| Item |
Information |
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Drug Groups
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approved |
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Description
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An inhibitor of DOPA decarboxylase, preventing conversion of levodopa to dopamine. It is used in parkinson disease to reduce peripheral adverse effects of levodopa. It has no antiparkinson actions by itself. [PubChem] |
| Indication |
For treatment of the symptoms of idiopathic Parkinson's disease (paralysis agitans), post-encephalitic parkinsonism |
| Pharmacology |
Carbidopa, a noncompetitive decarboxylase inhibitor, is used in combination with levodopa for the treatment of Parkinson's disease. |
| Toxicity |
Symptoms of a carbidopa toxicity include muscle spasms or weakness, spasms of the eyelid, nausea, vomiting, diarrhea, an irregular heartbeat, confusion, agitation, hallucinations, and unconsciousness. |
| Affected Organisms |
| • |
Humans and other mammals |
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| Biotransformation |
The loss of the hydrazine functional group (probably as molecular nitrogen) represents the major metabolic pathway for carbidopa. There are several metabolites of carbidopa metabolism including 3-(3,4-dihydroxyphenyl)-2-methylpropionic acid, 3-(4-hydroxy-3-methoxyphenyl)-2-methylpropionic acid, 3-(3-hydroxyphenyl)-2-methylpropionic acid, 3-(4-hydroxy-3-methoxyphenyl)-2-methyllactic acid, 3-(3-hydroxyphenyl)-2-methyllactic acid, and 3,4-dihydroxyphenylacetone (1,2). [PMID: 4150141] |
| Absorption |
Rapidly decarboxylated to dopamine in extracerebral tissues so that only a small portion of a given dose is transported unchanged to the central nervous system. |
| Half Life |
1-2 hours |
| Protein Binding |
76% |
| Elimination |
In clinical pharmacologic studies, simultaneous administration of separate tablets of carbidopa and levodopa produced greater urinary excretion of levodopa in proportion to the excretion of dopamine when compared to the two drugs administered at separate times. |
| References |
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Vickers S, Stuart EK, Bianchine JR, Hucker HB, Jaffe ME, Rhodes RE, Vandenheuvel WJ: Metabolism of carbidopa (1-(-)-alpha-hydrazino-3,4-dihydroxy-alpha-methylhydrocinnamic acid monohydrate), an aromatic amino acid decarboxylase inhibitor, in the rat, rhesus monkey, and man. Drug Metab Dispos. 1974 Jan-Feb;2(1):9-22.
[Pubmed]
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Vickers S, Stuart EK, Hucker HB: Further studies on the metabolism of carbidopa, (minus)-L-alpha-hydrazino-3,4-dihydroxy-alpha-methylbenzenepropanoic acid monohydrate, in the human, Rhesus monkey, dog, and rat. J Med Chem. 1975 Feb;18(2):134-8.
[Pubmed]
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