Monoamine precursors

thumb|Tyrosine ball and stick model spinning -Tyrosine or tyrosine (symbol Tyr or Y) or 4-hydroxyphenylalanine is one of the 20 standard amino acids that are used by cells to synthesize proteins. It is a conditionally essential amino acid with a polar side group. The word "tyrosine" is from the Greek tyrós, meaning cheese, as it was first discovered in 1846 by German chemist Justus von Liebig in the protein casein from cheese. It is called tyrosyl when referred to as a functional group or side chain. While tyrosine is generally classified as a hydrophobic amino acid, it is more hydrophilic tha

-DOPA, also known as -3,4-dihydroxyphenylalanine and used medically as levodopa, is made and used as part of the normal biology of some plants and animals, including humans. Humans, as well as a portion of the other animals that utilize -DOPA, make it via biosynthesis from the amino acid -tyrosine.

5-Hydroxytryptophan (5-HTP), used medically as oxitriptan, is a naturally occurring amino acid and chemical precursor as well as a metabolic intermediate in the biosynthesis of the neurotransmitter serotonin.

Carbidopa/levodopa, also known as levocarb and co-careldopa, is the combination of the two medications carbidopa and levodopa. It is primarily used to manage the symptoms of Parkinson's disease, although it does not slow down the disease or slow down progression. It can take two to three weeks of treatment before benefits are seen. Each dose then begins working in about ten minutes to two hours, with a duration of effect of about five hours. Carbidopa/levodopa is taken orally.

Dipivefrine, or dipivefrin, also known as epinephrine pivalate and sold under the brand name Propine among others, is a sympathomimetic medication which is used in the treatment of open-angle glaucoma. It is available as a 0.1% ophthalmic solution (eye drop).

Droxidopa, also known as 'L-threo-dihydroxyphenylserine (L-DOPS) and sold under the brand names Northera and Dops' among others, is sympathomimetic medication which is used in the treatment of hypotension (low blood pressure) and for other indications. It is taken by mouth.

Etilevodopa (developmental code name TV-1203) is a dopaminergic agent which was developed as a treatment for Parkinson's disease. It is the ethyl ester of levodopa. It was never marketed.

Melevodopa, also known as levodopa methyl ester (LDME) and sold under the brand name Levomet, is a dopaminergic agent. It is the methyl ester of levodopa. It is used in oral tablet form as an effervescent prodrug with 250times the water solubility of tablet levodopa. In combination with carbidopa, as melevodopa/carbidopa (brand name Sirio), it is approved for use in the treatment of Parkinson's disease.