Carbidopa acts as a peripheral DDC inhibitor, as carbidopa, itself, cannot cross the blood–brain barrier. In other words, carbidopa has no effect on brain DDC conversion of levodopa/L-DOPA to dopamine. Ultimately, a greater proportion of the exogenously provided levodopa/L-DOPA reaches the brain. Commercially, carbidopa/levodopa combinations are available in the treatment of central dopamine deficiencies. Along with carbidopa, other DDC inhibitors are benserazide (Ro-4-4602), difluromethyldopa, and α-methyldopa. pharmacology 2
Carbidopa, an inhibitor of aromatic amino acid decarboxylation, is a white, crystalline compound, slightly soluble in water, with a molecular weight of 244.3. It is designated chemically as N-amino-α-methyl-3-hydroxy-L-tyrosine monohydrate. Its empirical formula is C10H14N2O4•H2O. Used in tandem with L-DOPA (also known as levodopa, a dopamine precursor converted in the body to dopamine), it increases the plasma half-life of levodopa from 50 minutes to 1½ hours. CarbiDOPA cannot cross the blood–brain barrier, so it inhibits only peripheral DDC. It thus prevents the conversion of L-DOPA to dopamine peripherally. This reduces the side effects caused by dopamine on the periphery, as well as increasing the concentration of L-DOPA and dopamine in the brain. The combination of carbidopa/levodopa carries the brand names of Kinson, Sinemet, Pharmacopa and Atamet; while Stalevo is a combination with entacapone, which enhances the bioavailability of carbidopa and levodopa. Carbidopa is most commonly used as a method to inhibit the activity of dopamine decarboxylase. This is an enzyme that breaks down L-Dopa in the periphery and converts it to dopamine.
Synthesis
The synthesis begins with a modified Strecker reaction using hydrazine and potassium cyanide on arylacetone (1) to give 2. This is then hydrolyzed with cold HCl to give carboxamide 3. More vigorous hydrolysis with 48% HBr cleaves the amide bond and the aryl ether group to produce carbidopa (4). References
External links
Lodosyn prescribing information
Sinemet datasheet for New Zealand