Methyldopa hydrazine

Blocking the conversion to DA would appear stupid unless this could be restricted to the periphery. More dopa would then be preserved for entry into the brain, where it could be decarboxylated to DA as usual. Drugs like carbidopa and benserazide do precisely that and are used successfully with levodopa. They are known as extracerebral dopa decarboxylase inhibitors (ExCDDIs). Carbidopa (a-methyldopa hydrazine) is structurally similar to dopa but its hydrazine group (NHNH2) reduces lipid solubility and CNS penetration (Fig. 15.4). 

Synonym. (— )-L-a-Methyldopa Hydrazine Proprietary Name. It is an ingredient of Sinemet. 5-2-(3,4-Dihydroxybenzyl)-2-hydrazinopropionic acid monohydrate... 

L-O(-Methyldopa Hydrazine Trade names Loposin Lodosyn Sinemet... 

Carbidopa (4.75), a hydrazine analog of a-methyldopa, is an important DOPA decarboxylase inhibitor. It is used to protect the DOPA that is administered in large doses in Parkinson s disease (section 4.4.4) from peripheral decarboxylation. DOPA concentrations in the CNS will therefore increase without requiring the administration of extremely high, toxic doses of DOPA. The exclusive peripheral mode of action of carbidopa is due to its ionic character and inability to cross the blood-brain barrier. Because of this effect, carbidopa is co-administered with DOPA in a single tablet formulation as a first-line therapy for Parkinson s disease. Benserazide (4.76) has similar activity. 

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