Carbidopa (Lodosyn) is a drug given to people with Parkinson's disease in order to inhibit peripheral metabolism oflevodopa. This property is significant in that it allows a greater proportion of peripheral levodopa to cross the blood–brain barrier for central nervous system effect.
CAT No: 10-101-135
CAS No:28860-95-9 (net), 38821-49-7 (monohydrate)
Synonyms/Alias:lodosyn; CARBIDOPA 1-HYDRATE; CARBIDOPA MONOHYDRATE; (S)-3-(3,4-Dihydroxyphenyl)-2- hydrazino-2-methylpropanoic acid · H2O; (S)-α-Hydrazino-3,4-dihydroxy-α-methylbenzenepropanoic acid monohydrate; (-)-L-α-Hydrazino-3,4-dihydroxy-α-methylhydrocinnamic acid monohydrate; α-Methyldopahydrazine monohydrate; MK485, MK 485, MK-485, Carbidopa, Lodosyn
Chemical Name:(2S)-3-(3,4-dihydroxyphenyl)-2-hydrazinyl-2-methylpropanoic acid
Carbidopa is a hydrazine derivative that functions as a peripheral aromatic L-amino acid decarboxylase (AADC) inhibitor, structurally related to amino acids and widely recognized for its role in modulating catecholamine biosynthesis. As a potent modulator of enzymatic activity in the dopamine synthesis pathway, it serves as a valuable biochemical tool for dissecting metabolic regulation and enzyme kinetics. Its selective inhibition of peripheral decarboxylase activity without crossing the blood-brain barrier makes it particularly significant in studies aiming to delineate central versus peripheral metabolic processes. Researchers value carbidopa for its capacity to clarify the pharmacokinetics and metabolism of L-DOPA and other aromatic amino acid substrates, providing insight into neurotransmitter regulation and metabolic flux.
Enzyme inhibition studies: Carbidopa is extensively utilized in research focused on the inhibition of aromatic L-amino acid decarboxylase. By selectively blocking peripheral decarboxylation of substrates such as L-DOPA, it enables scientists to differentiate between central and peripheral metabolic pathways. This selective inhibition is instrumental in delineating the role of AADC in various tissues, facilitating precise mapping of enzyme distribution and activity in experimental models.
Neurotransmitter biosynthesis research: In studies investigating the synthesis and regulation of catecholamines, carbidopa serves as a critical tool for controlling the conversion of L-DOPA to dopamine outside the central nervous system. By preventing peripheral dopamine formation, it allows researchers to maintain higher systemic levels of L-DOPA, thereby enabling controlled studies of neurotransmitter precursor uptake, transport, and conversion within neural tissues. This application is vital for elucidating the dynamics of dopamine and other catecholamine biosynthetic pathways.
Pharmacokinetic analysis: The compound is frequently employed in pharmacokinetic and metabolic profiling experiments to assess the absorption, distribution, metabolism, and excretion of L-DOPA and related substrates. Carbidopa's inhibition of peripheral AADC activity alters the metabolic fate of these compounds, allowing for detailed investigation of their systemic circulation and central availability. Such studies are essential for optimizing dosing regimens and understanding the metabolic interplay between peripheral and central compartments.
Metabolic pathway elucidation: Carbidopa is a valuable reagent for tracing metabolic flux through aromatic amino acid pathways. By modulating the enzymatic conversion rates of key intermediates, it supports the use of isotope-labeled substrates and advanced analytical techniques in metabolic tracing studies. Researchers leverage its specific action to dissect pathway regulation, enzyme-substrate specificity, and the impact of pathway modulation on broader metabolic networks.
Analytical method development: The compound is also incorporated into the development and validation of analytical assays designed to quantify L-DOPA, dopamine, and related metabolites in biological samples. Its use as a decarboxylase inhibitor enhances the stability and recovery of analytes during sample preparation, improving the accuracy and reliability of chromatographic and spectrometric methods. This application is particularly relevant in laboratories focused on neurochemical analysis and metabolic biomarker quantification.
A double-blind study comparing the effects of carbidopa and levodopa combined in a single tablet with levodopa alone was undertaken in 50 patients with Parkinson's disease. After 6 months, there was a statistically significant improvement over baseline in total score, rigidity, and tremor only in the patients randomized to carbidopa/levodopa. In addition, 40 percent of the patients treated with carbidopa/levodopa showed obvious clinical improvement (a greater than 50 percent reduction in their total score) over treatment with levodopa alone. However, after 2 years, only 20 percent continued to show this improvement. Nausea, vomiting, and anorexia developed in 56 percent of patients on levodopa but in only 27 percent of patients on carbidopa/levodopa. However, abnormal involuntary movements, observed in 48 percent of patients on levodopa, were present in 77 percent of patients on carbidopa/levodopa. Despite the increase in abnormal involuntary movements, carbidopa/levodopa is more effective than levodopa.
Lieberman, A., Goodgold, A., Jonas, S., & Leibowitz, M. (1975). Comparison of dopa decarboxylase inhibitor (carbidopa) combined with levodopa and levodopa alone in Parkinson's disease. Neurology, 25(10), 911-911.
Levodopa is the most efficacious agent for the treatment of motor features of Parkinson's disease but its chronic use is associated with the development of motor complications. Mounting evidence indicates the short half-life of levodopa and resultant pulsatile stimulation of striatal dopamine receptors leads to wearing off, motor fluctuations and dyskinesias. Longer acting dopaminergic agents, such as dopamine agonists, are less likely to cause motor fluctuations and dyskinesias but are not as efficacious for control of motor symptoms. Therefore, there is interest in exploring ways to deliver levodopa in a more continuous fashion, in an effort to maintain benefit through the day and reduce the development of motor fluctuations and dyskinesias. A dopa decarboxylase inhibitor (DDCI), such as carbidopa or benserazide, is administered with levodopa to attenuate its peripheral conversion to dopamine, reduce nausea and increase central bioavailability. When levodopa is administered with a DDCI, its main route of peripheral metabolism is via catechol-O-methyl transferase (COMT).
Seeberger, L. C., & Hauser, R. A. (2009). Levodopa/carbidopa/entacapone in Parkinson’s disease. Expert review of neurotherapeutics, 9(7), 929-940.
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