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.

Dextrothyroxine is the dextrorotary isomer of the synthetic thyroxine. It is an antihyperlipidemic agent. The mechanism of action is not completely understood, but dextrothyroxine apparently acts in the liver to stimulate formation of low-density lipoprotein (LDL) and, to a much greater extent, to increase catabolism of LDL. This leads to increased excretion of cholesterol and bile acids via the biliary route into the feces, with a resulting reduction in serum cholesterol and LDL. Dextrothyroxine has no significant effect on high-density lipoproteins (HDL). Inherently, it will also bind to thyroid receptors and as it is a prohormone, it will bind as a substrate to iodide peroxidase.

Tyrosine (L-form) is a non-essential amino acid, which is primarily required for the protein synthesis. This amino acid is the precursor of dopamine, norepinephrine, and epinephrine; therefore the lower concentration of tyrosine could be a peripheral marker of the hyperdopaminergic condition hypothesized to explain psychosis. Tyrosine supplements can improve cognition, increase energy, reduce anxiety, reduce depression, reduce levels of pain.

N-Acetyltyrosine is an acetylated derivative of the amino acid L-tyrosine. Ordinary L-tyrosine is less stable and also less soluble in water, which may result in reduced bioavailability. Acetylation enhances the solubility and stability of certain amino acids. N-Acetyltyrosine is commonly used in place of tyrosine in parenteral nutrition. It converts to tyrosine and then can be used in neurotransmitter treatment as a precursor of cathecholamine. N-Acetyltyrosine supports brain function by supporting the synthesis of the catecholamines norepinephrine and dopamine (neurotransmitters). N-Acetyltyrosine supplements are used to improve memory and cognitive performance in humans while they are experiencing psychological stress.

Methyldopa is an aromatic-amino-acid decarboxylase inhibitor in animals and in man. Methyldopa is a medication that has been used to treat high blood pressure since the 1960s. Methyldopa is indicated in the treatment of moderate to severe hypertension, including that complicated by renal disease. Only methyldopa, the L-isomer of alpha-methyldopa, has the ability to inhibit dopa decarboxylase and to deplete animal tissues of norepinephrine. D-isomer is relatively inactive. In man the antihypertensive activity appears to be due solely to the L-isomer, which became generally known as methyldopa (Aldomet). About twice the dose of the racemate (Methyldopa anhydrous, (±)-; DL-alpha-methyldopa) is required for equal antihypertensive effect. Racemic alpha-methyldopa was shown to be much less effective or ineffective for the treatment of hypertension. The comparative study of the hypotensive effect of L-alpha-methyl-dopa (L-isomer) versus the racemic form was performed. The short-term hypotensive effects of the racemic form and the L-isomer of alpha-methyl-dopa were compared in 13 hospitalized patients with arterial hypertension. After a placebo period the active preparations in a fixed dose of 1.5 g daily were administered for three-day periods separated by a second placebo period of three days, the sequence of the active drugs being alternated. Both substances were shown to exert significant hypotensive effects. The L-isomer produced significant blood-pressure reductions irrespective of whether or not it was given first, whereas the racemic form was effective only when given first. The blood-pressure levels obtained with the L-isomer were throughout lower than those with the racemic form. Methyldopa is a centrally acting antihypertensive agent. It is metabolized to alpha-methylnorepinephrine in the brain, and this compound is thought to activate central alpha-2 adrenergic receptors

18F-FET (18F-Fluoroethyl-L-tyrosine) is a radiolabelled amino acid. It penetrates the blood-brain barrier by a specific amino acid transport system. In the brain, it is taken up into upregulated tumoral cells but not incorporated into proteins. It is used as a biomarker for positron emission tomography for imaging brain tumors, where it has higher specificity than 18F-FDG.

Dibromotyrosine is a brominated derivative of a natural amino acid tyrosine. In the human body, dibromotyrosine is produced by eosinophil peroxidase secreted from activated eosinophils. Dibromotyrosine is naturally produced by marine sponges. Dibromotyrosine is used in medicine for the treatment of functional hyperthyroidisms. It acts by competing with iodination of tyrosines, thus reducing the active form of the thyroid hormones. Dibromotyrosine also appears to maintain the ability to control TSH production through negative feedback on the pituitary gland, reducing the biological activity of the thyroid. Dibromotyrosine is marketed in Italy under tradename Bromotiren.