropanic acid and its salt sodium tyropanoate are radiocontrast agents used in cholecystography (X-ray diagnosis of gallstones). Tyropanic acid is sold under the trade names Bilopaque, Lumopaque, Tyropaque, and Bilopac. The molecule contains three heavy iodine atoms which obstruct X-rays in the same way as the calcium in bones to produce a visible image. After injection it is rapidly excreted into the bile.

Nalidixic acid is a quinolone antibacterial indicated for the treatment of urinary tract infections. Nalidixic acid has marked antibacterial activity against gram-negative bacteria including Enterobacter species, Escherichia coli, Morganella Morganii; Proteus Mirabilis, Proteus vulgaris, and Providencia rettgeri. Pseudomonas species are generally resistant to the drug. It is suggested that nalidixic acid acts by inhibiting bacterial DNA gyrase.

Idoxuridine is an antiviral agent use in keratitis caused by herpes simplex virus. As a prescription drug it comes as a 0.1% ophthalmic solution/drops (Herplex and Dendrid). The first studies of the compound for treatment of human herpes simplex started in early 1960s. Being a structural analog of thymidine idoxuridine inhibits viral DNA replication by substituting thymidine. The effect of idoxuridine results in the inability of the virus to reproduce and/or infect tissues. Idoxuridine also blocks viral thymidine kinase as its substrate analog.