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l-DOPA can be manufactured and in its pure form is sold as a drug with the INN Tooltip International Nonproprietary Name levodopa. Trade names include Sinemet, Pharmacopa, Atamet, and Stalevo. As a drug, it is used in the clinical treatment of Parkinson's disease and dopamine-responsive dystonia. l-DOPA has a counterpart with opposite chirality ...
Levodopa crosses the protective blood–brain barrier, whereas dopamine itself cannot. [3] [4] Thus, levodopa is used to increase dopamine concentrations in the treatment of Parkinson's disease, Parkinsonism, dopamine-responsive dystonia and Parkinson-plus syndrome. The therapeutic efficacy is different for different kinds of symptoms.
For this reason levodopa is usually administered in combination with a DOPA decarboxylase inhibitor (DDCI), in this case carbidopa, which is very polar (and charged at physiologic pH) and cannot cross the blood brain barrier, however prevents peripheral conversion of levodopa to dopamine and thereby reduces the unwanted peripheral side effects ...
A dopamine agonist is a compound that activates dopamine receptors. There are two families of dopamine receptors, D 1-like and D 2-like. They are all G protein-coupled receptors. D 1 - and D 5-receptors belong to the D 1-like family and the D 2-like family includes D 2, D 3 and D 4 receptors. [1]
Levodopa (or L-DOPA) has been the most widely used treatment for over 30 years. [3] L-DOPA is transformed into dopamine in the dopaminergic neurons by dopa-decarboxylase. [3] Since motor symptoms are produced by a lack of dopamine in the substantia nigra, the administration of L-DOPA temporarily diminishes the motor symptoms. [3]
Peripherally selective DDCIs incapable of crossing the protective blood–brain barrier (BBB) are used in augmentation of L-DOPA (levodopa) in the treatment of Parkinson's disease (PD) to block the conversion of L-DOPA into dopamine outside the brain, for the purpose of reducing adverse side effects. [3]
The compound occurs naturally and is the immediate precursor for dopamine synthesis in the dopaminergic neurons of the substantia nigra. [166] Levodopa administration reduces the dopamine deficiency, alleviating parkinsonian symptoms. [167] [168]
When given with an inhibitor of dopa decarboxylase (carbidopa or benserazide), levodopa is optimally saved. This "triple therapy" is becoming a standard in the treatment of Parkinson's disease. Specific reactions catalyzed by COMT include: L-DOPA (levodopa) → 3-O-methyldopa; Dopamine → 3-methoxytyramine; DOPAC → HVA (homovanillic acid)